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+<!-- title The Go Programming Language Specification -->
+<!-- subtitle Version of July 14, 2011 -->
+
+<!--
+TODO
+[ ] need language about function/method calls and parameter passing rules
+[ ] last paragraph of #Assignments (constant promotion) should be elsewhere
+    and mention assignment to empty interface.
+[ ] need to say something about "scope" of selectors?
+[ ] clarify what a field name is in struct declarations
+    (struct{T} vs struct {T T} vs struct {t T})
+[ ] need explicit language about the result type of operations
+[ ] should probably write something about evaluation order of statements even
+	though obvious
+[ ] review language on implicit dereferencing
+[ ] clarify what it means for two functions to be "the same" when comparing them
+-->
+
+
+<h2 id="Introduction">Introduction</h2>
+
+<p>
+This is a reference manual for the Go programming language. For
+more information and other documents, see <a href="http://golang.org/">http://golang.org</a>.
+</p>
+
+<p>
+Go is a general-purpose language designed with systems programming
+in mind. It is strongly typed and garbage-collected and has explicit
+support for concurrent programming.  Programs are constructed from
+<i>packages</i>, whose properties allow efficient management of
+dependencies. The existing implementations use a traditional
+compile/link model to generate executable binaries.
+</p>
+
+<p>
+The grammar is compact and regular, allowing for easy analysis by
+automatic tools such as integrated development environments.
+</p>
+
+<h2 id="Notation">Notation</h2>
+<p>
+The syntax is specified using Extended Backus-Naur Form (EBNF):
+</p>
+
+<pre class="grammar">
+Production  = production_name "=" [ Expression ] "." .
+Expression  = Alternative { "|" Alternative } .
+Alternative = Term { Term } .
+Term        = production_name | token [ "…" token ] | Group | Option | Repetition .
+Group       = "(" Expression ")" .
+Option      = "[" Expression "]" .
+Repetition  = "{" Expression "}" .
+</pre>
+
+<p>
+Productions are expressions constructed from terms and the following
+operators, in increasing precedence:
+</p>
+<pre class="grammar">
+|   alternation
+()  grouping
+[]  option (0 or 1 times)
+{}  repetition (0 to n times)
+</pre>
+
+<p>
+Lower-case production names are used to identify lexical tokens.
+Non-terminals are in CamelCase. Lexical symbols are enclosed in
+double quotes <code>""</code> or back quotes <code>``</code>.
+</p>
+
+<p>
+The form <code>a … b</code> represents the set of characters from
+<code>a</code> through <code>b</code> as alternatives. The horizontal
+ellipis … is also used elsewhere in the spec to informally denote various
+enumerations or code snippets that are not further specified. The character …
+(as opposed to the three characters <code>...</code>) is not a token of the Go
+language.
+</p>
+
+<h2 id="Source_code_representation">Source code representation</h2>
+
+<p>
+Source code is Unicode text encoded in
+<a href="http://en.wikipedia.org/wiki/UTF-8">UTF-8</a>. The text is not
+canonicalized, so a single accented code point is distinct from the
+same character constructed from combining an accent and a letter;
+those are treated as two code points.  For simplicity, this document
+will use the term <i>character</i> to refer to a Unicode code point.
+</p>
+<p>
+Each code point is distinct; for instance, upper and lower case letters
+are different characters.
+</p>
+<p>
+Implementation restriction: For compatibility with other tools, a
+compiler may disallow the NUL character (U+0000) in the source text.
+</p>
+
+<h3 id="Characters">Characters</h3>
+
+<p>
+The following terms are used to denote specific Unicode character classes:
+</p>
+<pre class="ebnf">
+newline        = /* the Unicode code point U+000A */ .
+unicode_char   = /* an arbitrary Unicode code point except newline */ .
+unicode_letter = /* a Unicode code point classified as "Letter" */ .
+unicode_digit  = /* a Unicode code point classified as "Decimal Digit" */ .
+</pre>
+
+<p>
+In <a href="http://www.unicode.org/versions/Unicode6.0.0/">The Unicode Standard 6.0</a>,
+Section 4.5 "General Category"
+defines a set of character categories.  Go treats
+those characters in category Lu, Ll, Lt, Lm, or Lo as Unicode letters,
+and those in category Nd as Unicode digits.
+</p>
+
+<h3 id="Letters_and_digits">Letters and digits</h3>
+
+<p>
+The underscore character <code>_</code> (U+005F) is considered a letter.
+</p>
+<pre class="ebnf">
+letter        = unicode_letter | "_" .
+decimal_digit = "0" … "9" .
+octal_digit   = "0" … "7" .
+hex_digit     = "0" … "9" | "A" … "F" | "a" … "f" .
+</pre>
+
+<h2 id="Lexical_elements">Lexical elements</h2>
+
+<h3 id="Comments">Comments</h3>
+
+<p>
+There are two forms of comments:
+</p>
+
+<ol>
+<li>
+<i>Line comments</i> start with the character sequence <code>//</code>
+and stop at the end of the line. A line comment acts like a newline.
+</li>
+<li>
+<i>General comments</i> start with the character sequence <code>/*</code>
+and continue through the character sequence <code>*/</code>. A general
+comment that spans multiple lines acts like a newline, otherwise it acts
+like a space.
+</li>
+</ol>
+
+<p>
+Comments do not nest.
+</p>
+
+
+<h3 id="Tokens">Tokens</h3>
+
+<p>
+Tokens form the vocabulary of the Go language.
+There are four classes: <i>identifiers</i>, <i>keywords</i>, <i>operators
+and delimiters</i>, and <i>literals</i>.  <i>White space</i>, formed from
+spaces (U+0020), horizontal tabs (U+0009),
+carriage returns (U+000D), and newlines (U+000A),
+is ignored except as it separates tokens
+that would otherwise combine into a single token. Also, a newline or end of file
+may trigger the insertion of a <a href="#Semicolons">semicolon</a>.
+While breaking the input into tokens,
+the next token is the longest sequence of characters that form a
+valid token.
+</p>
+
+<h3 id="Semicolons">Semicolons</h3>
+
+<p>
+The formal grammar uses semicolons <code>";"</code> as terminators in
+a number of productions. Go programs may omit most of these semicolons
+using the following two rules:
+</p>
+
+<ol>
+<li>
+<p>
+When the input is broken into tokens, a semicolon is automatically inserted
+into the token stream at the end of a non-blank line if the line's final
+token is
+</p>
+<ul>
+	<li>an
+	    <a href="#Identifiers">identifier</a>
+	</li>
+	
+	<li>an
+	    <a href="#Integer_literals">integer</a>,
+	    <a href="#Floating-point_literals">floating-point</a>,
+	    <a href="#Imaginary_literals">imaginary</a>,
+	    <a href="#Character_literals">character</a>, or
+	    <a href="#String_literals">string</a> literal
+	</li>
+	
+	<li>one of the <a href="#Keywords">keywords</a>
+	    <code>break</code>,
+	    <code>continue</code>,
+	    <code>fallthrough</code>, or
+	    <code>return</code>
+	</li>
+	
+	<li>one of the <a href="#Operators_and_Delimiters">operators and delimiters</a>
+	    <code>++</code>,
+	    <code>--</code>,
+	    <code>)</code>,
+	    <code>]</code>, or
+	    <code>}</code>
+	</li>
+</ul>
+</li>
+
+<li>
+To allow complex statements to occupy a single line, a semicolon
+may be omitted before a closing <code>")"</code> or <code>"}"</code>.
+</li>
+</ol>
+
+<p>
+To reflect idiomatic use, code examples in this document elide semicolons
+using these rules.
+</p>
+
+
+<h3 id="Identifiers">Identifiers</h3>
+
+<p>
+Identifiers name program entities such as variables and types.
+An identifier is a sequence of one or more letters and digits.
+The first character in an identifier must be a letter.
+</p>
+<pre class="ebnf">
+identifier = letter { letter | unicode_digit } .
+</pre>
+<pre>
+a
+_x9
+ThisVariableIsExported
+αβ
+</pre>
+
+<p>
+Some identifiers are <a href="#Predeclared_identifiers">predeclared</a>.
+</p>
+
+
+<h3 id="Keywords">Keywords</h3>
+
+<p>
+The following keywords are reserved and may not be used as identifiers.
+</p>
+<pre class="grammar">
+break        default      func         interface    select
+case         defer        go           map          struct
+chan         else         goto         package      switch
+const        fallthrough  if           range        type
+continue     for          import       return       var
+</pre>
+
+<h3 id="Operators_and_Delimiters">Operators and Delimiters</h3>
+
+<p>
+The following character sequences represent <a href="#Operators">operators</a>, delimiters, and other special tokens:
+</p>
+<pre class="grammar">
++    &amp;     +=    &amp;=     &amp;&amp;    ==    !=    (    )
+-    |     -=    |=     ||    &lt;     &lt;=    [    ]
+*    ^     *=    ^=     &lt;-    &gt;     &gt;=    {    }
+/    &lt;&lt;    /=    &lt;&lt;=    ++    =     :=    ,    ;
+%    &gt;&gt;    %=    &gt;&gt;=    --    !     ...   .    :
+     &amp;^          &amp;^=
+</pre>
+
+<h3 id="Integer_literals">Integer literals</h3>
+
+<p>
+An integer literal is a sequence of digits representing an
+<a href="#Constants">integer constant</a>.
+An optional prefix sets a non-decimal base: <code>0</code> for octal, <code>0x</code> or
+<code>0X</code> for hexadecimal.  In hexadecimal literals, letters
+<code>a-f</code> and <code>A-F</code> represent values 10 through 15.
+</p>
+<pre class="ebnf">
+int_lit     = decimal_lit | octal_lit | hex_lit .
+decimal_lit = ( "1" … "9" ) { decimal_digit } .
+octal_lit   = "0" { octal_digit } .
+hex_lit     = "0" ( "x" | "X" ) hex_digit { hex_digit } .
+</pre>
+
+<pre>
+42
+0600
+0xBadFace
+170141183460469231731687303715884105727
+</pre>
+
+<h3 id="Floating-point_literals">Floating-point literals</h3>
+<p>
+A floating-point literal is a decimal representation of a
+<a href="#Constants">floating-point constant</a>.
+It has an integer part, a decimal point, a fractional part,
+and an exponent part.  The integer and fractional part comprise
+decimal digits; the exponent part is an <code>e</code> or <code>E</code>
+followed by an optionally signed decimal exponent.  One of the
+integer part or the fractional part may be elided; one of the decimal
+point or the exponent may be elided.
+</p>
+<pre class="ebnf">
+float_lit = decimals "." [ decimals ] [ exponent ] |
+            decimals exponent |
+            "." decimals [ exponent ] .
+decimals  = decimal_digit { decimal_digit } .
+exponent  = ( "e" | "E" ) [ "+" | "-" ] decimals .
+</pre>
+
+<pre>
+0.
+72.40
+072.40  // == 72.40
+2.71828
+1.e+0
+6.67428e-11
+1E6
+.25
+.12345E+5
+</pre>
+
+<h3 id="Imaginary_literals">Imaginary literals</h3>
+<p>
+An imaginary literal is a decimal representation of the imaginary part of a
+<a href="#Constants">complex constant</a>.
+It consists of a
+<a href="#Floating-point_literals">floating-point literal</a>
+or decimal integer followed
+by the lower-case letter <code>i</code>.
+</p>
+<pre class="ebnf">
+imaginary_lit = (decimals | float_lit) "i" .
+</pre>
+
+<pre>
+0i
+011i  // == 11i
+0.i
+2.71828i
+1.e+0i
+6.67428e-11i
+1E6i
+.25i
+.12345E+5i
+</pre>
+
+
+<h3 id="Character_literals">Character literals</h3>
+
+<p>
+A character literal represents an <a href="#Constants">integer constant</a>,
+typically a Unicode code point, as one or more characters enclosed in single
+quotes.  Within the quotes, any character may appear except single
+quote and newline. A single quoted character represents itself,
+while multi-character sequences beginning with a backslash encode
+values in various formats.
+</p>
+<p>
+The simplest form represents the single character within the quotes;
+since Go source text is Unicode characters encoded in UTF-8, multiple
+UTF-8-encoded bytes may represent a single integer value.  For
+instance, the literal <code>'a'</code> holds a single byte representing
+a literal <code>a</code>, Unicode U+0061, value <code>0x61</code>, while
+<code>'ä'</code> holds two bytes (<code>0xc3</code> <code>0xa4</code>) representing
+a literal <code>a</code>-dieresis, U+00E4, value <code>0xe4</code>.
+</p>
+<p>
+Several backslash escapes allow arbitrary values to be represented
+as ASCII text.  There are four ways to represent the integer value
+as a numeric constant: <code>\x</code> followed by exactly two hexadecimal
+digits; <code>\u</code> followed by exactly four hexadecimal digits;
+<code>\U</code> followed by exactly eight hexadecimal digits, and a
+plain backslash <code>\</code> followed by exactly three octal digits.
+In each case the value of the literal is the value represented by
+the digits in the corresponding base.
+</p>
+<p>
+Although these representations all result in an integer, they have
+different valid ranges.  Octal escapes must represent a value between
+0 and 255 inclusive.  Hexadecimal escapes satisfy this condition
+by construction. The escapes <code>\u</code> and <code>\U</code>
+represent Unicode code points so within them some values are illegal,
+in particular those above <code>0x10FFFF</code> and surrogate halves.
+</p>
+<p>
+After a backslash, certain single-character escapes represent special values:
+</p>
+<pre class="grammar">
+\a   U+0007 alert or bell
+\b   U+0008 backspace
+\f   U+000C form feed
+\n   U+000A line feed or newline
+\r   U+000D carriage return
+\t   U+0009 horizontal tab
+\v   U+000b vertical tab
+\\   U+005c backslash
+\'   U+0027 single quote  (valid escape only within character literals)
+\"   U+0022 double quote  (valid escape only within string literals)
+</pre>
+<p>
+All other sequences starting with a backslash are illegal inside character literals.
+</p>
+<pre class="ebnf">
+char_lit         = "'" ( unicode_value | byte_value ) "'" .
+unicode_value    = unicode_char | little_u_value | big_u_value | escaped_char .
+byte_value       = octal_byte_value | hex_byte_value .
+octal_byte_value = `\` octal_digit octal_digit octal_digit .
+hex_byte_value   = `\` "x" hex_digit hex_digit .
+little_u_value   = `\` "u" hex_digit hex_digit hex_digit hex_digit .
+big_u_value      = `\` "U" hex_digit hex_digit hex_digit hex_digit
+                           hex_digit hex_digit hex_digit hex_digit .
+escaped_char     = `\` ( "a" | "b" | "f" | "n" | "r" | "t" | "v" | `\` | "'" | `"` ) .
+</pre>
+
+<pre>
+'a'
+'ä'
+'本'
+'\t'
+'\000'
+'\007'
+'\377'
+'\x07'
+'\xff'
+'\u12e4'
+'\U00101234'
+</pre>
+
+
+<h3 id="String_literals">String literals</h3>
+
+<p>
+A string literal represents a <a href="#Constants">string constant</a>
+obtained from concatenating a sequence of characters. There are two forms:
+raw string literals and interpreted string literals.
+</p>
+<p>
+Raw string literals are character sequences between back quotes
+<code>``</code>.  Within the quotes, any character is legal except
+back quote. The value of a raw string literal is the
+string composed of the uninterpreted characters between the quotes;
+in particular, backslashes have no special meaning and the string may
+span multiple lines.
+</p>
+<p>
+Interpreted string literals are character sequences between double
+quotes <code>&quot;&quot;</code>. The text between the quotes,
+which may not span multiple lines, forms the
+value of the literal, with backslash escapes interpreted as they
+are in character literals (except that <code>\'</code> is illegal and
+<code>\"</code> is legal).  The three-digit octal (<code>\</code><i>nnn</i>)
+and two-digit hexadecimal (<code>\x</code><i>nn</i>) escapes represent individual
+<i>bytes</i> of the resulting string; all other escapes represent
+the (possibly multi-byte) UTF-8 encoding of individual <i>characters</i>.
+Thus inside a string literal <code>\377</code> and <code>\xFF</code> represent
+a single byte of value <code>0xFF</code>=255, while <code>ÿ</code>,
+<code>\u00FF</code>, <code>\U000000FF</code> and <code>\xc3\xbf</code> represent
+the two bytes <code>0xc3</code> <code>0xbf</code> of the UTF-8 encoding of character
+U+00FF.
+</p>
+
+<pre class="ebnf">
+string_lit             = raw_string_lit | interpreted_string_lit .
+raw_string_lit         = "`" { unicode_char | newline } "`" .
+interpreted_string_lit = `"` { unicode_value | byte_value } `"` .
+</pre>
+
+<pre>
+`abc`  // same as "abc"
+`\n
+\n`    // same as "\\n\n\\n"
+"\n"
+""
+"Hello, world!\n"
+"日本語"
+"\u65e5本\U00008a9e"
+"\xff\u00FF"
+</pre>
+
+<p>
+These examples all represent the same string:
+</p>
+
+<pre>
+"日本語"                                 // UTF-8 input text
+`日本語`                                 // UTF-8 input text as a raw literal
+"\u65e5\u672c\u8a9e"                    // The explicit Unicode code points
+"\U000065e5\U0000672c\U00008a9e"        // The explicit Unicode code points
+"\xe6\x97\xa5\xe6\x9c\xac\xe8\xaa\x9e"  // The explicit UTF-8 bytes
+</pre>
+
+<p>
+If the source code represents a character as two code points, such as
+a combining form involving an accent and a letter, the result will be
+an error if placed in a character literal (it is not a single code
+point), and will appear as two code points if placed in a string
+literal.
+</p>
+
+
+<h2 id="Constants">Constants</h2>
+
+<p>There are <i>boolean constants</i>, <i>integer constants</i>,
+<i>floating-point constants</i>, <i>complex constants</i>,
+and <i>string constants</i>. Integer, floating-point,
+and complex constants are
+collectively called <i>numeric constants</i>.
+</p>
+
+<p>
+A constant value is represented by an
+<a href="#Integer_literals">integer</a>,
+<a href="#Floating-point_literals">floating-point</a>,
+<a href="#Imaginary_literals">imaginary</a>,
+<a href="#Character_literals">character</a>, or
+<a href="#String_literals">string</a> literal,
+an identifier denoting a constant,
+a <a href="#Constant_expressions">constant expression</a>,
+a <a href="#Conversions">conversion</a> with a result that is a constant, or
+the result value of some built-in functions such as
+<code>unsafe.Sizeof</code> applied to any value,
+<code>cap</code> or <code>len</code> applied to
+<a href="#Length_and_capacity">some expressions</a>,
+<code>real</code> and <code>imag</code> applied to a complex constant
+and <code>complex</code> applied to numeric constants.
+The boolean truth values are represented by the predeclared constants
+<code>true</code> and <code>false</code>. The predeclared identifier
+<a href="#Iota">iota</a> denotes an integer constant.
+</p>
+
+<p>
+In general, complex constants are a form of
+<a href="#Constant_expressions">constant expression</a>
+and are discussed in that section.
+</p>
+
+<p>
+Numeric constants represent values of arbitrary precision and do not overflow.
+</p>
+
+<p>
+Constants may be <a href="#Types">typed</a> or untyped.
+Literal constants, <code>true</code>, <code>false</code>, <code>iota</code>,
+and certain <a href="#Constant_expressions">constant expressions</a>
+containing only untyped constant operands are untyped.
+</p>
+
+<p>
+A constant may be given a type explicitly by a <a href="#Constant_declarations">constant declaration</a>
+or <a href="#Conversions">conversion</a>, or implicitly when used in a
+<a href="#Variable_declarations">variable declaration</a> or an
+<a href="#Assignments">assignment</a> or as an
+operand in an <a href="#Expressions">expression</a>.
+It is an error if the constant value
+cannot be represented as a value of the respective type.
+For instance, <code>3.0</code> can be given any integer or any
+floating-point type, while <code>2147483648.0</code> (equal to <code>1&lt;&lt;31</code>)
+can be given the types <code>float32</code>, <code>float64</code>, or <code>uint32</code> but
+not <code>int32</code> or <code>string</code>.
+</p>
+
+<p>
+There are no constants denoting the IEEE-754 infinity and not-a-number values,
+but the <a href="/pkg/math/"><code>math</code> package</a>'s
+<a href="/pkg/math/#Inf">Inf</a>,
+<a href="/pkg/math/#NaN">NaN</a>,
+<a href="/pkg/math/#IsInf">IsInf</a>, and
+<a href="/pkg/math/#IsNaN">IsNaN</a>
+functions return and test for those values at run time.
+</p>
+
+<p>
+Implementation restriction: A compiler may implement numeric constants by choosing
+an internal representation with at least twice as many bits as any machine type;
+for floating-point values, both the mantissa and exponent must be twice as large.
+</p>
+
+
+<h2 id="Types">Types</h2>
+
+<p>
+A type determines the set of values and operations specific to values of that
+type.  A type may be specified by a (possibly qualified) <i>type name</i>
+(§<a href="#Qualified_identifiers">Qualified identifier</a>, §<a href="#Type_declarations">Type declarations</a>) or a <i>type literal</i>,
+which composes a new type from previously declared types.
