"{ Package: 'stx:goodies' }"

SequenceableCollection subclass:#ReindexedCollection

	instanceVariableNames:'sequence interval'

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Sequenceable'

!

!ReindexedCollection class methodsFor:'documentation'!

documentation

"

    ReindexedCollection is a wrapper around a sequenceable collection that remaps the indices 

    with in linear algorithm.  

    The elements in the ReindexedCollection are elements in the sequenceable collection at 

    some start to some stop at some step.  

    ReindexedCollection allows for efficient use of first/rest-like algorithms (i.e. aka Lisp)

    applied to Sequenceable collections, as they avoid element-copying.

    See class side examples.

    [Instance Variables:]

        sequence        <SequenceableCollection>        the sequence that will be reindexed.

        interval        <Interval>      the object that describes indicies of interest in the sequence.

    [Origin:]

        Part of the Engineering Math Goodies package from Travis.

    [Author:]

        Travis Griggs (tgriggs@keyww.com or tkc@bmi.net)

        Ported from Squeak by Claus Gittinger (not much of a port, though)

"

!

examples

"

    |coll|

    |coll|

    coll := (1 to:10) asOrderedCollection from:3 to:8.

    coll.     

    coll size.  

    coll at:1.   

    coll do:[:each | Transcript showCR:each].

    |coll|

    coll := (1 to:10) asOrderedCollection to:4.

    coll.     

    coll size.  

    coll at:1.   

    coll last.   

    coll do:[:each | Transcript showCR:each].

"

! !

!ReindexedCollection class methodsFor:'instance creation'!

on: aSequence from: start 

    "Create a reindexedCollection on aSequence from start to the end of aSequence"

    ^ self

        on: aSequence

        from: start

        to: aSequence size

        by: 1

!

on: aSequence from: start by: step 

    "Create a reindexedCollection on aSequence start to the end of aSequence 

     if step is positive, else  

     from start to the beginning of the sequence if step is negative."

    ^ self

        on: aSequence

        from: start

        to: (step > 0

                ifTrue: [aSequence size]

                ifFalse: [1])

        by: step

!

on: aSequence from: start to: stop 

    "Create a reindexedCollection on aSequence from start to stop by 1 

     (or -1 if start is greater than stop)"

    ^ self

        on: aSequence

        from: start

        to: stop

        by: (start <= stop

                ifTrue: [1]

                ifFalse: [-1])

!

on: aSequence from: start to: stop by: step 

    "Create a reindexedCollection on aSequence from start to stop by step"

    ^ self new

            initialize: aSequence

            from: start

            to: stop

            by: step

!

on: aSequence to: stop 

    "Create a reindexedCollection on aSequence from 1 to stop by 1"

    ^ self

        on: aSequence

        from: 1

        to: stop

        by: 1

!

on: aSequence to: stop by: step 

    "Create a reindexedCollection on aSequence from 1 to stop (if step is 

     positive) or the end to stop (if  

     step is negative). Note: if step is not 1 or -1, there is a chance that the 

     index specified by stop may  

     not be in the interval."

    ^ self

        on: aSequence

        from: (step > 0

                ifTrue: [1]

                ifFalse: [aSequence size])

        to: stop

        by: step

!

on: aSequence with: anInterval 

    "Create a reindexedCollection on aSequence"

    ^ self new initialize: aSequence with: anInterval

! !

!ReindexedCollection methodsFor:'accessing'!

at: index 

    "Answer the value of an indexable field in the sequence instance variable. "

    ^ sequence at: (interval at: index)

!

at: index put: value 

    "Store the argument value in the indexable field of the sequence 

     instance variable indicated by index.  

     Answer the value that was stored."

    ^ sequence at: (interval at: index) put: value

!

size

    "Answer how many elements the receiver contains."

    ^ interval size

!

slide

    "slide by 1"

    self slide: 1

!

slide: anIncrement 

    "given an increment, adjust the reindex map by sliding it that far"

    interval := interval + anIncrement

! !

!ReindexedCollection methodsFor:'adding & removing'!

add: anObject 

    self shouldNotImplement

! !

!ReindexedCollection methodsFor:'converting-reindexed'!

from:startIndex

    "return a new collection representing the receivers elements starting at startIndex."

    interval step == 1 ifTrue:[

        ^ ReindexedCollection 

            on:sequence 

            from:(interval start + startIndex - 1) 

            to:(interval stop)

            by:(interval step)

    ].

    "could be more intelligent here..."

    ^ super from:startIndex

    "

     |coll cdr cddr cdddr|

     coll := #(1 2 3 4 5 6 7 8 9 10).

     cdr := coll from:2.            

     cddr := cdr from:2.        

     cdddr := cddr from:2.

    "

!

from:startIndex to:stopIndex

    "return a new collection representing the receivers elements 

     starting at startIndex upTo and including endIndex."

    interval step == 1 ifTrue:[

        ^ ReindexedCollection 

            on:sequence 

            from:(interval start + startIndex - 1) 

            to:((interval start + stopIndex - 1) min:interval stop)

            by:1

    ].

    "could be more intelligent here..."

    ^ super from:startIndex to:stopIndex

    "

     |coll cdrButLast cddrButLast2 cdddrButLast3|

     coll := #(1 2 3 4 5 6 7 8 9 10).

     cdrButLast := coll from:2 to:9.             

     cddrButLast2 := cdrButLast from:2 to:7.          

     cdddrButLast3 := cddrButLast2 from:2 to:5.     

    "

    "

     |coll cdrButLast cddrButLast2 cdddrButLast3|

     coll := 1 to:100.

     cdrButLast := coll from:2 to:99.             

     cddrButLast2 := cdrButLast from:2 to:97.          

     cdddrButLast3 := cddrButLast2 from:2 to:95.     

    "

!

to:stopIndex

    "return a new collection representing the receivers elements upTo and including endIndex."

    interval step == 1 ifTrue:[

        ^ ReindexedCollection 

            on:sequence 

            from:(interval start) 

            to:((interval start + stopIndex - 1) min:interval stop)

            by:1

    ].

    "could be more intelligent here..."

    ^ super to:stopIndex

    "

     |coll butLast butLast2 butLast3|

     coll := #(1 2 3 4 5 6 7 8 9 10).

     butLast := coll to:9.              

     butLast2 := butLast to:8.          

     butLast3 := butLast2 to:7.     

    "

! !

!ReindexedCollection methodsFor:'initialization'!

initialize: aSequence from: start to: stop by: step 

    sequence := aSequence.

    interval := Interval from: start to: stop by: step

!

initialize: aSequence with: anInterval 

        sequence := aSequence.

        interval := anInterval

! !

!ReindexedCollection methodsFor:'queries'!

species

    "Answer the preferred class for reconstructing the receiver, that is, the sequence."

    ^ sequence species

! !

!ReindexedCollection class methodsFor:'documentation'!

version

! !