Re: [Help-smalltalk] [PATCH] Add #atAll:, improve MappedCollection

[Paolo Bonzini]

> Great!  I'll add that
>
> aSeqCollect atAll: anInterval
>
> is a powerfully expressive idiom

Fully agreed -- to the point that I was surprised of its absence.

>  enabled by this extension, replacing 
> all sorts of specialized collection methods

What are you thinking of?

I should add that MappedCollection is also a powerful tool with this 
respect, since basically

    MappedCollection collection: foo map: aCollection

is a lazy version of "foo atAll: aCollection".  For Intervals, using a 
MappedCollection may save lots of memory.

An interesting example is that of matrices, implemented over a single 
array with rows*cols elements:

    initialize
        rowSections := (0 to: rows - 1) collect: [ :n |
             MappedCollection
                  collection: data
                  map: (n * cols + 1 to: (n + 1) * cols) ].
        columnSections := (1 to: cols) collect: [ :n |
             MappedCollection
                  collection: data
                  map: (n to: rows * cols by: cols) ].

    at: n
        ^rowSections at: n

    columnAt: n
        ^columnSections at: n

    at: row at: column
        ^(self at: row) at: column

Paolo