Differents results when debug is enabled ...

[victor]

Hello,

I found this strange bug, using this predicate :

:- object(test2).
:- public(union/3).
mymemberchk(E, T) :-
  varlist::memberchk(E, T), !.
mymemberchk(E, T) :-
  list::member(E, T).

union([], L, L).
union([H|T], L, R) :-
  ( mymemberchk(H, L) *->
    union(T, L, R)
  ; union(T, L, R2),
    R = [H|R2]
  ).
:- end_object.

?- set_logtalk_flag(debug, on).
true.

?- logtalk_load(test2).
% test2.pl compiled 0.00 sec, 4,252 bytes
true.

?- test2::union([a], [a], R).
R = [a] ;
R = [a, a].

?- set_logtalk_flag(debug, off).
true.

?- logtalk_load(test2).
% test2.pl compiled 0.00 sec, -812 bytes
true.

?- test2::union([a], [a], R).
R = [a].

As you can see, when debug is on, union/3 backtracks in a strange way.

I tried to look at the trace, but I am not sure to understand what is happening :>

[pmoura]

The problem is likely due to the use of the non-standard construct *->/2.

[pmoura]

Problem corrected in r4401. Unfortunately, fixing this problem with non-standard control constructs implied incompatible changes to all config files.