%Source: https://sites.google.com/site/prologsite/prolog-problems %query:encode_direct(g,g,f). % 1.19 (**): Rotate a list N places to the left % rotate(L1,N,L2) :- the list L2 is obtained from the list L1 by % rotating the elements of L1 N places to the left. % Examples: % rotate([a,b,c,d,e,f,g,h],3,[d,e,f,g,h,a,b,c]) % rotate([a,b,c,d,e,f,g,h],-2,[g,h,a,b,c,d,e,f]) % (list,integer,list) (+,+,?) rotate([],_,[]) :- !. rotate(L1,N,L2) :- length(L1,NL1), N1 is N mod NL1, split(L1,N1,S1,S2), append(S2,S1,L2). split(L,0,[],L). split([X|Xs],N,[X|Ys],Zs) :- N > 0, N1 is N - 1, split(Xs,N1,Ys,Zs).
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