prolog program to find equality of two lists in any order
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by Happy Mittal
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Published on 2010-04-26T00:11:44Z
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2010/04/26
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I wanted to write a prolog program to find equality of two lists, the order of elements
doesn't matter.
So I wrote following:
del( _ , [ ] , [ ] ) .
del( X , [ X|T ] , T ).
del( X , [ H|T ] , [ H|T1 ] ) :- X \= H , del( X , T , T1 ).
member( X, [ X | _ ] ) .
member( X, [ _ | T ] ) :- member( X, T ).
equal( [ ], [ ] ).
equal( [X], [X] ).
equal( [H1|T], L2 ) :- member( H1, L2 ), del( H1, L2, L3), equal(T , L3 ).
But when I give input like equal([1,2,3],X)., it doesn't show all possible values of X.
instead the program hangs in the middle.
What could be the reason?
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