%query: perm(i,o). % mode: ap1[o,o,i] ap1(nil, X, X). ap1(cons(H, X), Y, cons(H, Z)) :- ap1(X, Y, Z). % mode: ap2[i,i,o] ap2(nil, X, X). ap2(cons(H, X), Y, cons(H, Z)) :- ap2(X, Y, Z). % mode: perm[i,o] perm(nil, nil). perm(Xs, cons(X, Ys)) :- ap1(X1s, cons(X, X2s), Xs), ap2(X1s, X2s, Zs), perm(Zs, Ys). % example 3 in % Transformational methodology for proving termination of logic programs % Rao, M.R.K.K.; Kapur, D.; Shyamasundar, R.K. % The Journal Of Logic Programming, Vol: 34, Issue: 1, January 1998
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