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"
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This is a Manchester Goodie protected by copyright.
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These conditions are imposed on the whole Goodie, and on any significant
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part of it which is separately transmitted or stored:
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* You must ensure that every copy includes this notice, and that
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source and author(s) of the material are acknowledged.
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* These conditions must be imposed on anyone who receives a copy.
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* The material shall not be used for commercial gain without the prior
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written consent of the author(s).
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Further information on the copyright conditions may be obtained by
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sending electronic mail:
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To: goodies-lib@cs.man.ac.uk
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Subject: copyright
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or by writing to The Smalltalk Goodies Library Manager, Dept of
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Computer Science, The University, Manchester M13 9PL, UK
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(C) Copyright 1992 University of Manchester
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For more information about the Manchester Goodies Library (from which
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this file was distributed) send e-mail:
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To: goodies-lib@cs.man.ac.uk
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Subject: help
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"
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"{ Package: 'stx:libbasic2' }"
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ProtoObject subclass:#Future
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instanceVariableNames:'result semaphore'
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classVariableNames:''
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poolDictionaries:''
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category:'Kernel-Processes'
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!
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!Future class methodsFor:'documentation'!
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copyright
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"
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This is a Manchester Goodie protected by copyright.
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These conditions are imposed on the whole Goodie, and on any significant
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part of it which is separately transmitted or stored:
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* You must ensure that every copy includes this notice, and that
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source and author(s) of the material are acknowledged.
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* These conditions must be imposed on anyone who receives a copy.
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* The material shall not be used for commercial gain without the prior
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written consent of the author(s).
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Further information on the copyright conditions may be obtained by
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sending electronic mail:
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To: goodies-lib@cs.man.ac.uk
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Subject: copyright
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or by writing to The Smalltalk Goodies Library Manager, Dept of
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Computer Science, The University, Manchester M13 9PL, UK
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(C) Copyright 1992 University of Manchester
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For more information about the Manchester Goodies Library (from which
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this file was distributed) send e-mail:
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To: goodies-lib@cs.man.ac.uk
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Subject: help
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484
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"
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!
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documentation
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"
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I represent an execution in progress.
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I will immediately start execution in a separate process.
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Any messages sent to me are delayed until execution has completed.'
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[author:]
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tph@cs.man.ac.uk
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[see also:]
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Block Lazy LazyValue
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"
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!
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examples
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"
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Starts evaluating the factorial immediately, but waits until
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the result is available before printing the answer
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[exBegin]
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| fac |
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fac := [5000 factorial] futureValue.
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Transcript showCR: 'evaluating factorial...'.
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Transcript showCR: fac printString
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[exEnd]
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An example illustrating the use of multiple futures and
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explicit resynchronisation.
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Starts evaluating both factorials immediately, but waits until
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both blocks have finished before continuing.
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[exBegin]
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| fac1 fac2 |
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fac1 := [Transcript showCR: 'Starting fac1.. '. 1000 factorial] futureValue.
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fac2 := [Transcript showCR: 'Starting fac2.. '. 2000 factorial] futureValue.
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fac2 isString.
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fac1 isString.
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Transcript showCR: 'both completed.'.
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[exEnd]
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Example showing how arguments may be passed to futures.
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[exBegin]
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| temp |
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temp := [:x :y | 10 * x * y] futureValue: 3 value: 4.
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Transcript showCR: temp printString.
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[exEnd]
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Claus:
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The above examples do not really show the power of Futures;
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they can be useful, whenever some long-time computation is
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to be done, and some other useful work can be done in the meanwhile.
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for example:
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Here, the input is read before - the readTime and view creation
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times sum up:
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[exBegin]
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|p text v|
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p := PipeStream readingFrom:'ls -l /bin /usr/bin /usr/lib'.
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text := p contents.
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p close.
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v := TextView new openAndWait.
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v contents:text
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[exEnd]
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The same here:
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[exBegin]
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|p text v|
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v := TextView new openAndWait.
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p := PipeStream readingFrom:'ls -l /bin /usr/bin /usr/lib'.
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text := p contents.
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p close.
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v contents:text
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[exEnd]
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Here, the view creation and reading are done in parallel:
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(if the user is slow when opening the view, the contents may
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be already available)
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[exBegin]
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|p text v|
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text := [ |p t|
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p := PipeStream readingFrom:'ls -l /bin /usr/bin /usr/lib'.
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t := p contents.
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p close.
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t
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] futureValue.
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v := TextView new openAndWait.
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v contents:text
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[exEnd]
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"
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! !
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!Future methodsFor:'evaluating'!
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block: aBlock
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"Execute aBlock in parallel with whatever called me, but
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ensure that any messages sent to me before execution
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of the block has terminated are suspended until it has terminated."
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semaphore := Semaphore new name:'Future'.
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[result := aBlock ensure:[semaphore signal]] fork
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!
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block: aBlock value: aValue
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"Execute aBlock in parallel with whatever called me, but
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ensure that any messages sent to me before execution
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of the block has terminated are suspended until it has terminated."
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semaphore := Semaphore new name:'Future'.
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[
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result := [
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aBlock value:aValue
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] ensure:[semaphore signal]
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] fork
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!
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block: aBlock value: value1 value: value2
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"Execute aBlock in parallel with whatever called me, but
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ensure that any messages sent to me before execution
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of the block has terminated are suspended until it has terminated."
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semaphore := Semaphore new name:'Future'.
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[
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result := [
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aBlock value: value1 value: value2
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] ensure:[semaphore signal]
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] fork
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!
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block: aBlock value: value1 value: value2 value: value3
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"Execute aBlock in parallel with whatever called me, but
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ensure that any messages sent to me before execution
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of the block has terminated are suspended until it has terminated."
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semaphore := Semaphore new name:'Future'.
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[
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result := [
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aBlock value: value1 value: value2 value: value3
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] ensure:[semaphore signal]
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] fork
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!
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block: aBlock valueWithArguments: anArray
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"Execute aBlock in parallel with whatever called me, but
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ensure that any messages sent to me before execution
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of the block has terminated are suspended until it has terminated."
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semaphore := Semaphore new name:'Future'.
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[
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result := [
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aBlock valueWithArguments: anArray
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] ensure:[semaphore signal]
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] fork
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! !
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!Future methodsFor:'synchronising'!
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doesNotUnderstand:aMessage
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"Any message to a Future will end up here."
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semaphore waitUncounted. "Wait for evaluation to complete"
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"(if not already completed)"
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^ result perform:aMessage selector withArguments:aMessage arguments
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! !
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!Future methodsFor:'testing'!
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hasValue
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^ semaphore wouldBlock not
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!
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isLazyValue
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^ semaphore wouldBlock
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! !
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!Future class methodsFor:'documentation'!
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version
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^ '$Header: /cvs/stx/stx/libbasic2/Future.st,v 1.11 2009-11-19 15:38:25 cg Exp $'
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! !
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