Re: [Amforth] AmForth Weekend 4

[<ho...@tj...>]

On 2025-11-05 08:46, Martin Nicholas via Amforth-devel wrote:
> On Sun, 02 Nov 2025 14:40:07 +0000

CUT

> You didn't ask for them, but I have a couple of ideas for
> amforth-shell.py:
> 
> 1.
> Have an "#ifndef FORTHWORD forthword.frt" directive. "#ifdef" also.
> 
> 2.
> Directives that take a path or filename will look for a partial path.
> i.e:	#require project1/main.frt
> 	#require project2/main.frt
> are considered different files.
> 
> If either of these can be achieved by some other means, then please
> chip in. I am aware of "#cd".

Hi Martin,

Thank you. Ideas are always welcome, and yours are very timely.

For 1. There might be an AmForth way or an amforth-shell way. Depends 
upon what we want to use #ifdef for.

AmForth way - with a "bigger" Forth than AmForth there would be the 
option of using [IF]..[ELSE]..[THEN]. AmForth does not have these 
extension words from [1] but it does have [DEFINED] and [UNDEFINED]. 
 From [2] on the website, a limited (by current SOURCE) Conditional 
Interpret can be achieved.

|S|    1|anew empty
|W|    2|
|S|    3|: ?\ ( f -- ) if postpone \ then ; immediate
|W|    4|
|S|    5|[defined]   3+ 0= ?\ : xx 3+ ;
|S|    6|[undefined] 3+ 0= ?\ : xx 2 + ;
|W|    7|
|S|    8|100 xx . cr
|O|    8|102
|W|    9|
|S|   10|: 3+ ( n -- n ) 3 + ;
|W|   11|
|S|   12|[defined]   3+ 0= ?\ : yy 3+ ;
|S|   13|[undefined] 3+ 0= ?\ : yy 2 + ;
|W|   14|
|S|   15|100 yy . cr
|O|   15|103

I *think* this can be extended a little

|S|   17|anew empty
|W|   18|
|S|   19|: ifdef  postpone   [defined] invert if postpone \ then  ; 
immediate
|S|   20|: ifndef postpone [undefined] invert if postpone \ then  ; 
immediate
|W|   21|
|S|   22|: zz
|S|   23|    ifdef  3+ 3+
|S|   24|    ifndef 3+ 2 +
|S|   25|;
|W|   26|
|S|   27|100 zz . cr
|O|   27|102
|W|   28|
|S|   29|: 3+ ( n -- n ) 3 + ;
|W|   30|
|S|   31|: zz
|S|   32|    ifdef  3+ 3+
|S|   33|    ifndef 3+ 2 +
|S|   34|;
|W|   35|
|S|   36|100 zz . cr
|O|   36|103

I've not tested this beyond the snippet above. It's not 
[IF]..[ELSE]..[THEN] by a long chalk but it's "all Forth" and it might 
do the job. Alternatively,

amforth-shell way - amforth-shell does some [pre|post]processing of 
serial streams to/from the mcu and can also interact using Forth with 
the mcu.  However, it has no conditional i.e. #ifdef ... capability. 
This is something I've wanted, but I've been putting off as

(a) amforth-shell.py is very reliable and I don't want to break it
(b) the serial "handshaking" needed is not easy - goto (a)

Recently, however, I have merged amforth-shell with a preprocessor. I've 
just added your idea, but renamed #ifdef to #ifword as #ifdef taken. 
Forth source can look like this. #dictionary queries mcu and fills local 
cache, #ifword queries local cache.

anew empty
#dictionary
: zz
     #ifword 3+
     3+
     #else
     2 +
     #endif
;
100 zz . cr
: 3+ ( n -- n ) 3 + ;
#dictionary
: zz
     #ifword 3+
     3+
     #else
     2 +
     #endif
;
100 zz . cr

which when uploaded to the mcu it looks like this. You only get to "see" 
what was left after the preprocessor has done its work.

|S|    1|anew empty
|S|    2|: zz
|S|    3|    2 +
|S|    4|;
|S|    5|100 zz . cr
|O|    5|102
|S|    6|: 3+ ( n -- n ) 3 + ;
|S|    7|: zz
|S|    8|    3+
|S|    9|;
|S|   10|100 zz . cr
|O|   10|103

It needs a lot more testing before it goes anywhere near the repo. If 
you are willing to alpha test it, I will tidy it up.

Best wishes,
Tristan

[1] 15.6.2 Programming-Tools extension words
     https://forth-standard.org/standard/tools

[2] 
https://amforth.sourceforge.net/TG/recipes/Conditional-Interpret.html