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Re: Trying to extend gforth's outer interpreter

From: Tristan Williams
Subject: Re: Trying to extend gforth's outer interpreter
Date: Mon, 22 Aug 2022 20:52:28 +0100

On 01Apr22 13:18, Anton Ertl wrote:
> On Fri, Apr 01, 2022 at 09:51:09AM +0100, Tristan Williams wrote:
> > Hello,
> > 
> > I am trying to extend gforth's outer interpreter so that how numbers
> > are treated is dependent on which mode (indicated by the value of
> > mode?) my program is in. In the code below, if mode? is true the
> > number is just dropped, otherwise it should be treated as usual and
> > placed on the host data stack. This seems to work if I type
> > definitions in interactively at the terminal, but if I include them at
> > the end of the source file or interactively using include "filename"
> > it does not. What am I doing wrong?
> You hook into 'quit, which is only used for text-interpretation of
> terminal input.
> If you use a recent development version of Gforth, the way to go is to
> define a new number recognizer, and replace the default number
> recognizer REC-NUM with the new one (or just insert the new one in
> front of REC-NUM in the recognizer stack).  The documentation is not
> finished yet, but look at the source of REC-NUM, and use
> GET-RECOGNIZERS and SET-RECOGNIZERS to change the recognizer stack.
> If you use Gforth-0.7, things are more complex: You need to replace
> INTERPRETER1 and COMPILER1.  These are not hooks, so you need to patch
> the existing colon definitions.  To do that, use:
> : >colon-body ( xt -- addr )
>     dup @ docol: <> -12 and throw >body ;
> : >prim-code ( xt -- x )
>     \ converts xt of a primitive into a form usable in the code of
>     \ colon definitions on the current engine
>     threading-method 0= IF @ THEN ;
> : replace-word ( xt1 xt2 -- ) \ gforth
>   \G make xt2 do xt1, both need to be colon definitions
>     swap >colon-body ['] branch >prim-code rot >colon-body 2! ;
> - anton

Hello Anton,

A small update. I was able to use custom recognizers in Gforth to help
extend my structured Forth cross-assembler for a PIC16F183X3 to a
Forth cross-compiler. They make switching between its two modes
of operation (assembler or Forth) much more manageable. Thank you.


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