20 lines
484 B
Prolog
20 lines
484 B
Prolog
:- module(terms, [numbervars/3]).
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:- use_module(library(error)).
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numbervars(Term, N0, N) :-
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catch(internal_numbervars(Term, N0, N),
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error(E,Ctx),
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( ( var(Ctx) -> Ctx = numbervars/3 ; true ), throw(error(E,Ctx) ) ) ).
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internal_numbervars(Term, N0, N) :-
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must_be(integer, N0),
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can_be(integer, N),
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term_variables(Term, Vars),
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numberlist(Vars, N0, N).
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numberlist([], N, N).
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numberlist(['$VAR'(N0)|Vars], N0, N) :-
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N1 is N0+1,
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numberlist(Vars, N1, N).
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