Modern Chan Channel IsNil

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IsNil

Returns true for a default-constructed channel, which blocks forever if used.

Syntax

IsNil( ) as boolean

Notes

• A nil channel blocks forever on Send and Receive. That is Go's rule, and it looks like a defect until select arrives -- where assigning a nil channel is how a case is disabled.
• This exists so a program can assert its own initialisation, because "my program hangs" is the symptom of forgetting it.
• Close on a nil channel raises.

Examples

#import "std/tasks"
using tasks

dim ch as Channel( of int32 )
print ch.IsNil( )            '' true -- default-constructed

'' Assert initialisation before anything blocks on it, because the
'' symptom of forgetting is a hang with no message
if ch.IsNil( ) then print "not initialised"

ch = Channel( of int32 )( 4 )
print ch.IsNil( )            '' false

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