Matrix functions should call error() on error conditions, not print()

[dcuny]

Errors caused by wrong-sized matrices in Matrix.lua use print() and then return.

For example:

  function mat.dot(m1,m2)
    if m1.cols ~= m2.rows then
      print("Erro in matrix dot, cols rows erro")
      return
    end
   ...

Because return does not return a matrix as expected (it will return nil), the code will fail later on when it attempts an operation on the non-existent matrix.

The routines should instead call error, so the call stack trace will reflect how the routine was called. For example:

  function mat.dot(m1,m2)
    if m1.cols ~= m2.rows then
      print("Error in mat.dot: "..(m1.cols).." columns in m1 do not match "..(m2.rows).."in m2")
      return
    end
   ...