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From: minforth@gmx.net (minforth)
Newsgroups: comp.lang.forth
Subject: Re: Parsing =?UTF-8?B?dGltZXN0YW1wcz8=?=
Date: Mon, 23 Jun 2025 10:02:44 +0000
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On Mon, 23 Jun 2025 5:40:37 +0000, mhx wrote:

> On Sun, 22 Jun 2025 21:27:40 +0000, minforth wrote:
>
> [..]
>> So, I made me a small extension to the locals word set. Using your
>> example SPIN (abc — cba), I can define it as follows:
>> : SPIN { a b c == c b a } ; \ no need for additional code before ;
>> or likewise for floats, doubles, strings, matrices
>> : FSPIN { f: a b c == c b a } ;
>> : DSPIN { d: a b c == c b a } ;
>> : "SPIN { s: a b c == c b a } ;
>> : MSPIN { m: a b c == c b a } ;
>> Code generation and register optimization is the computer's job.
>>
>> SPIN/STOW or similar microexamples can, of course, be defined quickly
>> with classic Forth stack juggling too. The power of the extension
>> becomes more apparent with mixed parameter types and/or more parameters,
>> and of course, with some non-trivial algorithm to solve.
>
> Do you mean your compiler automatically handles/allows combinations
> like
> ... 22e-12 69. A{{ ( F: -- a ) ( D: -- b ) ( M: -- c ) SPIN ...
>
> I found that handling mixed types explodes the code that needs
> to be written for a simple compiler like, e.g., Tiny-KISS . It
> would be great if that can be automated.

I don't know if I got you right, because as previously
defined, SPIN expects three integers on the data stack.

However, following your idea, a mixed SPIN could be defined e.g.

: XSPIN { f: a d: b m: c == c b a } ;

that can work with

... 22e-12 69. A{{ XSPIN ...

I think gforth has allowed mixed type locals for a long time,
so they are nothing really special.

The only new word is == which pushes the locals following
== on the stack before the word terminates with a ; or EXIT.

This releaves you of the need to keep track of the data stack.
A brief stack depth check can also catch some mistakes.

I always found the conventional syntax wasteful, where
everything after a -- does nothing but inform the reader.

--