+</p>
+
+<pre class="ebnf">
+Type      = TypeName | TypeLit | "(" Type ")" .
+TypeName  = QualifiedIdent .
+TypeLit   = ArrayType | StructType | PointerType | FunctionType | InterfaceType |
+	    SliceType | MapType | ChannelType .
+</pre>
+
+<p>
+Named instances of the boolean, numeric, and string types are
+<a href="#Predeclared_identifiers">predeclared</a>.
+<i>Composite types</i>&mdash;array, struct, pointer, function,
+interface, slice, map, and channel types&mdash;may be constructed using
+type literals.
+</p>
+
+<p>
+The <i>static type</i> (or just <i>type</i>) of a variable is the
+type defined by its declaration.  Variables of interface type
+also have a distinct <i>dynamic type</i>, which
+is the actual type of the value stored in the variable at run-time.
+The dynamic type may vary during execution but is always
+<a href="#Assignability">assignable</a>
+to the static type of the interface variable.  For non-interface
+types, the dynamic type is always the static type.
+</p>
+
+<p>
+Each type <code>T</code> has an <i>underlying type</i>: If <code>T</code>
+is a predeclared type or a type literal, the corresponding underlying
+type is <code>T</code> itself. Otherwise, <code>T</code>'s underlying type
+is the underlying type of the type to which <code>T</code> refers in its
+<a href="#Type_declarations">type declaration</a>.
+</p>
+
+<pre>
+   type T1 string
+   type T2 T1
+   type T3 []T1
+   type T4 T3
+</pre>
+
+<p>
+The underlying type of <code>string</code>, <code>T1</code>, and <code>T2</code>
+is <code>string</code>. The underlying type of <code>[]T1</code>, <code>T3</code>,
+and <code>T4</code> is <code>[]T1</code>.
+</p>
+
+<h3 id="Method_sets">Method sets</h3>
+<p>
+A type may have a <i>method set</i> associated with it
+(§<a href="#Interface_types">Interface types</a>, §<a href="#Method_declarations">Method declarations</a>).
+The method set of an <a href="#Interface_types">interface type</a> is its interface.
+The method set of any other named type <code>T</code>
+consists of all methods with receiver type <code>T</code>.
+The method set of the corresponding pointer type <code>*T</code>
+is the set of all methods with receiver <code>*T</code> or <code>T</code>
+(that is, it also contains the method set of <code>T</code>).
+Any other type has an empty method set.
+In a method set, each method must have a unique name.
+</p>
+
+
+<h3 id="Boolean_types">Boolean types</h3>
+
+A <i>boolean type</i> represents the set of Boolean truth values
+denoted by the predeclared constants <code>true</code>
+and <code>false</code>. The predeclared boolean type is <code>bool</code>.
+
+
+<h3 id="Numeric_types">Numeric types</h3>
+
+<p>
+A <i>numeric type</i> represents sets of integer or floating-point values.
+The predeclared architecture-independent numeric types are:
+</p>
+
+<pre class="grammar">
+uint8       the set of all unsigned  8-bit integers (0 to 255)
+uint16      the set of all unsigned 16-bit integers (0 to 65535)
+uint32      the set of all unsigned 32-bit integers (0 to 4294967295)
+uint64      the set of all unsigned 64-bit integers (0 to 18446744073709551615)
+
+int8        the set of all signed  8-bit integers (-128 to 127)
+int16       the set of all signed 16-bit integers (-32768 to 32767)
+int32       the set of all signed 32-bit integers (-2147483648 to 2147483647)
+int64       the set of all signed 64-bit integers (-9223372036854775808 to 9223372036854775807)
+
+float32     the set of all IEEE-754 32-bit floating-point numbers
+float64     the set of all IEEE-754 64-bit floating-point numbers
+
+complex64   the set of all complex numbers with float32 real and imaginary parts
+complex128  the set of all complex numbers with float64 real and imaginary parts
+
+byte        familiar alias for uint8
+</pre>
+
+<p>
+The value of an <i>n</i>-bit integer is <i>n</i> bits wide and represented using
+<a href="http://en.wikipedia.org/wiki/Two's_complement">two's complement arithmetic</a>.
+</p>
+
+<p>
+There is also a set of predeclared numeric types with implementation-specific sizes:
+</p>
+
+<pre class="grammar">
+uint     either 32 or 64 bits
+int      same size as uint
+uintptr  an unsigned integer large enough to store the uninterpreted bits of a pointer value
+</pre>
+
+<p>
+To avoid portability issues all numeric types are distinct except
+<code>byte</code>, which is an alias for <code>uint8</code>.
+Conversions
+are required when different numeric types are mixed in an expression
+or assignment. For instance, <code>int32</code> and <code>int</code>
+are not the same type even though they may have the same size on a
+particular architecture.
+
+
+<h3 id="String_types">String types</h3>
+
+<p>
+A <i>string type</i> represents the set of string values.
+Strings behave like arrays of bytes but are immutable: once created,
+it is impossible to change the contents of a string.
+The predeclared string type is <code>string</code>.
+
+<p>
+The elements of strings have type <code>byte</code> and may be
+accessed using the usual <a href="#Indexes">indexing operations</a>.  It is
+illegal to take the address of such an element; if
+<code>s[i]</code> is the <i>i</i>th byte of a
+string, <code>&amp;s[i]</code> is invalid.  The length of string
+<code>s</code> can be discovered using the built-in function
+<code>len</code>. The length is a compile-time constant if <code>s</code>
+is a string literal.
+</p>
+
+
+<h3 id="Array_types">Array types</h3>
+
+<p>
+An array is a numbered sequence of elements of a single
+type, called the element type.
+The number of elements is called the length and is never
+negative.
+</p>
+
+<pre class="ebnf">
+ArrayType   = "[" ArrayLength "]" ElementType .
+ArrayLength = Expression .
+ElementType = Type .
+</pre>
+
+<p>
+The length is part of the array's type and must be a
+<a href="#Constant_expressions">constant expression</a> that evaluates to a non-negative
+integer value.  The length of array <code>a</code> can be discovered
+using the built-in function <a href="#Length_and_capacity"><code>len(a)</code></a>.
+The elements can be indexed by integer
+indices 0 through the <code>len(a)-1</code> (§<a href="#Indexes">Indexes</a>).
+Array types are always one-dimensional but may be composed to form
+multi-dimensional types.
+</p>
+
+<pre>
+[32]byte
+[2*N] struct { x, y int32 }
+[1000]*float64
+[3][5]int
+[2][2][2]float64  // same as [2]([2]([2]float64))
+</pre>
+
+<h3 id="Slice_types">Slice types</h3>
+
+<p>
+A slice is a reference to a contiguous segment of an array and
+contains a numbered sequence of elements from that array.  A slice
+type denotes the set of all slices of arrays of its element type.
+The value of an uninitialized slice is <code>nil</code>.
+</p>
+
+<pre class="ebnf">
+SliceType = "[" "]" ElementType .
+</pre>
+
+<p>
+Like arrays, slices are indexable and have a length.  The length of a
+slice <code>s</code> can be discovered by the built-in function
+<a href="#Length_and_capacity"><code>len(s)</code></a>; unlike with arrays it may change during
+execution.  The elements can be addressed by integer indices 0
+through <code>len(s)-1</code> (§<a href="#Indexes">Indexes</a>).  The slice index of a
+given element may be less than the index of the same element in the
+underlying array.
+</p>
+<p>
+A slice, once initialized, is always associated with an underlying
+array that holds its elements.  A slice therefore shares storage
+with its array and with other slices of the same array; by contrast,
+distinct arrays always represent distinct storage.
+</p>
+<p>
+The array underlying a slice may extend past the end of the slice.
+The <i>capacity</i> is a measure of that extent: it is the sum of
+the length of the slice and the length of the array beyond the slice;
+a slice of length up to that capacity can be created by `slicing' a new
+one from the original slice (§<a href="#Slices">Slices</a>).
+The capacity of a slice <code>a</code> can be discovered using the
+built-in function <a href="#Length_and_capacity"><code>cap(a)</code></a>.
+</p>
+
+<p>
+A new, initialized slice value for a given element type <code>T</code> is
+made using the built-in function
+<a href="#Making_slices_maps_and_channels"><code>make</code></a>,
+which takes a slice type
+and parameters specifying the length and optionally the capacity:
+</p>
+
+<pre>
+make([]T, length)
+make([]T, length, capacity)
+</pre>
+
+<p>
+A call to <code>make</code> allocates a new, hidden array to which the returned
+slice value refers. That is, executing
+</p>
+
+<pre>
+make([]T, length, capacity)
+</pre>
+
+<p>
+produces the same slice as allocating an array and slicing it, so these two examples
+result in the same slice:
+</p>
+
+<pre>
+make([]int, 50, 100)
+new([100]int)[0:50]
+</pre>
+
+<p>
+Like arrays, slices are always one-dimensional but may be composed to construct
+higher-dimensional objects.
+With arrays of arrays, the inner arrays are, by construction, always the same length;
+however with slices of slices (or arrays of slices), the lengths may vary dynamically.
+Moreover, the inner slices must be allocated individually (with <code>make</code>).
+</p>
+
+<h3 id="Struct_types">Struct types</h3>
+
+<p>
+A struct is a sequence of named elements, called fields, each of which has a
+name and a type. Field names may be specified explicitly (IdentifierList) or
+implicitly (AnonymousField).
+Within a struct, non-<a href="#Blank_identifier">blank</a> field names must
+be unique.
+</p>
+
+<pre class="ebnf">
+StructType     = "struct" "{" { FieldDecl ";" } "}" .
+FieldDecl      = (IdentifierList Type | AnonymousField) [ Tag ] .
+AnonymousField = [ "*" ] TypeName .
+Tag            = string_lit .
+</pre>
+
+<pre>
+// An empty struct.
+struct {}
+
+// A struct with 6 fields.
+struct {
+	x, y int
+	u float32
+	_ float32  // padding
+	A *[]int
+	F func()
+}
+</pre>
+
+<p>
+A field declared with a type but no explicit field name is an <i>anonymous field</i>
+(colloquially called an embedded field).
+Such a field type must be specified as
+a type name <code>T</code> or as a pointer to a non-interface type name <code>*T</code>,
+and <code>T</code> itself may not be
+a pointer type. The unqualified type name acts as the field name.
+</p>
+
+<pre>
+// A struct with four anonymous fields of type T1, *T2, P.T3 and *P.T4
+struct {
+	T1        // field name is T1
+	*T2       // field name is T2
+	P.T3      // field name is T3
+	*P.T4     // field name is T4
+	x, y int  // field names are x and y
+}
+</pre>
+
+<p>
+The following declaration is illegal because field names must be unique
+in a struct type:
+</p>
+
+<pre>
+struct {
+	T         // conflicts with anonymous field *T and *P.T
+	*T        // conflicts with anonymous field T and *P.T
+	*P.T      // conflicts with anonymous field T and *T
+}
+</pre>
+
+<p>
+Fields and methods (§<a href="#Method_declarations">Method declarations</a>) of an anonymous field are
+promoted to be ordinary fields and methods of the struct (§<a href="#Selectors">Selectors</a>).
+The following rules apply for a struct type named <code>S</code> and
+a type named <code>T</code>:
+</p>
+<ul>
+	<li>If <code>S</code> contains an anonymous field <code>T</code>, the
+	    <a href="#Method_sets">method set</a> of <code>S</code> includes the
+	    method set of <code>T</code>.
+	</li>
+
+	<li>If <code>S</code> contains an anonymous field <code>*T</code>, the
+	    method set of <code>S</code> includes the method set of <code>*T</code>
+	    (which itself includes the method set of <code>T</code>).
+	</li>
+
+	<li>If <code>S</code> contains an anonymous field <code>T</code> or
+	    <code>*T</code>, the method set of <code>*S</code> includes the
+	    method set of <code>*T</code> (which itself includes the method
+	    set of <code>T</code>).
+	</li>
+</ul>
+<p>
+A field declaration may be followed by an optional string literal <i>tag</i>,
+which becomes an attribute for all the fields in the corresponding
+field declaration. The tags are made
+visible through a <a href="#Package_unsafe">reflection interface</a>
+but are otherwise ignored.
+</p>
+
+<pre>
+// A struct corresponding to the TimeStamp protocol buffer.
+// The tag strings define the protocol buffer field numbers.
+struct {
+	microsec  uint64 "field 1"
+	serverIP6 uint64 "field 2"
+	process   string "field 3"
+}
+</pre>
+
+<h3 id="Pointer_types">Pointer types</h3>
+
+<p>
+A pointer type denotes the set of all pointers to variables of a given
+type, called the <i>base type</i> of the pointer.
+The value of an uninitialized pointer is <code>nil</code>.
+</p>
+
+<pre class="ebnf">
+PointerType = "*" BaseType .
+BaseType = Type .
+</pre>
+
+<pre>
+*int
+*map[string] *chan int
+</pre>
+
+<h3 id="Function_types">Function types</h3>
+
+<p>
+A function type denotes the set of all functions with the same parameter
+and result types. The value of an uninitialized variable of function type
+is <code>nil</code>.
+</p>
+
+<pre class="ebnf">
+FunctionType   = "func" Signature .
+Signature      = Parameters [ Result ] .
+Result         = Parameters | Type .
+Parameters     = "(" [ ParameterList [ "," ] ] ")" .
+ParameterList  = ParameterDecl { "," ParameterDecl } .
+ParameterDecl  = [ IdentifierList ] [ "..." ] Type .
+</pre>
+
+<p>
+Within a list of parameters or results, the names (IdentifierList)
+must either all be present or all be absent. If present, each name
+stands for one item (parameter or result) of the specified type; if absent, each
+type stands for one item of that type.  Parameter and result
+lists are always parenthesized except that if there is exactly
+one unnamed result it may be written as an unparenthesized type.
+</p>
+
+<p>
+The final parameter in a function signature may have
+a type prefixed with <code>...</code>.
+A function with such a parameter is called <i>variadic</i> and
+may be invoked with zero or more arguments for that parameter.
+</p>
+
+<pre>
+func()
+func(x int)
+func() int
+func(prefix string, values ...int)
+func(a, b int, z float32) bool
+func(a, b int, z float32) (bool)
+func(a, b int, z float64, opt ...interface{}) (success bool)
+func(int, int, float64) (float64, *[]int)
+func(n int) func(p *T)
+</pre>
+
+
+<h3 id="Interface_types">Interface types</h3>
+
+<p>
+An interface type specifies a <a href="#Method_sets">method set</a> called its <i>interface</i>.
+A variable of interface type can store a value of any type with a method set
+that is any superset of the interface. Such a type is said to
+<i>implement the interface</i>.
+The value of an uninitialized variable of interface type is <code>nil</code>.
+</p>
+
+<pre class="ebnf">
+InterfaceType      = "interface" "{" { MethodSpec ";" } "}" .
+MethodSpec         = MethodName Signature | InterfaceTypeName .
+MethodName         = identifier .
+InterfaceTypeName  = TypeName .
+</pre>
+
+<p>
+As with all method sets, in an interface type, each method must have a unique name.
+</p>
+
+<pre>
+// A simple File interface
+interface {
+	Read(b Buffer) bool
+	Write(b Buffer) bool
+	Close()
+}
+</pre>
+
+<p>
+More than one type may implement an interface.
+For instance, if two types <code>S1</code> and <code>S2</code>
+have the method set
+</p>
+
+<pre>
+func (p T) Read(b Buffer) bool { return … }
+func (p T) Write(b Buffer) bool { return … }
+func (p T) Close() { … }
+</pre>
+
+<p>
+(where <code>T</code> stands for either <code>S1</code> or <code>S2</code>)
+then the <code>File</code> interface is implemented by both <code>S1</code> and
+<code>S2</code>, regardless of what other methods
+<code>S1</code> and <code>S2</code> may have or share.
+</p>
+
+<p>
+A type implements any interface comprising any subset of its methods
+and may therefore implement several distinct interfaces. For
+instance, all types implement the <i>empty interface</i>:
+</p>
+
+<pre>
+interface{}
+</pre>
+
+<p>
+Similarly, consider this interface specification,
+which appears within a <a href="#Type_declarations">type declaration</a>
+to define an interface called <code>Lock</code>:
+</p>
+
+<pre>
+type Lock interface {
+	Lock()
+	Unlock()
+}
+</pre>
+
+<p>
+If <code>S1</code> and <code>S2</code> also implement
+</p>
+
+<pre>
+func (p T) Lock() { … }
+func (p T) Unlock() { … }
+</pre>
+
+<p>
+they implement the <code>Lock</code> interface as well
+as the <code>File</code> interface.
+</p>
+<p>
+An interface may contain an interface type name <code>T</code>
+in place of a method specification.
+The effect is equivalent to enumerating the methods of <code>T</code> explicitly
+in the interface.
+</p>
+
+<pre>
+type ReadWrite interface {
+	Read(b Buffer) bool
+	Write(b Buffer) bool
+}
+
+type File interface {
+	ReadWrite  // same as enumerating the methods in ReadWrite
+	Lock       // same as enumerating the methods in Lock
+	Close()
+}
+</pre>
+
+<h3 id="Map_types">Map types</h3>
+
+<p>
+A map is an unordered group of elements of one type, called the
+element type, indexed by a set of unique <i>keys</i> of another type,
+called the key type.
+The value of an uninitialized map is <code>nil</code>.
+</p>
+
+<pre class="ebnf">
+MapType     = "map" "[" KeyType "]" ElementType .
+KeyType     = Type .
+</pre>
+
+<p>
+The comparison operators <code>==</code> and <code>!=</code>
+(§<a href="#Comparison_operators">Comparison operators</a>) must be fully defined
+for operands of the key type; thus the key type must not be a struct, array or slice.
+If the key type is an interface type, these
+comparison operators must be defined for the dynamic key values;
+failure will cause a <a href="#Run_time_panics">run-time panic</a>.
+
+</p>
+
+<pre>
+map [string] int
+map [*T] struct { x, y float64 }
+map [string] interface {}
+</pre>
+
+<p>
+The number of map elements is called its length.
+For a map <code>m</code>, it can be discovered using the
+built-in function <a href="#Length_and_capacity"><code>len(m)</code></a>
+and may change during execution. Elements may be added and removed
+during execution using special forms of <a href="#Assignments">assignment</a>;
+and they may be accessed with <a href="#Indexes">index</a> expressions.
+</p>
+<p>
+A new, empty map value is made using the built-in
+function <a href="#Making_slices_maps_and_channels"><code>make</code></a>,
+which takes the map type and an optional capacity hint as arguments:
+</p>
+
+<pre>
+make(map[string] int)
+make(map[string] int, 100)
+</pre>
+
+<p>
+The initial capacity does not bound its size:
+maps grow to accommodate the number of items
+stored in them, with the exception of <code>nil</code> maps.
+A <code>nil</code> map is equivalent to an empty map except that no elements
+may be added.
+
+<h3 id="Channel_types">Channel types</h3>
+
+<p>
+A channel provides a mechanism for two concurrently executing functions
+to synchronize execution and communicate by passing a value of a
+specified element type.
+The value of an uninitialized channel is <code>nil</code>.
+</p>
+
+<pre class="ebnf">
+ChannelType = ( "chan" [ "&lt;-" ] | "&lt;-" "chan" ) ElementType .
+</pre>
+
+<p>
+The <code>&lt;-</code> operator specifies the channel <i>direction</i>,
+<i>send</i> or <i>receive</i>. If no direction is given, the channel is
+<i>bi-directional</i>.
+A channel may be constrained only to send or only to receive by
+<a href="#Conversions">conversion</a> or <a href="#Assignments">assignment</a>.
+</p>
+
+<pre>
+chan T         // can be used to send and receive values of type T
+chan&lt;- float64 // can only be used to send float64s
+&lt;-chan int     // can only be used to receive ints
+</pre>
+
+<p>
+The <code>&lt;-</code> operator associates with the leftmost <code>chan</code>
+possible:
+</p>
+
+<pre>
+chan&lt;- chan int     // same as chan&lt;- (chan int)
+chan&lt;- &lt;-chan int   // same as chan&lt;- (&lt;-chan int)
+&lt;-chan &lt;-chan int   // same as &lt;-chan (&lt;-chan int)
+chan (&lt;-chan int)
+</pre>
+
+<p>
+A new, initialized channel
+value can be made using the built-in function
+<a href="#Making_slices_maps_and_channels"><code>make</code></a>,
+which takes the channel type and an optional capacity as arguments:
+</p>
+
+<pre>
+make(chan int, 100)
+</pre>
+
+<p>
+The capacity, in number of elements, sets the size of the buffer in the channel. If the
+capacity is greater than zero, the channel is asynchronous: communication operations 
+succeed without blocking if the buffer is not full (sends) or not empty (receives),
+and elements are received in the order they are sent.
+If the capacity is zero or absent, the communication succeeds only when both a sender and
+receiver are ready.
+A <code>nil</code> channel is never ready for communication.
+</p>
+
+<p>
+A channel may be closed with the built-in function
+<a href="#Close"><code>close</code></a>; the
+multi-valued assignment form of the
+<a href="#Receive_operator">receive operator</a>
+tests whether a channel has been closed.
+</p>
+
+<h2 id="Properties_of_types_and_values">Properties of types and values</h2>
+
+<h3 id="Type_identity">Type identity</h3>
+
+<p>
+Two types are either <i>identical</i> or <i>different</i>.
