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spec: clarify receive operator

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- receiving from a closed channel returns immediately
- in the ,ok form, the 2nd result is of type bool, not
  just boolean (gc and ggcgo agree).

Per dsymonds' suggestion.

R=r, rsc, ken, iant, dsymonds
CC=golang-dev
https://golang.org/cl/6333057
This commit is contained in:
Robert Griesemer 2012-06-25 11:28:24 -07:00
parent 277e7e57ca
commit 689931c5b0
1 changed files with 9 additions and 6 deletions
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15
doc/go_spec.html
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@ -1,6 +1,6 @@
<!--{
"Title": "The Go Programming Language Specification",
"Subtitle": "Version of June 4, 2012",
"Subtitle": "Version of June 22, 2012",
"Path": "/ref/spec"
}-->
@ -3184,6 +3184,9 @@ 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.
Receiving from a <a href="#Close">closed</a> channel always succeeds,
immediately returning the element type's <a href="#The_zero_value">zero
value</a>.
</p>
<pre>
@ -3204,11 +3207,11 @@ 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>).
yields an additional result of type <code>bool</code> reporting whether the
communication succeeded. The value of <code>ok</code> is <code>true</code>
if the value received was delivered by a successful send operation to the
channel, or <code>false</code> if it is a zero value generated because the
channel is closed and empty.
</p>
<!--