34 lines
1.0 KiB
Prolog
34 lines
1.0 KiB
Prolog
:- module(freeze, [freeze/2]).
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:- use_module(library(atts)).
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:- attribute frozen/1.
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verify_attributes(Var, Other, Goals) :-
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get_atts(Var, frozen(Fa)), !, % are we involved?
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( var(Other) -> % must be attributed then
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( get_atts(Other, frozen(Fb)) % has a pending goal?
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-> put_atts(Other, -frozen(Fb)),
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put_atts(Other, frozen((Fb,Fa))) % rescue conjunction
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; put_atts(Other, frozen(Fa)) % rescue the pending goal
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),
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Goals = []
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; Goals = [Fa]
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).
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verify_attributes(_, _, []).
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freeze(X, Goal) :-
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put_atts(Fresh, frozen(Goal)),
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Fresh = X.
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gather_freeze_goals(Attrs, _, _) :-
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var(Attrs), !.
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gather_freeze_goals([frozen(X) | Attrs], Var, [frozen(Var, X) | Goals]) :-
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gather_freeze_goals(Attrs, Var, Goals).
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gather_freeze_goals([_ | Attrs], Var, Goals) :-
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gather_freeze_goals(Attrs, Var, Goals).
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attribute_goals(X, Goals) :-
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'$get_attr_list'(X, Attrs),
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gather_freeze_goals(Attrs, X, Goals).
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