%query: perm1(i,o). %% perm1(Xs, Ys) :- Ys is a permutation of the list Xs. %% %TWTYPES :- type perm1(list,list). perm1([], []). perm1(Xs, [X | Ys]) :- select(X, Xs, Zs), perm1(Zs, Ys). %TWTYPES :- type select(poly,list,list). select(X, [X | Xs], Xs). select(X, [Y | Xs], [Y | Zs]) :- select(X, Xs, Zs). /*TWDESC perm1(Xs, Ys) :- Ys is a permutation of the list Xs. */ /*TWTYPES list([]). list([X|Xs]) :- poly(X), list(Xs). poly(dummy). */ /*TWDEMO selected_norms([list,poly]). query(perm1(b,f,f,f)). query(perm1(f,b,f,f)). query(select(f,f,b,f,f,f)). query(select(f,f,f,b,f,f)). query(select(f,f,f,f,b,f)). query(select(f,f,f,f,f,b)). */
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