"
 COPYRIGHT (c) 1993 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.
"

Set subclass:#IdentitySet
         instanceVariableNames:''
         classVariableNames:''
         poolDictionaries:''
         category:'Collections-Unordered'
!

IdentitySet comment:'

COPYRIGHT (c) 1993 by Claus Gittinger
              All Rights Reserved

same as a Set but compares elements using == (i.e. they must be identical
- not just equal in structure).
Since compare is on identity, hashing is also done via
identityHash instead of hash.

%W% %E%

written jan 93 by claus
'!

!IdentitySet methodsFor:'private'!

find:key ifAbsent:aBlock
    "Look for the key in the receiver.  If it is found, return
     the index of the slot containing the key, otherwise
     return the value of evaluating aBlock.
     Redefined to compare for identity instead of equality"

    |index      "{ Class:SmallInteger }"
     length     "{ Class:SmallInteger }"
     startIndex "{ Class:SmallInteger }" 
     probe |

    length := contentsArray basicSize.
    startIndex := key identityHash \\ length + 1.

    index := startIndex.
    [true] whileTrue:[
        probe := (contentsArray basicAt:index).
        probe == key ifTrue:[^ index].
        probe isNil ifTrue:[^ aBlock value].

        index == length ifTrue:[
            index := 1
        ] ifFalse:[
	    index := index + 1
	].
        index == startIndex ifTrue:[
            ^ aBlock value
        ]
    ]
!

findElementOrNil:key
    "Look for the key in the receiver.  Redefined to compare for
     identity instead of equality"

    |index      "{ Class:SmallInteger }"
     length     "{ Class:SmallInteger }"
     startIndex "{ Class:SmallInteger }"
     probe |

    length := contentsArray basicSize.
    startIndex := key identityHash \\ length + 1.

    index := startIndex.
    [true] whileTrue:[
        probe := contentsArray basicAt:index.
        (probe isNil or: [key == probe]) ifTrue:[^ index].

        index == length ifTrue:[
            index := 1
        ] ifFalse:[
	    index := index + 1
	].
        index == startIndex ifTrue: [
            ^ self grow findElementOrNil:key
        ]
    ]
! !