X-VM-v5-Data: ([nil nil nil nil t nil nil nil nil] ["1965" "Mon" "5" "October" "92" "13:13:58" "EDT" "Charles Wells" "cfw2@PO.CWRU.EDU" "<9210051816.AA02314@sc.zib-berlin.dbp.de>" "65" "Commands with empty input" "^Date:" nil nil "10"]) Return-Path: Received: from sc.ZIB-Berlin.DE (serv01) by dagobert.ZIB-Berlin.DE (4.1/SMI-4.0/1.9.92 ) id AA09250; Mon, 5 Oct 92 19:17:12 +0100 Received: from vm.urz.Uni-Heidelberg.de (vm.hd-net.uni-heidelberg.de) by sc.ZIB-Berlin.DE (4.0/SMI-4.0-sc/19.6.92) id AA02314; Mon, 5 Oct 92 19:16:09 +0100 Message-Id: <9210051816.AA02314@sc.zib-berlin.dbp.de> Received: from DHDURZ1 by vm.urz.Uni-Heidelberg.de (IBM VM SMTP V2R2) with BSMTP id 5587; Mon, 05 Oct 92 19:16:29 CET Received: from DHDURZ1 by DHDURZ1 (Mailer R2.08 R208004) with BSMTP id 5566; Mon, 05 Oct 92 19:16:22 CET Received: from DHDURZ1 by DHDURZ1 (Mailer R2.08 R208004) with BSMTP id 5563; Mon, 05 Oct 92 19:16:18 CET Reply-To: Mailing list for the LaTeX3 project Date: Mon, 5 Oct 92 13:13:58 EDT From: Charles Wells Sender: Mailing list for the LaTeX3 project To: Multiple recipients of Subject: Commands with empty input Status: R X-Status: X-Keywords: X-UID: 843 The letter style provided with the PCTeX LaTeX implementation (and probably with others) has a flaw that I have found elsewhere in tex macro collections: Some macros don't work properly if provided with empty input. For example, the following gives an error message. cut here----------------------- \documentstyle{letter} \begin{document} \name{Charles Wells} \signature{Charles Wells\\ Professor of Mathematics\\ cfw2@po.cwru.edu} \begin{letter}{} \opening{Dear Somebody:} Blah Blah. \closing{Yours sincerely,} \end{letter} \end{document} ------------------------------cut here This is the error message: ---------------------------- ! Bad use of \\. \@latexerr ...for immediate help.}\errmessage {#1} \\->\ifhmode \unskip \else \@badcrerr \fi \par \@ifstar {\penalty \@M \@xcen... \opening ... {2\parskip } {\raggedright \toname \\ \toaddress \par }\vspace ... l.9 \opening{Dear Somebody:} ---------------------------- There is a legitimate reason for writing a letter with no to-address (for example, a letter of reference), and the style file should not cause the attempt to fail. There are other situations in which empty input should not be allowed, but in those cases an explicit error message complaining of empty input should be generated instead of messages such as the mysterious one generated by the example above. Handling empty input correctly is a standard requirement of good programming practice, and I hope that the LaTeX3 committee will keep such standards in mind. By the way, I write letters in TeX all the time, even letters to the editor and such that don't contain technical content. But perhaps letter.sty should be different for different countries and not part of a standard distribution. -- Charles Wells Department of Mathematics, Case Western Reserve University University Circle, Cleveland, OH 44106-7058, USA 216 368 2893