Question

I am really new in prolog programing and I can just ask simple questions.

I want to rotate lists to left in prolog like following:

rotatelist([1,2,3,4],R)   
R=[2,3,4,1]

I tried the following code:

rotatelist([],[]).   
rotatelist([H1|T1],[H2|T2]) :- rotatelist(H1,T2).

Answer 1

Something like this ought to do the trick:

rotatelist(List, R):- rotatelist(List, R1, H), R = [H|R1].
rotatelist([H], [], H).
rotatelist([H|T], L, R) :- rotatelist(T, T1, R), L = [H|T1].