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From: jeffrey@cs.chalmers.se (Alan Jeffrey)
Newsgroups: comp.text.tex
Subject: Gripe about _ and ^
Message-ID: <4377@undis.cs.chalmers.se>
Date: 23 Feb 91 17:38:36 GMT
Sender: news@cs.chalmers.se
Organization: Dept. of CS, Chalmers, Sweden
Lines: 44

Why oh why oh why do ^ and _ in TeX not take their arguments in the 
`standard' way?  For example, if you say
 
   \def\nil{[]}
   $a_\nil$
 
you get `a ]' and not `a  '.
          [             []
 
In this case we're OK, because \nil should be an ord, so we can just say 
 
   \def\nil{{[]}}
 
instead, and we're all right.  But if we want to define a bin, rel, op, 
or whatever, we're in real trouble, for example
 
   \def\may{\mathrel{\it may}}
   $a_\may$
 
produces the error message
 
   ! Missing { inserted.
   <to be read again>
                      \mathrel
   \may ->\mathrel
                   {\it may}
   <*> $a_\may
              $
 
because TeX interprets this as $a_\mathrel{\it may}$, and `obviously' 
a_\mathrel is rubbish.  As far as I can see, the only options are
 
   a) either type _\foo or _{\foo} depending on what the definition of 
      \foo is, which rather spoils the point of logical markup, or
   b) consistently type _{\foo}, which is a right pain, or
   c) redefine _ and ^.
 
Has anyone any better suggestions?
 
Cheers,
 
Alan.
Alan Jeffrey         Tel: +46 31 72 10 98         jeffrey@cs.chalmers.se
Department of Computer Sciences, Chalmers University, Gothenburg, Sweden