+</p>
+
+<p>
+Two named types are identical if their type names originate in the same
+type <a href="#Declarations_and_scope">declaration</a>.
+A named and an unnamed type are always different. Two unnamed types are identical
+if the corresponding type literals are identical, that is, if they have the same
+literal structure and corresponding components have identical types. In detail:
+</p>
+
+<ul>
+	<li>Two array types are identical if they have identical element types and
+	    the same array length.</li>
+
+	<li>Two slice types are identical if they have identical element types.</li>
+
+	<li>Two struct types are identical if they have the same sequence of fields,
+	    and if corresponding fields have the same names, and identical types,
+	    and identical tags.
+	    Two anonymous fields are considered to have the same name. Lower-case field
+	    names from different packages are always different.</li>
+
+	<li>Two pointer types are identical if they have identical base types.</li>
+
+	<li>Two function types are identical if they have the same number of parameters
+	    and result values, corresponding parameter and result types are
+	    identical, and either both functions are variadic or neither is.
+	    Parameter and result names are not required to match.</li>
+
+	<li>Two interface types are identical if they have the same set of methods
+	    with the same names and identical function types. Lower-case method names from
+	    different packages are always different. The order of the methods is irrelevant.</li>
+
+	<li>Two map types are identical if they have identical key and value types.</li>
+
+	<li>Two channel types are identical if they have identical value types and
+	    the same direction.</li>
+</ul>
+
+<p>
+Given the declarations
+</p>
+
+<pre>
+type (
+	T0 []string
+	T1 []string
+	T2 struct { a, b int }
+	T3 struct { a, c int }
+	T4 func(int, float64) *T0
+	T5 func(x int, y float64) *[]string
+)
+</pre>
+
+<p>
+these types are identical:
+</p>
+
+<pre>
+T0 and T0
+[]int and []int
+struct { a, b *T5 } and struct { a, b *T5 }
+func(x int, y float64) *[]string and func(int, float64) (result *[]string)
+</pre>
+
+<p>
+<code>T0</code> and <code>T1</code> are different because they are named types
+with distinct declarations; <code>func(int, float64) *T0</code> and
+<code>func(x int, y float64) *[]string</code> are different because <code>T0</code>
+is different from <code>[]string</code>.
+</p>
+
+
+<h3 id="Assignability">Assignability</h3>
+
+<p>
+A value <code>x</code> is <i>assignable</i> to a variable of type <code>T</code>
+("<code>x</code> is assignable to <code>T</code>") in any of these cases:
+</p>
+
+<ul>
+<li>
+<code>x</code>'s type is identical to <code>T</code>.
+</li>
+<li>
+<code>x</code>'s type <code>V</code> and <code>T</code> have identical
+<a href="#Types">underlying types</a> and at least one of <code>V</code>
+or <code>T</code> is not a named type.
+</li>
+<li>
+<code>T</code> is an interface type and
+<code>x</code> <a href="#Interface_types">implements</a> <code>T</code>.
+</li>
+<li>
+<code>x</code> is a bidirectional channel value, <code>T</code> is a channel type,
+<code>x</code>'s type <code>V</code> and <code>T</code> have identical element types,
+and at least one of <code>V</code> or <code>T</code> is not a named type.
+</li>
+<li>
+<code>x</code> is the predeclared identifier <code>nil</code> and <code>T</code>
+is a pointer, function, slice, map, channel, or interface type.
+</li>
+<li>
+<code>x</code> is an untyped <a href="#Constants">constant</a> representable
+by a value of type <code>T</code>.
+</li>
+</ul>
+
+<p>
+If <code>T</code> is a struct type with non-<a href="#Exported_identifiers">exported</a>
+fields, the assignment must be in the same package in which <code>T</code> is declared,
+or <code>x</code> must be the receiver of a method call.
+In other words, a struct value can be assigned to a struct variable only if
+every field of the struct may be legally assigned individually by the program,
+or if the assignment is initializing the receiver of a method of the struct type.
+</p>
+
+<p>
+Any value may be assigned to the <a href="#Blank_identifier">blank identifier</a>.
+</p>
+
+
+<h2 id="Blocks">Blocks</h2>
+
+<p>
+A <i>block</i> is a sequence of declarations and statements within matching
+brace brackets.
+</p>
+
+<pre class="ebnf">
+Block = "{" { Statement ";" } "}" .
+</pre>
+
+<p>
+In addition to explicit blocks in the source code, there are implicit blocks:
+</p>
+
+<ol>
+	<li>The <i>universe block</i> encompasses all Go source text.</li>
+
+	<li>Each <a href="#Packages">package</a> has a <i>package block</i> containing all
+	    Go source text for that package.</li>
+
+	<li>Each file has a <i>file block</i> containing all Go source text
+	    in that file.</li>
+
+	<li>Each <code>if</code>, <code>for</code>, and <code>switch</code>
+	    statement is considered to be in its own implicit block.</li>
+
+	<li>Each clause in a <code>switch</code> or <code>select</code> statement
+	    acts as an implicit block.</li>
+</ol>
+
+<p>
+Blocks nest and influence <a href="#Declarations_and_scope">scoping</a>.
+</p>
+
+
+<h2 id="Declarations_and_scope">Declarations and scope</h2>
+
+<p>
+A declaration binds a non-<a href="#Blank_identifier">blank</a>
+identifier to a constant, type, variable, function, or package.
+Every identifier in a program must be declared.
+No identifier may be declared twice in the same block, and
+no identifier may be declared in both the file and package block.
+</p>
+
+<pre class="ebnf">
+Declaration   = ConstDecl | TypeDecl | VarDecl .
+TopLevelDecl  = Declaration | FunctionDecl | MethodDecl .
+</pre>
+
+<p>
+The <i>scope</i> of a declared identifier is the extent of source text in which
+the identifier denotes the specified constant, type, variable, function, or package.
+</p>
+
+<p>
+Go is lexically scoped using blocks:
+</p>
+
+<ol>
+	<li>The scope of a predeclared identifier is the universe block.</li>
+
+	<li>The scope of an identifier denoting a constant, type, variable,
+	    or function (but not method) declared at top level (outside any
+	    function) is the package block.</li>
+
+	<li>The scope of an imported package identifier is the file block
+	    of the file containing the import declaration.</li>
+
+	<li>The scope of an identifier denoting a function parameter or
+	    result variable is the function body.</li>
+
+	<li>The scope of a constant or variable identifier declared
+	    inside a function begins at the end of the ConstSpec or VarSpec
+	    (ShortVarDecl for short variable declarations)
+	    and ends at the end of the innermost containing block.</li>
+
+	<li>The scope of a type identifier declared inside a function
+	    begins at the identifier in the TypeSpec
+	    and ends at the end of the innermost containing block.</li>
+</ol>
+
+<p>
+An identifier declared in a block may be redeclared in an inner block.
+While the identifier of the inner declaration is in scope, it denotes
+the entity declared by the inner declaration.
+</p>
+
+<p>
+The <a href="#Package_clause">package clause</a> is not a declaration; the package name
+does not appear in any scope. Its purpose is to identify the files belonging
+to the same <a href="#Packages">package</a> and to specify the default package name for import
+declarations.
+</p>
+
+
+<h3 id="Label_scopes">Label scopes</h3>
+
+<p>
+Labels are declared by <a href="#Labeled_statements">labeled statements</a> and are
+used in the <code>break</code>, <code>continue</code>, and <code>goto</code>
+statements (§<a href="#Break_statements">Break statements</a>, §<a href="#Continue_statements">Continue statements</a>, §<a href="#Goto_statements">Goto statements</a>).
+It is illegal to define a label that is never used.
+In contrast to other identifiers, labels are not block scoped and do
+not conflict with identifiers that are not labels. The scope of a label
+is the body of the function in which it is declared and excludes
+the body of any nested function.
+</p>
+
+
+<h3 id="Predeclared_identifiers">Predeclared identifiers</h3>
+
+<p>
+The following identifiers are implicitly declared in the universe block:
+</p>
+<pre class="grammar">
+Basic types:
+	bool byte complex64 complex128 float32 float64
+	int8 int16 int32 int64 string uint8 uint16 uint32 uint64
+
+Architecture-specific convenience types:
+	int uint uintptr
+
+Constants:
+	true false iota
+
+Zero value:
+	nil
+
+Functions:
+	append cap close complex copy imag len
+	make new panic print println real recover
+</pre>
+
+
+<h3 id="Exported_identifiers">Exported identifiers</h3>
+
+<p>
+An identifier may be <i>exported</i> to permit access to it from another package
+using a <a href="#Qualified_identifiers">qualified identifier</a>. An identifier
+is exported if both:
+</p>
+<ol>
+	<li>the first character of the identifier's name is a Unicode upper case letter (Unicode class "Lu"); and</li>
+	<li>the identifier is declared in the <a href="#Blocks">package block</a> or denotes a field or method of a type
+	    declared in that block.</li>
+</ol>
+<p>
+All other identifiers are not exported.
+</p>
+
+
+<h3 id="Blank_identifier">Blank identifier</h3>
+
+<p>
+The <i>blank identifier</i>, represented by the underscore character <code>_</code>, may be used in a declaration like
+any other identifier but the declaration does not introduce a new binding.
+</p>
+
+
+<h3 id="Constant_declarations">Constant declarations</h3>
+
+<p>
+A constant declaration binds a list of identifiers (the names of
+the constants) to the values of a list of <a href="#Constant_expressions">constant expressions</a>.
+The number of identifiers must be equal
+to the number of expressions, and the <i>n</i>th identifier on
+the left is bound to the value of the <i>n</i>th expression on the
+right.
+</p>
+
+<pre class="ebnf">
+ConstDecl      = "const" ( ConstSpec | "(" { ConstSpec ";" } ")" ) .
+ConstSpec      = IdentifierList [ [ Type ] "=" ExpressionList ] .
+
+IdentifierList = identifier { "," identifier } .
+ExpressionList = Expression { "," Expression } .
+</pre>
+
+<p>
+If the type is present, all constants take the type specified, and
+the expressions must be <a href="#Assignability">assignable</a> to that type.
+If the type is omitted, the constants take the
+individual types of the corresponding expressions.
+If the expression values are untyped <a href="#Constants">constants</a>,
+the declared constants remain untyped and the constant identifiers
+denote the constant values. For instance, if the expression is a
+floating-point literal, the constant identifier denotes a floating-point
+constant, even if the literal's fractional part is zero.
+</p>
+
+<pre>
+const Pi float64 = 3.14159265358979323846
+const zero = 0.0             // untyped floating-point constant
+const (
+	size int64 = 1024
+	eof = -1             // untyped integer constant
+)
+const a, b, c = 3, 4, "foo"  // a = 3, b = 4, c = "foo", untyped integer and string constants
+const u, v float32 = 0, 3    // u = 0.0, v = 3.0
+</pre>
+
+<p>
+Within a parenthesized <code>const</code> declaration list the
+expression list may be omitted from any but the first declaration.
+Such an empty list is equivalent to the textual substitution of the
+first preceding non-empty expression list and its type if any.
+Omitting the list of expressions is therefore equivalent to
+repeating the previous list.  The number of identifiers must be equal
+to the number of expressions in the previous list.
+Together with the <a href="#Iota"><code>iota</code> constant generator</a>
+this mechanism permits light-weight declaration of sequential values:
+</p>
+
+<pre>
+const (
+	Sunday = iota
+	Monday
+	Tuesday
+	Wednesday
+	Thursday
+	Friday
+	Partyday
+	numberOfDays  // this constant is not exported
+)
+</pre>
+
+
+<h3 id="Iota">Iota</h3>
+
+<p>
+Within a <a href="#Constant_declarations">constant declaration</a>, the predeclared identifier
+<code>iota</code> represents successive untyped integer <a href="#Constants">
+constants</a>. It is reset to 0 whenever the reserved word <code>const</code>
+appears in the source and increments after each <a href="#ConstSpec">ConstSpec</a>.
+It can be used to construct a set of related constants:
+</p>
+
+<pre>
+const (  // iota is reset to 0
+	c0 = iota  // c0 == 0
+	c1 = iota  // c1 == 1
+	c2 = iota  // c2 == 2
+)
+
+const (
+	a = 1 &lt;&lt; iota  // a == 1 (iota has been reset)
+	b = 1 &lt;&lt; iota  // b == 2
+	c = 1 &lt;&lt; iota  // c == 4
+)
+
+const (
+	u         = iota * 42  // u == 0     (untyped integer constant)
+	v float64 = iota * 42  // v == 42.0  (float64 constant)
+	w         = iota * 42  // w == 84    (untyped integer constant)
+)
+
+const x = iota  // x == 0 (iota has been reset)
+const y = iota  // y == 0 (iota has been reset)
+</pre>
+
+<p>
+Within an ExpressionList, the value of each <code>iota</code> is the same because
+it is only incremented after each ConstSpec:
+</p>
+
+<pre>
+const (
+	bit0, mask0 = 1 &lt;&lt; iota, 1 &lt;&lt; iota - 1  // bit0 == 1, mask0 == 0
+	bit1, mask1                             // bit1 == 2, mask1 == 1
+	_, _                                    // skips iota == 2
+	bit3, mask3                             // bit3 == 8, mask3 == 7
+)
+</pre>
+
+<p>
+This last example exploits the implicit repetition of the
+last non-empty expression list.
+</p>
+
+
+<h3 id="Type_declarations">Type declarations</h3>
+
+<p>
+A type declaration binds an identifier, the <i>type name</i>, to a new type
+that has the same <a href="#Types">underlying type</a> as
+an existing type.  The new type is <a href="#Type_identity">different</a> from
+the existing type.
+</p>
+
+<pre class="ebnf">
+TypeDecl     = "type" ( TypeSpec | "(" { TypeSpec ";" } ")" ) .
+TypeSpec     = identifier Type .
+</pre>
+
+<pre>
+type IntArray [16]int
+
+type (
+	Point struct { x, y float64 }
+	Polar Point
+)
+
+type TreeNode struct {
+	left, right *TreeNode
+	value *Comparable
+}
+
+type Cipher interface {
+	BlockSize() int
+	Encrypt(src, dst []byte)
+	Decrypt(src, dst []byte)
+}
+</pre>
+
+<p>
+The declared type does not inherit any <a href="#Method_declarations">methods</a>
+bound to the existing type, but the <a href="#Method_sets">method set</a>
+of an interface type or of elements of a composite type remains unchanged:
+</p>
+
+<pre>
+// A Mutex is a data type with two methods, Lock and Unlock.
+type Mutex struct         { /* Mutex fields */ }
+func (m *Mutex) Lock()    { /* Lock implementation */ }
+func (m *Mutex) Unlock()  { /* Unlock implementation */ }
+
+// NewMutex has the same composition as Mutex but its method set is empty.
+type NewMutex Mutex
+
+// The method set of the <a href="#Pointer_types">base type</a> of PtrMutex remains unchanged,
+// but the method set of PtrMutex is empty.
+type PtrMutex *Mutex
+
+// The method set of *PrintableMutex contains the methods
+// Lock and Unlock bound to its anonymous field Mutex.
+type PrintableMutex struct {
+	Mutex
+}
+
+// MyCipher is an interface type that has the same method set as Cipher.
+type MyCipher Cipher
+</pre>
+
+<p>
+A type declaration may be used to define a different boolean, numeric, or string
+type and attach methods to it:
+</p>
+
+<pre>
+type TimeZone int
+
+const (
+	EST TimeZone = -(5 + iota)
+	CST
+	MST
+	PST
+)
+
+func (tz TimeZone) String() string {
+	return fmt.Sprintf("GMT+%dh", tz)
+}
+</pre>
+
+
+<h3 id="Variable_declarations">Variable declarations</h3>
+
+<p>
+A variable declaration creates a variable, binds an identifier to it and
+gives it a type and optionally an initial value.
+</p>
+<pre class="ebnf">
+VarDecl     = "var" ( VarSpec | "(" { VarSpec ";" } ")" ) .
+VarSpec     = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
+</pre>
+
+<pre>
+var i int
+var U, V, W float64
+var k = 0
+var x, y float32 = -1, -2
+var (
+	i int
+	u, v, s = 2.0, 3.0, "bar"
+)
+var re, im = complexSqrt(-1)
+var _, found = entries[name]  // map lookup; only interested in "found"
+</pre>
+
+<p>
+If a list of expressions is given, the variables are initialized
+by assigning the expressions to the variables (§<a href="#Assignments">Assignments</a>)
+in order; all expressions must be consumed and all variables initialized from them.
+Otherwise, each variable is initialized to its <a href="#The_zero_value">zero value</a>.
+</p>
+
+<p>
+If the type is present, each variable is given that type.
+Otherwise, the types are deduced from the assignment
+of the expression list.
+</p>
+
+<p>
+If the type is absent and the corresponding expression evaluates to an
+untyped <a href="#Constants">constant</a>, the type of the declared variable
+is <code>bool</code>, <code>int</code>, <code>float64</code>, or <code>string</code>
+respectively, depending on whether the value is a boolean, integer,
+floating-point, or string constant:
+</p>
+
+<pre>
+var b = true    // t has type bool
+var i = 0       // i has type int
+var f = 3.0     // f has type float64
+var s = "OMDB"  // s has type string
+</pre>
+
+<h3 id="Short_variable_declarations">Short variable declarations</h3>
+
+<p>
+A <i>short variable declaration</i> uses the syntax:
+</p>
+
+<pre class="ebnf">
+ShortVarDecl = IdentifierList ":=" ExpressionList .
+</pre>
+
+<p>
+It is a shorthand for a regular variable declaration with
+initializer expressions but no types:
+</p>
+
+<pre class="grammar">
+"var" IdentifierList = ExpressionList .
+</pre>
+
+<pre>
+i, j := 0, 10
+f := func() int { return 7 }
+ch := make(chan int)
+r, w := os.Pipe(fd)  // os.Pipe() returns two values
+_, y, _ := coord(p)  // coord() returns three values; only interested in y coordinate
+</pre>
+
+<p>
+Unlike regular variable declarations, a short variable declaration may redeclare variables provided they
+were originally declared in the same block with the same type, and at
+least one of the non-<a href="#Blank_identifier">blank</a> variables is new.  As a consequence, redeclaration
+can only appear in a multi-variable short declaration.
+Redeclaration does not introduce a new
+variable; it just assigns a new value to the original.
+</p>
+
+<pre>
+field1, offset := nextField(str, 0)
+field2, offset := nextField(str, offset)  // redeclares offset
+</pre>
+
+<p>
+Short variable declarations may appear only inside functions.
+In some contexts such as the initializers for <code>if</code>,
+<code>for</code>, or <code>switch</code> statements,
+they can be used to declare local temporary variables (§<a href="#Statements">Statements</a>).
+</p>
+
+<h3 id="Function_declarations">Function declarations</h3>
+
+<p>
+A function declaration binds an identifier to a function (§<a href="#Function_types">Function types</a>).
+</p>
+
+<pre class="ebnf">
+FunctionDecl = "func" identifier Signature [ Body ] .
+Body         = Block .
+</pre>
+
+<p>
+A function declaration may omit the body. Such a declaration provides the
+signature for a function implemented outside Go, such as an assembly routine.
+</p>
+
+<pre>
+func min(x int, y int) int {
+	if x &lt; y {
+		return x
+	}
+	return y
+}
+
+func flushICache(begin, end uintptr)  // implemented externally
+</pre>
+
+<h3 id="Method_declarations">Method declarations</h3>
+
+<p>
+A method is a function with a <i>receiver</i>.
+A method declaration binds an identifier to a method.
+</p>
+<pre class="ebnf">
+MethodDecl   = "func" Receiver MethodName Signature [ Body ] .
+Receiver     = "(" [ identifier ] [ "*" ] BaseTypeName ")" .
+BaseTypeName = identifier .
+</pre>
+
+<p>
+The receiver type must be of the form <code>T</code> or <code>*T</code> where
+<code>T</code> is a type name. <code>T</code> is called the
+<i>receiver base type</i> or just <i>base type</i>.
+The base type must not be a pointer or interface type and must be
+declared in the same package as the method.
+The method is said to be <i>bound</i> to the base type
+and is visible only within selectors for that type
+(§<a href="#Type_declarations">Type declarations</a>, §<a href="#Selectors">Selectors</a>).
+</p>
+
+<p>
+Given type <code>Point</code>, the declarations
+</p>
+
+<pre>
+func (p *Point) Length() float64 {
+	return math.Sqrt(p.x * p.x + p.y * p.y)
+}
+
+func (p *Point) Scale(factor float64) {
+	p.x *= factor
+	p.y *= factor
+}
+</pre>
+
+<p>
+bind the methods <code>Length</code> and <code>Scale</code>,
+with receiver type <code>*Point</code>,
+to the base type <code>Point</code>.
+</p>
+
+<p>
+If the receiver's value is not referenced inside the body of the method,
+its identifier may be omitted in the declaration. The same applies in
+general to parameters of functions and methods.
+</p>
+
+<p>
+The type of a method is the type of a function with the receiver as first
+argument.  For instance, the method <code>Scale</code> has type
+</p>
+
+<pre>
+func(p *Point, factor float64)
+</pre>
+
+<p>
+However, a function declared this way is not a method.
