Calling a predicate in an imported module with "binding-environment" of an importing file?

[haijinSk]

I (not an Emacs user) was inspired by this:

“I want to tell you about an idea that has had a huge influence on the way that I write software. And I mean that in the literal sense: it’s changed the way that I write software; it’s re-shaped my development workflow.

The idea is this: you can write programs that modify themselves.

And I don’t mean macros or metaprogramming or anything fancy like that. I mean that you can write programs that edit their own source code. Like, the files themselves. The actual text files on disk that have your source code in them.

That’s not the whole idea, though. There’s more to it: you write programs that can edit themselves, and then you use that as your REPL.”

Ian Henry: My Kind of REPL, 2023: https://ianthehenry.com/posts/my-kind-of-repl/

---

This is a fragment from my loaded/consulted file, say, stranka-slovo.pl:

[...]

:- use_module('self-edit.pl').

[...]

reportOdkazy(Ls2) :-
  kwUrlObrFrazy(UrlFrazyPary),
  maplist(\Par^E^(Par=Url-Frazy,reportOdkazy_(Url,Frazy,E)),UrlFrazyPary,Ls),
  phrase(seqq(Ls),O),phrase(seqq(O),Ls2).

%? reportOdkazy(Ls).

[...]

Then, after this imperative query (selfSave/0 is imported):

?- selfSave.
   true
;  false.

my source file stranka-slovo.pl, the fragment, looks like this:

[...]

reportOdkazy(Ls2) :-
  kwUrlObrFrazy(UrlFrazyPary),
  maplist(\Par^E^(Par=Url-Frazy,reportOdkazy_(Url,Frazy,E)),UrlFrazyPary,Ls),
  phrase(seqq(Ls),O),phrase(seqq(O),Ls2).

%? reportOdkazy(Ls).
/*
[["milujem-ta/我愛你: 2. znak 愛 -> laska","rodina/家和萬事興: 2. znak 和 -> harmonia","odvaha/勇氣: 2. znak 氣 -> qi","sila/力氣: 2. znak 氣 -> qi","pravda/真金不怕火煉: 5. znak 火 -> ohen","feng-shui/風水: 2. znak 水 -> voda","japonsko/日本: 1. znak 日 -> slnko","dusa/精神: 2. znak 神 -> boh","vodnar-znamenie/水瓶座: 1. znak 水 -> voda"]].
*/

[...]

Or, with this fragment:

[...]

%? reportOdkazy([]).

[...]

the new, modified source file will have:

[...]

%? reportOdkazy([]).
% false.

[...]

---

This is my first, experimental, very quick and dirty prototype of the imported file self-edit.pl:

% If I uncomment the next "module" line, a "marked predicate to REPL" from my working file is no longer recognized:
% :- module('self-edit',[selfPrint/0, selfSave/0]). 

:- use_module(library(lists)).
:- use_module(library(lambda)).
:- use_module(library(dcgs)).
:- use_module(library(format)).
:- use_module(library(pio)).
:- use_module(library(dif)).
:- use_module(library(reif)).
:- use_module(library(charsio)).

fileToTest("stranka-slovo.pl").

str_lines("",[]).
str_lines([C],[[C]]) :- dif(C,'\n').
str_lines(['\n'|Str],[[]|["\n"|Ls]]) :- str_lines(Str,Ls).
str_lines([C|Str],[[C|Cs]|Ls]) :- dif(C,'\n'), str_lines(Str,[Cs|Ls]).

fileLines(LinesTests) :-
  fileToTest(FileName),
  once(phrase_from_file(seq(Str),FileName)),
  str_lines(Str,LinesWithEmpties),
  tfilter(dif([]),LinesWithEmpties,Lines),
  maplist(\Line^Test^test(Line,Test),Lines,LinesTests).

test("\n","\n").
test(Line,Line) :- phrase(([C1,C2],...),Line), dif([C1,C2],"%?"). 
% Or: test([C1,C2|R],[C1,C2|R]) :- dif([C1,C2],"%?"). Or...
test(Line,TestStr) :-
  phrase(("%? ",seq(Str)),Line),
  read_from_chars(Str, T),
  term_variables(T,Variables),
  ( call(T) ->
      ( phrase(portray_clause_(Variables),VariablesStr),
        phrase((Line,"\n/*\n",VariablesStr,"*/"),TestStr))
      ; phrase((Line,"\n% false."),TestStr)
  ).

selfPrint :-
  fileLines(LinesTests),
  phrase_to_stream(seqq(LinesTests),user_output).

selfSave :-
  fileToTest(FileName),
  fileLines(LinesTests),
  phrase_to_file(seqq(LinesTests),FileName).

---

So far, so good; and I was thinking, everything is so simple in Prolog...

But then, I was thinking: Wait a minute, I don't want name clashes, I need a real module...

If I add this line to my self-edit.pl file/module:

:- module('self-edit',[selfPrint/0, selfSave/0]).

I get this:

?- selfSave.
   error(existence_error(procedure,reportOdkazy/1),reportOdkazy/1).

It seems reasonable: an attempt to call the predicate reportOdkazy/1 in the imported module, but the predicate is not defined in the module.

Yes, I'm a naive user, crazy ideas etc.: is it possible, in Scryer, to have a proper/isolated module imported and yet from that module to call a predicate with the "environment/context" of an importing file? And I mean simplicity of:

%? reportOdkazy(Ls).

?- selfSave.

Or, now I "have two problems"?

Thank you.

[hurufu]

Code generation is good (both on-line [just before or during runtime] and off-line [before runtime]), self-modifying code (in memory) is also good, but I don't know what to say about program that modifies it's own source code text – sounds like something very fragile. I usually don't even like when programs modify their config files, let alone source code. Maybe I haven't reached zen of programming like Ian Henry.

[haijinSk]

As I (mis)understand it, he was inspired by some thing in OCaml world:

https://github.com/janestreet/ppx_expect

and this thing in Rust world:

https://github.com/boujeepossum/k9

I did not study the things, I didn't study even his thing in detail. I was inspired by the idea or his words as I (mis)understand it and I wanted to try it immediately in Scryer/Trealla, with my naive-programming way, and I realized that Scryer and Trealla/SWI-Prolog don't work in the same way with the same "module code".

Thank you for your visit/view.

[bakaq]

Well, here's the best article I know showing the benefits of this approach, written by the guy who popularized this in the Rust and Zig ecosystems:

https://tigerbeetle.com/blog/2024-05-14-snapshot-testing-for-the-masses/

[hurufu]

For testing, this is cool. I wasn't aware of this approach.