Class: VirtualArrayWithCache

• Inheritance
• Description
• Class protocol
  • defaults
• Instance protocol
  • collection protocol
  • initialization
• Examples

Inheritance:

   Object
   |
   +--Collection
      |
      +--SequenceableCollection
         |
         +--VirtualArray
            |
            +--VirtualArrayWithCache
               |
               +--VirtualReadOnlyTextFileContents

Package:

stx:libbasic2

Category:

Collections-Arrayed

Version:

rev: 1.6 date: 2023/11/15 07:22:11

user: cg

file: VirtualArrayWithCache.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Description:

like a VirtualArray, but caches the results of the last few accesses.
This might behave better, if it is expensive to compute the elements,
and they are often accessed repeatedly (as when showing in a listView).
Similar to a LazyArray, however, this only remembers a number of elements in
an LRU fashion, whereas a LazyArray remembers all.


[instance variables:]

[class variables:]

copyright
COPYRIGHT (c) 2018 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:

 defaultLRUCacheSize

Instance protocol:

 at: index

return the element at index.
The value is computed by the generator and remembered in the lruCache

 lruCache: aCacheDictionaryOrNil

useful to setup a cache with a different size

Usage example(s):

|v| v := VirtualArrayWithCache new:10000. v generator:[:idx | idx factorial]. v lruCache:(CacheDictionary new:10). v inspect.

Examples:

    |factorialLines|

    factorialLines := VirtualArrayWithCache new:10000.
    factorialLines generator:[:index | index factorial printString].
    factorialLines at:1000.
    factorialLines at:1000.
    factorialLines at:10000.
    

    |top textView factorialLines generator|

    generator := 
        [
            |lastN lastComputed|
            [:n |
                lastN == (n-1) ifTrue:[
                    Transcript showCR:'fast'.
                    lastComputed := lastComputed * n
                ] ifFalse:[
                    Transcript showCR:'slow'.
                    lastComputed := n factorial
                ].
                lastN := n.
                lastComputed
            ].
        ] value.

    factorialLines := VirtualArrayWithCache new:10000.
    factorialLines generator:[:index | e'{index}: {generator value:index}'].

    top := StandardSystemView new.
    top label:'Factorials computed as you scroll'.
    textView := HVScrollableView for:TextView in:top.
    textView origin:0@0 corner:1.0@1.0.
    textView list:factorialLines expandTabs:false
             scanForNonStrings:false includesNonStrings:false.
    textView checkedLinesForWidthOfContentsComputation:0.
    textView setWidthOfContents:1000.
    top open.