"{ Encoding: utf8 }"

"

 COPYRIGHT (c) 2012 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:libbasic2' }"

"{ NameSpace: Smalltalk }"

SequenceableCollection subclass:#VirtualArray

	instanceVariableNames:'generator size'

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Arrayed'

!

!VirtualArray class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 2012 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

"

    An Array which computes its values on demand and does NOT remember those values.

    This does not use any memory for the elements - however, trading speed for size, this

    takes longer to access elements, as they are computed on the fly (for every access).

    Use this to present huge files/hex dumps to a text editor.

    [author:]

        Claus Gittinger

    [see also:]

        LazyArray

"

!

examples

"

                                                                [exBegin]

    |squaresLines|

    squaresLines := VirtualArray new:100000.

    squaresLines generator:[:index | index squared printString].

    squaresLines inspect.

    (TextView openWith:#()) list:squaresLines expandTabs:false

                                                                [exEnd]

"

! !

!VirtualArray class methodsFor:'instance creation'!

new:size

     ^ self new setSize:size.

    "Created: / 01-03-2019 / 20:30:21 / Claus Gittinger"

! !

!VirtualArray methodsFor:'accessing'!

generator

    "the element value generator; a block which gets the index as argument"

    ^ generator

!

generator:aBlock

    "set the element value generator; a block which gets the index as argument"

    generator := aBlock.

!

setSize:anInteger 

    size := anInteger.

!

size

    "the virtual size"

    ^ size

! !

!VirtualArray methodsFor:'collection protocol'!

at:index

    ^ generator value:index

    "Created: / 27-02-2012 / 20:40:03 / cg"

!

at:index put:value

    self noModificationError.

    "Created: / 27-02-2012 / 20:40:33 / cg"

!

grow:howBig

    "change the receiver's size"

    self setSize:howBig

! !

!VirtualArray methodsFor:'inspecting'!

displayOn:aGCOrStream

    "print a representation of the receiver on aGCOrStream for display in inspectors etc."

    "/ what a kludge - Dolphin and Squeak mean: printOn: a stream;

    "/ old ST80 means: draw-yourself on a GC.

    (aGCOrStream isStream) ifFalse:[

        ^ super displayOn:aGCOrStream

    ].

    aGCOrStream nextPutAll:('VirtualArray(size=%1, generator=%2)' 

                                bindWith:size with:generator printString).

    "Modified (comment): / 22-02-2017 / 16:49:54 / cg"

! !

!VirtualArray methodsFor:'queries'!

species

    "return the type of collection to be returned by collect, select etc."

    ^ OrderedCollection

! !

!VirtualArray class methodsFor:'documentation'!

version

    ^ '$Header$'

!

version_CVS

    ^ '$Header$'

! !