[texhax] Forcing size changes in exponents

[bnb at ams.org]

On Sun, 16 Aug 2015, Michael Barr wrote:

    I have often been criticized by posters on these boards for "not using LaTeX".  Why I should care is a real question.  But here is something I really tried to do in LaTeX and failed, although it is almost trivial using the deprecated command \rm:
    
    \def\op{^{\rm op}}
     $A\op$
     $A^{A\op}$
     
    When I tried do it using \textrm, the size did not change.  So I added \scriptsize.  I expected the first line to be correct, I expected the second would not.  Instead I got a missing $ error.  I tried sprinkling some $ signs into the defiinition and the first one worked (although I don't see why), but the second still caused an error.
    
    So how can you do this in pure LaTeX?

try this:

\documentclass{article}
\newcommand{\op}{^{\mathrm{op}}}
\begin{document}
 $A\op$
 $A^{A\op}$
\end{document}

if you have the latest version of tex live
(tex live 2015), \rm and the other 2-letter
font changes (except, i think, \em) have
been disabled.

\mathrm has been the recommended latex
math font specification for many years.
it does change sizes as expected.

i sympathize with your desire to be able
to use the same vocabulary in plain tex
and latex, but it really isn't possible.
					-- bb