[texhax] xspace

Tom Sgouros tomfool at as220.org
Fri Dec 8 21:34:14 CET 2006

Hello all:

Can anyone tell me what's going on here?

I have this macro defined to test a reference and give me some alternate
text if the label doesn't exist.

  \expandafter\ifx\csname r@#1\endcsname\relax #2\else #3\fi}

It's used like this:

\renewcommand{\tableref}[1]{\testref{#1}{User Guide\xspace}{Table~\ref{#1}\xspace}}

It exists so that I can copy chunks of text from one document into
another without having to go back and fix all the cross-references.

The \xspace macro in the arguments to \testref is apparently seeing
a token that makes it think a space is required, and inserting a space
for me, no matter what.

My questions:

 o What token does the \xspace macro think is following it in a sentence
   like "The \tableref{mg} lists the elements..."

 o How can I persuade it to look at the token that follows the \tableref
   macro instead of whatever it's seeing?

Incidentally, I do know that I could change \tableref to this, and it would work: 

\renewcommand{\tableref}[1]{\testref{#1}{User Guide}{Table~\ref{#1}}\xspace}

But I'm still curious about what's going on in the other case.  I can't
explain it, so I'm apparently missing something I wish I understood better.

Many thanks,


 tomfool at as220 dot org

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