Modern Chan Spawn

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Spawn

Runs a procedure alongside the program, copying its arguments at that moment.

Syntax

spawn Procedure( [ args ] )

Notes

• A statement, not a function -- spawn Worker( a, b ) is compiler syntax, and its arguments are copied at the spawn point, so a loop variable does not race with the goroutine that captured it.
• It returns nothing and there is no handle: a goroutine is not joinable. Use a WaitGroup to wait for a fan-out, or a channel to collect results.
• The work runs on a pool of OS threads, so a goroutine that blocks in a syscall occupies a worker for the duration.
• Requires -mt.

Examples

#import "std/tasks"
using tasks

'' THE SHAPE, with the Add BEFORE the spawn -- never inside the
'' goroutine, or Wait can see zero and return before the worker starts:
''
''     dim wg as WaitGroup
''     for i as long = 1 to 4
''         wg.Add( )
''         spawn Worker( i, @wg )   '' Worker does `defer wg->Done( )`
''     next
''     wg.Wait( )
''
'' Note that every Add MUST be matched by a Done, or Wait never returns.
dim wg as WaitGroup
print wg.Count( )            '' 0 -- nothing outstanding
wg.Wait( )                   '' so this returns at once
print "all done"

'' The arguments are COPIED at the spawn point, which is what makes
'' `spawn Work( i )` inside a loop safe

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Library: Goroutines and Channels
Category: Goroutines and Channels
Documented under: Members