Dlaczego kompilowanie tego kodu:

triples( [], _,_,_)->
  [];

triples( Self, X, Y, none )->
  [ Result || Result = { X, Y, _} <- Self ].

raport:

./simple_graph.erl:63: Warning: variable 'X' is unused
./simple_graph.erl:63: Warning: variable 'Y' is unused
./simple_graph.erl:64: Warning: variable 'X' is unused
./simple_graph.erl:64: Warning: variable 'X' shadowed in generate
./simple_graph.erl:64: Warning: variable 'Y' is unused
./simple_graph.erl:64: Warning: variable 'Y' shadowed in generate

I zwróć zły wynik: pełna Jaźń.