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defer statement

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Robert Griesemer 2009-01-27 09:29:40 -08:00
parent fa615a3b30
commit 4a903e0b32
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34
doc/go_spec.txt
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@ -3,7 +3,7 @@ The Go Programming Language Specification (DRAFT)
Robert Griesemer, Rob Pike, Ken Thompson
(January 23, 2009)
(January 26, 2009)
----
@ -235,6 +235,7 @@ Contents
Continue statements
Label declaration
Goto statements
Defer statements
Function declarations
Method declarations
@ -682,8 +683,8 @@ Reserved words
The following words are reserved and must not be used as identifiers:
break default func interface select
case else go map struct
chan goto package switch
case defer go map struct
chan else goto package switch
const fallthrough if range type
continue for import return var
@ -2501,7 +2502,8 @@ Statements control execution.
Statement =
Declaration | LabelDecl | EmptyStat |
SimpleStat | GoStat | ReturnStat | BreakStat | ContinueStat | GotoStat |
FallthroughStat | Block | IfStat | SwitchStat | SelectStat | ForStat .
FallthroughStat | Block | IfStat | SwitchStat | SelectStat | ForStat |
DeferStat .
SimpleStat =
ExpressionStat | IncDecStat | Assignment | SimpleVarDecl .
@ -3015,6 +3017,30 @@ clause of the switch statement.
FallthroughStat = "fallthrough" .
Defer statements
----
A defer statement invokes a function whose execution is deferred to the moment
when the surrounding function returns.
DeferStat = "defer" Expression .
The expression must be a function call. Each time the defer statement executes,
the parameters to the function call are evaluated and saved anew but the
function is not invoked. Immediately before the innermost function surrounding
the defer statement returns, but after its return value (if any) is evaluated,
each deferred function is executed with its saved parameters. Deferred functions
are executed in LIFO order.
lock(l);
defer unlock(l); // unlocking happens before surrounding function returns
// prints 3 2 1 0 before surrounding function returns
for i := 0; i <= 3; i++ {
defer print(i);
}
----
Function declarations