use new nth0/3 from library(lists)
@@ -6917,12 +6917,6 @@ contribution_at(T, Task, Offset-Bs, Contribution) :-
?(Contribution) #= B*C
).
-nth0(0, [E|_], E) :- !.
-nth0(N, [_|Ls], E) :-
- N > 0,
- N1 is N - 1,
- nth0(N1, Ls, E).
-
nth1(I, Es, E) :-
I0 is I-1,
nth0(I0, Es, E).
