Re: Question about defining a math macro

[Hans Hagen <pragma@wxs.nl>]

Aditya Mahajan wrote:
> On Sat, 24 Feb 2007, Taco Hoekwater wrote:
>
>   
>> 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.
>>     
>
> Wow Taco. This is great.
>   
some applications of this mechanism can be found in the context source code (supp-box etc) 

Hans 


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