"

 COPYRIGHT (c) 1988 by Claus Gittinger

              All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

Object subclass:#Boolean

       instanceVariableNames:''

       classVariableNames:''

       poolDictionaries:''

       category:'Kernel-Objects'

!

Boolean comment:'

COPYRIGHT (c) 1988 by Claus Gittinger

              All Rights Reserved

Boolean is an abstract class defining the common protocol for logical

values. The logical values are represented by its two subclasses True and False.

There are no instances of Boolean in the system and there is only one

instance of True (which is the global true) and one of False (false).

Boolean catches some messages which deal with copying Booleans to make

certain there is only one instance of each.

The system will behave strange if you fiddle around here and create

new instances of True or False.

written 1988 by claus

$Header: /cvs/stx/stx/libbasic/Boolean.st,v 1.7 1994-02-25 12:54:43 claus Exp $

'!

!Boolean class methodsFor:'instance creation'!

basicNew

    "catch instance creation

     - there must be exactly one instance of each - no more"

    self error:'new instances of True/False are not allowed'

! !

!Boolean class methodsFor:'queries'!

isBuiltInClass

    "this class is known by the run-time-system"

    ^ true

! !

!Boolean methodsFor:'copying'!

shallowCopy

    "return a shallow copy of the receiver

     - since both true and false are unique, return the receiver"

    ^ self

!

deepCopy

    "return a deep copy of the receiver

     - since both true and false are unique, return the receiver"

    ^ self

!

deepCopyUsing:aDictionary

    "return a deep copy of the receiver

     - since both true and false are unique, return the receiver"

    ^ self

!

simpleDeepCopy

    "return a deep copy of the receiver

     - since both true and false are unique, return the receiver"

    ^ self

! !

!Boolean methodsFor:'printing & storing'!

printOn:aStream

    "append a character sequence representing the receiver to the argument,

     aStream"

    aStream nextPutAll:self printString

!

storeString

    "return  a character sequence to the argument, aStream from which the

     receiver can be reconstructed."

    ^ self printString

!

storeOn:aStream

    "append a character sequence to the argument, aStream from which the

     receiver can be reconstructed."

    ^ self printOn:aStream

! !

!Boolean methodsFor: 'binary storage'!

hasSpecialBinaryRepresentation

    "return true, if the receiver has a special binary representation"

        ^true

! !