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spec: remove closed from language, replaced by x, ok = <-c

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R=gri, r, r2
CC=golang-dev
https://golang.org/cl/4249065
This commit is contained in:
Russ Cox 2011-03-11 14:47:02 -05:00
parent d3d672998f
commit 9f2cb86fe2
1 changed files with 15 additions and 28 deletions
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39
doc/go_spec.html
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@ -1,5 +1,5 @@
<!-- title The Go Programming Language Specification -->
<!-- subtitle Version of March 7, 2011 -->
<!-- subtitle Version of March 11, 2011 -->
<!--
TODO
@ -1235,8 +1235,11 @@ receiver are ready.
</p>
<p>
A channel may be closed and tested for closure with the built-in functions
<a href="#Close_and_closed"><code>close</code> and <code>closed</code></a>.
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>
@ -1496,7 +1499,7 @@ Zero value:
nil
Functions:
append cap close closed complex copy imag len
append cap close complex copy imag len
make new panic print println real recover
</pre>
@ -3029,9 +3032,6 @@ f(&lt;-ch)
&lt;-strobe // wait until clock pulse and discard received value
</pre>
<!--
TODO(rsc): Add after a release or two without any x,ok := <-c.
<p>
A receive expression used in an assignment or initialization of the form
</p>
@ -3049,7 +3049,6 @@ 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>
Receiving from a <code>nil</code> channel causes a
@ -4009,9 +4008,8 @@ iteration values for each entry will be produced at most once.
<li>
For channels, the iteration values produced are the successive values sent on
the channel until the channel is closed; it does not produce the zero value sent
before the channel is closed
(§<a href="#Close_and_closed"><code>close</code> and <code>closed</code></a>).
the channel until the channel is closed
(§<a href="#Close"><code>close</code>).
</li>
</ol>
@ -4086,12 +4084,9 @@ cases all referring to communication operations.
SelectStmt = "select" "{" { CommClause } "}" .
CommClause = CommCase ":" { Statement ";" } .
CommCase = "case" ( SendStmt | RecvStmt ) | "default" .
RecvStmt = [ Expression ( "=" | ":=" ) ] RecvExpr .
RecvStmt = [ Expression [ "," Expression ] ( "=" | ":=" ) ] RecvExpr .
RecvExpr = Expression .
</pre>
<!-- TODO(rsc):
RecvStmt = [ Expression [ "," Expression ] ( "=" | ":=" ) ] RecvExpr .
-->
<p>
RecvExpr must be a <a href="#Receive_operator">receive operation</a>.
@ -4122,27 +4117,24 @@ in the "select" statement.
If multiple cases can proceed, a pseudo-random fair choice is made to decide
which single communication will execute.
<p>
<!-- TODO(rsc): s/variable/& or &s/ -->
The receive case may declare a new variable using a
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 chan int
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")
<!-- TODO(rsc): add , c3 to channel list above too
case i3, ok := &lt;-c3:
if ok {
print("received ", i3, " from c3\n")
} else {
print("c3 is closed\n")
}
-->
default:
print("no communication\n")
}
@ -4401,8 +4393,7 @@ BuiltinCall = identifier "(" [ BuiltinArgs [ "," ] ] ")" .
BuiltinArgs = Type [ "," ExpressionList ] | ExpressionList .
</pre>
<!-- TODO(rsc): s/.and.closed//g -->
<h3 id="Close_and_closed">Close and closed</h3>
<h3 id="Close">Close</h3>
<p>
For a channel <code>c</code>, the built-in function <code>close(c)</code>
@ -4412,12 +4403,8 @@ 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.
<!-- TODO(rsc): delete next sentence, replace with
The multi-valued <a href="#Receive_operator">receive operation</a>
returns a received value along with an indication of whether the channel is closed.
-->
After at least one such zero value has been
received, <code>closed(c)</code> returns true.
</p>