fib(0, 0).
fib(N,F) :-
  N > 0,
  fib(N, F, _).

fib(1,1,0).
fib(N, F1, F2) :-
  N > 1,
  N1 is N-1,
  fib(N1, F2, F3),
  F1 is F2 + F3.

rovarsprak([], []).
rovarsprak(T, Tr, Letter, Letter, 111, Letter)  :- rovarsprak(T, Tr).
rovarsprak(T, Tr, Letter, Letter, A, B):- rovarsprak(Tr, [A, B|Tr]).
rovarsprak([H|T], [Hr, A, B |Tr]) :-
  rovarsprak(T, Tr, H, Hr, A, B).

medellangd([H], isSpace(32), CountW, CountC, _, AvgLen) :- AvgLen is CountC/(CountW+1).
medellangd([H], _, CountW, CountC, _, AvgLen) :- AvgLen is (CountC+1)/CountW.

medellangd([H |T], AvgLen) :-
  medellangd([H | T], isSpace(H), 0, 0, 1, AvgLen).

medellangd([H2,H3|T], isSpace(32), CountW, CountC, IsSpace, AvgLen) :-
  medellangd([H3|T], isSpace(H3), CountW, CountC, 1, AvgLen).

medellangd([H2, H3|T], _, CountW, CountC, 0, AvgLen) :-
    N2 is CountC + 1,
    medellangd([H3|T], isSpace(H3), CountW, N2, 0, AvgLen).

medellangd([H2, H3|T], _, CountW, CountC, 1, AvgLen) :-
    N2 is CountC + 1,
    N1 is CountW + 1,
    medellangd([H3|T], isSpace(H3), N1, N2, 0, AvgLen).

isSpace(32).