Path: utzoo!attcan!uunet!mcsun!ukc!edcastle!edcogsci!lex
From: lex@cogsci.ed.ac.uk (Alexander Holt)
Newsgroups: comp.text.tex
Subject: How can I get TeX to see LaTeX \ref{...} as a <number>?
Message-ID: <1538@scott.ed.ac.uk>
Date: 13 Jul 90 15:39:00 GMT
Organization: Centre for Cognitive Science, Edinburgh, UK
Lines: 48

[I did try <latex-help@sumex-aim.stanford.edu> a month ago, but no
response]

I'm writing some LaTeX macros in which I would like to turn an integer
into the corresponding lowercase letter, thus 1 -> a, 2 -> b, etc.
LaTeX sometimes needs to do this itself for the value of counters and
uses these definitions:

\def\@alph#1{\ifcase#1\or a\or b\or c\or d\else\@ialph{#1}\fi}
\def\@ialph#1{\ifcase#1\or \or \or \or \or e\or f\or g\or h\or i\or j\or
   k\or l\or m\or n\or o\or p\or q\or r\or s\or t\or u\or v\or w\or x\or y\or
   z\else\@ctrerr\fi}
\def\@ctrerr{\@latexerr{Counter too large}\@ehb}

Here the TeX command \ifcase is used - which expects a <number>.  My
problem is that I would sometimes like to do:

    \@alph{\ref{...}}

where the \ref{...} is a LaTeX reference to a counter.  But I get the
error:

! Missing number, treated as zero.
<to be read again> 
                   \edef 
<argument> \edef 
                 \@tempa {\@nameuse {r@ex:big2}}\expandafter \@car \@tempa \...

\@ifundefined ...me #1\endcsname \relax #2\else #3
                                                  \fi 
\@alph #1->\ifcase #1
                     \or a\or b\or c\or d\else \@ialph {#1}\fi 
...

since the \ref{...} expands into this \edef ... sequence and TeX cannot
interpret this as a number.

How can I arrange things so that \ifcase finds the number eventually
produced by \ref?

(This all assumes that the label being \ref'd is defined at this point
- when it is not, then I have a different problem!  I would like a way
to detect this case by examining the output of \ref so that I can
bypass the call to \@alph and avoid an error.)

I would be very grateful for any advice on this.

Lex Holt (lex@cogsci.ed.ac.uk)