title: Can't concatenate a char with a string ML
body: <p>Hello i am trying to do a incFirst function in ML. The function does the following: incFirst "bad" = "cad" incFirst "shin" = "thin". This is what i try to do <code>fun incFirst s = chr(ord s + 1) ^ substring(s, 1, size s -1);</code>
  I get the following error: Can't unify string (<em>In Basis</em>) with char (<em>In Basis</em>)
           (Different type constructors)
  Found near chr (ord s + 1) ^ substring (s, 1, ... - ...)
  Exception- Fail "Static Errors" raised
  Any idea how i can concatenate a char with a string if the "^" operator is not working?</p>