Hi,
The combine-single word has too many shuffle words for what it does; 3
shuffle words and 3 logic words is a good sign that there's a simpler
way to express the algorithm at hand.
You can get rid of the 'tuck' and one of the 'swap's using 'keep' instead:
: combine-single ( obj seq -- newseq ) [ length swap <repetition> ] keep zip ;
However there is in fact a simpler implementation of the same
algorithm that doesn't involve any shuffling at all. What you're doing
is transforming each element X of the sequence into { Y X } where Y is
a fixed value. You can express this using map:
: combine-single ( obj seq -- newseq ) [ 2array ] with map ;
Slava
On Wed, Jan 21, 2009 at 1:50 AM, Rajat Datta <[email protected]> wrote:
> Hi! I wonder if I can get a critique of the following two words:
>
> : combine-single ( obj seq -- newseq ) tuck length swap <repetition>
> swap zip ;
> : combine-multiple ( seq seq -- newseq ) [ combine-single ] curry map
> concat [ flatten ] map ;
>
> So, { 1 2 3 4 } dup dup combine-multiple combine-multiple will
> produce the following sequence:
>
> {
> { 1 1 1 } { 1 1 2 } { 1 1 3 } { 1 2 1 } { 1 2 2 } { 1 2
> 3 } { 1 3 1 } { 1 3 2 } { 1 3 3 }
> { 2 1 1 } { 2 1 2 } { 2 1 3 } { 2 2 1 } { 2 2 2 } { 2 2
> 3 } { 2 3 1 } { 2 3 2 } { 2 3 3 }
> { 3 1 1 } { 3 1 2 } { 3 1 3 } { 3 2 1 } { 3 2 2 } { 3 2
> 3 } { 3 3 1 } { 3 3 2 } { 3 3 3 }
> }
>
> I have just started using Factor, and I'm sure I'm missing words that
> will do this more elegantly.
>
> Thanks,
>
> rajat
>
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