The parser for symbolic expressions in infix form parses negative numbers strangly

[gkronber]

Some examples:

• Input: -1.0*x + 2.0
• Expected:

    (+ 
       (* -1.0 x) 
       2.0)
  

• Output:

  (+ 
    (- (* 1.0 x))
    2.0)
  

• Input: exp(-1.0*x - 2.0)
• Output:

  (exp (* 
         -1.0 
         (+ 
           (* 1.0 x) 
           2.0)))
  

• Expected:

  (exp (- 
         (* -1.0 x)
          2.0))