The headache an eGovernment might get from Prolog (Was: DCG is easily affected)

From	Mild Shock <janburse@fastmail.fm>
Newsgroups	comp.lang.prolog
Subject	The headache an eGovernment might get from Prolog (Was: DCG is easily affected)
Date	2025-07-15 15:20 +0200
Message-ID	<1055ki3$2abt8$1@solani.org> (permalink)
References	<104o5kc$20fno$1@solani.org> <104qf0n$21rh6$1@solani.org>

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Hi,

That false/0 and not fail/0 is now all over the place,
I don't mean in person but for example here:

?- X=f(f(X), X), Y=f(Y, f(Y)), X = Y.
false.

Is a little didactical nightmare.

Syntactic unification has mathematical axioms (1978),
to fully formalize unifcation you would need to
formalize both (=)/2 and (≠)/2 (sic!), otherwise you
rely on some negation as failure concept.

Keith L. Clark, Negation as Failure
https://link.springer.com/chapter/10.1007/978-1-4684-3384-5_11

You can realize a subset of a mixture of (=)/2
and (≠)/2 in the form of a vanilla unify Prolog
predicate using some of the meta programming
facilities of Prolog, like var/1 and having some

negation as failure reading:

/* Vanilla Unify */
unify(V, W) :- var(V), var(W), !, (V \== W -> V = W; true).
unify(V, T) :- var(V), !, V = T.
unify(S, W) :- var(W), !, W = S.
unify(S, T) :- functor(S, F, N), functor(T, F, N),
      S =.. [F|L], T =.. [F|R], maplist(unify, L, R).

I indeed get:

?- X=f(f(X), X), Y=f(Y, f(Y)), unify(X,Y).
false.

If the vanilla unify/2 already fails then unify
with and without subject to occurs check, will also
fail, and unify with and without ability to
handle rational terms, will also fail:

Bye

Mild Shock schrieb:
> 
> Interestingly, DCG is also affect. Here a
> DCG take of an append app/3, it has the 2nd
> and 3rd argument swapped:
> 
> ?- [user].
> app([]) --> [].
> app([X|Y]) --> [X], app(Y).
> ^D
> 
> Looks like an append, taking the argument swap
> into account, the A=B is redundant, could
> be optimized away:
> 
> /* SWI-Prolog 9.3.25 */
> ?- listing(app/3).
> app([], A, B) :-
>      A=B.
> app([A|B], [A|C], D) :-
>      app(B, C, D).
> 
> And works like an append, again taking the
> argument swap into account:
> 
> ?- app([1],X,[2,3]).
> X = [1, 2, 3].
> 
> Now the multi-argument indexing test, still
> taking the argument swap into account;
> 
> /* ECLiPSe Prolog 7.1beta #13 */
> [eclipse 3]: app(X, [1], Y).
> 
> X = []
> Y = [1]
> Yes (0.00s cpu, solution 1, maybe more) ? ;
> 
> X = [1]
> Y = []
> Yes (0.00s cpu, solution 2)
> 
> Versus:
> 
> /* SWI-Prolog 9.3.25 */
> ?- app(X, [1], Y).
> X = [],
> Y = [1] ;
> X = [1],
> Y = [] ;
> false.
> 
> Mild Shock schrieb:
>> I am currently doing a re-evaluation of an old
>> Prolog system, checking what features I could adopt.
>> This is unlike the current trend where people have
>> turned their focus on GUIs, like XPCE,
>>
>> or a are stuck in an endless loop of parser
>> problems, like in Trealla. But I would nevertheless
>> share my finding. Take this simple example of
>> a list append:
>>
>> app([], X, X).
>> app([X|Y], Z, [X|T]) :- app(Y, Z, T).
>>
>> ECLiPSe Prolog gives me, only one redo question
>> in the top-level:
>>
>> /* ECLiPSe Prolog 7.1beta #13 */
>> [eclipse 2]: app(X,Y,[1]).
>>
>> X = []
>> Y = [1]
>> Yes (0.00s cpu, solution 1, maybe more) ? ;
>>
>> X = [1]
>> Y = []
>> Yes (0.00s cpu, solution 2)
>>
>> In SWI-Prolog I find, two redo questions
>> in the top.level:
>>
>> /* SWI-Prolog 9.3.25 */
>> ?- app(X,Y,[1]).
>> X = [],
>> Y = [1] ;
>> X = [1],
>> Y = [] ;
>> false.
>>
>> I know SWI-Prolog handles lists differently
>> than other Prolog terms during indexing. Could
>> this be the reason? Or maybe that the call is
>> not “hot” enough, so it doesn’t get JIT-ed.
>>
>> ECLiPSe Prolog does it on the very first call,
>> and I assume its due to a kind of index on
>> the 3rd argument.
>>
>

