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From: dhosek@cbrown.claremont.edu (Don Hosek)
Newsgroups: comp.text.tex
Subject: Re: Labels that store the kind of object being labeled
Message-ID: <1991Mar20.133639.1@cbrown.claremont.edu>
Date: 20 Mar 91 21:36:39 GMT
References: <63335@bbn.BBN.COM>
Sender: news@jarthur.Claremont.EDU
Followup-To: comp.text.tex
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Lines: 76

In article <63335@bbn.BBN.COM>, hersh@bbn.com (Hershel Safer) writes:
 
> Rather than write
 
> 	Theorem~\ref{foo}
 
> all the time, I use
 
> 	\newcommand{\thmref}[1]{Theorem~\ref{#1}} .
 
> Actually, it's fancier; since I may want the same label for a theorem,
> an associated figure, and the section in which they are found, I have
 
> 	\newcommand{\thmref}[1]{Theorem~\ref{th:#1}} ,
> 	\newcommand{\secref}[1]{Section~\ref{s:#1}} ,
 
> and a variety of other referencing commands with different prefixes.  I
> also have corresponding labeling commands, such as
 
> 	\newcommand{\thmlabel}[1]{\label{th:#1}} and
> 	\newcommand{\seclabel}[1]{\label{s:#1}} .
 
> Here's the problem.  Suppose that I change a theorem to a proposition.
> Changing \thmlabel to \proplabel is easy enough, but then I also have to
> change all references to the claim from \thmref to \propref.
 
> What I would like is a single labeling command and a single referencing
> command.  The labeling command would take two arguments; the first would
> be the _kind_ of item and the second would be the label.  It would store
> the kind of item.
 
> The referencing command would take a single argument, the label.  It
> would use the stored item information to prepend the correct word to the
> reference number.
 
> Any references to existing solutions or suggestions for how to do this?
> Either TeX or LaTeX would be fine.  Thank you.

LaTeX has a command \p@ITEM which is normally null to refer to
each counter. Defining, e.g., \p@section to be Section~ will
cause those words to be prepended to any reference to a section
reference. This works for nearly everything (the one exception I
have envountered is eqalign does not prepend \p@equation to the
equation number in labels generated there).

This use of \p@WHICHEVER, however, is not recommended since it
does limit the portability of your documents across styles. Its
intended purpose is to allow things like sections numbered as:
I
 A
  1
   a
and referred to as
I.A
 I.A
   I.A.1
       I.A.1(a)
(this is, in fact, what happens in the enumerate environment).
More sophisticated things are possible as well (for example, I've
written a p@section which would give "A" if the section is in the
current chapter and "A in Chapter 2" if the section is in a
different chapter. In general, sophisticated uses of \p@WHATEVER,
however, will become rather complicated. Macro expansion timings
can get really unpleasant.

-dh

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