title: insert parentheses in a string
body: <p>I have a mathematical expression which is given via a string.For example:
  -4^2+3*(-23^2+5), I want the resultat to be (0-4)^2+3*((0-23)^2+5)
  I need to write a function which does that kind of thing for the full string.
  Can anyone help?
  thanx in advance</p>