En/Je/On 2013-05-01 23:15, John Allsup escribió / skribis / wrote :
Hi John, welcome!
As you show, execution tokens (on the stack, in lists or any other data
structure), can be used to make decisions based on calculations. That's
a powerful feature of Forth.
> : jif 0 = if 0 else 1 then ;
A simpler alternative:
: jyf 0<> abs ;
Usually in Forth a calculation can be used instead of a condition.
> so as to have two nicely named words: jiffy and jemmy that do the
> work of interpret time conditional execution.
You can use also '[if]', '[else]' and '[then]'. They work quite
differently than 'if', 'else' and 'then', but they provide the same
syntax.
> As to taking this much further, we hit a place where it is really
> nice to have more stacks (since you ideally want an operator stack
> to do the picking from rather than the data stack
There are several Forth extra stack tools you can use. I think they are
not hard to find on the web. Anyway the simpler implementations need
only a few lines of code.
Cheers,
Marcos
--
http://programandala.net