Thread

The Ghosts in my Cabinet: Indexing Mild Shock <janburse@fastmail.fm> - 2025-07-10 12:45 +0200
  Observed while watching FAIL/REDO ports (Was: The Ghosts in my Cabinet: Indexing) Mild Shock <janburse@fastmail.fm> - 2025-07-10 12:46 +0200
    Shocking Revelation: No eGovernment can trust Prolog! (Was: Observed while watching FAIL/REDO ports) Mild Shock <janburse@fastmail.fm> - 2025-07-10 13:26 +0200
      Easier certification with 100% Prolog Prolog? (Was: Shocking Revelation: No eGovernment can trust Prolog!) Mild Shock <janburse@fastmail.fm> - 2025-07-10 14:05 +0200
        Doing a Prolog system without any iterator API (Was: Easier certification with 100% Prolog Prolog?) Mild Shock <janburse@fastmail.fm> - 2025-07-10 14:14 +0200
          The headache with JIT indexing: Native -> Prolog (Was: Doing a Prolog system without any iterator API) Mild Shock <janburse@fastmail.fm> - 2025-07-10 14:40 +0200
            Just lets burn another candle for Barty Boy (Was: The headache with JIT indexing: Native -> Prolog) Mild Shock <janburse@fastmail.fm> - 2025-07-10 18:13 +0200
              Physics PhDs might never have heard of Quantifier Eliminations (Re: Just lets burn another candle for Barty Boy) Mild Shock <janburse@fastmail.fm> - 2025-07-10 18:33 +0200
                How long willl I piss on Bart Demoen (Was: Physics PhDs might never have heard of Quantifier Eliminations) Mild Shock <janburse@fastmail.fm> - 2025-07-10 18:39 +0200
                But I shouldn't waste too much time (Was: How long willl I piss on Bart Demoen) Mild Shock <janburse@fastmail.fm> - 2025-07-10 19:13 +0200
  DCG is easily affected (Was: The Ghosts in my Cabinet: Indexing) Mild Shock <janburse@fastmail.fm> - 2025-07-11 09:38 +0200
    The headache an eGovernment might get from Prolog (Was: DCG is easily affected) Mild Shock <janburse@fastmail.fm> - 2025-07-15 15:20 +0200
      Wait till they find out about compare/3 (Was: The headache an eGovernment might get from Prolog) Mild Shock <janburse@fastmail.fm> - 2025-07-15 15:24 +0200
        Corr. (Was: Wait till they find out about compare/3) Mild Shock <janburse@fastmail.fm> - 2025-07-15 15:28 +0200
          eGovernements will need AGI to survive (Was: Corr. (Was: Wait till they find out about compare/3)) Mild Shock <janburse@fastmail.fm> - 2025-07-15 18:41 +0200
            Having 2544 issues is probably a bad sign (Re: eGovernements will need AGI to survive) Mild Shock <janburse@fastmail.fm> - 2025-07-15 18:41 +0200
              The Signal Collapse gives us System Uncertainty (Re: Having 2544 issues is probably a bad sign) Mild Shock <janburse@fastmail.fm> - 2025-07-15 19:02 +0200
                Rename GitHub, to TurdPit, and make Amber Heard their CEO (Was: The Signal Collapse gives us System Uncertainty) Mild Shock <janburse@fastmail.fm> - 2025-07-15 19:52 +0200
            Humans are just overwhelmed by computers (Was: eGovernements will need AGI to survive) Mild Shock <janburse@fastmail.fm> - 2025-07-16 18:59 +0200
              Fishy 🐟 in Scryer Prolog and SWI-Prolog (Was: Humans are just overwhelmed by computers) Mild Shock <janburse@fastmail.fm> - 2025-07-16 20:08 +0200
                So we are essentially all using Trojan Horses 🐎 daily? (Re: Fishy 🐟 in Scryer Prolog and SWI-Prolog) Mild Shock <janburse@fastmail.fm> - 2025-07-17 10:57 +0200
                Strudel Rust gives Scryer Frust 💩: Try C+20 Pipes (Was: Fishy 🐟 in Scryer Prolog and SWI-Prolog( Mild Shock <janburse@fastmail.fm> - 2025-11-25 22:55 +0100
              SWI-Prolog as a Test Bed for Copilots (Was: Humans are just overwhelmed by computers) Mild Shock <janburse@fastmail.fm> - 2025-07-20 14:36 +0200
                Mathematics currently hates Computer Science because of AI (Re: SWI-Prolog as a Test Bed for Copilots) Mild Shock <janburse@fastmail.fm> - 2025-07-20 15:13 +0200

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