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+====== Term substitution ======
+{{tag>terms}}
+===== Description =====
+A program for substituting in a term
+**Source**:  The Art of Prolog
+===== Download =====
+Program source code: {{term_substitution.pl}}
+===== Listing =====
+<code prolog>
+/*
+  substitute(Old,New,OldTerm,NewTerm) :- NewTerm is the result of replacing
+	all occurences of Old in OldTerm by New.
+*/
+     substitute(Old,New,Old,New).
+     substitute(Old,New,Term,Term) :-
+        constant(Term), Term \== Old.
+     substitute(Old,New,Term,Term1) :-
+        compound(Term),
+        functor(Term,F,N),
+        functor(Term1,F,N),
+        substitute(N,Old,New,Term,Term1).
+	substitute(N,Old,New,Term,Term1) :-
+            N > 0,
+	    arg(N,Term,Arg),
+	    substitute(Old,New,Arg,Arg1),
+	    arg(N,Term1,Arg1),
+	    N1 is N-1,
+	    substitute(N1,Old,New,Term,Term1).
+        substitute(0,Old,New,Term,Term1).
+%  Program 9.3  A program for substituting in a term
+</code>
+===== Comments =====

pl/prolog/pllib/term_substitution.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)

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