Slava Pestov wrote:
> On Sun, Apr 5, 2009 at 6:10 PM, Kyle Cordes <[email protected]> wrote:
>> I am still unhappy with the obtuseness of "tuck - swap", is there a
>> better way to do that?
>
> Yes. If you have 'a b' on the stack, then 'tuck - swap' gives you 'a-b
> b'. Another way to get this result is [ - ] keep.
Ah, much better. It is one token longer, but more obvious (to me) what
it does.
: change ( amount -- coins )
{ 25 10 5 1 }
[
[
[ 2dup >= ] [ [ - ] keep dup , ] while
drop ] each
] { } make nip ;
I now understand Dan's code (pasted below), and like it better still
because it thinks in lists rather than per-value, and because it needs
fewer nested quotations, a max-depth of 2 instead of 4.
: change-dan ( amount -- coins )
{ 25 10 5 1 }
[ [ /mod swap ] map nip ] keep
[ <repetition> ] 2map concat ;
--
Kyle Cordes
http://kylecordes.com
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