Ruby

the documentation of cross_product is inconsistent. The doc says:
Vector[1, 0, 0].cross_product Vector[0, 1, 0] => Vector[0, 0, 1]

which seems good to me, but the definition given in the "click to toggle source" actually produces: Vector[0,0,-1], which according to a closed bug report seems to be what the function actually once produced. The documented code is still wrong. this would be correct and clear:

def cross_product(v)
Vector.Raise ErrDimensionMismatch unless size == v.size && v.size == 3
Vector[ @elements[1]*v[2] - @elements[2]*v[1],
@elements[2]*v[0] - @elements[0]*v[2],
@elements[0]*v[1] - @elements[1]*v[0] ]
end

I recommend also altering the demonstration code so that a reasonably complete test case is shown:

Vector[1, 0, 0].cross_product Vector[0, 1, 0] => Vector[0, 0, 1]
Vector[0, 1, 0].cross_product Vector[0, 0, 1] => Vector[1, 0, 0]
Vector[0, 0, 1].cross_product Vector[1, 0, 0] => Vector[0, 1, 0]