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% Prolog 4乗を定義は以下が代表的なもの。

pow4(X,Y) :- Y is X * X * X * X.

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pow4(X,Y) :- Y is X ^ 4.

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pow4(X,Y) :- pow4(4,X,Y).

pow4(1,X,X) :- !.
pow4(N,X,Y) :- N1 is N - 1,pow4(N1,X,Z),Y is X * Z.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
pow4(X,Y) :- pow4(1,4,X,Y).

pow4(M,N,_,1) :- M > N,!.
pow4(M,N,X,Y) :- M1 is M + 1,pow4(M1,N,X,Z),Y is X * Z.