Why would you want to have something like this translated into code:

  a + b
  -----
  c + d

Math, in this sense, is already a language, and what you see is already code. (So, basically, all you are talking about is translation, like, from Ruby to Python.)

This is not what I meant at all.

What I want is that I can select "sum symbol" for example, and I can get small description in a popup window. (for more complicated things that is)

That would be difficult. How would it know if f * g is a product or a convolution for example?

It could be ordered from most to least likely like search results. Multiplication is more common so put it at the top. People will assume that it's not the right thing and work down the list

Well if it's mathematics then it's almost certainly a convolution.

Although it could also be a mistyped sub or superscript star on f, which has various different meanings.