+</p>
+
+
+<h2 id="Expressions">Expressions</h2>
+
+<p>
+An expression specifies the computation of a value by applying
+operators and functions to operands.
+</p>
+
+<h3 id="Operands">Operands</h3>
+
+<p>
+Operands denote the elementary values in an expression.
+</p>
+
+<pre class="ebnf">
+Operand    = Literal | QualifiedIdent | MethodExpr | "(" Expression ")" .
+Literal    = BasicLit | CompositeLit | FunctionLit .
+BasicLit   = int_lit | float_lit | imaginary_lit | char_lit | string_lit .
+</pre>
+
+
+<h3 id="Qualified_identifiers">Qualified identifiers</h3>
+
+<p>
+A qualified identifier is a non-<a href="#Blank_identifier">blank</a> identifier qualified by a package name prefix.
+</p>
+
+<pre class="ebnf">
+QualifiedIdent = [ PackageName "." ] identifier .
+</pre>
+
+<p>
+A qualified identifier accesses an identifier in a separate package.
+The identifier must be <a href="#Exported_identifiers">exported</a> by that
+package, which means that it must begin with a Unicode upper case letter.
+</p>
+
+<pre>
+math.Sin
+</pre>
+
+<!--
+<p>
+<span class="alert">TODO: Unify this section with Selectors - it's the same syntax.</span>
+</p>
+-->
+
+<h3 id="Composite_literals">Composite literals</h3>
+
+<p>
+Composite literals construct values for structs, arrays, slices, and maps
+and create a new value each time they are evaluated.
+They consist of the type of the value
+followed by a brace-bound list of composite elements. An element may be
+a single expression or a key-value pair.
+</p>
+
+<pre class="ebnf">
+CompositeLit  = LiteralType LiteralValue .
+LiteralType   = StructType | ArrayType | "[" "..." "]" ElementType |
+                SliceType | MapType | TypeName .
+LiteralValue  = "{" [ ElementList [ "," ] ] "}" .
+ElementList   = Element { "," Element } .
+Element       = [ Key ":" ] Value .
+Key           = FieldName | ElementIndex .
+FieldName     = identifier .
+ElementIndex  = Expression .
+Value         = Expression | LiteralValue .
+</pre>
+
+<p>
+The LiteralType must be a struct, array, slice, or map type
+(the grammar enforces this constraint except when the type is given
+as a TypeName).
+The types of the expressions must be <a href="#Assignability">assignable</a>
+to the respective field, element, and key types of the LiteralType;
+there is no additional conversion.
+The key is interpreted as a field name for struct literals,
+an index expression for array and slice literals, and a key for map literals.
+For map literals, all elements must have a key. It is an error
+to specify multiple elements with the same field name or
+constant key value.
+</p>
+
+<p>
+For struct literals the following rules apply:
+</p>
+<ul>
+	<li>A key must be a field name declared in the LiteralType.
+	</li>
+	<li>A literal that does not contain any keys must
+	    list an element for each struct field in the
+	    order in which the fields are declared.
+	</li>
+	<li>If any element has a key, every element must have a key.
+	</li>
+	<li>A literal that contains keys does not need to
+	    have an element for each struct field. Omitted fields
+	    get the zero value for that field.
+	</li>
+	<li>A literal may omit the element list; such a literal evaluates
+		to the zero value for its type.
+	</li>
+	<li>It is an error to specify an element for a non-exported
+	    field of a struct belonging to a different package.
+	</li>
+</ul>
+
+<p>
+Given the declarations
+</p>
+<pre>
+type Point3D struct { x, y, z float64 }
+type Line struct { p, q Point3D }
+</pre>
+
+<p>
+one may write
+</p>
+
+<pre>
+origin := Point3D{}                            // zero value for Point3D
+line := Line{origin, Point3D{y: -4, z: 12.3}}  // zero value for line.q.x
+</pre>
+
+<p>
+For array and slice literals the following rules apply:
+</p>
+<ul>
+	<li>Each element has an associated integer index marking
+	    its position in the array.
+	</li>
+	<li>An element with a key uses the key as its index; the
+	    key must be a constant integer expression.
+	</li>
+	<li>An element without a key uses the previous element's index plus one.
+	    If the first element has no key, its index is zero.
+	</li>
+</ul>
+
+<p>
+Taking the address of a composite literal (§<a href="#Address_operators">Address operators</a>)
+generates a pointer to a unique instance of the literal's value.
+</p>
+<pre>
+var pointer *Point3D = &amp;Point3D{y: 1000}
+</pre>
+
+<p>
+The length of an array literal is the length specified in the LiteralType.
+If fewer elements than the length are provided in the literal, the missing
+elements are set to the zero value for the array element type.
+It is an error to provide elements with index values outside the index range
+of the array. The notation <code>...</code> specifies an array length equal
+to the maximum element index plus one.
+</p>
+
+<pre>
+buffer := [10]string{}               // len(buffer) == 10
+intSet := [6]int{1, 2, 3, 5}         // len(intSet) == 6
+days := [...]string{"Sat", "Sun"}    // len(days) == 2
+</pre>
+
+<p>
+A slice literal describes the entire underlying array literal.
+Thus, the length and capacity of a slice literal are the maximum
+element index plus one. A slice literal has the form
+</p>
+
+<pre>
+[]T{x1, x2, … xn}
+</pre>
+
+<p>
+and is a shortcut for a slice operation applied to an array literal:
+</p>
+
+<pre>
+[n]T{x1, x2, … xn}[0 : n]
+</pre>
+
+<p>
+Within a composite literal of array, slice, or map type <code>T</code>,
+elements that are themselves composite literals may elide the respective
+literal type if it is identical to the element type of <code>T</code>.
+</p>
+
+<pre>
+[...]Point{{1.5, -3.5}, {0, 0}}  // same as [...]Point{Point{1.5, -3.5}, Point{0, 0}}
+[][]int{{1, 2, 3}, {4, 5}}       // same as [][]int{[]int{1, 2, 3}, []int{4, 5}}
+</pre>
+
+<p>
+A parsing ambiguity arises when a composite literal using the
+TypeName form of the LiteralType appears between the
+<a href="#Keywords">keyword</a> and the opening brace of the block of an
+"if", "for", or "switch" statement, because the braces surrounding
+the expressions in the literal are confused with those introducing
+the block of statements. To resolve the ambiguity in this rare case,
+the composite literal must appear within
+parentheses.
+</p>
+
+<pre>
+if x == (T{a,b,c}[i]) { … }
+if (x == T{a,b,c}[i]) { … }
+</pre>
+
+<p>
+Examples of valid array, slice, and map literals:
+</p>
+
+<pre>
+// list of prime numbers
+primes := []int{2, 3, 5, 7, 9, 11, 13, 17, 19, 991}
+
+// vowels[ch] is true if ch is a vowel
+vowels := [128]bool{'a': true, 'e': true, 'i': true, 'o': true, 'u': true, 'y': true}
+
+// the array [10]float32{-1, 0, 0, 0, -0.1, -0.1, 0, 0, 0, -1}
+filter := [10]float32{-1, 4: -0.1, -0.1, 9: -1}
+
+// frequencies in Hz for equal-tempered scale (A4 = 440Hz)
+noteFrequency := map[string]float32{
+	"C0": 16.35, "D0": 18.35, "E0": 20.60, "F0": 21.83,
+	"G0": 24.50, "A0": 27.50, "B0": 30.87,
+}
+</pre>
+
+
+<h3 id="Function_literals">Function literals</h3>
+
+<p>
+A function literal represents an anonymous function.
+It consists of a specification of the function type and a function body.
+</p>
+
+<pre class="ebnf">
+FunctionLit = FunctionType Body .
+</pre>
+
+<pre>
+func(a, b int, z float64) bool { return a*b &lt; int(z) }
+</pre>
+
+<p>
+A function literal can be assigned to a variable or invoked directly.
+</p>
+
+<pre>
+f := func(x, y int) int { return x + y }
+func(ch chan int) { ch &lt;- ACK } (reply_chan)
+</pre>
+
+<p>
+Function literals are <i>closures</i>: they may refer to variables
+defined in a surrounding function. Those variables are then shared between
+the surrounding function and the function literal, and they survive as long
+as they are accessible.
+</p>
+
+
+<h3 id="Primary_expressions">Primary expressions</h3>
+
+<p>
+Primary expressions are the operands for unary and binary expressions.
+</p>
+
+<pre class="ebnf">
+PrimaryExpr =
+	Operand |
+	Conversion |
+	BuiltinCall |
+	PrimaryExpr Selector |
+	PrimaryExpr Index |
+	PrimaryExpr Slice |
+	PrimaryExpr TypeAssertion |
+	PrimaryExpr Call .
+
+Selector       = "." identifier .
+Index          = "[" Expression "]" .
+Slice          = "[" [ Expression ] ":" [ Expression ] "]" .
+TypeAssertion  = "." "(" Type ")" .
+Call           = "(" [ ArgumentList [ "," ] ] ")" .
+ArgumentList   = ExpressionList [ "..." ] .
+</pre>
+
+
+<pre>
+x
+2
+(s + ".txt")
+f(3.1415, true)
+Point{1, 2}
+m["foo"]
+s[i : j + 1]
+obj.color
+math.Sin
+f.p[i].x()
+</pre>
+
+
+<h3 id="Selectors">Selectors</h3>
+
+<p>
+A primary expression of the form
+</p>
+
+<pre>
+x.f
+</pre>
+
+<p>
+denotes the field or method <code>f</code> of the value denoted by <code>x</code>
+(or sometimes <code>*x</code>; see below). The identifier <code>f</code>
+is called the (field or method)
+<i>selector</i>; it must not be the <a href="#Blank_identifier">blank identifier</a>.
+The type of the expression is the type of <code>f</code>.
+</p>
+<p>
+A selector <code>f</code> may denote a field or method <code>f</code> of
+a type <code>T</code>, or it may refer
+to a field or method <code>f</code> of a nested anonymous field of
+<code>T</code>.
+The number of anonymous fields traversed
+to reach <code>f</code> is called its <i>depth</i> in <code>T</code>.
+The depth of a field or method <code>f</code>
+declared in <code>T</code> is zero.
+The depth of a field or method <code>f</code> declared in
+an anonymous field <code>A</code> in <code>T</code> is the
+depth of <code>f</code> in <code>A</code> plus one.
+</p>
+<p>
+The following rules apply to selectors:
+</p>
+<ol>
+<li>
+For a value <code>x</code> of type <code>T</code> or <code>*T</code>
+where <code>T</code> is not an interface type,
+<code>x.f</code> denotes the field or method at the shallowest depth
+in <code>T</code> where there
+is such an <code>f</code>.
+If there is not exactly one <code>f</code> with shallowest depth, the selector
+expression is illegal.
+</li>
+<li>
+For a variable <code>x</code> of type <code>I</code>
+where <code>I</code> is an interface type,
+<code>x.f</code> denotes the actual method with name <code>f</code> of the value assigned
+to <code>x</code> if there is such a method.
+If no value or <code>nil</code> was assigned to <code>x</code>, <code>x.f</code> is illegal.
+</li>
+<li>
+In all other cases, <code>x.f</code> is illegal.
+</li>
+</ol>
+<p>
+Selectors automatically dereference pointers to structs.
+If <code>x</code> is a pointer to a struct, <code>x.y</code>
+is shorthand for <code>(*x).y</code>; if the field <code>y</code>
+is also a pointer to a struct, <code>x.y.z</code> is shorthand
+for <code>(*(*x).y).z</code>, and so on.
+If <code>x</code> contains an anonymous field of type <code>*A</code>,
+where <code>A</code> is also a struct type,
+<code>x.f</code> is a shortcut for <code>(*x.A).f</code>.
+</p>
+<p>
+For example, given the declarations:
+</p>
+
+<pre>
+type T0 struct {
+	x int
+}
+
+func (recv *T0) M0()
+
+type T1 struct {
+	y int
+}
+
+func (recv T1) M1()
+
+type T2 struct {
+	z int
+	T1
+	*T0
+}
+
+func (recv *T2) M2()
+
+var p *T2  // with p != nil and p.T1 != nil
+</pre>
+
+<p>
+one may write:
+</p>
+
+<pre>
+p.z         // (*p).z
+p.y         // ((*p).T1).y
+p.x         // (*(*p).T0).x
+
+p.M2        // (*p).M2
+p.M1        // ((*p).T1).M1
+p.M0        // ((*p).T0).M0
+</pre>
+
+
+<!--
+<span class="alert">
+TODO: Specify what happens to receivers.
+</span>
+-->
+
+
+<h3 id="Indexes">Indexes</h3>
+
+<p>
+A primary expression of the form
+</p>
+
+<pre>
+a[x]
+</pre>
+
+<p>
+denotes the element of the array, slice, string or map <code>a</code> indexed by <code>x</code>.
+The value <code>x</code> is called the
+<i>index</i> or <i>map key</i>, respectively. The following
+rules apply:
+</p>
+
+<p>
+For <code>a</code> of type <code>A</code> or <code>*A</code>
+where <code>A</code> is an <a href="#Array_types">array type</a>,
+or for <code>a</code> of type <code>S</code> where <code>S</code> is a <a href="#Slice_types">slice type</a>:
+</p>
+<ul>
+	<li><code>x</code> must be an integer value and <code>0 &lt;= x &lt; len(a)</code></li>
+	<li><code>a[x]</code> is the array element at index <code>x</code> and the type of
+	  <code>a[x]</code> is the element type of <code>A</code></li>
+	<li>if <code>a</code> is <code>nil</code> or if the index <code>x</code> is out of range,
+	a <a href="#Run_time_panics">run-time panic</a> occurs</li>
+</ul>
+
+<p>
+For <code>a</code> of type <code>T</code>
+where <code>T</code> is a <a href="#String_types">string type</a>:
+</p>
+<ul>
+	<li><code>x</code> must be an integer value and <code>0 &lt;= x &lt; len(a)</code></li>
+	<li><code>a[x]</code> is the byte at index <code>x</code> and the type of
+	  <code>a[x]</code> is <code>byte</code></li>
+	<li><code>a[x]</code> may not be assigned to</li>
+	<li>if the index <code>x</code> is out of range,
+	a <a href="#Run_time_panics">run-time panic</a> occurs</li>
+</ul>
+
+<p>
+For <code>a</code> of type <code>M</code>
+where <code>M</code> is a <a href="#Map_types">map type</a>:
+</p>
+<ul>
+	<li><code>x</code>'s type must be
+	<a href="#Assignability">assignable</a>
+	to the key type of <code>M</code></li>
+	<li>if the map contains an entry with key <code>x</code>,
+	  <code>a[x]</code> is the map value with key <code>x</code>
+	  and the type of <code>a[x]</code> is the value type of <code>M</code></li>
+	<li>if the map is <code>nil</code> or does not contain such an entry,
+	  <code>a[x]</code> is the <a href="#The_zero_value">zero value</a>
+	  for the value type of <code>M</code></li>
+</ul>
+
+<p>
+Otherwise <code>a[x]</code> is illegal.
+</p>
+
+<p>
+An index expression on a map <code>a</code> of type <code>map[K]V</code>
+may be used in an assignment or initialization of the special form
+</p>
+
+<pre>
+v, ok = a[x]
+v, ok := a[x]
+var v, ok = a[x]
+</pre>
+
+<p>
+where the result of the index expression is a pair of values with types
+<code>(V, bool)</code>. In this form, the value of <code>ok</code> is
+<code>true</code> if the key <code>x</code> is present in the map, and
+<code>false</code> otherwise. The value of <code>v</code> is the value
+<code>a[x]</code> as in the single-result form.
+</p>
+
+<p>
+Similarly, if an assignment to a map element has the special form
+</p>
+
+<pre>
+a[x] = v, ok
+</pre>
+
+<p>
+and boolean <code>ok</code> has the value <code>false</code>,
+the entry for key <code>x</code> is deleted from the map; if
+<code>ok</code> is <code>true</code>, the construct acts like
+a regular assignment to an element of the map.
+</p>
+
+<p>
+Assigning to an element of a <code>nil</code> map causes a
+<a href="#Run_time_panics">run-time panic</a>.
+</p>
+
+
+<h3 id="Slices">Slices</h3>
+
+<p>
+For a string, array, or slice <code>a</code>, the primary expression
+</p>
+
+<pre>
+a[low : high]
+</pre>
+
+<p>
+constructs a substring or slice. The index expressions <code>low</code> and
+<code>high</code> select which elements appear in the result. The result has
+indexes starting at 0 and length equal to
+<code>high</code>&nbsp;-&nbsp;<code>low</code>.
+After slicing the array <code>a</code>
+</p>
+
+<pre>
+a := [5]int{1, 2, 3, 4, 5}
+s := a[1:4]
+</pre>
+
+<p>
+the slice <code>s</code> has type <code>[]int</code>, length 3, capacity 4, and elements
+</p>
+
+<pre>
+s[0] == 2
+s[1] == 3
+s[2] == 4
+</pre>
+
+<p>
+For convenience, any of the index expressions may be omitted. A missing <code>low</code>
+index defaults to zero; a missing <code>high</code> index defaults to the length of the
+sliced operand:
+</p>
+
+<pre>
+a[2:]	// same a[2 : len(a)]
+a[:3]   // same as a[0 : 3]
+a[:]    // same as a[0 : len(a)]
+</pre>
+
+<p>
+For arrays or strings, the indexes <code>low</code> and <code>high</code> must
+satisfy 0 &lt;= <code>low</code> &lt;= <code>high</code> &lt;= length; for
+slices, the upper bound is the capacity rather than the length.
+</p>
+
+<p>
+If the sliced operand is a string or slice, the result of the slice operation
+is a string or slice of the same type.
+If the sliced operand is an array, it must be <a href="#Address_operators">addressable</a>
+and the result of the slice operation is a slice with the same element type as the array.
+</p>
+
+
+<h3 id="Type_assertions">Type assertions</h3>
+
+<p>
+For an expression <code>x</code> of <a href="#Interface_types">interface type</a>
+and a type <code>T</code>, the primary expression
+</p>
+
+<pre>
+x.(T)
+</pre>
+
+<p>
+asserts that <code>x</code> is not <code>nil</code>
+and that the value stored in <code>x</code> is of type <code>T</code>.
+The notation <code>x.(T)</code> is called a <i>type assertion</i>.
+</p>
+<p>
+More precisely, if <code>T</code> is not an interface type, <code>x.(T)</code> asserts
+that the dynamic type of <code>x</code> is <a href="#Type_identity">identical</a>
+to the type <code>T</code>.
+If <code>T</code> is an interface type, <code>x.(T)</code> asserts that the dynamic type
+of <code>x</code> implements the interface <code>T</code> (§<a href="#Interface_types">Interface types</a>).
+</p>
+<p>
+If the type assertion holds, the value of the expression is the value
+stored in <code>x</code> and its type is <code>T</code>. If the type assertion is false,
+a <a href="#Run_time_panics">run-time panic</a> occurs.
+In other words, even though the dynamic type of <code>x</code>
+is known only at run-time, the type of <code>x.(T)</code> is
+known to be <code>T</code> in a correct program.
+</p>
+<p>
+If a type assertion is used in an assignment or initialization of the form
+</p>
+
+<pre>
+v, ok = x.(T)
+v, ok := x.(T)
+var v, ok = x.(T)
+</pre>
+
+<p>
+the result of the assertion is a pair of values with types <code>(T, bool)</code>.
+If the assertion holds, the expression returns the pair <code>(x.(T), true)</code>;
+otherwise, the expression returns <code>(Z, false)</code> where <code>Z</code>
+is the <a href="#The_zero_value">zero value</a> for type <code>T</code>.
+No run-time panic occurs in this case.
+The type assertion in this construct thus acts like a function call
+returning a value and a boolean indicating success.  (§<a href="#Assignments">Assignments</a>)
+</p>
+
+
+<h3 id="Calls">Calls</h3>
+
+<p>
+Given an expression <code>f</code> of function type
+<code>F</code>,
+</p>
+
+<pre>
+f(a1, a2, … an)
+</pre>
+
+<p>
+calls <code>f</code> with arguments <code>a1, a2, … an</code>.
+Except for one special case, arguments must be single-valued expressions
+<a href="#Assignability">assignable</a> to the parameter types of
+<code>F</code> and are evaluated before the function is called.
+The type of the expression is the result type
+of <code>F</code>.
+A method invocation is similar but the method itself
+is specified as a selector upon a value of the receiver type for
+the method.
+</p>
+
+<pre>
+math.Atan2(x, y)    // function call
+var pt *Point
+pt.Scale(3.5)  // method call with receiver pt
+</pre>
+
+<p>
+As a special case, if the return parameters of a function or method
+<code>g</code> are equal in number and individually
+assignable to the parameters of another function or method
+<code>f</code>, then the call <code>f(g(<i>parameters_of_g</i>))</code>
+will invoke <code>f</code> after binding the return values of
+<code>g</code> to the parameters of <code>f</code> in order.  The call
+of <code>f</code> must contain no parameters other than the call of <code>g</code>.
+If <code>f</code> has a final <code>...</code> parameter, it is
+assigned the return values of <code>g</code> that remain after
+assignment of regular parameters.
