Re: Question about defining a math macro

[Taco Hoekwater <taco@elvenkind.com>]

Aditya Mahajan wrote:
> 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?

Actually, there is, by using a bit of black magic in the
macro definition:

   \def\EXP#1#{\bgroup\def\EXParg{#1}\doEXP}
   \def\doEXP#1{\mfunction{E}\EXParg({\rm #1})\egroup}

That extra hash mark has the effect of putting everything
upto the next explicit left brace into #1.

Cheers, Taco