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spec: remove closed from language, replaced by x, ok = <-c
R=gri, r, r2 CC=golang-dev https://golang.org/cl/4249065
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@ -1,5 +1,5 @@
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<!-- title The Go Programming Language Specification -->
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<!-- subtitle Version of March 7, 2011 -->
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<!-- subtitle Version of March 11, 2011 -->
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<!--
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TODO
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@ -1235,8 +1235,11 @@ receiver are ready.
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</p>
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<p>
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A channel may be closed and tested for closure with the built-in functions
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<a href="#Close_and_closed"><code>close</code> and <code>closed</code></a>.
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A channel may be closed with the built-in function
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<a href="#Close"><code>close</code></a>; the
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multi-valued assignment form of the
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<a href="#Receive_operator">receive operator</a>
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tests whether a channel has been closed.
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</p>
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<h2 id="Properties_of_types_and_values">Properties of types and values</h2>
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@ -1496,7 +1499,7 @@ Zero value:
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nil
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Functions:
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append cap close closed complex copy imag len
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append cap close complex copy imag len
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make new panic print println real recover
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</pre>
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@ -3029,9 +3032,6 @@ f(<-ch)
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<-strobe // wait until clock pulse and discard received value
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</pre>
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<!--
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TODO(rsc): Add after a release or two without any x,ok := <-c.
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<p>
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A receive expression used in an assignment or initialization of the form
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</p>
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@ -3049,7 +3049,6 @@ the received value was sent on the channel (<code>true</code>)
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or is a <a href="#The_zero_value">zero value</a> returned
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because the channel is closed and empty (<code>false</code>).
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</p>
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-->
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<p>
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Receiving from a <code>nil</code> channel causes a
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@ -4009,9 +4008,8 @@ iteration values for each entry will be produced at most once.
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<li>
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For channels, the iteration values produced are the successive values sent on
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the channel until the channel is closed; it does not produce the zero value sent
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before the channel is closed
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(§<a href="#Close_and_closed"><code>close</code> and <code>closed</code></a>).
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the channel until the channel is closed
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(§<a href="#Close"><code>close</code>).
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</li>
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</ol>
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@ -4086,12 +4084,9 @@ cases all referring to communication operations.
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SelectStmt = "select" "{" { CommClause } "}" .
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CommClause = CommCase ":" { Statement ";" } .
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CommCase = "case" ( SendStmt | RecvStmt ) | "default" .
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RecvStmt = [ Expression ( "=" | ":=" ) ] RecvExpr .
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RecvStmt = [ Expression [ "," Expression ] ( "=" | ":=" ) ] RecvExpr .
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RecvExpr = Expression .
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</pre>
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<!-- TODO(rsc):
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RecvStmt = [ Expression [ "," Expression ] ( "=" | ":=" ) ] RecvExpr .
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-->
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<p>
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RecvExpr must be a <a href="#Receive_operator">receive operation</a>.
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@ -4122,27 +4117,24 @@ in the "select" statement.
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If multiple cases can proceed, a pseudo-random fair choice is made to decide
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which single communication will execute.
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<p>
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<!-- TODO(rsc): s/variable/& or &s/ -->
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The receive case may declare a new variable using a
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The receive case may declare one or two new variables using a
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<a href="#Short_variable_declarations">short variable declaration</a>.
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</p>
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<pre>
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var c, c1, c2 chan int
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var c, c1, c2, c3 chan int
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var i1, i2 int
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select {
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case i1 = <-c1:
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print("received ", i1, " from c1\n")
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case c2 <- i2:
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print("sent ", i2, " to c2\n")
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<!-- TODO(rsc): add , c3 to channel list above too
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case i3, ok := <-c3:
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if ok {
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print("received ", i3, " from c3\n")
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} else {
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print("c3 is closed\n")
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}
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-->
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default:
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print("no communication\n")
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}
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@ -4401,8 +4393,7 @@ BuiltinCall = identifier "(" [ BuiltinArgs [ "," ] ] ")" .
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BuiltinArgs = Type [ "," ExpressionList ] | ExpressionList .
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</pre>
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<!-- TODO(rsc): s/.and.closed//g -->
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<h3 id="Close_and_closed">Close and closed</h3>
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<h3 id="Close">Close</h3>
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<p>
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For a channel <code>c</code>, the built-in function <code>close(c)</code>
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@ -4412,12 +4403,8 @@ After calling <code>close</code>, and after any previously
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sent values have been received, receive operations will return
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the zero value for the channel's type without blocking.
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<!-- TODO(rsc): delete next sentence, replace with
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The multi-valued <a href="#Receive_operator">receive operation</a>
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returns a received value along with an indication of whether the channel is closed.
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-->
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After at least one such zero value has been
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received, <code>closed(c)</code> returns true.
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The multi-valued <a href="#Receive_operator">receive operation</a>
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returns a received value along with an indication of whether the channel is closed.
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</p>
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