Class: ReindexedCollection

• Inheritance
• Description
• Class protocol
  • instance creation
• Instance protocol
  • accessing
  • adding & removing
  • converting-reindexed
  • copying
  • initialization
  • queries
• Examples

Inheritance:

   Object
   |
   +--Collection
      |
      +--SequenceableCollection
         |
         +--ReindexedCollection

Package:

stx:libbasic2

Category:

Collections-Sequenceable

Version:

rev: 1.21 date: 2022/06/10 11:30:09

user: cg

file: ReindexedCollection.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Description:

ReindexedCollection is a wrapper around a sequenceable collection that remaps the indices 
with in linear algorithm.  
The elements in the ReindexedCollection are the elements of the original collection 
at 'some start' to 'some stop' (optionally 'by 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.

For example,
    coll1 := #(1 2 3 4 5 6 7 8 9 10).
    coll2 := coll1 from:8.
gives us a collection in coll2, which 'contains' 3 elements, 8, 9, 10
with indices 1,2,3. 
I.e. a slice from the other array.

The reindexed collection is 'read-only'. I.e. it does not allow for elements to be changed.

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.


copyright
COPYRIGHT (c) 2006 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.

Class protocol:

 on: aSequence from: start

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

 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.

 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)

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

Create a reindexedCollection on aSequence from start to stop by step

 on: aSequence to: stop

Create a reindexedCollection 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.

 on: aSequence with: anInterval

Create a reindexedCollection on aSequence

Instance protocol:

 at: index

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

 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.

 size

Answer how many elements the receiver contains.

 slide

slide by 1

 slide: anIncrement

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

 add: anObject

report an error; reindexedCollections cannot add elements

 from: startIndex

return a new collection representing the receiver's elements starting at startIndex.

Usage example(s):

|coll cdr cddr cdddr cdddr2| coll := #(1 2 3 4 5 6 7 8 9 10). cdr := coll from:2. cddr := cdr from:2. cdddr := cddr from:2. cdddr2 := coll from:4.

Usage example(s):

|coll coll2| coll := #(1 2 3 4 5 6 7 8 9 10). coll2 := coll from:2 by:2. Transcript showCR:coll2.

Usage example(s):

|coll coll2 coll3| coll := #(1 2 3 4 5 6 7 8 9 10). coll2 := coll from:2 by:2. coll3 := coll2 from:2. Transcript showCR:coll3.

 from: startIndex to: stopIndex

return a new collection representing the receiver's elements
starting at startIndex upTo and including endIndex.

Usage example(s):

|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.

Usage example(s):

|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 receiver's elements upTo and including endIndex.

Usage example(s):

|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.

Usage example(s):

|coll coll2| coll := #(1 2 3 4 5 6 7 8 9 10). coll2 := coll to:9 by:2.

Usage example(s):

|coll coll2 coll3| coll := #(1 2 3 4 5 6 7 8 9 10 11 12). coll2 := coll to:9 by:2. coll3 := coll2 to:3.

 copy

return a new Collection containing the elements of the receiver.

Usage example(s):

redefinition is a consequence of the implementation, which references the underlying array. otherwise we get a shallow copy of the sequence, which is not what we want here

Usage example(s):

(#(1 2 3 4 5 6 7 8 9 10) from:3) copy (#(1 2 3 4 5 6 7 8 9 10) butLast:3) copy (#(1 2 3 4 5 6 7 8 9 10) from:2 to:7) copy

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

 initialize: aSequence with: anInterval

Modified (format): / 22-02-2017 / 10:46:38 / cg

 characterSize

 isFixedSize

return true if the receiver cannot grow

 species

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

 speciesForAdding

Answer the preferred class for reconstructing the receiver incrementally

Examples:

taking a sub-slice of a bigger collection (elements 8,9 and 10)
  |coll|

  coll := #(1 2 3 4 5 6 7 8 9 10) from:8.
  Transcript show:'from 8: '; showCR:coll.     
  Transcript show:'size: '; showCR:(coll size).  
  Transcript show:'at 1: '; showCR:(coll at:1).   
  Transcript show:'first: '; showCR:(coll first).   
  Transcript show:'last: '; showCR:(coll last).   
  coll do:[:each | Transcript show:'do: '; showCR:each].
  coll reverseDo:[:each | Transcript show:'reverseDo: '; showCR:each].


taking a sub-slice of a bigger collection (elements 3,4,5,6,7 and 8)
  |coll|

  coll := (1 to:10) asOrderedCollection from:3 to:8.
  coll.     
  coll size.  
  coll at:1.   
  coll do:[:each | Transcript showCR:each].


taking the first 4 elements of a bigger collection
  |coll|

  coll := (1 to:10) asOrderedCollection to:4.
  coll.     
  coll size.  
  coll at:1.   
  coll last.   
  coll do:[:each | Transcript showCR:each].


taking every second element from a bigger collection
  |coll|

  coll := (1 to:10) asOrderedCollection from:1 to:8 by:2.
  coll.     
  coll size.  
  coll at:1.   
  coll last.   
  coll do:[:each | Transcript showCR:each].


taking every second element from a bigger collection
  |coll|

  coll := (1 to:10) from:1 to:8 by:2.
  coll.     
  coll size.  
  coll at:1.   
  coll last.   
  coll do:[:each | Transcript showCR:each].