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Prolog：リストに関する質問

2008/05/01 00:47

prefix(L1, L2)：L1がL2のサブリストかどうか調べる述語を作ってるんですがサブリストに含まれているものしか判定できないまま悩み続けています。含まれていないものを入力すると無限ループに入ります。compoundを使ってみてもRedoでその行だけで無限ループに入ります。。。なにか打開策はないでしょうか？ /*---------------------無限ループ------------------------*/ [debug] ?- trace, prefix([c], [a, b, c]). Call: (8) prefix([c], [a, b, c]) ? creep Call: (9) prefix([c], [b, c]) ? creep Call: (10) prefix([c], [c]) ? creep Exit: (10) prefix([c], [c]) ? creep Exit: (9) prefix([c], [b, c]) ? creep Exit: (8) prefix([c], [a, b, c]) ? creep Yes [debug] ?- | . ERROR: Stream user_input:0:30 Syntax error: Unexpected end of clause [debug] ?- trace, prefix([g], [a, b, c]). Call: (8) prefix([g], [a, b, c]) ? creep Call: (9) prefix([g], [b, c]) ? creep Call: (10) prefix([g], [c]) ? creep Call: (11) prefix([g], []) ? creep Call: (12) prefix([g], []) ? creep Call: (13) prefix([g], []) ? creep Call: (14) prefix([g], []) ? creep Call: (15) prefix([g], []) ? creep Call: (16) prefix([g], []) ? creep Call: (17) prefix([g], []) ? /*-----------------Redo-----------------*/ ?- trace, prefix([g], [a, b, c]). Call: (9) prefix([g], [a, b, c]) ? cree Call: (10) compound([b, c]) ? creep Exit: (10) compound([b, c]) ? creep Call: (10) prefix([g], [b, c]) ? creep Call: (11) compound([c]) ? creep Exit: (11) compound([c]) ? creep Call: (11) prefix([g], [c]) ? creep Call: (12) compound([]) ? creep Fail: (12) compound([]) ? creep Redo: (11) prefix([g], [c]) ? creep Call: (12) prefix([g], [c]) ? creep Call: (13) compound([]) ? creep Fail: (13) compound([]) ? creep Redo: (12) prefix([g], [c]) ? creep Call: (13) prefix([g], [c]) ? creep Call: (14) compound([]) ? creep Fail: (14) compound([]) ? creep Redo: (13) prefix([g], [c]) ? creep Call: (14) prefix([g], [c]) ? creep Call: (15) compound([]) ? creep Fail: (15) compound([]) ? creep Redo: (14) prefix([g], [c]) ? creep Call: (15) prefix([g], [c]) ? creep Call: (16) compound([]) ? creep Fail: (16) compound([]) ? creep /*-------------ソース----------------*/ prefix([], _). prefix([X], [X|_]). prefix([X], [_|Y1]) :- prefix([X], Y1). prefix([X|Y], Y1) :- prefix([X], Y1), prefix(Y, Y1). /*-------------compound---------------*/ prefix([], _). prefix([X], [X|_]). prefix([X], [_|Y1]) :- compound(Y1), prefix([X], Y1). prefix([X|Y], Y1) :- prefix([X], Y1), prefix(Y, Y1).