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Diffstat (limited to 'doc/go_spec.html')
| -rw-r--r-- | doc/go_spec.html | 126 |
1 files changed, 67 insertions, 59 deletions
diff --git a/doc/go_spec.html b/doc/go_spec.html index 5f8b5e6ba..0c08e1464 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -1,5 +1,5 @@ <!-- title The Go Programming Language Specification --> -<!-- subtitle Version of May 15, 2011 --> +<!-- subtitle Version of May 24, 2011 --> <!-- TODO @@ -10,7 +10,6 @@ TODO [ ] 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 -[ ] may want to have some examples for the types of shift operations [ ] should string(1<<s) and float32(1<<s) be valid? [ ] should probably write something about evaluation order of statements even though obvious @@ -49,7 +48,7 @@ The syntax is specified using Extended Backus-Naur Form (EBNF): Production = production_name "=" [ Expression ] "." . Expression = Alternative { "|" Alternative } . Alternative = Term { Term } . -Term = production_name | token [ "..." token ] | Group | Option | Repetition . +Term = production_name | token [ "…" token ] | Group | Option | Repetition . Group = "(" Expression ")" . Option = "[" Expression "]" . Repetition = "{" Expression "}" . @@ -73,8 +72,12 @@ 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 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> @@ -123,9 +126,9 @@ 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" . +decimal_digit = "0" … "9" . +octal_digit = "0" … "7" . +hex_digit = "0" … "9" | "A" … "F" | "a" … "f" . </pre> <h2 id="Lexical_elements">Lexical elements</h2> @@ -287,7 +290,7 @@ An optional prefix sets a non-decimal base: <code>0</code> for octal, <code>0x</ </p> <pre class="ebnf"> int_lit = decimal_lit | octal_lit | hex_lit . -decimal_lit = ( "1" ... "9" ) { decimal_digit } . +decimal_lit = ( "1" … "9" ) { decimal_digit } . octal_lit = "0" { octal_digit } . hex_lit = "0" ( "x" | "X" ) hex_digit { hex_digit } . </pre> @@ -822,7 +825,7 @@ make([]T, length, capacity) </pre> <p> -The <code>make()</code> call allocates a new, hidden array to which the returned +A call to <code>make</code> allocates a new, hidden array to which the returned slice value refers. That is, executing </p> @@ -1054,9 +1057,9 @@ 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() { ... } +func (p T) Read(b Buffer) bool { return … } +func (p T) Write(b Buffer) bool { return … } +func (p T) Close() { … } </pre> <p> @@ -1094,8 +1097,8 @@ If <code>S1</code> and <code>S2</code> also implement </p> <pre> -func (p T) Lock() { ... } -func (p T) Unlock() { ... } +func (p T) Lock() { … } +func (p T) Unlock() { … } </pre> <p> @@ -1177,7 +1180,6 @@ 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. -</code> <h3 id="Channel_types">Channel types</h3> @@ -1697,7 +1699,7 @@ 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. +// 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 */ } @@ -2100,7 +2102,7 @@ element index plus one. A slice literal has the form </p> <pre> -[]T{x1, x2, ... xn} +[]T{x1, x2, … xn} </pre> <p> @@ -2108,7 +2110,7 @@ and is a shortcut for a slice operation applied to an array literal: </p> <pre> -[n]T{x1, x2, ... xn}[0 : n] +[n]T{x1, x2, … xn}[0 : n] </pre> <p> @@ -2134,8 +2136,8 @@ parentheses. </p> <pre> -if x == (T{a,b,c}[i]) { ... } -if (x == T{a,b,c}[i]) { ... } +if x == (T{a,b,c}[i]) { … } +if (x == T{a,b,c}[i]) { … } </pre> <p> @@ -2568,11 +2570,11 @@ Given an expression <code>f</code> of function type </p> <pre> -f(a1, a2, ... an) +f(a1, a2, … an) </pre> <p> -calls <code>f</code> with arguments <code>a1, a2, ... an</code>. +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. @@ -2651,7 +2653,7 @@ arguments bound to the final parameter and may differ for each call site. Given the function and call </p> <pre> -func Greeting(prefix string, who ... string) +func Greeting(prefix string, who ...string) Greeting("hello:", "Joe", "Anna", "Eileen") </pre> @@ -2702,42 +2704,34 @@ unary_op = "+" | "-" | "!" | "^" | "*" | "&" | "<-" . <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 channels, shifts, or untyped <a href="#Constants">constants</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> -In a channel send, the first operand is always a channel and the second -must be a value <a href="#Assignability">assignable</a> -to the channel's element type. -</p> - -<p> -Except for shift operations, -if one operand is an untyped <a href="#Constants">constant</a> +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 operation must have unsigned integer type +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. -</p> - -<p> -If the left operand of a non-constant shift operation is an untyped constant, -the type of constant is what it would be if the shift operation were replaced by -the left operand alone. +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. </p> <pre> var s uint = 33 -var i = 1<<s // 1 has type int -var j = int32(1<<s) // 1 has type int32; j == 0 -var u = uint64(1<<s) // 1 has type uint64; u == 1<<33 -var f = float32(1<<s) // illegal: 1 has type float32, cannot shift -var g = float32(1<<33) // legal; 1<<33 is a constant shift operation; g == 1<<33 +var i = 1<<s // 1 has type int +var j int32 = 1<<s // 1 has type int32; j == 0 +var k = uint64(1<<s) // 1 has type uint64; k == 1<<33 +var m int = 1.0<<s // legal: 1.0 has type int +var u = 1.0<<s // illegal: 1.0 has type float64, cannot shift +var v float32 = 1<<s // illegal: 1 has type float32, cannot shift +var w int64 = 1.0<<33 // legal: 1.0<<33 is a constant shift expression </pre> <h3 id="Operator_precedence">Operator precedence</h3> @@ -2869,8 +2863,8 @@ be replaced by a bitwise "and" operation: <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. The shift count must -be an unsigned integer. There is no upper limit on the shift count. Shifts behave +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 << 1</code> is the same as <code>x*2</code> @@ -3382,21 +3376,35 @@ 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 +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> -Applying an operator to untyped constants results in an untyped +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), except for -<a href="#Comparison_operators">comparison operators</a>, which result in -a constant of type <code>bool</code>. +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 << 3.0 // d == 8 (integer constant) +const e = 1.0 << 3 // e == 8 (integer constant) +const f = int32(1) << 33 // f == 0 (type int32) +const g = float64(2) >> 1 // illegal (float64(2) is a typed floating-point constant) +const h = "foo" > "bar" // h == true (type bool) +</pre> + <p> Imaginary literals are untyped complex constants (with zero real part) and may be combined in binary @@ -4886,7 +4894,7 @@ package main import "fmt" -// Send the sequence 2, 3, 4, ... to channel 'ch'. +// Send the sequence 2, 3, 4, … to channel 'ch'. func generate(ch chan<- int) { for i := 2; ; i++ { ch <- i // Send 'i' to channel 'ch'. @@ -4926,7 +4934,7 @@ func main() { <h3 id="The_zero_value">The zero value</h3> <p> When memory is allocated to store a value, either through a declaration -or <code>make()</code> or <code>new()</code> call, +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, @@ -4984,7 +4992,7 @@ func init() <p> defined in its source. A package may contain multiple -<code>init()</code> functions, even +<code>init</code> functions, even within a single source file; they execute in unspecified order. </p> @@ -5014,8 +5022,8 @@ 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, +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> @@ -5037,7 +5045,7 @@ arguments and returns no value. </p> <pre> -func main() { ... } +func main() { … } </pre> <p> |