Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!samsung!umich!vela!rjohnson
From: rjohnson@vela.acs.oakland.edu (R o d Johnson)
Newsgroups: comp.text.tex
Subject: Re: Testing for null arguments
Keywords: latex
Message-ID: <5407@vela.acs.oakland.edu>
Date: 15 Mar 91 03:48:02 GMT
References: <5396@vela.acs.oakland.edu>
Reply-To: rjohnson@vela.acs.oakland.edu (R o d Johnson)
Organization: Academics Anonymous
Lines: 19


Thanks to everyone that sent help on this, especially Raymond Chen,
Richard Hughey (who contributed an idea unlike any other) and Bill
Mitchell, whose version I actually used.

Incidentally, Raymond's solution was

  \def\ifnull#1{\def\@tempa{#1}\ifx\@tempa\empty}

which doesn't work.  I'm still not sure why.  If instead we use

  \def\ifnull#1{\def\@tempa{#1}\def\@tempb{}\ifx\@tempa\@tempb}

it works fine.  Since \@tempb is defined the same way as \empty I'm
puzzled by this.  Can anyone confirm this (mis)behavior or explain it?

-- 
 Rod Johnson  *  rjohnson@vela.acs.oakland.edu  *  (313) 650 2315 

  "House, bridge, well, gate, jug, olive tree, window"  --Rilke