%% no_repeats_var(+Var) is det. % % Attribute a varaible to

%% no_repeats_var(+Var) is det.
%
% Attribute a varaible to never be bound to the same value twice
%
%  ==
%  ?- no_repeats_var(X),member(X,[1,2,3,3,3,1,2,3]).
%  X = 1;
%  X = 2;
%  X = 3;
%  false.
%  ==
no_repeats_var(Var):-must_be(var,Var),put_attr(Var,nr,old_vals([])).
nr:attr_unify_hook(AttValue,VarValue):- AttValue=old_vals(Waz), \+ memberchk_same(VarValue,Waz),nb_setarg(1,AttValue,[VarValue|Waz]).

memberchk_same(X, [Y0|Ys]) :- is_list(Ys),!,C=..[v,Y0|Ys],!, arg(_,C,Y), ( X =@= Y ->  (var(X) -> X==Y ; true)),!.
memberchk_same(X, [Y|Ys]) :- (   X =@= Y ->  (var(X) -> X==Y ; true) ;   (nonvar(Ys),memberchk_same(X, Ys) )).