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| -rw-r--r-- | doc/go_spec.html | 68 |
1 files changed, 51 insertions, 17 deletions
diff --git a/doc/go_spec.html b/doc/go_spec.html index 382387645..cd46744b9 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -900,7 +900,7 @@ Signature = Parameters [ Result ] . Result = Parameters | Type . Parameters = "(" [ ParameterList [ "," ] ] ")" . ParameterList = ParameterDecl { "," ParameterDecl } . -ParameterDecl = [ IdentifierList ] ( Type | "..." ) . +ParameterDecl = [ IdentifierList ] ( Type | "..." [ Type ] ) . </pre> <p> @@ -913,9 +913,12 @@ one unnamed result it may written as an unparenthesized type. </p> <p> For the last parameter only, instead of a type one may write -<code>...</code> to indicate that the function may be invoked with -zero or more additional arguments of any -type. +<code>...</code> or <code>... T</code> to indicate that the function +may be invoked with zero or more additional arguments. If the type +<code>T</code> is present in the parameter declaration, the additional +arguments must all be +<a href="#Assignment_compatibility">assignment compatible</a> +with type <code>T</code>; otherwise they may be of any type. </p> <pre> @@ -923,6 +926,7 @@ func() func(x int) func() int func(string, float, ...) +func(prefix string, values ... int) func(a, b int, z float) bool func(a, b int, z float) (bool) func(a, b int, z float, opt ...) (success bool) @@ -1189,7 +1193,9 @@ identical types. In detail: <li>Two function types are identical if they have the same number of parameters and result values and if corresponding parameter and result types are - identical. All "..." parameters are defined to have identical type. + identical. All "..." parameters without a specified type are defined to have + identical type. All "..." parameters with specified identical type + <code>T</code> are defined to have identical type. Parameter and result names are not required to match.</li> <li>Two interface types are identical if they have the same set of methods @@ -2596,15 +2602,15 @@ parameter. </p> <p> -Within <code>f</code>, the <code>...</code> parameter has static -type <code>interface{}</code> (the empty interface). For each call, -its dynamic type is a structure whose sequential fields are the -trailing arguments of the call. That is, the actual arguments -provided for a <code>...</code> parameter are wrapped into a struct -that is passed to the function instead of the actual arguments. -Using the <a href="#Package_unsafe">reflection</a> interface, <code>f</code> may -unpack the elements of the dynamic type to recover the actual -arguments. +Within <code>f</code>, a <code>...</code> parameter with no +specified type has static type <code>interface{}</code> (the empty +interface). For each call, its dynamic type is a structure whose +sequential fields are the trailing arguments of the call. That is, +the actual arguments provided for a <code>...</code> parameter are +wrapped into a struct that is passed to the function instead of the +actual arguments. Using the <a href="#Package_unsafe">reflection</a> +interface, <code>f</code> may unpack the elements of the dynamic +type to recover the actual arguments. </p> <p> @@ -2621,12 +2627,40 @@ call will be, schematically, <code> struct { string; int }</code>. </p> +<p> +If the final parameter of <code>f</code> has type <code>... T</code>, +within the function it is equivalent to a parameter of type +<code>[]T</code>. At each call of <code>f</code>, the actual +arguments provided for the <code>... T</code> parameter are placed +into a new slice of type <code>[]T</code> whose successive elements are +the actual arguments. The length of the slice is therefore the +number of arguments bound to the <code>... T</code> parameter and +may differ for each call site. +</p> <p> -As a special case, if a function passes its own <code>...</code> parameter as the argument -for a <code>...</code> in a call to another function with a <code>...</code> parameter, +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 value +<code>[]string{"Joe", "Anna", "Eileen")</code> +</p> + + +<p> +As a special case, if a function passes its own <code>...</code> parameter, +with or without specified type, as the argument +for a <code>...</code> in a call to another function with a <code>...</code> parameter +of identical type, the parameter is not wrapped again but passed directly. In short, a formal <code>...</code> -parameter is passed unchanged as an actual <code>...</code> parameter. +parameter is passed unchanged as an actual <code>...</code> parameter provided the +types match. +</p> <h3 id="Operators">Operators</h3> |