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spec: remove ... (keeping ...T)

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R=gri, iant, ken2, r, r2
CC=golang-dev
https://golang.org/cl/1632041
This commit is contained in:
Russ Cox 2010-06-12 11:37:13 -07:00
parent 76da2780c3
commit 9562592342
1 changed files with 21 additions and 60 deletions
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doc/go_spec.html
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@ -986,7 +986,7 @@ Signature = Parameters [ Result ] .
Result = Parameters | Type .
Parameters = "(" [ ParameterList [ "," ] ] ")" .
ParameterList = ParameterDecl { "," ParameterDecl } .
ParameterDecl = [ IdentifierList ] ( Type | "..." [ Type ] ) .
ParameterDecl = [ IdentifierList ] [ "..." ] Type .
</pre>
<p>
@ -998,23 +998,22 @@ lists are always parenthesized except that if there is exactly
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> 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="#Assignability">assignable</a>
to <code>T</code>; otherwise they may be of any type.
If the function's last parameter has a type prefixed with <code>...</code>,
the function may be invoked with zero or more arguments for that parameter,
each of which must be <a href="#Assignability">assignable</a>
to the type that follows the <code>...</code>.
Such a function is called <i>variadic</i>.
</p>
<pre>
func()
func(x int)
func() int
func(string, float, ...)
func(prefix string, values ... int)
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)
func(a, b int, z float, opt ...interface{}) (success bool)
func(int, int, float) (float, *[]int)
func(n int) func(p *T)
</pre>
@ -1271,10 +1270,8 @@ literal structure and corresponding components have identical types. In detail:
<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 and if corresponding parameter and result types are
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.
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
@ -2602,48 +2599,13 @@ There is no distinct method type and there are no method literals.
<h3 id="Passing_arguments_to_..._parameters">Passing arguments to <code>...</code> parameters</h3>
<p>
When a function <code>f</code> has a <code>...</code> parameter,
it is always the last formal parameter. Within calls to <code>f</code>,
the arguments before the <code>...</code> are treated normally.
After those, an arbitrary number (including zero) of trailing
arguments may appear in the call and are bound to the <code>...</code>
parameter.
</p>
<p>
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>
Given the function and call
</p>
<pre>
func Fprintf(f io.Writer, format string, args ...)
Fprintf(os.Stdout, "%s %d", "hello", 23)
</pre>
<p>
Within <code>Fprintf</code>, the dynamic type of <code>args</code> for this
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
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. The length of the slice is therefore the
number of arguments bound to the <code>... T</code> parameter and
number of arguments bound to the final parameter and
may differ for each call site.
</p>
@ -2662,11 +2624,10 @@ Within <code>Greeting</code>, <code>who</code> will have value
<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 <a href="#Type_identity">identical type</a>,
the parameter is not wrapped again but passed directly. In short, a formal <code>...</code>
As a special case, if a function passes its own <code>...</code> parameter
as the <code>...</code> argument in a call to another function with
a <code>...</code> parameter of <a href="#Type_identity">identical type</a>,
the parameter is passed directly. In short, a formal <code>...</code>
parameter is passed unchanged as an actual <code>...</code> parameter provided the
types match.
</p>