"

 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.

"

"{ Package: 'stx:libbasic' }"

Collection subclass:#Bag

	instanceVariableNames:'contents'

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Unordered'

!

!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 occurrence

    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

    [author:]

	Claus Gittinger

    [See also:]

	Set IdentitySet

	Dictionary IdentityDictionary

	OrderedCollection Array

"

! !

!Bag class methodsFor:'instance creation'!

contentsClass

    "the default class to use for the underlying contents array,

     used when instantiated with new/new:"

    ^ Dictionary

!

equalityNew

    "return a new empty Bag.

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

    ^ self basicNew initContentsForEquality

!

equalityNew:size

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

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

    ^ self basicNew initContentsForEquality:size

!

identityNew

    "return a new empty Identity-Bag.

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

    ^ self basicNew initContentsForIdentity

!

identityNew:size

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

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

    ^ self basicNew initContentsForIdentity:size

!

new

    "return a new empty Bag which compares for equality (i.e. not identity)"

    ^ self basicNew initContents

!

new:size

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

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

    ^ self equalityNew:size

! !

!Bag methodsFor:'Compatibility-Dolphin'!

asAssociations

    "return the dictionary which associates occurrence-counts

     to the bags elements. 

     Same as #contents for dolphin compatibility."

    ^ self contents

! !

!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 (sigh).

     WARNING: do not add/remove elements while iterating over the receiver.

              Iterate over a copy to do this."

    |n|

    n := contents at:newObject ifAbsent:0.

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

    ^ newObject

    "Modified: 1.3.1996 / 21:43:06 / cg"

!

add:newObject withOccurrences:anInteger

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

     Returns the object.

     WARNING: do not add/remove elements while iterating over the receiver.

	      Iterate over a copy to do this."

    |n|

    n := contents at:newObject ifAbsent:0.

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

    ^ newObject

    "Modified: 1.3.1996 / 21:43:12 / cg"

    "Created: 11.5.1996 / 12:13:43 / cg"

!

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.

     WARNING: do not add/remove elements while iterating over the receiver.

	      Iterate over a copy to do this."

    |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

    "Modified: 1.3.1996 / 21:43:18 / cg"

!

removeAll

    "remove all objects from the receiver collection (i.e. make it empty).

     Returns the receiver."

    contents := contents species new.

    "

     |b|

     b := Bag new.

     b add:1; add:2; add:3; add:2; add:1.

     Transcript showCR:b.

     b removeAll.

     Transcript showCR:b

    "

    "Modified: 12.4.1996 / 13:34:34 / cg"

!

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.

     WARNING: do not add/remove elements while iterating over the receiver.

	      Iterate over a copy to do this."

    |count|

    count := contents at:oldObject ifAbsent:0.

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

    contents removeKey:oldObject.

    ^ oldObject

    "Modified: 1.3.1996 / 21:43:26 / cg"

! !

!Bag methodsFor:'bulk operations'!

sum

    "sum up all elements; return 0 for an empty collection.

     can be done easier, using bags knowledge."

    |accu|

    self isEmpty ifTrue:[ ^ 0 ].

    accu := nil.

    self 

        valuesAndCountsDo:[:n :count |

            |thisAmount|

            thisAmount := count * n.

            accu := (accu isNil ifTrue:[thisAmount] ifFalse:[accu + thisAmount]) ].

    ^ accu

    "

     TestCase assert:((Bag new add:1; add:2; add:3; add:1; add:2; add:1; yourself) sum = 10).

    "

! !

!Bag methodsFor:'comparing'!

= aBag

    "Compare the receiver with the argument and return true if the

     receiver is equal to the argument (i.e. has the same size and elements).

     Otherwise return false."

    aBag species == self species ifFalse:[^ false].

    self size == aBag size ifFalse:[^ false].

    self valuesAndCountsDo:[:val :cnt |

        (aBag occurrencesOf:val) == cnt ifFalse:[^ false]

    ].

    ^ true

!

hash

    "return an integer useful for hashing on the receiver;

     redefined since = is redefined here."

    |h|

    h := self size.

    self valuesAndCountsDo:[:val :cnt |

        h := h + cnt hash.

    ].

    ^ h

! !

!Bag methodsFor:'converting'!

asBag

    "return the receiver as a bag"

    "could be an instance of a subclass..."

    self class == Bag ifTrue:[

	^ self

    ].

    ^ super asBag

!

asSet

    "return the receiver as a set"

    ^ contents keys copy

    "

     |b|

     b := Bag new.

     b add:1; add:2; add:3; add:1; add:1.

     b asSet.

    "

! !

!Bag methodsFor:'copying'!

postCopy

    "must copy the contents as well"

    contents := contents copy

! !

!Bag methodsFor:'enumerating'!

do:aBlock

    "evaluate the block for all elements in the collection.

     WARNING: do not add/remove elements while iterating over the receiver.

	      Iterate over a copy to do this."

    contents keysAndValuesDo:[:key :value|

	value timesRepeat:[

	    aBlock value:key

	]

    ]

    "Modified: 1.3.1996 / 21:42:39 / cg"

!

valuesAndCounts

    "return an orderedCollection containing value->count associations"

    |coll|

    coll := OrderedCollection new.

    self valuesAndCountsDo:[:value :count | coll add:(value->count)].

    ^ coll

    "Modified: 1.3.1996 / 21:42:44 / cg"

!

valuesAndCountsDo:aTwoArgBlock

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

     passing both the element and the occurrence count as arguments.

     WARNING: do not add/remove elements while iterating over the receiver.

	      Iterate over a copy to do this."

    ^ contents keysAndValuesDo:aTwoArgBlock

    "Modified: 1.3.1996 / 21:42:44 / cg"

! !

!Bag methodsFor:'printing & storing'!

printElementsDo:aBlock

    self valuesAndCountsDo:[:value :count|

        aBlock value:('%1(*%2)' bindWith:value with:count).

    ]

! !

!Bag methodsFor:'private'!

initContents

    "set the contents to be an empty Dictionary.

     This is the default method for initialization, which can be redefined in subclasses."

    contents := self class contentsClass new

!

initContents:size

    "set the contents to be an empty Dictionary with initial size.

     This is the default method for initialization, which can be redefined in subclasses."

    contents := self class contentsClass new: size

!

initContentsForEquality

    "set the contents to be an empty Dictionary"

    contents := Dictionary new

!

initContentsForEquality:size

    "set the contents to be an empty Dictionary with initial size"

    contents := Dictionary new:size

!

initContentsForIdentity

    "set the contents to be an empty IdentityDictionary"

    contents := IdentityDictionary new

!

initContentsForIdentity:size

    "set the contents to be an empty IdentityDictionary with initial size"

    contents := IdentityDictionary new:size

! !

!Bag methodsFor:'queries'!

size

    "return the number of bag elements"

    |count|

    count := 0.

    contents do:[:element | count := count + element].

    ^ count

! !

!Bag methodsFor:'testing'!

includes:anObject

    "return true, if anObject is in the receiver"

    ^ (self occurrencesOf:anObject) > 0

!

occurrencesOf:anObject

    "return how many times anObject is in the receiver"

    ^ contents at:anObject ifAbsent:0

! !

!Bag class methodsFor:'documentation'!

version

!

version_CVS

! !