31 lines
829 B
Prolog
31 lines
829 B
Prolog
:- module(freeze, [freeze/2]).
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:- use_module(library(atts)).
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:- use_module(library(dcgs)).
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:- meta_predicate freeze(-, 0).
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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,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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attribute_goals(Var) -->
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{ get_atts(Var, frozen(Goals)),
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put_atts(Var, -frozen(_)) },
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[freeze(Var, Goals)].
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