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spec: narrow syntax for expression and select statements

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This is not a language change, it simply expresses the
accepted cases explicitly in the respective productions.

R=rsc, r, iant
CC=golang-dev
https://golang.org/cl/4428057
This commit is contained in:
Robert Griesemer 2011-04-29 09:49:10 -07:00
parent 0add1c3ed8
commit 95f544a199
1 changed files with 6 additions and 7 deletions
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13
doc/go_spec.html
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@ -1,5 +1,5 @@
<!-- title The Go Programming Language Specification --> <!-- title The Go Programming Language Specification -->
<!-- subtitle Version of Apr 22, 2011 --> <!-- subtitle Version of Apr 29, 2011 -->
<!-- <!--
TODO TODO
@ -3035,7 +3035,7 @@ f(&lt;-ch)
</pre> </pre>
<p> <p>
A receive expression used in an assignment or initialization of the form A receive operation used in an assignment or initialization of the form
</p> </p>
<pre> <pre>
@ -3521,13 +3521,14 @@ Error: log.Panic("error encountered")
<h3 id="Expression_statements">Expression statements</h3> <h3 id="Expression_statements">Expression statements</h3>
<p> <p>
Function calls, method calls, and receive operations Function calls, method calls, and
<a href="#Receive_operator">receive operations</a>
can appear in statement context. can appear in statement context.
</p> </p>
<pre class="ebnf"> <pre class="ebnf">
ExpressionStmt = Expression . ExpressionStmt = PrimaryExpr Call | RecvExpr .
RecvExpr = "&lt;-" UnaryExpr .
</pre> </pre>
<pre> <pre>
@ -4087,11 +4088,9 @@ SelectStmt = "select" "{" { CommClause } "}" .
CommClause = CommCase ":" { Statement ";" } . CommClause = CommCase ":" { Statement ";" } .
CommCase = "case" ( SendStmt | RecvStmt ) | "default" . CommCase = "case" ( SendStmt | RecvStmt ) | "default" .
RecvStmt = [ Expression [ "," Expression ] ( "=" | ":=" ) ] RecvExpr . RecvStmt = [ Expression [ "," Expression ] ( "=" | ":=" ) ] RecvExpr .
RecvExpr = Expression .
</pre> </pre>
<p> <p>
RecvExpr must be a <a href="#Receive_operator">receive operation</a>.
For all the cases in the "select" For all the cases in the "select"
statement, the channel expressions are evaluated in top-to-bottom order, along with statement, the channel expressions are evaluated in top-to-bottom order, along with
any expressions that appear on the right hand side of send statements. any expressions that appear on the right hand side of send statements.