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| -rw-r--r-- | doc/go_spec.html | 38 |
1 files changed, 18 insertions, 20 deletions
diff --git a/doc/go_spec.html b/doc/go_spec.html index 1cbab6dff..b37d1c357 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -1,5 +1,5 @@ <!-- title The Go Programming Language Specification --> -<!-- subtitle Version of May 4, 2010 --> +<!-- subtitle Version of May 7, 2010 --> <!-- Todo @@ -1154,41 +1154,39 @@ A value of channel type may be <code>nil</code>. </p> <pre class="ebnf"> -ChannelType = Channel | SendChannel | RecvChannel . -Channel = "chan" ElementType . -SendChannel = "chan" "<-" ElementType . -RecvChannel = "<-" "chan" ElementType . +ChannelType = ( "chan" [ "<-" ] | "<-" "chan" ) ElementType . </pre> <p> -To avoid a parsing ambiguity in cases such as <code>chan<- chan int</code>, -the Channel production's ElementType cannot be a RecvChannel. -To construct such a type, parenthesize the RecvChannel first. +The <code><-</code> operator specifies the channel <i>direction</i>, +<i>send</i> or <i>receive</i>. If no direction is given, the channel is +<i>bi-directional</i>. +A channel may be constrained only to send or only to receive by +<a href="#Conversions">conversion</a> or <a href="#Assignments">assignment</a>. </p> <pre> -chan<- chan int // same as chan<- (chan int) -chan<- <-chan int // same as chan<- (<-chan int) -<-chan <-chan int // same as <-chan (<-chan int) -chan (<-chan int) +chan T // can be used to send and receive values of type T +chan<- float // can only be used to send floats +<-chan int // can only be used to receive ints </pre> <p> -Upon creation, a channel can be used both to send and to receive values. -By conversion or assignment, a channel may be constrained only to send or -to receive. This constraint is called a channel's <i>direction</i>; either -<i>send</i>, <i>receive</i>, or <i>bi-directional</i> (unconstrained). +The <code><-</code> operator associates with the leftmost <code>chan</code> +possible: </p> <pre> -chan T // can be used to send and receive values of type T -chan<- float // can only be used to send floats -<-chan int // can only be used to receive ints +chan<- chan int // same as chan<- (chan int) +chan<- <-chan int // same as chan<- (<-chan int) +<-chan <-chan int // same as <-chan (<-chan int) +chan (<-chan int) </pre> <p> The value of an uninitialized channel is <code>nil</code>. A new, initialized channel -value can be made using the built-in function <code>make</code>, +value can be made using the built-in function +<a href="#Making_slices_maps_and_channels"><code>make</code></a>, which takes the channel type and an optional capacity as arguments: </p> |