"
 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' }"

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 (i.e. only keeps size items),
    and also keeps a factoryBlock ,to automatically compute missing elements.

    [author:]
        Claus Gittinger (cg@alan)

    [instance variables:]

    [class variables:]

    [see also:]

"
!

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: /cvs/stx/stx/libbasic2/CacheDictionaryWithFactory.st,v 1.1 2003-05-09 17:15:11 cg Exp $'
! !