12 lines
242 B
Perl
12 lines
242 B
Perl
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% tree structure
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parent(pam,bob).
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parent(tom,bob).
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parent(tom,liz).
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parent(bob,ann).
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parent(bob,pat).
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parent(pat,jim).
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predecessor(X, Z) :- parent(X, Z).
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predecessor(X, Z) :- parent(X, Y), predecessor(Y, Z).
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offspring(Y, X) :- parent(X, Y).
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