Question about defining a math macro

[Aditya Mahajan <adityam@umich.edu>]

Hi,

Can I define a math macro, say \EXP that does the following:

1) \EXP{something} gives me, say E(something)
2) \EXP_a^b{something} gives my E_a^b(something)

That is, I want to write a macro that will only be used in the math 
mode, that does something with its argument. But, I also want it to 
handle _ and ^ if they are present.

The only method that I can think of is to check _ or ^ with 
\ifnextcharacter and go through all 5 cases (nothing, only _, only ^, 
_ followed by ^, ^ followed by _) but this seems very inefficient. Is 
there a better way?

Aditya