Re: [gforth] If then else in interpreted mode

[Marcos Cruz]

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

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