Prog i need your wisdom

No this isn't a joke, or a meme or a fad or whatever you think it is. It just a
regular programming problem.

I'm making a ASCII-art math generator. So you can input in your document
Maxima-notation math and get a corresponding representation. Example:

>Integrate(x^2,x,0,5)

  5 __
   / 2
 _/ x  dx
 0

While a got the AST right. When making the representation on ASCII-text I hit a
problem. The inner-term can change the structure of the outer ones, so this
isn't straight forward

>integrate(x,x,0,5)
>integrate(x+3/2,x,0,5)

  5 __
   / 
 _/ x  dx
 0           

   5 ______
    /   3
   /x + -   dx
 _/     2
 0

 Which is the simplest approach to this?

 Pd: I am not telling in what I'm implementing it so it doesn't derail.

>>8
I meant something like a NAT.