55 lines
1.6 KiB
Prolog
55 lines
1.6 KiB
Prolog
:- module(dif, [dif/2]).
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:- use_module(library(atts)).
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:- attribute dif/2.
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dif_set_variables([], _, _).
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dif_set_variables([Var|Vars], X, Y) :-
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put_atts(Var, dif(X, Y)),
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dif_set_variables(Vars, X, Y).
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verify_dif_attrs([dif(X, Y) | Attrs], Value, [X \== Y | Goals]) :-
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( get_atts(Value, +dif(X, Y)) -> true
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; put_atts(Value, +dif(X, Y))
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),
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verify_dif_attrs(Attrs, Value, Goals).
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verify_dif_attrs([_ | Attrs], Value, Goals) :-
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verify_dif_attrs(Attrs, Value, Goals).
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verify_dif_attrs([], _, []).
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verify_dif_attrs_no_var([dif(X, Y) | Attrs], Value, [X \== Y | Goals]) :-
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term_variables(Value, ValueVars),
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dif_set_variables(ValueVars, X, Y),
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verify_dif_attrs_no_var(Attrs, Value, Goals).
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verify_dif_attrs_no_var([_ | Attrs], Value, Goals) :-
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verify_dif_attrs_no_var(Attrs, Value, Goals).
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verify_dif_attrs_no_var([], _, []).
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verify_attributes(Var, Value, Goals) :-
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( get_atts(Var, Attrs) ->
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( var(Value) -> verify_dif_attrs(Attrs, Value, Goals)
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; verify_dif_attrs_no_var(Attrs, Value, Goals)
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)
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).
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% Probably the world's worst dif/2 implementation. I'm open to
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% suggestions for improvement.
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dif(X, Y) :- X \== Y,
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( term_variables(X, XVars), term_variables(Y, YVars),
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dif_set_variables(XVars, X, Y),
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dif_set_variables(YVars, X, Y)
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).
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gather_dif_goals(Attrs, _) :-
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var(Attrs), !.
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gather_dif_goals([dif(X, Y) | Attrs], [dif(X, Y) | Goals]) :-
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gather_dif_goals(Attrs, Goals).
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gather_dif_goals([_ | Attrs], Goals) :-
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gather_dif_goals(Attrs, Goals).
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attribute_goals(X, Goal) :-
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'$get_attr_list'(X, Attrs),
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gather_dif_goals(Attrs, Goal).
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