+</p>
+
+<pre>
+func Split(s string, pos int) (string, string) {
+	return s[0:pos], s[pos:]
+}
+
+func Join(s, t string) string {
+	return s + t
+}
+
+if Join(Split(value, len(value)/2)) != value {
+	log.Panic("test fails")
+}
+</pre>
+
+<p>
+A method call <code>x.m()</code> is valid if the <a href="#Method_sets">method set</a>
+of (the type of) <code>x</code> contains <code>m</code> and the
+argument list can be assigned to the parameter list of <code>m</code>.
+If <code>x</code> is <a href="#Address_operators">addressable</a> and <code>&amp;x</code>'s method
+set contains <code>m</code>, <code>x.m()</code> is shorthand
+for <code>(&amp;x).m()</code>:
+</p>
+
+<pre>
+var p Point
+p.Scale(3.5)
+</pre>
+
+<p>
+There is no distinct method type and there are no method literals.
+</p>
+
+<h3 id="Passing_arguments_to_..._parameters">Passing arguments to <code>...</code> parameters</h3>
+
+<p>
+If <code>f</code> is variadic with final parameter type <code>...T</code>,
+then within the function the argument is equivalent to a parameter of type
+<code>[]T</code>.  At each call of <code>f</code>, the argument
+passed to the final parameter is
+a new slice of type <code>[]T</code> whose successive elements are
+the actual arguments, which all must be <a href="#Assignability">assignable</a>
+to the type <code>T</code>. The length of the slice is therefore the number of
+arguments bound to the final parameter and may differ for each call site.
+</p>
+
+<p>
+Given the function and call
+</p>
+<pre>
+func Greeting(prefix string, who ...string)
+Greeting("hello:", "Joe", "Anna", "Eileen")
+</pre>
+
+<p>
+within <code>Greeting</code>, <code>who</code> will have the value
+<code>[]string{"Joe", "Anna", "Eileen"}</code>
+</p>
+
+<p>
+If the final argument is assignable to a slice type <code>[]T</code>, it may be
+passed unchanged as the value for a <code>...T</code> parameter if the argument
+is followed by <code>...</code>. In this case no new slice is created.
+</p>
+
+<p>
+Given the slice <code>s</code> and call
+</p>
+
+<pre>
+s := []string{"James", "Jasmine"}
+Greeting("goodbye:", s...)
+</pre>
+
+<p>
+within <code>Greeting</code>, <code>who</code> will have the same value as <code>s</code>
+with the same underlying array.
+</p>
+
+
+<h3 id="Operators">Operators</h3>
+
+<p>
+Operators combine operands into expressions.
+</p>
+
+<pre class="ebnf">
+Expression = UnaryExpr | Expression binary_op UnaryExpr .
+UnaryExpr  = PrimaryExpr | unary_op UnaryExpr .
+
+binary_op  = "||" | "&amp;&amp;" | rel_op | add_op | mul_op .
+rel_op     = "==" | "!=" | "&lt;" | "&lt;=" | ">" | ">=" .
+add_op     = "+" | "-" | "|" | "^" .
+mul_op     = "*" | "/" | "%" | "&lt;&lt;" | "&gt;&gt;" | "&amp;" | "&amp;^" .
+
+unary_op   = "+" | "-" | "!" | "^" | "*" | "&amp;" | "&lt;-" .
+</pre>
+
+<p>
+Comparisons are discussed <a href="#Comparison_operators">elsewhere</a>.
+For other binary operators, the operand types must be <a href="#Type_identity">identical</a>
+unless the operation involves shifts or untyped <a href="#Constants">constants</a>.
+For operations involving constants only, see the section on
+<a href="#Constant_expressions">constant expressions</a>.
+</p>
+
+<p>
+Except for shift operations, if one operand is an untyped <a href="#Constants">constant</a>
+and the other operand is not, the constant is <a href="#Conversions">converted</a>
+to the type of the other operand.
+</p>
+
+<p>
+The right operand in a shift expression must have unsigned integer type
+or be an untyped constant that can be converted to unsigned integer type.
+If the left operand of a non-constant shift expression is an untyped constant,
+the type of the constant is what it would be if the shift expression were
+replaced by its left operand alone; the type is <code>int</code> if it cannot
+be determined from the context (for instance, if the shift expression is an
+operand in a comparison against an untyped constant).
+</p>
+
+<pre>
+var s uint = 33
+var i = 1&lt;&lt;s           // 1 has type int
+var j int32 = 1&lt;&lt;s     // 1 has type int32; j == 0
+var k = uint64(1&lt;&lt;s)   // 1 has type uint64; k == 1&lt;&lt;33
+var m int = 1.0&lt;&lt;s     // legal: 1.0 has type int
+var n = 1.0&lt;&lt;s != 0    // legal: 1.0 has type int; n == false if ints are 32bits in size
+var o = 1&lt;&lt;s == 2&lt;&lt;s   // legal: 1 and 2 have type int; o == true if ints are 32bits in size
+var p = 1&lt;&lt;s == 1&lt;&lt;33  // illegal if ints are 32bits in size: 1 has type int, but 1&lt;&lt;33 overflows int
+var u = 1.0&lt;&lt;s         // illegal: 1.0 has type float64, cannot shift
+var v float32 = 1&lt;&lt;s   // illegal: 1 has type float32, cannot shift
+var w int64 = 1.0&lt;&lt;33  // legal: 1.0&lt;&lt;33 is a constant shift expression
+</pre>
+
+<h3 id="Operator_precedence">Operator precedence</h3>
+<p>
+Unary operators have the highest precedence.
+As the  <code>++</code> and <code>--</code> operators form
+statements, not expressions, they fall
+outside the operator hierarchy.
+As a consequence, statement <code>*p++</code> is the same as <code>(*p)++</code>.
+<p>
+There are five precedence levels for binary operators.
+Multiplication operators bind strongest, followed by addition
+operators, comparison operators, <code>&amp;&amp;</code> (logical and),
+and finally <code>||</code> (logical or):
+</p>
+
+<pre class="grammar">
+Precedence    Operator
+    5             *  /  %  &lt;&lt;  &gt;&gt;  &amp;  &amp;^
+    4             +  -  |  ^
+    3             ==  !=  &lt;  &lt;=  &gt;  &gt;=
+    2             &amp;&amp;
+    1             ||
+</pre>
+
+<p>
+Binary operators of the same precedence associate from left to right.
+For instance, <code>x / y * z</code> is the same as <code>(x / y) * z</code>.
+</p>
+
+<pre>
++x
+23 + 3*x[i]
+x &lt;= f()
+^a &gt;&gt; b
+f() || g()
+x == y+1 &amp;&amp; &lt;-chan_ptr &gt; 0
+</pre>
+
+
+<h3 id="Arithmetic_operators">Arithmetic operators</h3>
+<p>
+Arithmetic operators apply to numeric values and yield a result of the same
+type as the first operand. The four standard arithmetic operators (<code>+</code>,
+<code>-</code>,  <code>*</code>, <code>/</code>) apply to integer,
+floating-point, and complex types; <code>+</code> also applies
+to strings. All other arithmetic operators apply to integers only.
+</p>
+
+<pre class="grammar">
++    sum                    integers, floats, complex values, strings
+-    difference             integers, floats, complex values
+*    product                integers, floats, complex values
+/    quotient               integers, floats, complex values
+%    remainder              integers
+
+&amp;    bitwise and            integers
+|    bitwise or             integers
+^    bitwise xor            integers
+&amp;^   bit clear (and not)    integers
+
+&lt;&lt;   left shift             integer &lt;&lt; unsigned integer
+&gt;&gt;   right shift            integer &gt;&gt; unsigned integer
+</pre>
+
+<p>
+Strings can be concatenated using the <code>+</code> operator
+or the <code>+=</code> assignment operator:
+</p>
+
+<pre>
+s := "hi" + string(c)
+s += " and good bye"
+</pre>
+
+<p>
+String addition creates a new string by concatenating the operands.
+</p>
+<p>
+For two integer values <code>x</code> and <code>y</code>, the integer quotient
+<code>q = x / y</code> and remainder <code>r = x % y</code> satisfy the following
+relationships:
+</p>
+
+<pre>
+x = q*y + r  and  |r| &lt; |y|
+</pre>
+
+<p>
+with <code>x / y</code> truncated towards zero
+(<a href="http://en.wikipedia.org/wiki/Modulo_operation">"truncated division"</a>).
+</p>
+
+<pre>
+ x     y     x / y     x % y
+ 5     3       1         2
+-5     3      -1        -2
+ 5    -3      -1         2
+-5    -3       1        -2
+</pre>
+
+<p>
+As an exception to this rule, if the dividend <code>x</code> is the most
+negative value for the int type of <code>x</code>, the quotient
+<code>q = x / -1</code> is equal to <code>x</code> (and <code>r = 0</code>).
+</p>
+
+<pre>
+			 x, q
+int8                     -128
+int16                  -32768
+int32             -2147483648
+int64    -9223372036854775808
+</pre>
+
+<p>
+If the divisor is zero, a <a href="#Run_time_panics">run-time panic</a> occurs.
+If the dividend is positive and the divisor is a constant power of 2,
+the division may be replaced by a right shift, and computing the remainder may
+be replaced by a bitwise "and" operation:
+</p>
+
+<pre>
+ x     x / 4     x % 4     x &gt;&gt; 2     x &amp; 3
+ 11      2         3         2          3
+-11     -2        -3        -3          1
+</pre>
+
+<p>
+The shift operators shift the left operand by the shift count specified by the
+right operand. They implement arithmetic shifts if the left operand is a signed
+integer and logical shifts if it is an unsigned integer.
+There is no upper limit on the shift count. Shifts behave
+as if the left operand is shifted <code>n</code> times by 1 for a shift
+count of <code>n</code>.
+As a result, <code>x &lt;&lt; 1</code> is the same as <code>x*2</code>
+and <code>x &gt;&gt; 1</code> is the same as
+<code>x/2</code> but truncated towards negative infinity.
+</p>
+
+<p>
+For integer operands, the unary operators
+<code>+</code>, <code>-</code>, and <code>^</code> are defined as
+follows:
+</p>
+
+<pre class="grammar">
++x                          is 0 + x
+-x    negation              is 0 - x
+^x    bitwise complement    is m ^ x  with m = "all bits set to 1" for unsigned x
+                                      and  m = -1 for signed x
+</pre>
+
+<p>
+For floating-point numbers,
+<code>+x</code> is the same as <code>x</code>,
+while <code>-x</code> is the negation of <code>x</code>.
+The result of a floating-point division by zero is not specified beyond the
+IEEE-754 standard; whether a <a href="#Run_time_panics">run-time panic</a>
+occurs is implementation-specific.
+</p>
+
+<h3 id="Integer_overflow">Integer overflow</h3>
+
+<p>
+For unsigned integer values, the operations <code>+</code>,
+<code>-</code>, <code>*</code>, and <code>&lt;&lt;</code> are
+computed modulo 2<sup><i>n</i></sup>, where <i>n</i> is the bit width of
+the unsigned integer's type
+(§<a href="#Numeric_types">Numeric types</a>). Loosely speaking, these unsigned integer operations
+discard high bits upon overflow, and programs may rely on ``wrap around''.
+</p>
+<p>
+For signed integers, the operations <code>+</code>,
+<code>-</code>, <code>*</code>, and <code>&lt;&lt;</code> may legally
+overflow and the resulting value exists and is deterministically defined
+by the signed integer representation, the operation, and its operands.
+No exception is raised as a result of overflow. A
+compiler may not optimize code under the assumption that overflow does
+not occur. For instance, it may not assume that <code>x &lt; x + 1</code> is always true.
+</p>
+
+
+<h3 id="Comparison_operators">Comparison operators</h3>
+
+<p>
+Comparison operators compare two operands and yield a value of type <code>bool</code>.
+</p>
+
+<pre class="grammar">
+==    equal
+!=    not equal
+&lt;     less
+&lt;=    less or equal
+>     greater
+>=    greater or equal
+</pre>
+
+<p>
+The operands must be <i>comparable</i>; that is, the first operand
+must be <a href="#Assignability">assignable</a>
+to the type of the second operand, or vice versa.
+</p>
+<p>
+The operators <code>==</code> and <code>!=</code> apply
+to operands of all types except arrays and structs.
+All other comparison operators apply only to integer, floating-point
+and string values. The result of a comparison is defined as follows:
+</p>
+
+<ul>
+	<li>
+	Integer values are compared in the usual way.
+	</li>
+	<li>
+	Floating point values are compared as defined by the IEEE-754
+	standard.
+	</li>
+	<li>
+	Two complex values <code>u</code>, <code>v</code> are
+	equal if both <code>real(u) == real(v)</code> and
+	<code>imag(u) == imag(v)</code>.
+	</li>
+	<li>
+	String values are compared byte-wise (lexically).
+	</li>
+	<li>
+	Boolean values are equal if they are either both
+	<code>true</code> or both <code>false</code>.
+	</li>
+	<li>
+	Pointer values are equal if they point to the same location
+	or if both are <code>nil</code>.
+	</li>
+	<li>
+	Function values are equal if they refer to the same function
+	or if both are <code>nil</code>.
+	</li>
+	<li>
+	A slice value may only be compared to <code>nil</code>.
+	</li>
+	<li>
+	Channel and map values are equal if they were created by the same call to <code>make</code>
+	(§<a href="#Making_slices_maps_and_channels">Making slices, maps, and channels</a>)
+	or if both are <code>nil</code>.
+	</li>
+	<li>
+	Interface values are equal if they have <a href="#Type_identity">identical</a> dynamic types and
+	equal dynamic values or if both are <code>nil</code>.
+	</li>
+	<li>
+	An interface value <code>x</code> is equal to a non-interface value
+	<code>y</code> if the dynamic type of <code>x</code> is identical to
+	the static type of <code>y</code> and the dynamic value of <code>x</code>
+	is equal to <code>y</code>.
+	</li>
+	<li>
+	A pointer, function, slice, channel, map, or interface value is equal
+	to <code>nil</code> if it has been assigned the explicit value
+	<code>nil</code>, if it is uninitialized, or if it has been assigned
+	another value equal to <code>nil</code>.
+	</li>
+</ul>
+
+
+<h3 id="Logical_operators">Logical operators</h3>
+
+<p>
+Logical operators apply to <a href="#Boolean_types">boolean</a> values
+and yield a result of the same type as the operands.
+The right operand is evaluated conditionally.
+</p>
+
+<pre class="grammar">
+&amp;&amp;    conditional and    p &amp;&amp; q  is  "if p then q else false"
+||    conditional or     p || q  is  "if p then true else q"
+!     not                !p      is  "not p"
+</pre>
+
+
+<h3 id="Address_operators">Address operators</h3>
+
+<p>
+For an operand <code>x</code> of type <code>T</code>, the address operation
+<code>&amp;x</code> generates a pointer of type <code>*T</code> to <code>x</code>.
+The operand must be <i>addressable</i>,
+that is, either a variable, pointer indirection, or slice indexing
+operation; or a field selector of an addressable struct operand;
+or an array indexing operation of an addressable array.
+As an exception to the addressability requirement, <code>x</code> may also be a
+<a href="#Composite_literals">composite literal</a>.
+</p>
+<p>
+For an operand <code>x</code> of pointer type <code>*T</code>, the pointer
+indirection <code>*x</code> denotes the value of type <code>T</code> pointed
+to by <code>x</code>.
+</p>
+
+<pre>
+&amp;x
+&amp;a[f(2)]
+*p
+*pf(x)
+</pre>
+
+
+<h3 id="Receive_operator">Receive operator</h3>
+
+<p>
+For an operand <code>ch</code> of <a href="#Channel_types">channel type</a>,
+the value of the receive operation <code>&lt;-ch</code> is the value received
+from the channel <code>ch</code>. The type of the value is the element type of
+the channel. The expression blocks until a value is available.
+Receiving from a <code>nil</code> channel blocks forever.
+</p>
+
+<pre>
+v1 := &lt;-ch
+v2 = &lt;-ch
+f(&lt;-ch)
+&lt;-strobe  // wait until clock pulse and discard received value
+</pre>
+
+<p>
+A receive expression used in an assignment or initialization of the form
+</p>
+
+<pre>
+x, ok = &lt;-ch
+x, ok := &lt;-ch
+var x, ok = &lt;-ch
+</pre>
+
+<p>
+yields an additional result.
+The boolean variable <code>ok</code> indicates whether
+the received value was sent on the channel (<code>true</code>)
+or is a <a href="#The_zero_value">zero value</a> returned
+because the channel is closed and empty (<code>false</code>).
+</p>
+
+<!--
+<p>
+<span class="alert">TODO: Probably in a separate section, communication semantics
+need to be presented regarding send, receive, select, and goroutines.</span>
+</p>
+-->
+
+
+<h3 id="Method_expressions">Method expressions</h3>
+
+<p>
+If <code>M</code> is in the <a href="#Method_sets">method set</a> of type <code>T</code>,
+<code>T.M</code> is a function that is callable as a regular function
+with the same arguments as <code>M</code> prefixed by an additional
+argument that is the receiver of the method.
+</p>
+
+<pre class="ebnf">
+MethodExpr    = ReceiverType "." MethodName .
+ReceiverType  = TypeName | "(" "*" TypeName ")" .
+</pre>
+
+<p>
+Consider a struct type <code>T</code> with two methods,
+<code>Mv</code>, whose receiver is of type <code>T</code>, and
+<code>Mp</code>, whose receiver is of type <code>*T</code>.
+</p>
+
+<pre>
+type T struct {
+	a int
+}
+func (tv  T) Mv(a int)     int     { return 0 }  // value receiver
+func (tp *T) Mp(f float32) float32 { return 1 }  // pointer receiver
+var t T
+</pre>
+
+<p>
+The expression
+</p>
+
+<pre>
+T.Mv
+</pre>
+
+<p>
+yields a function equivalent to <code>Mv</code> but
+with an explicit receiver as its first argument; it has signature
+</p>
+
+<pre>
+func(tv T, a int) int
+</pre>
+
+<p>
+That function may be called normally with an explicit receiver, so
+these three invocations are equivalent:
+</p>
+
+<pre>
+t.Mv(7)
+T.Mv(t, 7)
+f := T.Mv; f(t, 7)
+</pre>
+
+<p>
+Similarly, the expression
+</p>
+
+<pre>
+(*T).Mp
+</pre>
+
+<p>
+yields a function value representing <code>Mp</code> with signature
+</p>
+
+<pre>
+func(tp *T, f float32) float32
+</pre>
+
+<p>
+For a method with a value receiver, one can derive a function
+with an explicit pointer receiver, so
+</p>
+
+<pre>
+(*T).Mv
+</pre>
+
+<p>
+yields a function value representing <code>Mv</code> with signature
+</p>
+
+<pre>
+func(tv *T, a int) int
+</pre>
+
+<p>
+Such a function indirects through the receiver to create a value
+to pass as the receiver to the underlying method;
+the method does not overwrite the value whose address is passed in
+the function call.
+</p>
+
+<p>
+The final case, a value-receiver function for a pointer-receiver method,
+is illegal because pointer-receiver methods are not in the method set
+of the value type.
+</p>
+
+<p>
+Function values derived from methods are called with function call syntax;
+the receiver is provided as the first argument to the call.
+That is, given <code>f := T.Mv</code>, <code>f</code> is invoked
+as <code>f(t, 7)</code> not <code>t.f(7)</code>.
+To construct a function that binds the receiver, use a
+<a href="#Function_literals">closure</a>.
+</p>
+
+<p>
+It is legal to derive a function value from a method of an interface type.
+The resulting function takes an explicit receiver of that interface type.
+</p>
+
+<h3 id="Conversions">Conversions</h3>
+
+<p>
+Conversions are expressions of the form <code>T(x)</code>
+where <code>T</code> is a type and <code>x</code> is an expression
+that can be converted to type <code>T</code>.
+</p>
+
+<pre class="ebnf">
+Conversion = Type "(" Expression ")" .
+</pre>
+
+<p>
+If the type starts with an operator it must be parenthesized:
+</p>
+
+<pre>
+*Point(p)        // same as *(Point(p))
+(*Point)(p)      // p is converted to (*Point)
+&lt;-chan int(c)    // same as &lt;-(chan int(c))
+(&lt;-chan int)(c)  // c is converted to (&lt;-chan int)
+</pre>
+
+<p>
+A <a href="#Constants">constant</a> value <code>x</code> can be converted to
+type <code>T</code> in any of these cases:
+</p>
+
+<ul>
+	<li>
+	<code>x</code> is representable by a value of type <code>T</code>.
+	</li>
+	<li>
+	<code>x</code> is an integer constant and <code>T</code> is a
+	<a href="#String_types">string type</a>.
+	The same rule as for non-constant <code>x</code> applies in this case
+	(§<a href="#Conversions_to_and_from_a_string_type">Conversions to and from a string type</a>).
+	</li>
+</ul>
+
+<p>
+Converting a constant yields a typed constant as result.
