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From: Mild Shock <janburse@fastmail.fm>
Newsgroups: comp.lang.prolog
Subject: =?UTF-8?Q?variable_ordering_guarantees_in_term=5fsingletons/2_=28Wa?=
 =?UTF-8?Q?s:_Prolog_Development_=c3=a0_la_Sigmund_Freud=29?=
Date: Sun, 25 May 2025 09:57:10 +0200
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Hi,

People from Vienna were always a little strange.
Why not adopt term_singletons/2 its already around
for a while. You can do quite some magic with it.

Example: Determining singletons during listing,
from Dogelog Player library(tester/tools):

% sys_listing_write(+Term, +Stream)
sys_listing_write(C, T) :-
    term_variables(C, V),
    term_singletons(C, A),
    sys_listing_names(V, A, 0, N),
    write_term(T, C, [quoted(true), variable_names(N), format(true)]),
    sys_answer_period(T).

If term_singletons/2 has the same variable ordering
guarantees, i.e. left to right, as in term_variables/2
you can use an algorithm without expensive lookup,

sys_listing_names([], _, _, []).
sys_listing_names([X|L], [Y|R], K, ['_'=X|S]) :- X==Y, !,
    sys_listing_names(L, R, K, S).
sys_listing_names([X|L], A, K, [N=X|R]) :-
    sys_listing_name(K, N),
    J is K+1,
    sys_listing_names(L, A, J, R).

Just run along the two lists , if something is both in
the term_variables/2 and term_singletons/2 list, generate
a '_' name, otherwise generate a synthetic name.

Bye

Mild Shock schrieb:
> Hi,
> 
> The development of Trealla Prolog and Scryer Prolog
> looks like a random search in a mental ocean.
> 
> It is like Prolog Development à la Sigmund Freud,
> you have only to dig deep enough, and a solution
> 
> will pop up. Otherwise blame your mother or other
> relatives that raised you for supression.
> 
> LoL
> 
> Bye
> 
> Examples: Still clueless how to detect singletons?
> https://github.com/trealla-prolog/trealla/issues/743