What about using local only to implement the difficult stack shuffling
that you named "????" ?
:: ???? ( a b c d e h -- d b c a e h )
d b c a e h ;
: swap-element ( i1 array1 i2 array2 -- )
[ [ nth ] 2keep ] 2bi@ ???? [ set-nth ] 2 smart-apply ;
And you could name "????" "(swap-element)" which is the convention
for helper words that don't have much sens by themselve. Or
"swap-data". Or leave it as "????" because really it's self
explaining.
Oh and your question reminded me of
http://useless-factor.blogspot.com/2007/07/thats-dirtiest-macro-ive-ever-seen.html
which was a fun read :)
Alternatively, why do you find yourself in need to swap elements
between 2 different arrays ? Maybe you could organize the data in a
different way ?
Jon
On Mon, Mar 12, 2012 at 2:00 PM, nicolas.o...@gmail.com
<nicolas.o...@gmail.com> wrote:
> Dear all,
>
> I am starting to learn Factor as my first concatenative language (from
> a FP background) and enjoy it very much.
>
> However, when trying to write simple words I get stuck on how to best
> express dataflow.
>
> As a (very very simple) example, I am trying to write a word
>
> : swap-element ( i1 array1 i2 array2 -- )
>
> that swaps two elements with indices i1 and i2 from 2 (aliased or not) arrays.
>
> It is very easy to write such a word using lexical variables.
>
> However, I have two problems with that:
> - I am not sure it is the right tool to use or just my brain bringing
> me back to what I know.
> - It does not show the symmetries of the dataflow of this word
>
> I quite like the style of something along the lines of:
>
> : swap-element ( i1 array1 i2 array2 -- )
> [ [ nth ] 2keep ] 2bi@ ???? [ set-nth ] 2 smart-apply ;
>
> because it shows the dataflow better than with lexical variables.
>
> But I can't find something nice to put instead of ????.
>
> So, I guess that my question is: how to solve this problem and, more
> importantly, how to learn to
> solve this kind of problem by myself?
>
> Thank you very much for your help,
>
> Best regards,
>
> Nicolas.
>
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