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pl:prolog:pllib:terms_variety [2019/06/27 15:50] (aktualna) |
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| + | ====== Terms variety ====== | ||
| + | {{tag>operators numbers}} | ||
| + | ===== Description ===== | ||
| + | Testing if terms are variants | ||
| + | |||
| + | **Source**: The Art of Prolog | ||
| + | ===== Download ===== | ||
| + | Program source code: {{terms_variety.pl}} | ||
| + | ===== Listing ===== | ||
| + | <code prolog> | ||
| + | /* | ||
| + | variants(Term1,Term2) :- Term1 and Term2 are variants. | ||
| + | */ | ||
| + | |||
| + | :- op(900, fx, [not]). | ||
| + | |||
| + | variants(Term1,Term2) :- | ||
| + | verify((numbervars(Term1,0,N), | ||
| + | numbervars(Term2,0,N), | ||
| + | Term1=Term2)). | ||
| + | |||
| + | verify(Goal) :- not (not Goal). | ||
| + | |||
| + | numbervars('$VAR'(N),N,N1) :- | ||
| + | N1 is N+1. | ||
| + | numbervars(Term,N1,N2) :- | ||
| + | nonvar(Term), functor(Term,Name,N), | ||
| + | numbervars(0,N,Term,N1,N2). | ||
| + | |||
| + | numbervars(N,N,Term,N1,N1). | ||
| + | numbervars(I,N,Term,N1,N3) :- | ||
| + | I < N, | ||
| + | I1 is I+1, | ||
| + | arg(I1,Term,Arg), | ||
| + | numbervars(Arg,N1,N2), | ||
| + | numbervars(I1,N,Term,N2,N3). | ||
| + | |||
| + | % Program 11.7 Testing if terms are variants | ||
| + | </code> | ||
| + | ===== Comments ===== | ||