+</p>
+
+<pre>
+uint(iota)               // iota value of type uint
+float32(2.718281828)     // 2.718281828 of type float32
+complex128(1)            // 1.0 + 0.0i of type complex128
+string('x')              // "x" of type string
+string(0x266c)           // "♬" of type string
+MyString("foo" + "bar")  // "foobar" of type MyString
+string([]byte{'a'})      // not a constant: []byte{'a'} is not a constant
+(*int)(nil)              // not a constant: nil is not a constant, *int is not a boolean, numeric, or string type
+int(1.2)                 // illegal: 1.2 cannot be represented as an int
+string(65.0)             // illegal: 65.0 is not an integer constant
+</pre>
+
+<p>
+A non-constant value <code>x</code> can be converted to type <code>T</code>
+in any of these cases:
+</p>
+
+<ul>
+	<li>
+	<code>x</code> is <a href="#Assignability">assignable</a>
+	to <code>T</code>.
+	</li>
+	<li>
+	<code>x</code>'s type and <code>T</code> have identical
+	<a href="#Types">underlying types</a>.
+	</li>
+	<li>
+	<code>x</code>'s type and <code>T</code> are unnamed pointer types
+	and their pointer base types have identical underlying types.
+	</li>
+	<li>
+	<code>x</code>'s type and <code>T</code> are both integer or floating
+	point types.
+	</li>
+	<li>
+	<code>x</code>'s type and <code>T</code> are both complex types.
+	</li>
+	<li>
+	<code>x</code> is an integer or has type <code>[]byte</code> or
+	<code>[]int</code> and <code>T</code> is a string type.
+	</li>
+	<li>
+	<code>x</code> is a string and <code>T</code> is <code>[]byte</code> or
+	<code>[]int</code>.
+	</li>
+</ul>
+
+<p>
+Specific rules apply to (non-constant) conversions between numeric types or
+to and from a string type.
+These conversions may change the representation of <code>x</code>
+and incur a run-time cost.
+All other conversions only change the type but not the representation
+of <code>x</code>.
+</p>
+
+<p>
+There is no linguistic mechanism to convert between pointers and integers.
+The package <a href="#Package_unsafe"><code>unsafe</code></a>
+implements this functionality under
+restricted circumstances.
+</p>
+
+<h4>Conversions between numeric types</h4>
+
+<p>
+For the conversion of non-constant numeric values, the following rules apply:
+</p>
+
+<ol>
+<li>
+When converting between integer types, if the value is a signed integer, it is
+sign extended to implicit infinite precision; otherwise it is zero extended.
+It is then truncated to fit in the result type's size.
+For example, if <code>v := uint16(0x10F0)</code>, then <code>uint32(int8(v)) == 0xFFFFFFF0</code>.
+The conversion always yields a valid value; there is no indication of overflow.
+</li>
+<li>
+When converting a floating-point number to an integer, the fraction is discarded
+(truncation towards zero).
+</li>
+<li>
+When converting an integer or floating-point number to a floating-point type,
+or a complex number to another complex type, the result value is rounded
+to the precision specified by the destination type.
+For instance, the value of a variable <code>x</code> of type <code>float32</code>
+may be stored using additional precision beyond that of an IEEE-754 32-bit number,
+but float32(x) represents the result of rounding <code>x</code>'s value to
+32-bit precision. Similarly, <code>x + 0.1</code> may use more than 32 bits
+of precision, but <code>float32(x + 0.1)</code> does not.
+</li>
+</ol>
+
+<p>
+In all non-constant conversions involving floating-point or complex values,
+if the result type cannot represent the value the conversion
+succeeds but the result value is implementation-dependent.
+</p>
+
+<h4 id="Conversions_to_and_from_a_string_type">Conversions to and from a string type</h4>
+
+<ol>
+<li>
+Converting a signed or unsigned integer value to a string type yields a
+string containing the UTF-8 representation of the integer. Values outside
+the range of valid Unicode code points are converted to <code>"\uFFFD"</code>.
+
+<pre>
+string('a')           // "a"
+string(-1)            // "\ufffd" == "\xef\xbf\xbd "
+string(0xf8)          // "\u00f8" == "ø" == "\xc3\xb8"
+type MyString string
+MyString(0x65e5)      // "\u65e5" == "日" == "\xe6\x97\xa5"
+</pre>
+</li>
+
+<li>
+Converting a value of type <code>[]byte</code> (or
+the equivalent <code>[]uint8</code>) to a string type yields a
+string whose successive bytes are the elements of the slice.  If
+the slice value is <code>nil</code>, the result is the empty string.
+
+<pre>
+string([]byte{'h', 'e', 'l', 'l', '\xc3', '\xb8'})  // "hellø"
+</pre>
+</li>
+
+<li>
+Converting a value of type <code>[]int</code> to a string type yields
+a string that is the concatenation of the individual integers
+converted to strings.  If the slice value is <code>nil</code>, the
+result is the empty string.
+<pre>
+string([]int{0x767d, 0x9d6c, 0x7fd4})  // "\u767d\u9d6c\u7fd4" == "白鵬翔"
+</pre>
+</li>
+
+<li>
+Converting a value of a string type to <code>[]byte</code> (or <code>[]uint8</code>)
+yields a slice whose successive elements are the bytes of the string.
+If the string is empty, the result is <code>[]byte(nil)</code>.
+
+<pre>
+[]byte("hellø")  // []byte{'h', 'e', 'l', 'l', '\xc3', '\xb8'}
+</pre>
+</li>
+
+<li>
+Converting a value of a string type to <code>[]int</code> yields a
+slice containing the individual Unicode code points of the string.
+If the string is empty, the result is <code>[]int(nil)</code>.
+<pre>
+[]int(MyString("白鵬翔"))  // []int{0x767d, 0x9d6c, 0x7fd4}
+</pre>
+</li>
+</ol>
+
+
+<h3 id="Constant_expressions">Constant expressions</h3>
+
+<p>
+Constant expressions may contain only <a href="#Constants">constant</a>
+operands and are evaluated at compile-time.
+</p>
+
+<p>
+Untyped boolean, numeric, and string constants may be used as operands
+wherever it is legal to use an operand of boolean, numeric, or string type,
+respectively. Except for shift operations, if the operands of a binary operation
+are an untyped integer constant and an untyped floating-point constant,
+the integer constant is converted to an untyped floating-point constant
+(relevant for <code>/</code> and <code>%</code>).
+Similarly, untyped integer or floating-point constants may be used as operands
+wherever it is legal to use an operand of complex type;
+the integer or floating point constant is converted to a
+complex constant with a zero imaginary part.
+</p>
+
+<p>
+A constant <a href="#Comparison_operators">comparison</a> always yields
+a constant of type <code>bool</code>. If the left operand of a constant
+<a href="#Operators">shift expression</a> is an untyped constant, the
+result is an integer constant; otherwise it is a constant of the same
+type as the left operand, which must be of integer type
+(§<a href="#Arithmetic_operators">Arithmetic operators</a>).
+Applying all other operators to untyped constants results in an untyped
+constant of the same kind (that is, a boolean, integer, floating-point,
+complex, or string constant).
+</p>
+
+<pre>
+const a = 2 + 3.0          // a == 5.0   (floating-point constant)
+const b = 15 / 4           // b == 3     (integer constant)
+const c = 15 / 4.0         // c == 3.75  (floating-point constant)
+const d = 1 &lt;&lt; 3.0         // d == 8     (integer constant)
+const e = 1.0 &lt;&lt; 3         // e == 8     (integer constant)
+const f = int32(1) &lt;&lt; 33   // f == 0     (type int32)
+const g = float64(2) &gt;&gt; 1  // illegal    (float64(2) is a typed floating-point constant)
+const h = "foo" &gt; "bar"    // h == true  (type bool)
+</pre>
+
+<p>
+Imaginary literals are untyped complex constants (with zero real part)
+and may be combined in binary
+operations with untyped integer and floating-point constants; the
+result is an untyped complex constant.
+Complex constants are always constructed from
+constant expressions involving imaginary
+literals or constants derived from them, or calls of the built-in function
+<a href="#Complex_numbers"><code>complex</code></a>.
+</p>
+
+<pre>
+const Σ = 1 - 0.707i
+const Δ = Σ + 2.0e-4 - 1/1i
+const Φ = iota * 1i
+const iΓ = complex(0, Γ)
+</pre>
+
+<p>
+Constant expressions are always evaluated exactly; intermediate values and the
+constants themselves may require precision significantly larger than supported
+by any predeclared type in the language. The following are legal declarations:
+</p>
+
+<pre>
+const Huge = 1 &lt;&lt; 100
+const Four int8 = Huge &gt;&gt; 98
+</pre>
+
+<p>
+The values of <i>typed</i> constants must always be accurately representable as values
+of the constant type. The following constant expressions are illegal:
+</p>
+
+<pre>
+uint(-1)       // -1 cannot be represented as a uint
+int(3.14)      // 3.14 cannot be represented as an int
+int64(Huge)    // 1&lt;&lt;100 cannot be represented as an int64
+Four * 300     // 300 cannot be represented as an int8
+Four * 100     // 400 cannot be represented as an int8
+</pre>
+
+<p>
+The mask used by the unary bitwise complement operator <code>^</code> matches
+the rule for non-constants: the mask is all 1s for unsigned constants
+and -1 for signed and untyped constants.
+</p>
+
+<pre>
+^1          // untyped integer constant, equal to -2
+uint8(^1)   // error, same as uint8(-2), out of range
+^uint8(1)   // typed uint8 constant, same as 0xFF ^ uint8(1) = uint8(0xFE)
+int8(^1)    // same as int8(-2)
+^int8(1)    // same as -1 ^ int8(1) = -2
+</pre>
+
+<!--
+<p>
+<span class="alert">
+TODO: perhaps ^ should be disallowed on non-uints instead of assuming twos complement.
+Also it may be possible to make typed constants more like variables, at the cost of fewer
+overflow etc. errors being caught.
+</span>
+</p>
+-->
+
+<h3 id="Order_of_evaluation">Order of evaluation</h3>
+
+<p>
+When evaluating the elements of an assignment or expression,
+all function calls, method calls and
+communication operations are evaluated in lexical left-to-right
+order.
+</p>
+
+<p>
+For example, in the assignment
+</p>
+<pre>
+y[f()], ok = g(h(), i() + x[j()], &lt;-c), k()
+</pre>
+<p>
+the function calls and communication happen in the order
+<code>f()</code>, <code>h()</code>, <code>i()</code>, <code>j()</code>,
+<code>&lt;-c</code>, <code>g()</code>, and <code>k()</code>.
+However, the order of those events compared to the evaluation
+and indexing of <code>x</code> and the evaluation
+of <code>y</code> is not specified.
+</p>
+
+<p>
+Floating-point operations within a single expression are evaluated according to
+the associativity of the operators.  Explicit parentheses affect the evaluation
+by overriding the default associativity.
+In the expression <code>x + (y + z)</code> the addition <code>y + z</code>
+is performed before adding <code>x</code>.
+</p>
+
+<h2 id="Statements">Statements</h2>
+
+<p>
+Statements control execution.
+</p>
+
+<pre class="ebnf">
+Statement =
+	Declaration | LabeledStmt | SimpleStmt |
+	GoStmt | ReturnStmt | BreakStmt | ContinueStmt | GotoStmt |
+	FallthroughStmt | Block | IfStmt | SwitchStmt | SelectStmt | ForStmt |
+	DeferStmt .
+
+SimpleStmt = EmptyStmt | ExpressionStmt | SendStmt | IncDecStmt | Assignment | ShortVarDecl .
+</pre>
+
+
+<h3 id="Empty_statements">Empty statements</h3>
+
+<p>
+The empty statement does nothing.
+</p>
+
+<pre class="ebnf">
+EmptyStmt = .
+</pre>
+
+
+<h3 id="Labeled_statements">Labeled statements</h3>
+
+<p>
+A labeled statement may be the target of a <code>goto</code>,
+<code>break</code> or <code>continue</code> statement.
+</p>
+
+<pre class="ebnf">
+LabeledStmt = Label ":" Statement .
+Label       = identifier .
+</pre>
+
+<pre>
+Error: log.Panic("error encountered")
+</pre>
+
+
+<h3 id="Expression_statements">Expression statements</h3>
+
+<p>
+Function calls, method calls, and receive operations
+can appear in statement context. Such statements may be parenthesized.
+</p>
+
+<pre class="ebnf">
+ExpressionStmt = Expression .
+</pre>
+
+<pre>
+h(x+y)
+f.Close()
+&lt;-ch
+(&lt;-ch)
+</pre>
+
+
+<h3 id="Send_statements">Send statements</h3>
+
+<p>
+A send statement sends a value on a channel.
+The channel expression must be of <a href="#Channel_types">channel type</a>
+and the type of the value must be <a href="#Assignability">assignable</a>
+to the channel's element type.
+</p>
+
+<pre class="ebnf">
+SendStmt = Channel "&lt;-" Expression .
+Channel  = Expression .
+</pre>
+
+<p>
+Both the channel and the value expression are evaluated before communication
+begins. Communication blocks until the send can proceed, at which point the
+value is transmitted on the channel.
+A send on an unbuffered channel can proceed if a receiver is ready.
+A send on a buffered channel can proceed if there is room in the buffer.
+A send on a <code>nil</code> channel blocks forever.
+</p>
+
+<pre>
+ch &lt;- 3
+</pre>
+
+
+<h3 id="IncDec_statements">IncDec statements</h3>
+
+<p>
+The "++" and "--" statements increment or decrement their operands
+by the untyped <a href="#Constants">constant</a> <code>1</code>.
+As with an assignment, the operand must be <a href="#Address_operators">addressable</a>
+or a map index expression.
+</p>
+
+<pre class="ebnf">
+IncDecStmt = Expression ( "++" | "--" ) .
+</pre>
+
+<p>
+The following <a href="#Assignments">assignment statements</a> are semantically
+equivalent:
+</p>
+
+<pre class="grammar">
+IncDec statement    Assignment
+x++                 x += 1
+x--                 x -= 1
+</pre>
+
+
+<h3 id="Assignments">Assignments</h3>
+
+<pre class="ebnf">
+Assignment = ExpressionList assign_op ExpressionList .
+
+assign_op = [ add_op | mul_op ] "=" .
+</pre>
+
+<p>
+Each left-hand side operand must be <a href="#Address_operators">addressable</a>,
+a map index expression, or the <a href="#Blank_identifier">blank identifier</a>.
+Operands may be parenthesized.
+</p>
+
+<pre>
+x = 1
+*p = f()
+a[i] = 23
+(k) = &lt;-ch  // same as: k = &lt;-ch
+</pre>
+
+<p>
+An <i>assignment operation</i> <code>x</code> <i>op</i><code>=</code>
+<code>y</code> where <i>op</i> is a binary arithmetic operation is equivalent
+to <code>x</code> <code>=</code> <code>x</code> <i>op</i>
+<code>y</code> but evaluates <code>x</code>
+only once.  The <i>op</i><code>=</code> construct is a single token.
+In assignment operations, both the left- and right-hand expression lists
+must contain exactly one single-valued expression.
+</p>
+
+<pre>
+a[i] &lt;&lt;= 2
+i &amp;^= 1&lt;&lt;n
+</pre>
+
+<p>
+A tuple assignment assigns the individual elements of a multi-valued
+operation to a list of variables.  There are two forms.  In the
+first, the right hand operand is a single multi-valued expression
+such as a function evaluation or <a href="#Channel_types">channel</a> or
+<a href="#Map_types">map</a> operation or a <a href="#Type_assertions">type assertion</a>.
+The number of operands on the left
+hand side must match the number of values.  For instance, if
+<code>f</code> is a function returning two values,
+</p>
+
+<pre>
+x, y = f()
+</pre>
+
+<p>
+assigns the first value to <code>x</code> and the second to <code>y</code>.
+The <a href="#Blank_identifier">blank identifier</a> provides a
+way to ignore values returned by a multi-valued expression:
+</p>
+
+<pre>
+x, _ = f()  // ignore second value returned by f()
+</pre>
+
+<p>
+In the second form, the number of operands on the left must equal the number
+of expressions on the right, each of which must be single-valued, and the
+<i>n</i>th expression on the right is assigned to the <i>n</i>th
+operand on the left.
+The expressions on the right are evaluated before assigning to
+any of the operands on the left, but otherwise the evaluation
+order is unspecified beyond <a href="#Order_of_evaluation">the usual rules</a>.
+</p>
+
+<pre>
+a, b = b, a  // exchange a and b
+</pre>
+
+<p>
+In assignments, each value must be
+<a href="#Assignability">assignable</a> to the type of the
+operand to which it is assigned. If an untyped <a href="#Constants">constant</a>
+is assigned to a variable of interface type, the constant is <a href="#Conversions">converted</a>
+to type <code>bool</code>, <code>int</code>, <code>float64</code>,
+<code>complex128</code> or <code>string</code>
+respectively, depending on whether the value is a boolean, integer, floating-point,
+complex, or string constant.
+</p>
+
+
+<h3 id="If_statements">If statements</h3>
+
+<p>
+"If" statements specify the conditional execution of two branches
+according to the value of a boolean expression.  If the expression
+evaluates to true, the "if" branch is executed, otherwise, if
+present, the "else" branch is executed.
+</p>
+
+<pre class="ebnf">
+IfStmt = "if" [ SimpleStmt ";" ] Expression Block [ "else" ( IfStmt | Block ) ] .
+</pre>
+
+<pre>
+if x &gt; max {
+	x = max
+}
+</pre>
+
+<p>
+The expression may be preceded by a simple statement, which
+executes before the expression is evaluated.
+</p>
+
+<pre>
+if x := f(); x &lt; y {
+	return x
+} else if x &gt; z {
+	return z
+} else {
+	return y
+}
+</pre>
+
+
+<h3 id="Switch_statements">Switch statements</h3>
+
+<p>
+"Switch" statements provide multi-way execution.
+An expression or type specifier is compared to the "cases"
+inside the "switch" to determine which branch
+to execute.
+</p>
+
+<pre class="ebnf">
+SwitchStmt = ExprSwitchStmt | TypeSwitchStmt .
+</pre>
+
+<p>
+There are two forms: expression switches and type switches.
+In an expression switch, the cases contain expressions that are compared
+against the value of the switch expression.
+In a type switch, the cases contain types that are compared against the
+type of a specially annotated switch expression.
+</p>
+
+<h4 id="Expression_switches">Expression switches</h4>
+
+<p>
+In an expression switch,
+the switch expression is evaluated and
+the case expressions, which need not be constants,
+are evaluated left-to-right and top-to-bottom; the first one that equals the
+switch expression
+triggers execution of the statements of the associated case;
+the other cases are skipped.
+If no case matches and there is a "default" case,
+its statements are executed.
+There can be at most one default case and it may appear anywhere in the
+"switch" statement.
+A missing switch expression is equivalent to
+the expression <code>true</code>.
+</p>
+
+<pre class="ebnf">
+ExprSwitchStmt = "switch" [ SimpleStmt ";" ] [ Expression ] "{" { ExprCaseClause } "}" .
+ExprCaseClause = ExprSwitchCase ":" { Statement ";" } .
+ExprSwitchCase = "case" ExpressionList | "default" .
+</pre>
+
+<p>
+In a case or default clause,
+the last statement only may be a "fallthrough" statement
+(§<a href="#Fallthrough_statements">Fallthrough statement</a>) to
+indicate that control should flow from the end of this clause to
+the first statement of the next clause.
+Otherwise control flows to the end of the "switch" statement.
+</p>
+
+<p>
+The expression may be preceded by a simple statement, which
+executes before the expression is evaluated.
+</p>
+
+<pre>
+switch tag {
+default: s3()
+case 0, 1, 2, 3: s1()
+case 4, 5, 6, 7: s2()
+}
+
+switch x := f(); {  // missing switch expression means "true"
+case x &lt; 0: return -x
+default: return x
+}
+
+switch {
+case x &lt; y: f1()
+case x &lt; z: f2()
+case x == 4: f3()
+}
+</pre>
+
+<h4 id="Type_switches">Type switches</h4>
+
+<p>
+A type switch compares types rather than values. It is otherwise similar
+to an expression switch. It is marked by a special switch expression that
+has the form of a <a href="#Type_assertions">type assertion</a>
+using the reserved word <code>type</code> rather than an actual type.
+Cases then match literal types against the dynamic type of the expression
+in the type assertion.
+</p>
+
+<pre class="ebnf">
+TypeSwitchStmt  = "switch" [ SimpleStmt ";" ] TypeSwitchGuard "{" { TypeCaseClause } "}" .
+TypeSwitchGuard = [ identifier ":=" ] PrimaryExpr "." "(" "type" ")" .
+TypeCaseClause  = TypeSwitchCase ":" { Statement ";" } .
+TypeSwitchCase  = "case" TypeList | "default" .
+TypeList        = Type { "," Type } .
+</pre>
+
+<p>
+The TypeSwitchGuard may include a
+<a href="#Short_variable_declarations">short variable declaration</a>.
+When that form is used, the variable is declared in each clause.
+In clauses with a case listing exactly one type, the variable
+has that type; otherwise, the variable has the type of the expression
+in the TypeSwitchGuard.
+</p>
+
+<p>
+The type in a case may be <code>nil</code>
+(§<a href="#Predeclared_identifiers">Predeclared identifiers</a>);
+that case is used when the expression in the TypeSwitchGuard
+is a <code>nil</code> interface value.
