On 20 August 2012 16:51,  <commits at source.squeak.org> wrote:
> Frank Shearar uploaded a new version of Collections to project The Inbox:
> http://source.squeak.org/inbox/Collections-fbs.489.mcz
>
> ==================== Summary ====================
>
> Name: Collections-fbs.489
> Author: fbs
> Time: 20 August 2012, 4:51:36.018 pm
> UUID: d1834809-65b5-46c0-9b26-fea7ec04a946
> Ancestors: Collections-ul.488
>
> SequenceableCollection >> flatten turns a nested SequenceableCollection - a collection of collections of ... -  into a simple collection. Thus, #(1 (2 3) (4)) flatten = #(1 2 3 4).
>
> =============== Diff against Collections-ul.488 ===============
>
> Item was added:
> + ----- Method: SequenceableCollection>>flatten (in category 'copying') -----
> + flatten
> +       | recur stream |
> +       stream := WriteStream on: (Array new: self size). "A lower bound on the final stream count."
> +       recur := [:coll | coll
> +               do: [:each |
> +                       each isCollection
> +                               ifTrue: [recur value: each]
> +                               ifFalse: [stream nextPut: each]]].
> +       recur value: self.
> +       ^ stream contents.!

I've had to implement this a few times now, so I thought it time to
offer it up for general consumption. My original implementation was
recursive, using #collect: and #inject:into:. This of course used a
lot of #copy sends. Using a WriteStream seems more efficient, both in
time trials and in looking at MessageTally outputs (where GC usage was
a fraction of the recursive implementation, and 40% of CPU time was
actually spent in primitives).

frank