"

 COPYRIGHT (c) 2003 by eXept Software AG

              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:libbasic2' }"

"{ NameSpace: Smalltalk }"

CacheDictionary subclass:#CacheDictionaryWithFactory

	instanceVariableNames:'factoryBlock'

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Unordered'

!

!CacheDictionaryWithFactory class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 2003 by eXept Software AG

              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

"

    like a Dictionary, but does not grow beyond a given max. size

    (i.e. only keeps size items),

    It can be used as a cache, for keeping recently used objects alive.

    Must be created with an initial (=maximal) size. 

    In addition to the normal CacheDictionary, 

    this also keeps a factoryBlock to automatically compute missing elements.

    [author:]

        Claus Gittinger (cg@alan)

    [see also:]

        CacheDictionary

        Dictionary

"

!

examples

"

  caches reverse strings (stupid usage)

                                                                [exBegin]

    |c|

    c := CacheDictionaryWithFactory

            new:100 factory:[:key | key reversed].

    c at:'hello'.

    c at:'hello'.

    1 to:1000 do:[:i | c at:i printString].

    c at:'hello'.

                                                                [exEnd]

  Test: should halt (compute 'hello') only twice.

                                                                [exBegin]

    |c numHalts|

    numHalts := 0.

    c := CacheDictionaryWithFactory

            new:100 factory:[:key | key = 'hello' ifTrue:[numHalts := numHalts + 1]. key reversed].

    c at:'hello'.

    c at:'hello'.

    1 to:1000 do:[:i | c at:i printString].

    c at:'hello'.

    self assert:( numHalts == 2 ).

                                                                [exEnd]

"

! !

!CacheDictionaryWithFactory class methodsFor:'instance creation'!

new:cacheSize factory:aBlock

    ^ (self new:cacheSize) factory:aBlock

! !

!CacheDictionaryWithFactory methodsFor:'accessing'!

at:key

    ^ super at:key ifAbsentPut:[factoryBlock value:key]

! !

!CacheDictionaryWithFactory methodsFor:'initialization'!

factory:aBlock

    factoryBlock := aBlock

! !

!CacheDictionaryWithFactory class methodsFor:'documentation'!

version

    ^ '$Header$'

! !