+</p>
+
+<p>
+Given an expression <code>x</code> of type <code>interface{}</code>,
+the following type switch:
+</p>
+
+<pre>
+switch i := x.(type) {
+case nil:
+	printString("x is nil")
+case int:
+	printInt(i)  // i is an int
+case float64:
+	printFloat64(i)  // i is a float64
+case func(int) float64:
+	printFunction(i)  // i is a function
+case bool, string:
+	printString("type is bool or string")  // i is an interface{}
+default:
+	printString("don't know the type")
+}
+</pre>
+
+<p>
+could be rewritten:
+</p>
+
+<pre>
+v := x  // x is evaluated exactly once
+if v == nil {
+	printString("x is nil")
+} else if i, is_int := v.(int); is_int {
+	printInt(i)  // i is an int
+} else if i, is_float64 := v.(float64); is_float64 {
+	printFloat64(i)  // i is a float64
+} else if i, is_func := v.(func(int) float64); is_func {
+	printFunction(i)  // i is a function
+} else {
+	i1, is_bool := v.(bool)
+	i2, is_string := v.(string)
+	if is_bool || is_string {
+		i := v
+		printString("type is bool or string")  // i is an interface{}
+	} else {
+		i := v
+		printString("don't know the type")  // i is an interface{}
+	}
+}
+</pre>
+
+<p>
+The type switch guard may be preceded by a simple statement, which
+executes before the guard is evaluated.
+</p>
+
+<p>
+The "fallthrough" statement is not permitted in a type switch.
+</p>
+
+<h3 id="For_statements">For statements</h3>
+
+<p>
+A "for" statement specifies repeated execution of a block. The iteration is
+controlled by a condition, a "for" clause, or a "range" clause.
+</p>
+
+<pre class="ebnf">
+ForStmt = "for" [ Condition | ForClause | RangeClause ] Block .
+Condition = Expression .
+</pre>
+
+<p>
+In its simplest form, a "for" statement specifies the repeated execution of
+a block as long as a boolean condition evaluates to true.
+The condition is evaluated before each iteration.
+If the condition is absent, it is equivalent to <code>true</code>.
+</p>
+
+<pre>
+for a &lt; b {
+	a *= 2
+}
+</pre>
+
+<p>
+A "for" statement with a ForClause is also controlled by its condition, but
+additionally it may specify an <i>init</i>
+and a <i>post</i> statement, such as an assignment,
+an increment or decrement statement. The init statement may be a
+<a href="#Short_variable_declarations">short variable declaration</a>, but the post statement must not.
+</p>
+
+<pre class="ebnf">
+ForClause = [ InitStmt ] ";" [ Condition ] ";" [ PostStmt ] .
+InitStmt = SimpleStmt .
+PostStmt = SimpleStmt .
+</pre>
+
+<pre>
+for i := 0; i &lt; 10; i++ {
+	f(i)
+}
+</pre>
+
+<p>
+If non-empty, the init statement is executed once before evaluating the
+condition for the first iteration;
+the post statement is executed after each execution of the block (and
+only if the block was executed).
+Any element of the ForClause may be empty but the
+<a href="#Semicolons">semicolons</a> are
+required unless there is only a condition.
+If the condition is absent, it is equivalent to <code>true</code>.
+</p>
+
+<pre>
+for cond { S() }    is the same as    for ; cond ; { S() }
+for      { S() }    is the same as    for true     { S() }
+</pre>
+
+<p>
+A "for" statement with a "range" clause
+iterates through all entries of an array, slice, string or map,
+or values received on a channel. For each entry it assigns <i>iteration values</i>
+to corresponding <i>iteration variables</i> and then executes the block.
+</p>
+
+<pre class="ebnf">
+RangeClause = Expression [ "," Expression ] ( "=" | ":=" ) "range" Expression .
+</pre>
+
+<p>
+The expression on the right in the "range" clause is called the <i>range expression</i>,
+which may be an array, pointer to an array, slice, string, map, or channel.
+As with an assignment, the operands on the left must be
+<a href="#Address_operators">addressable</a> or map index expressions; they
+denote the iteration variables. If the range expression is a channel, only
+one iteration variable is permitted, otherwise there may be one or two.
+If the second iteration variable is the <a href="#Blank_identifier">blank identifier</a>,
+the range clause is equivalent to the same clause with only the first variable present.
+</p>
+
+<p>
+The range expression is evaluated once before beginning the loop
+except if the expression is an array, in which case, depending on
+the expression, it might not be evaluated (see below).
+Function calls on the left are evaluated once per iteration.
+For each iteration, iteration values are produced as follows:
+</p>
+
+<pre class="grammar">
+Range expression                          1st value          2nd value (if 2nd variable is present)
+
+array or slice  a  [n]E, *[n]E, or []E    index    i  int    a[i]       E
+string          s  string type            index    i  int    see below  int
+map             m  map[K]V                key      k  K      m[k]       V
+channel         c  chan E                 element  e  E
+</pre>
+
+<ol>
+<li>
+For an array, pointer to array, or slice value <code>a</code>, the index iteration
+values are produced in increasing order, starting at element index 0. As a special
+case, if only the first iteration variable is present, the range loop produces
+iteration values from 0 up to <code>len(a)</code> and does not index into the array
+or slice itself. For a <code>nil</code> slice, the number of iterations is 0.
+</li>
+
+<li>
+For a string value, the "range" clause iterates over the Unicode code points
+in the string starting at byte index 0.  On successive iterations, the index value will be the
+index of the first byte of successive UTF-8-encoded code points in the string,
+and the second value, of type <code>int</code>, will be the value of
+the corresponding code point.  If the iteration encounters an invalid
+UTF-8 sequence, the second value will be <code>0xFFFD</code>,
+the Unicode replacement character, and the next iteration will advance
+a single byte in the string.
+</li>
+
+<li>
+The iteration order over maps is not specified.
+If map entries that have not yet been reached are deleted during iteration,
+the corresponding iteration values will not be produced. If map entries are
+inserted during iteration, the behavior is implementation-dependent, but the
+iteration values for each entry will be produced at most once. If the map
+is <code>nil</code>, the number of iterations is 0.
+</li>
+
+<li>
+For channels, the iteration values produced are the successive values sent on
+the channel until the channel is <a href="#Close">closed</a>. If the channel
+is <code>nil</code>, the range expression blocks forever.
+</li>
+</ol>
+
+<p>
+The iteration values are assigned to the respective
+iteration variables as in an <a href="#Assignments">assignment statement</a>.
+</p>
+
+<p>
+The iteration variables may be declared by the "range" clause (<code>:=</code>).
+In this case their types are set to the types of the respective iteration values
+and their <a href="#Declarations_and_scope">scope</a> ends at the end of the "for"
+statement; they are re-used in each iteration.
+If the iteration variables are declared outside the "for" statement,
+after execution their values will be those of the last iteration.
+</p>
+
+<pre>
+var testdata *struct {
+	a *[7]int
+}
+for i, _ := range testdata.a {
+	// testdata.a is never evaluated; len(testdata.a) is constant
+	// i ranges from 0 to 6
+	f(i)
+}
+
+var a [10]string
+m := map[string]int{"mon":0, "tue":1, "wed":2, "thu":3, "fri":4, "sat":5, "sun":6}
+for i, s := range a {
+	// type of i is int
+	// type of s is string
+	// s == a[i]
+	g(i, s)
+}
+
+var key string
+var val interface {}  // value type of m is assignable to val
+for key, val = range m {
+	h(key, val)
+}
+// key == last map key encountered in iteration
+// val == map[key]
+
+var ch chan Work = producer()
+for w := range ch {
+	doWork(w)
+}
+</pre>
+
+
+<h3 id="Go_statements">Go statements</h3>
+
+<p>
+A "go" statement starts the execution of a function or method call
+as an independent concurrent thread of control, or <i>goroutine</i>,
+within the same address space.
+</p>
+
+<pre class="ebnf">
+GoStmt = "go" Expression .
+</pre>
+
+<p>
+The expression must be a call, and
+unlike with a regular call, program execution does not wait
+for the invoked function to complete.
+</p>
+
+<pre>
+go Server()
+go func(ch chan&lt;- bool) { for { sleep(10); ch &lt;- true; }} (c)
+</pre>
+
+
+<h3 id="Select_statements">Select statements</h3>
+
+<p>
+A "select" statement chooses which of a set of possible communications
+will proceed.  It looks similar to a "switch" statement but with the
+cases all referring to communication operations.
+</p>
+
+<pre class="ebnf">
+SelectStmt = "select" "{" { CommClause } "}" .
+CommClause = CommCase ":" { Statement ";" } .
+CommCase   = "case" ( SendStmt | RecvStmt ) | "default" .
+RecvStmt   = [ Expression [ "," Expression ] ( "=" | ":=" ) ] RecvExpr .
+RecvExpr   = Expression .
+</pre>
+
+<p>
+RecvExpr must be a <a href="#Receive_operator">receive operation</a>.
+For all the cases in the "select"
+statement, the channel expressions are evaluated in top-to-bottom order, along with
+any expressions that appear on the right hand side of send statements.
+A channel may be <code>nil</code>,
+which is equivalent to that case not
+being present in the select statement
+except, if a send, its expression is still evaluated.
+If any of the resulting operations can proceed, one of those is
+chosen and the corresponding communication and statements are
+evaluated.  Otherwise, if there is a default case, that executes;
+if there is no default case, the statement blocks until one of the communications can
+complete.
+If there are no cases with non-<code>nil</code> channels,
+the statement blocks forever.
+Even if the statement blocks,
+the channel and send expressions are evaluated only once,
+upon entering the select statement.
+</p>
+<p>
+Since all the channels and send expressions are evaluated, any side
+effects in that evaluation will occur for all the communications
+in the "select" statement.
+</p>
+<p>
+If multiple cases can proceed, a pseudo-random fair choice is made to decide
+which single communication will execute.
+<p>
+The receive case may declare one or two new variables using a
+<a href="#Short_variable_declarations">short variable declaration</a>.
+</p>
+
+<pre>
+var c, c1, c2, c3 chan int
+var i1, i2 int
+select {
+case i1 = &lt;-c1:
+	print("received ", i1, " from c1\n")
+case c2 &lt;- i2:
+	print("sent ", i2, " to c2\n")
+case i3, ok := (&lt;-c3):  // same as: i3, ok := &lt;-c3
+	if ok {
+		print("received ", i3, " from c3\n")
+	} else {
+		print("c3 is closed\n")
+	}
+default:
+	print("no communication\n")
+}
+
+for {  // send random sequence of bits to c
+	select {
+	case c &lt;- 0:  // note: no statement, no fallthrough, no folding of cases
+	case c &lt;- 1:
+	}
+}
+
+select { }  // block forever
+</pre>
+
+
+<h3 id="Return_statements">Return statements</h3>
+
+<p>
+A "return" statement terminates execution of the containing function
+and optionally provides a result value or values to the caller.
+</p>
+
+<pre class="ebnf">
+ReturnStmt = "return" [ ExpressionList ] .
+</pre>
+
+<p>
+In a function without a result type, a "return" statement must not
+specify any result values.
+</p>
+<pre>
+func no_result() {
+	return
+}
+</pre>
+
+<p>
+There are three ways to return values from a function with a result
+type:
+</p>
+
+<ol>
+	<li>The return value or values may be explicitly listed
+		in the "return" statement. Each expression must be single-valued
+		and <a href="#Assignability">assignable</a>
+		to the corresponding element of the function's result type.
+<pre>
+func simple_f() int {
+	return 2
+}
+
+func complex_f1() (re float64, im float64) {
+	return -7.0, -4.0
+}
+</pre>
+	</li>
+	<li>The expression list in the "return" statement may be a single
+		call to a multi-valued function. The effect is as if each value
+		returned from that function were assigned to a temporary
+		variable with the type of the respective value, followed by a
+		"return" statement listing these variables, at which point the
+		rules of the previous case apply.
+<pre>
+func complex_f2() (re float64, im float64) {
+	return complex_f1()
+}
+</pre>
+	</li>
+	<li>The expression list may be empty if the function's result
+		type specifies names for its result parameters (§<a href="#Function_types">Function Types</a>).
+		The result parameters act as ordinary local variables
+		and the function may assign values to them as necessary.
+		The "return" statement returns the values of these variables.
+<pre>
+func complex_f3() (re float64, im float64) {
+	re = 7.0
+	im = 4.0
+	return
+}
+
+func (devnull) Write(p []byte) (n int, _ os.Error) {
+	n = len(p)
+	return
+} 
+</pre>
+	</li>
+</ol>
+
+<p>
+Regardless of how they are declared, all the result values are initialized to the zero values for their type (§<a href="#The_zero_value">The zero value</a>) upon entry to the function.
+</p>
+
+<!--
+<p>
+<span class="alert">
+TODO: Define when return is required.<br />
+TODO: Language about result parameters needs to go into a section on
+      function/method invocation<br />
+</span>
+</p>
+-->
+
+<h3 id="Break_statements">Break statements</h3>
+
+<p>
+A "break" statement terminates execution of the innermost
+"for", "switch" or "select" statement.
+</p>
+
+<pre class="ebnf">
+BreakStmt = "break" [ Label ] .
+</pre>
+
+<p>
+If there is a label, it must be that of an enclosing
+"for", "switch" or "select" statement, and that is the one whose execution
+terminates
+(§<a href="#For_statements">For statements</a>, §<a href="#Switch_statements">Switch statements</a>, §<a href="#Select_statements">Select statements</a>).
+</p>
+
+<pre>
+L:
+	for i &lt; n {
+		switch i {
+		case 5:
+			break L
+		}
+	}
+</pre>
+
+<h3 id="Continue_statements">Continue statements</h3>
+
+<p>
+A "continue" statement begins the next iteration of the
+innermost "for" loop at its post statement (§<a href="#For_statements">For statements</a>).
+</p>
+
+<pre class="ebnf">
+ContinueStmt = "continue" [ Label ] .
+</pre>
+
+<p>
+If there is a label, it must be that of an enclosing
+"for" statement, and that is the one whose execution
+advances
+(§<a href="#For_statements">For statements</a>).
+</p>
+
+<h3 id="Goto_statements">Goto statements</h3>
+
+<p>
+A "goto" statement transfers control to the statement with the corresponding label.
+</p>
+
+<pre class="ebnf">
+GotoStmt = "goto" Label .
+</pre>
+
+<pre>
+goto Error
+</pre>
+
+<p>
+Executing the "goto" statement must not cause any variables to come into
+<a href="#Declarations_and_scope">scope</a> that were not already in scope at the point of the goto.
+For instance, this example:
+</p>
+
+<pre>
+	goto L  // BAD
+	v := 3
+L:
+</pre>
+
+<p>
+is erroneous because the jump to label <code>L</code> skips
+the creation of <code>v</code>.
+</p>
+
+<p>
+A "goto" statement outside a <a href="#Blocks">block</a> cannot jump to a label inside that block.
+For instance, this example:
+</p>
+
+<pre>
+if n%2 == 1 {
+	goto L1
+}
+for n &gt; 0 {
+	f()
+	n--
+L1:
+	f()
+	n--
+}
+</pre>
+
+<p>
+is erroneous because the label <code>L1</code> is inside 
+the "for" statement's block but the <code>goto</code> is not.
+</p>
+
+<h3 id="Fallthrough_statements">Fallthrough statements</h3>
+
+<p>
+A "fallthrough" statement transfers control to the first statement of the
+next case clause in a expression "switch" statement (§<a href="#Expression_switches">Expression switches</a>). It may
+be used only as the final non-empty statement in a case or default clause in an
+expression "switch" statement.
+</p>
+
+<pre class="ebnf">
+FallthroughStmt = "fallthrough" .
+</pre>
+
+
+<h3 id="Defer_statements">Defer statements</h3>
+
+<p>
+A "defer" statement invokes a function whose execution is deferred to the moment
+the surrounding function returns.
+</p>
+
+<pre class="ebnf">
+DeferStmt = "defer" Expression .
+</pre>
+
+<p>
+The expression must be a function or method call.
+Each time the "defer" statement
+executes, the parameters to the function call are evaluated and saved anew but the
+function is not invoked.
+Deferred function calls are executed in LIFO order
+immediately before the surrounding function returns,
+after the return values, if any, have been evaluated, but before they
+are returned to the caller. For instance, if the deferred function is
+a <a href="#Function_literals">function literal</a> and the surrounding
+function has <a href="#Function_types">named result parameters</a> that
+are in scope within the literal, the deferred function may access and modify
+the result parameters before they are returned.
+</p>
+
+<pre>
+lock(l)
+defer unlock(l)  // unlocking happens before surrounding function returns
+
+// prints 3 2 1 0 before surrounding function returns
+for i := 0; i &lt;= 3; i++ {
+	defer fmt.Print(i)
+}
+
+// f returns 1
+func f() (result int) {
+	defer func() {
+		result++
+	}()
+	return 0
+}
+</pre>
+
+<h2 id="Built-in_functions">Built-in functions</h2>
+
+<p>
+Built-in functions are
+<a href="#Predeclared_identifiers">predeclared</a>.
+They are called like any other function but some of them
+accept a type instead of an expression as the first argument.
+</p>
+
+<p>
+The built-in functions do not have standard Go types,
+so they can only appear in <a href="#Calls">call expressions</a>;
+they cannot be used as function values.
+</p>
+
+<pre class="ebnf">
+BuiltinCall = identifier "(" [ BuiltinArgs [ "," ] ] ")" .
+BuiltinArgs = Type [ "," ExpressionList ] | ExpressionList .
+</pre>
+
+<h3 id="Close">Close</h3>
+
+<p>
+For a channel <code>c</code>, the built-in function <code>close(c)</code>
+marks the channel as unable to accept more values through a send operation;
+sending to or closing a closed channel causes a <a href="#Run_time_panics">run-time panic</a>.
+After calling <code>close</code>, and after any previously
+sent values have been received, receive operations will return
+the zero value for the channel's type without blocking.
+
+The multi-valued <a href="#Receive_operator">receive operation</a>
+returns a received value along with an indication of whether the channel is closed.
+</p>
+
+
+<h3 id="Length_and_capacity">Length and capacity</h3>
+
+<p>
+The built-in functions <code>len</code> and <code>cap</code> take arguments
+of various types and return a result of type <code>int</code>.
+The implementation guarantees that the result always fits into an <code>int</code>.
+</p>
+
+<pre class="grammar">
+Call      Argument type    Result
+
+len(s)    string type      string length in bytes
+          [n]T, *[n]T      array length (== n)
+          []T              slice length
+          map[K]T          map length (number of defined keys)
+          chan T           number of elements queued in channel buffer
+
+cap(s)    [n]T, *[n]T      array length (== n)
+          []T              slice capacity
+          chan T           channel buffer capacity
+</pre>
+
+<p>
+The capacity of a slice is the number of elements for which there is
+space allocated in the underlying array.
+At any time the following relationship holds:
+</p>
+
+<pre>
+0 &lt;= len(s) &lt;= cap(s)
+</pre>
+
+<p>
+The length and capacity of a <code>nil</code> slice, map, or channel are 0.
+</p>
+
+<p>
+The expression <code>len(s)</code> is <a href="#Constants">constant</a> if
+<code>s</code> is a string constant. The expressions <code>len(s)</code> and
+<code>cap(s)</code> are constants if the type of <code>s</code> is an array
+or pointer to an array and the expression <code>s</code> does not contain
+<a href="#Receive_operator">channel receives</a> or
+<a href="#Calls">function calls</a>; in this case <code>s</code> is not evaluated.
+Otherwise, invocations of <code>len</code> and <code>cap</code> are not
+constant and <code>s</code> is evaluated.
+</p>
+
+
+<h3 id="Allocation">Allocation</h3>
+
+<p>
+The built-in function <code>new</code> takes a type <code>T</code> and
+returns a value of type <code>*T</code>.
+The memory is initialized as described in the section on initial values
+(§<a href="#The_zero_value">The zero value</a>).
+</p>
+
+<pre class="grammar">
+new(T)
+</pre>
+
+<p>
+For instance
+</p>
+
+<pre>
+type S struct { a int; b float64 }
+new(S)
+</pre>
+
+<p>
+dynamically allocates memory for a variable of type <code>S</code>,
+initializes it (<code>a=0</code>, <code>b=0.0</code>),
+and returns a value of type <code>*S</code> containing the address
+of the memory.
+</p>
+
+<h3 id="Making_slices_maps_and_channels">Making slices, maps and channels</h3>
+
+<p>
+Slices, maps and channels are reference types that do not require the
+extra indirection of an allocation with <code>new</code>.
+The built-in function <code>make</code> takes a type <code>T</code>,
+which must be a slice, map or channel type,
+optionally followed by a type-specific list of expressions.
+It returns a value of type <code>T</code> (not <code>*T</code>).
+The memory is initialized as described in the section on initial values
+(§<a href="#The_zero_value">The zero value</a>).
+</p>
+
+<pre class="grammar">
+Call             Type T     Result
+
+make(T, n)       slice      slice of type T with length n and capacity n
+make(T, n, m)    slice      slice of type T with length n and capacity m
+
+make(T)          map        map of type T
+make(T, n)       map        map of type T with initial space for n elements
+
+make(T)          channel    synchronous channel of type T
+make(T, n)       channel    asynchronous channel of type T, buffer size n
+</pre>
+
+
+<p>
+The arguments <code>n</code> and <code>m</code> must be of integer type.
