[albrewer]

The solution is not to stick strictly to prefix, postifx, or infix notation. Instead, all three should be valid.

All these should be equivalent:

  + a b + c d + 
  + + + a b c d
  a + b + c + d
  a b c d + + +

More insidiously, these should be equivalent:

  x = a + b
  = + x a b
  x a b = +
  + x = a b
  x = a b +
  x a + b =