🚀 go-pugleaf

In article <9210122012.AA08759@enuxha.eas.asu.edu> gomez@enuxha.eas.asu.edu (JL Gomez) writes:
>I've been learning PROLOG and building up some list predicates.
> 
>One of them is a subsequence predicate which returns yes if the elements
>in the first list match the elements in the second list.
>
>The others are rotate predicates like:
>
>rotate([a,b,c,d,e],2,X).
>X = [c,d,e,a,b]
>
>which rotates right, and then
>
>rotate([a,b,c,d,e,f],-2,X]
>X = [e,f,a,b,c,d]


	% true if Sub is a "subsequence" (not necessarily contiguous)
	% of Seq
subseq([], _).
subseq(A.Sub, A.Seq) :-
	subseq(Sub, Seq).
subseq(Sub, _.Seq) :-
	subseq(Sub, Seq).

	% rotates list to right or left (shift can be negative)
rotate(List, Shift, RotatedList) :-
	length(List, Len),
	LenH is (Shift + Len) mod Len,
	length(H, LenH),
	append(H, T, List),
	append(T, H, RotatedList).