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"
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COPYRIGHT (c) 1988 by Claus Gittinger
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All Rights Reserved
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This software is furnished under a license and may be used
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only in accordance with the terms of that license and with the
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inclusion of the above copyright notice. This software may not
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be provided or otherwise made available to, or used by, any
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other person. No title to or ownership of the software is
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hereby transferred.
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"
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Boolean subclass:#False
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instanceVariableNames:''
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classVariableNames:''
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poolDictionaries:''
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category:'Kernel-Objects'
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!
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False comment:'
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88
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COPYRIGHT (c) 1988 by Claus Gittinger
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All Rights Reserved
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'!
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1
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88
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!False class methodsFor:'documentation'!
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copyright
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"
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COPYRIGHT (c) 1988 by Claus Gittinger
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38
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All Rights Reserved
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1
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88
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This software is furnished under a license and may be used
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only in accordance with the terms of that license and with the
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inclusion of the above copyright notice. This software may not
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be provided or otherwise made available to, or used by, any
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other person. No title to or ownership of the software is
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hereby transferred.
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"
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!
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1
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88
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version
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"
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$Header: /cvs/stx/stx/libbasic/False.st,v 1.7 1994-06-02 16:20:14 claus Exp $
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"
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!
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documentation
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"
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False has only one instance, false, representing logical falsehood.
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Some methods are implemented here and in True, instead of the common
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superclass Boolean. This has the advantage, that no truth-value checks
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are needed, but instead the thruth check is done in the method lookup.
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However, remember that some messages to booleans are inline coded in
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the compilers (both interpreted and machine code). Therefore redefinition
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of some methods here will not have any effect on compiled code.
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(redefining ifTrue: to something else will probably crash the smalltalk
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world anyway ...)
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"
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! !
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!False methodsFor:'logical operations'!
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& aBoolean
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"return true, if both the receiver and the argument are true
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(since the receiver is false, return false)"
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^ false
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!
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| aBoolean
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"return true, if either the receiver or the argument is true
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(since the receiver is false, return the argument)"
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^ aBoolean
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!
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not
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"return true, if the receiver is false, false otherwise
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(since the receiver is false, return true)"
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^ true
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!
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eqv:aBoolean
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"return true, if the receiver and the argument are the same truth value
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(since the receiver is false, return true if the argument is also false)"
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^ aBoolean not
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!
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xor:aBoolean
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"return true, if the receiver and the argument are different truth values
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(since the receiver is false, return true, if the armument is not false)"
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^ aBoolean
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! !
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!False methodsFor:'conditional evaluation'!
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and:aBlock
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"evaluate aBlock if the receiver is true.
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(since the receiver is false return false).
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- open coded by compiler"
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^ self
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!
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or:aBlock
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"evaluate aBlock if the receiver is false.
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(since the receiver is false return the value of evaluating aBlock).
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- open coded by compiler"
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^ aBlock value
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!
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ifFalse:aBlock
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"return the value of evaluating aBlock if the receiver is false.
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(since the receiver is known to be false always evaluate)
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- open coded by compiler"
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^ aBlock value
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!
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ifTrue:aBlock
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"return the false alternative, nil (since the receiver is false)
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- open coded by compiler"
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^ nil
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!
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ifTrue:trueBlock ifFalse:falseBlock
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"return the value of evaluating falseBlock (since the receiver is false)
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- open coded by compiler"
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^ falseBlock value
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!
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ifFalse:falseBlock ifTrue:trueBlock
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"return the value of evaluating falseBlock (since the receiver is false)
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- open coded by compiler"
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^ falseBlock value
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! !
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!False methodsFor: 'printing'!
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printString
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"return character sequence representing the receiver"
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1
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^ 'false'
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! !
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2
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!False methodsFor: 'binary storage'!
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storeBinaryOn: stream manager: manager
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"store a binary representation of the receiver on stream;
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redefined, since false is stored with a special type-code"
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2
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stream nextPut: manager codeForFalse
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! !
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