32 lines
1.1 KiB
Prolog
32 lines
1.1 KiB
Prolog
:- module(numbervars, [numbervars/2, numbervars/3]).
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numbervars(Term, NewTerm) :- duplicate_term(Term, NewTerm), numbervars(Term, NewTerm, 0, _).
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numbervars(Term, NewTerm, N) :-
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( integer(N), N >= 0 -> duplicate_term(Term, NewTerm), numbervars(Term, NewTerm, N, _)
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; integer(N) -> throw(error(domain_error(not_less_than_zero, N), numbervars/3))
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; throw(error(type_error(integer, N), numbervars/3))
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).
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numbervars(Term, NewTerm, N1, N2) :-
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var(Term), !, NewTerm = '$VAR'(N1), N2 is N1 + 1.
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numbervars(Term, NewTerm, N1, N2) :- compound(Term), !,
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Term =.. [Name | Args],
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NewTerm =.. [Name | NewArgs],
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fold_numbervars(Args, NewArgs, N1, N2).
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numbervars(_, _, _, _).
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marked_already(Term, NewTerm) :-
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var(Term), nonvar(NewTerm), NewTerm = '$VAR'(_).
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marked_already(Term, NewTerm) :-
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atomic(Term).
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fold_numbervars([HeadTerm | Terms], [NewHeadTerm | NewTerms], N1, Nn) :-
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( marked_already(HeadTerm, NewHeadTerm) -> N1 = N2
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; numbervars(HeadTerm, NewHeadTerm, N1, N2),
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( var(N2) -> N1 = N2
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; true )
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),
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fold_numbervars(Terms, NewTerms, N2, Nn).
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fold_numbervars([], [], _, _).
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