"

 COPYRIGHT (c) 1991 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.

"

Collection subclass:#Bag

!

!Bag class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1991 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.

"

!

documentation

"

    Bag implements collections whose elements are unordered and have no

    external key. Elements may occur more than once in a bag. There is no defined

    order within a bag. 

    The default implementation uses a dictionary to store each objects occurence 

    count, using the object itself as key (i.e. using = and hash for inclusion 

    tests).

    There is also an instance creation variant (#identityNew:) creating a

    bag which compares using #== and hashes using #identityHash.

    (I'd say that an IdentityBag was a better thing to implement ... 

     ... but for compatibility ... we do it here as well)

    Instance variables:

	contents        <Dictionary>    for each element, the number of occurrences

"

! !

!Bag class methodsFor:'instance creation'!

equalityNew:size

    "return a new empty Bag with initial space for size elements.

     Elements will be compared using equality compare (i.e. #= not #== identity)."

    ^ super new initContents:size

!

identityNew:size

    "return a new empty Bag with initial space for size elements.

     Elements will be compared using identity compare (i.e. #== not #= equality)."

    ^ super new initContentsForIdentity:size

!

!

! !

!Bag methodsFor:'accessing'!

at:index

    "report an error: at: is not allowed for Bags"

    ^ self errorNotKeyed

!

at:index put:anObject

    "report an error: at:put: is not allowed for Bags"

    ^ self errorNotKeyed

!

contents

    "return the dictionary which associates occurrence-counts

     to the bags elements."

    ^ contents

! !

!Bag methodsFor:'adding & removing'!

add:newObject

    "add the argument, anObject to the receiver.

     Returns the object."

    |n|

    n := contents at:newObject ifAbsent:[0].

    contents at:newObject put:(n + 1).

    ^ newObject

!

add:newObject withOccurences:anInteger

    "add the argument, anObject anInteger times to the receiver.

     Returns the object."

    |n|

    n := contents at:newObject ifAbsent:[0].

    contents at:newObject put:(n + anInteger).

    ^ newObject

!

remove:oldObject ifAbsent:anExceptionBlock

    "Remove oldObject from the collection.

     If it was not present, return the value of the exceptionBlock;

     otherwise return the removed object."

    |count|

    count := contents at:oldObject ifAbsent:[0].

    (count == 0) ifTrue:[^ anExceptionBlock value].

    (count == 1) ifTrue:[

	contents removeKey:oldObject

    ] ifFalse:[ 

	contents at:oldObject put:(count - 1)

    ].

    ^ oldObject

!

removeAllOccurrencesOf:oldObject ifAbsent:anExceptionBlock

    "Remove all occurrences of oldObject from the collection.

     If it was not present, return the value of the exceptionBlock;

     otherwise return the number of removes."

    |count|

    count := contents at:oldObject ifAbsent:[0].

    (count == 0) ifTrue:[^ anExceptionBlock value].

    contents removeKey:oldObject.

    ^ oldObject

! !

!Bag methodsFor:'enumerating'!

do:aBlock

    "evaluate the block for all elements in the collection."

    contents keysAndValuesDo:[:key :value|

	value timesRepeat:[

	    aBlock value:key

	]

    ]

!

valuesAndCountsDo:aTwoArgBlock

    "evaluate the block for all distinct elements in the collection,

     passing both the element and the occurence count as arguments."

    ^ contents keysAndValuesDo:aTwoArgBlock

! !