+A <a href="#Run_time_panics">run-time panic</a> occurs if <code>n</code>
+is negative or larger than <code>m</code>, or if <code>n</code> or
+<code>m</code> cannot be represented by an <code>int</code>.
+</p>
+
+<pre>
+s := make([]int, 10, 100)        // slice with len(s) == 10, cap(s) == 100
+s := make([]int, 10)             // slice with len(s) == cap(s) == 10
+c := make(chan int, 10)          // channel with a buffer size of 10
+m := make(map[string] int, 100)  // map with initial space for 100 elements
+</pre>
+
+
+<h3 id="Appending_and_copying_slices">Appending to and copying slices</h3>
+
+<p>
+Two built-in functions assist in common slice operations.
+</p>
+
+<p>
+The <a href="#Function_types">variadic</a> function <code>append</code>
+appends zero or more values <code>x</code>
+to <code>s</code> of type <code>S</code>, which must be a slice type, and
+returns the resulting slice, also of type <code>S</code>.
+The values <code>x</code> are passed to a parameter of type <code>...T</code>
+where <code>T</code> is the <a href="#Slice_types">element type</a> of
+<code>S</code> and the respective
+<a href="#Passing_arguments_to_..._parameters">parameter passing rules</a> apply.
+</p>
+
+<pre class="grammar">
+append(s S, x ...T) S  // T is the element type of S
+</pre>
+
+<p>
+If the capacity of <code>s</code> is not large enough to fit the additional
+values, <code>append</code> allocates a new, sufficiently large slice that fits
+both the existing slice elements and the additional values. Thus, the returned
+slice may refer to a different underlying array. 
+</p>
+
+<pre>
+s0 := []int{0, 0}
+s1 := append(s0, 2)        // append a single element     s1 == []int{0, 0, 2}
+s2 := append(s1, 3, 5, 7)  // append multiple elements    s2 == []int{0, 0, 2, 3, 5, 7}
+s3 := append(s2, s0...)    // append a slice              s3 == []int{0, 0, 2, 3, 5, 7, 0, 0}
+
+var t []interface{}
+t = append(t, 42, 3.1415, "foo")                          t == []interface{}{42, 3.1415, "foo"}
+</pre>
+
+<p>
+The function <code>copy</code> copies slice elements from
+a source <code>src</code> to a destination <code>dst</code> and returns the
+number of elements copied. Source and destination may overlap.
+Both arguments must have <a href="#Type_identity">identical</a> element type <code>T</code> and must be
+<a href="#Assignability">assignable</a> to a slice of type <code>[]T</code>.
+The number of elements copied is the minimum of
+<code>len(src)</code> and <code>len(dst)</code>.
+As a special case, <code>copy</code> also accepts a destination argument assignable
+to type <code>[]byte</code> with a source argument of a string type.
+This form copies the bytes from the string into the byte slice.
+</p>
+
+<pre class="grammar">
+copy(dst, src []T) int
+copy(dst []byte, src string) int
+</pre>
+
+<p>
+Examples:
+</p>
+
+<pre>
+var a = [...]int{0, 1, 2, 3, 4, 5, 6, 7}
+var s = make([]int, 6)
+var b = make([]byte, 5)
+n1 := copy(s, a[0:])            // n1 == 6, s == []int{0, 1, 2, 3, 4, 5}
+n2 := copy(s, s[2:])            // n2 == 4, s == []int{2, 3, 4, 5, 4, 5}
+n3 := copy(b, "Hello, World!")  // n3 == 5, b == []byte("Hello")
+</pre>
+
+<h3 id="Complex_numbers">Assembling and disassembling complex numbers</h3>
+
+<p>
+Three functions assemble and disassemble complex numbers.
+The built-in function <code>complex</code> constructs a complex
+value from a floating-point real and imaginary part, while
+<code>real</code> and <code>imag</code>
+extract the real and imaginary parts of a complex value.
+</p>
+
+<pre class="grammar">
+complex(realPart, imaginaryPart floatT) complexT
+real(complexT) floatT
+imag(complexT) floatT
+</pre>
+
+<p>
+The type of the arguments and return value correspond.
+For <code>complex</code>, the two arguments must be of the same
+floating-point type and the return type is the complex type
+with the corresponding floating-point constituents:
+<code>complex64</code> for <code>float32</code>,
+<code>complex128</code> for <code>float64</code>.
+The <code>real</code> and <code>imag</code> functions
+together form the inverse, so for a complex value <code>z</code>,
+<code>z</code> <code>==</code> <code>complex(real(z),</code> <code>imag(z))</code>.
+</p>
+
+<p>
+If the operands of these functions are all constants, the return
+value is a constant.
+</p>
+
+<pre>
+var a = complex(2, -2)             // complex128
+var b = complex(1.0, -1.4)         // complex128
+x := float32(math.Cos(math.Pi/2))  // float32
+var c64 = complex(5, -x)           // complex64
+var im = imag(b)                   // float64
+var rl = real(c64)                 // float32
+</pre>
+
+<h3 id="Handling_panics">Handling panics</h3>
+
+<p> Two built-in functions, <code>panic</code> and <code>recover</code>,
+assist in reporting and handling <a href="#Run_time_panics">run-time panics</a>
+and program-defined error conditions. 
+</p>
+
+<pre class="grammar">
+func panic(interface{})
+func recover() interface{}
+</pre>
+
+<p>
+When a function <code>F</code> calls <code>panic</code>, normal
+execution of <code>F</code> stops immediately.  Any functions whose
+execution was <a href="#Defer_statements">deferred</a> by the
+invocation of <code>F</code> are run in the usual way, and then
+<code>F</code> returns to its caller.  To the caller, <code>F</code>
+then behaves like a call to <code>panic</code>, terminating its own
+execution and running deferred functions.  This continues until all
+functions in the goroutine have ceased execution, in reverse order.
+At that point, the program is
+terminated and the error condition is reported, including the value of
+the argument to <code>panic</code>.  This termination sequence is
+called <i>panicking</i>.
+</p>
+
+<pre>
+panic(42)
+panic("unreachable")
+panic(Error("cannot parse"))
+</pre>
+
+<p>
+The <code>recover</code> function allows a program to manage behavior
+of a panicking goroutine.  Executing a <code>recover</code> call
+<i>inside</i> a deferred function (but not any function called by it) stops
+the panicking sequence by restoring normal execution, and retrieves
+the error value passed to the call of <code>panic</code>.  If
+<code>recover</code> is called outside the deferred function it will
+not stop a panicking sequence.  In this case, or when the goroutine
+is not panicking, or if the argument supplied to <code>panic</code>
+was <code>nil</code>, <code>recover</code> returns <code>nil</code>.
+</p>
+
+<p>
+The <code>protect</code> function in the example below invokes
+the function argument <code>g</code> and protects callers from
+run-time panics raised by <code>g</code>.
+</p>
+
+<pre>
+func protect(g func()) {
+	defer func() {
+		log.Println("done")  // Println executes normally even in there is a panic
+		if x := recover(); x != nil {
+			log.Printf("run time panic: %v", x)
+		}
+	}()
+	log.Println("start")
+	g()
+}
+</pre>
+
+
+<h3 id="Bootstrapping">Bootstrapping</h3>
+
+<p>
+Current implementations provide several built-in functions useful during
+bootstrapping. These functions are documented for completeness but are not
+guaranteed to stay in the language. They do not return a result.
+</p>
+
+<pre class="grammar">
+Function   Behavior
+
+print      prints all arguments; formatting of arguments is implementation-specific
+println    like print but prints spaces between arguments and a newline at the end
+</pre>
+
+
+<h2 id="Packages">Packages</h2>
+
+<p>
+Go programs are constructed by linking together <i>packages</i>.
+A package in turn is constructed from one or more source files
+that together declare constants, types, variables and functions
+belonging to the package and which are accessible in all files
+of the same package. Those elements may be
+<a href="#Exported_identifiers">exported</a> and used in another package.
+</p>
+
+<h3 id="Source_file_organization">Source file organization</h3>
+
+<p>
+Each source file consists of a package clause defining the package
+to which it belongs, followed by a possibly empty set of import
+declarations that declare packages whose contents it wishes to use,
+followed by a possibly empty set of declarations of functions,
+types, variables, and constants.
+</p>
+
+<pre class="ebnf">
+SourceFile       = PackageClause ";" { ImportDecl ";" } { TopLevelDecl ";" } .
+</pre>
+
+<h3 id="Package_clause">Package clause</h3>
+
+<p>
+A package clause begins each source file and defines the package
+to which the file belongs.
+</p>
+
+<pre class="ebnf">
+PackageClause  = "package" PackageName .
+PackageName    = identifier .
+</pre>
+
+<p>
+The PackageName must not be the <a href="#Blank_identifier">blank identifier</a>.
+</p>
+
+<pre>
+package math
+</pre>
+
+<p>
+A set of files sharing the same PackageName form the implementation of a package.
+An implementation may require that all source files for a package inhabit the same directory.
+</p>
+
+<h3 id="Import_declarations">Import declarations</h3>
+
+<p>
+An import declaration states that the source file containing the
+declaration uses identifiers
+<a href="#Exported_identifiers">exported</a> by the <i>imported</i>
+package and enables access to them.  The import names an
+identifier (PackageName) to be used for access and an ImportPath
+that specifies the package to be imported.
+</p>
+
+<pre class="ebnf">
+ImportDecl       = "import" ( ImportSpec | "(" { ImportSpec ";" } ")" ) .
+ImportSpec       = [ "." | PackageName ] ImportPath .
+ImportPath       = string_lit .
+</pre>
+
+<p>
+The PackageName is used in <a href="#Qualified_identifiers">qualified identifiers</a>
+to access the exported identifiers of the package within the importing source file.
+It is declared in the <a href="#Blocks">file block</a>.
+If the PackageName is omitted, it defaults to the identifier specified in the
+<a href="#Package_clause">package clause</a> of the imported package.
+If an explicit period (<code>.</code>) appears instead of a name, all the
+package's exported identifiers will be declared in the current file's
+file block and can be accessed without a qualifier.
+</p>
+
+<p>
+The interpretation of the ImportPath is implementation-dependent but
+it is typically a substring of the full file name of the compiled
+package and may be relative to a repository of installed packages.
+</p>
+
+<p>
+Assume we have compiled a package containing the package clause
+<code>package math</code>, which exports function <code>Sin</code>, and
+installed the compiled package in the file identified by
+<code>"lib/math"</code>.
+This table illustrates how <code>Sin</code> may be accessed in files
+that import the package after the
+various types of import declaration.
+</p>
+
+<pre class="grammar">
+Import declaration          Local name of Sin
+
+import   "lib/math"         math.Sin
+import M "lib/math"         M.Sin
+import . "lib/math"         Sin
+</pre>
+
+<p>
+An import declaration declares a dependency relation between
+the importing and imported package.
+It is illegal for a package to import itself or to import a package without
+referring to any of its exported identifiers. To import a package solely for
+its side-effects (initialization), use the <a href="#Blank_identifier">blank</a>
+identifier as explicit package name:
+</p>
+
+<pre>
+import _ "lib/math"
+</pre>
+
+
+<h3 id="An_example_package">An example package</h3>
+
+<p>
+Here is a complete Go package that implements a concurrent prime sieve.
+</p>
+
+<pre>
+package main
+
+import "fmt"
+
+// Send the sequence 2, 3, 4, … to channel 'ch'.
+func generate(ch chan&lt;- int) {
+	for i := 2; ; i++ {
+		ch &lt;- i  // Send 'i' to channel 'ch'.
+	}
+}
+
+// Copy the values from channel 'src' to channel 'dst',
+// removing those divisible by 'prime'.
+func filter(src &lt;-chan int, dst chan&lt;- int, prime int) {
+	for i := range src {	// Loop over values received from 'src'.
+		if i%prime != 0 {
+			dst &lt;- i  // Send 'i' to channel 'dst'.
+		}
+	}
+}
+
+// The prime sieve: Daisy-chain filter processes together.
+func sieve() {
+	ch := make(chan int)  // Create a new channel.
+	go generate(ch)       // Start generate() as a subprocess.
+	for {
+		prime := &lt;-ch
+		fmt.Print(prime, "\n")
+		ch1 := make(chan int)
+		go filter(ch, ch1, prime)
+		ch = ch1
+	}
+}
+
+func main() {
+	sieve()
+}
+</pre>
+
+<h2 id="Program_initialization_and_execution">Program initialization and execution</h2>
+
+<h3 id="The_zero_value">The zero value</h3>
+<p>
+When memory is allocated to store a value, either through a declaration
+or a call of <code>make</code> or <code>new</code>,
+and no explicit initialization is provided, the memory is
+given a default initialization.  Each element of such a value is
+set to the <i>zero value</i> for its type: <code>false</code> for booleans,
+<code>0</code> for integers, <code>0.0</code> for floats, <code>""</code>
+for strings, and <code>nil</code> for pointers, functions, interfaces, slices, channels, and maps.
+This initialization is done recursively, so for instance each element of an
+array of structs will have its fields zeroed if no value is specified.
+</p>
+<p>
+These two simple declarations are equivalent:
+</p>
+
+<pre>
+var i int
+var i int = 0
+</pre>
+
+<p>
+After
+</p>
+
+<pre>
+type T struct { i int; f float64; next *T }
+t := new(T)
+</pre>
+
+<p>
+the following holds:
+</p>
+
+<pre>
+t.i == 0
+t.f == 0.0
+t.next == nil
+</pre>
+
+<p>
+The same would also be true after
+</p>
+
+<pre>
+var t T
+</pre>
+
+<h3 id="Program_execution">Program execution</h3>
+<p>
+A package with no imports is initialized by assigning initial values to
+all its package-level variables
+and then calling any
+package-level function with the name and signature of
+</p>
+<pre>
+func init()
+</pre>
+<p>
+defined in its source.
+A package may contain multiple
+<code>init</code> functions, even
+within a single source file; they execute
+in unspecified order.
+</p>
+<p>
+Within a package, package-level variables are initialized,
+and constant values are determined, in
+data-dependent order: if the initializer of <code>A</code>
+depends on the value of <code>B</code>, <code>A</code>
+will be set after <code>B</code>.
+It is an error if such dependencies form a cycle.
+Dependency analysis is done lexically: <code>A</code>
+depends on <code>B</code> if the value of <code>A</code>
+contains a mention of <code>B</code>, contains a value
+whose initializer
+mentions <code>B</code>, or mentions a function that
+mentions <code>B</code>, recursively.
+If two items are not interdependent, they will be initialized
+in the order they appear in the source.
+Since the dependency analysis is done per package, it can produce
+unspecified results  if <code>A</code>'s initializer calls a function defined
+in another package that refers to <code>B</code>.
+</p>
+<p>
+Initialization code may contain "go" statements, but the functions
+they invoke do not begin execution until initialization of the entire
+program is complete. Therefore, all initialization code is run in a single
+goroutine.
+</p>
+<p>
+An <code>init</code> function cannot be referred to from anywhere
+in a program. In particular, <code>init</code> cannot be called explicitly,
+nor can a pointer to <code>init</code> be assigned to a function variable.
+</p>
+<p>
+If a package has imports, the imported packages are initialized
+before initializing the package itself. If multiple packages import
+a package <code>P</code>, <code>P</code> will be initialized only once.
+</p>
+<p>
+The importing of packages, by construction, guarantees that there can
+be no cyclic dependencies in initialization.
+</p>
+<p>
+A complete program is created by linking a single, unimported package
+called the <i>main package</i> with all the packages it imports, transitively.
+The main package must
+have package name <code>main</code> and
+declare a function <code>main</code> that takes no 
+arguments and returns no value.
+</p>
+
+<pre>
+func main() { … }
+</pre>
+
+<p>
+Program execution begins by initializing the main package and then
+invoking the function <code>main</code>.
+</p>
+<p>
+When the function <code>main</code> returns, the program exits.
+It does not wait for other (non-<code>main</code>) goroutines to complete.
+</p>
+
+<h2 id="Run_time_panics">Run-time panics</h2>
+
+<p>
+Execution errors such as attempting to index an array out
+of bounds trigger a <i>run-time panic</i> equivalent to a call of
+the built-in function <a href="#Handling_panics"><code>panic</code></a>
+with a value of the implementation-defined interface type <code>runtime.Error</code>.
+That type defines at least the method
+<code>String() string</code>.  The exact error values that
+represent distinct run-time error conditions are unspecified,
+at least for now.
+</p>
+
+<pre>
+package runtime
+
+type Error interface {
+	String() string
+	// and perhaps others
+}
+</pre>
+
+<h2 id="System_considerations">System considerations</h2>
+
+<h3 id="Package_unsafe">Package <code>unsafe</code></h3>
+
+<p>
+The built-in package <code>unsafe</code>, known to the compiler,
+provides facilities for low-level programming including operations
+that violate the type system. A package using <code>unsafe</code>
+must be vetted manually for type safety.  The package provides the
+following interface:
+</p>
+
+<pre class="grammar">
+package unsafe
+
+type ArbitraryType int  // shorthand for an arbitrary Go type; it is not a real type
+type Pointer *ArbitraryType
+
+func Alignof(variable ArbitraryType) uintptr
+func Offsetof(selector ArbitraryType) uinptr
+func Sizeof(variable ArbitraryType) uintptr
+
+func Reflect(val interface{}) (typ runtime.Type, addr uintptr)
+func Typeof(val interface{}) (typ interface{})
+func Unreflect(typ runtime.Type, addr uintptr) interface{}
+</pre>
+
+<p>
+Any pointer or value of type <code>uintptr</code> can be converted into
+a <code>Pointer</code> and vice versa.
+</p>
+<p>
+The function <code>Sizeof</code> takes an expression denoting a
+variable of any type and returns the size of the variable in bytes.
+</p>
+<p>
+The function <code>Offsetof</code> takes a selector (§<a href="#Selectors">Selectors</a>) denoting a struct
+field of any type and returns the field offset in bytes relative to the
+struct's address.
+For a struct <code>s</code> with field <code>f</code>:
+</p>
+
+<pre>
+uintptr(unsafe.Pointer(&amp;s)) + unsafe.Offsetof(s.f) == uintptr(unsafe.Pointer(&amp;s.f))
+</pre>
+
+<p>
+Computer architectures may require memory addresses to be <i>aligned</i>;
+that is, for addresses of a variable to be a multiple of a factor,
+the variable's type's <i>alignment</i>.  The function <code>Alignof</code>
+takes an expression denoting a variable of any type and returns the
+alignment of the (type of the) variable in bytes.  For a variable
+<code>x</code>:
+</p>
+
+<pre>
+uintptr(unsafe.Pointer(&amp;x)) % unsafe.Alignof(x) == 0
+</pre>
+
+<p>
+Calls to <code>Alignof</code>, <code>Offsetof</code>, and
+<code>Sizeof</code> are compile-time constant expressions of type <code>uintptr</code>.
+</p>
+<p>
+The functions <code>unsafe.Typeof</code>,
+<code>unsafe.Reflect</code>,
+and <code>unsafe.Unreflect</code> allow access at run time to the dynamic
+types and values stored in interfaces.
+<code>Typeof</code> returns a representation of
+<code>val</code>'s
+dynamic type as a <code>runtime.Type</code>.
+<code>Reflect</code> allocates a copy of
+<code>val</code>'s dynamic
+value and returns both the type and the address of the copy.
+<code>Unreflect</code> inverts <code>Reflect</code>,
+creating an
+interface value from a type and address.
+The <a href="/pkg/reflect/"><code>reflect</code> package</a> built on these primitives
+provides a safe, more convenient way to inspect interface values.
+</p>
+
+
+<h3 id="Size_and_alignment_guarantees">Size and alignment guarantees</h3>
+
+<p>
+For the numeric types (§<a href="#Numeric_types">Numeric types</a>), the following sizes are guaranteed:
+</p>
+
+<pre class="grammar">
+type                                 size in bytes
+
+byte, uint8, int8                     1
+uint16, int16                         2
+uint32, int32, float32                4
+uint64, int64, float64, complex64     8
+complex128                           16
+</pre>
+
+<p>
+The following minimal alignment properties are guaranteed:
+</p>
+<ol>
+<li>For a variable <code>x</code> of any type: <code>unsafe.Alignof(x)</code> is at least 1.
+</li>
+
+<li>For a variable <code>x</code> of struct type: <code>unsafe.Alignof(x)</code> is the largest of
+   all the values <code>unsafe.Alignof(x.f)</code> for each field <code>f</code> of <code>x</code>, but at least 1.
+</li>
+
+<li>For a variable <code>x</code> of array type: <code>unsafe.Alignof(x)</code> is the same as
+   <code>unsafe.Alignof(x[0])</code>, but at least 1.
+</li>
+</ol>
+
+<span class="alert">
+<h2 id="Implementation_differences">Implementation differences - TODO</h2>
+<ul>
+	<li><code>len(a)</code> is only a constant if <code>a</code> is a (qualified) identifier denoting an array or pointer to an array.</li>
+	<li><code>nil</code> maps are not treated like empty maps.</li>
+	<li>Trying to send/receive from a <code>nil</code> channel causes a run-time panic.</li>
+	<li><code>unsafe.Alignof</code>, <code>unsafe.Offsetof</code>, and <code>unsafe.Sizeof</code> return an <code>int</code>.</li>
+</ul>
+</span>