Kyle,
Well, here's my attempt at solving the same problem. I use a different
algorithm from you; I think mine should be more efficient. I don't
think there's much shuffling in this version, though maybe the use of
/mod inside map isn't perfectly intention-revealing.
: change ( amount -- coins )
{ 25 10 5 1 }
[ [ /mod swap ] map nip ] keep
[ <repetition> ] 2map concat ;
Dan
On Sun, Apr 5, 2009 at 4:21 PM, Kyle Cordes <[email protected]> wrote:
> I'm trying to get my head around writing (good?) Factor code. Could
> someone point me in the right direction on the snippet below? Even after
> a few rounds of cleanup, I haven't been able to make it very
> intention-revealing, mostly (maybe?) because of juggling three values on
> the stack.
>
>
> USING: kernel sequences math ;
> IN: coins
>
> <PRIVATE
>
> : make-change-with-coin ( coins cents coin -- coins cents )
> [ 2dup >= ]
> [ tuck - swap tuck [ prefix ] 2dip ] while
> drop ;
>
> PRIVATE>
>
> : change ( cents -- coins )
> { } swap
> { 25 10 5 1 } [ make-change-with-coin ] each
> drop ;
>
>
>
> ( scratchpad ) 99 change .
> { 1 1 1 1 10 10 25 25 25 }
>
> --
> Kyle Cordes
> http://kylecordes.com
>
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