Shape.hs:52:30:
    No instance for (Num (Vector -> Float))
      arising from a use of `signum' at Shape.hs:52:30-35
    Possible fix:
      add an instance declaration for (Num (Vector -> Float))
    In the first argument of `(.)', namely `signum'
    In the first argument of `zipWith', namely
        `(signum . crossProduct)'
    In the expression: zipWith (signum . crossProduct) vectors vectors2