[tesseract]

Mathematica will do

    In[1]:= Unevaluated[y = Integrate[x^2, {x, 0, 100}]] // TeXForm
    Out[1]= y=\int_0^{100} x^2 \, dx

which in that case is rather pointless but I suppose it could be helpful in the case of something more complicated.

Maybe Maple can do that too; I don't know since I've only ever used Maple for one 20-minute session and don't have a copy handy.

[jacobolus]

Yes, it can, and the input syntax is much nicer, even:

  > latex('y = int(x^2, x=0..100)')
  
  y=\int _{0}^{100}\!{x}^{2}{dx}