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Boolean Constraint Solving in Prolog

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Problem with weighted_maximum and */1

Given the following:

works(A, B) :-
    sat(*([+[A, B], B])),
    labeling([A, B]).

doesnt(A, B) :-
    sat(*([+[A, B], B])),
    weighted_maximum([-1,-1], [A, B], _).

works2(A, B) :-
    sat(A + B * B),
    weighted_maximum([-1,-1], [A, B], _).

running doesnt throws the following error:

[debug]  ?- doesnt(A, B).
ERROR: Uninstantiated argument expected, found 1
ERROR: In:
ERROR:   [19] throw(error(uninstantiation_error(1),_11940))
ERROR:   [18] error:uninstantiation_error(1) at /usr/lib/swi-prolog/library/error.pl:161
ERROR:   [17] error:is_not(var,1) at /usr/lib/swi-prolog/library/error.pl:282
ERROR:   [16] error:element_is_not([1],var) at /usr/lib/swi-prolog/library/error.pl:324
ERROR:   [15] error:element_is_not([_12080,1],var) at /usr/lib/swi-prolog/library/error.pl:321
ERROR:   [14] error:not_a_list(list(var),[_12128,1]) at /usr/lib/swi-prolog/library/error.pl:304
ERROR:   [13] error:is_not(list(var),[_12176,1]) at /usr/lib/swi-prolog/library/error.pl:270
ERROR:   [12] error:must_be(list(var),[_12224,1]) at /usr/lib/swi-prolog/library/error.pl:248
ERROR:   [11] clpb:weighted_maximum([-1,-1],[_12282,1],_12266) at /usr/lib/swi-prolog/library/clp/clpb.pl:1442
ERROR:   [10] doesnt(_12314,1) at ...
ERROR:    [9] <user>
   Exception: (12) error:must_be(list(var), [_9118{...}, 1]) ? creep
   Exception: (11) clpb:weighted_maximum([-1, -1], [_9118{...}, 1], _12538) ? creep
   Exception: (10) doesnt(_8658, _8660) ? creep

while works and works2 both work, which seems odd to me, but perhaps I'm misunderstanding something?

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