Received: from mail.proteosys.com ([213.139.130.197]) by nummer-3.proteosys with Microsoft SMTPSVC(5.0.2195.6713); Thu, 25 Mar 2004 14:19:38 +0100 Received: by mail.proteosys.com (8.12.10/8.12.2) with ESMTP id i2PDJYlo004981 for ; Thu, 25 Mar 2004 14:19:35 +0100 Received: from listserv.uni-heidelberg.de (listserv.uni-heidelberg.de [129.206.119.176]) by relay.uni-heidelberg.de (8.12.10/8.12.10) with ESMTP id i2PDDMiv012946; Thu, 25 Mar 2004 14:13:22 +0100 (MET) MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C4126B.D2C2D100" Received: from listserv (listserv.uni-heidelberg.de [129.206.119.176]) by listserv.uni-heidelberg.de (8.12.7/8.12.7/SuSE Linux 0.6) with ESMTP id i2P700cw014195; Thu, 25 Mar 2004 14:12:17 +0100 Received: from LISTSERV.UNI-HEIDELBERG.DE by LISTSERV.UNI-HEIDELBERG.DE (LISTSERV-TCP/IP release 1.8e) with spool id 62741 for LATEX-L@LISTSERV.UNI-HEIDELBERG.DE; Thu, 25 Mar 2004 14:12:16 +0100 X-MimeOLE: Produced By Microsoft Exchange V6.5 Received: from relay.uni-heidelberg.de (relay.uni-heidelberg.de [129.206.100.212]) by listserv.uni-heidelberg.de (8.12.7/8.12.7/SuSE Linux 0.6) with ESMTP id i2PD2FN6020188 for ; Thu, 25 Mar 2004 14:02:15 +0100 Received: from fencepost.gnu.org (fencepost.gnu.org [199.232.76.164]) by relay.uni-heidelberg.de (8.12.10/8.12.10) with ESMTP id i2PD2miv009475 for ; Thu, 25 Mar 2004 14:02:48 +0100 (MET) Received: from fencepost.gnu.org ([127.0.0.1] helo=lola.goethe.zz) by fencepost.gnu.org with esmtp (Exim 4.24) id 1B6UQs-0000AK-8G for LATEX-L@listserv.uni-heidelberg.de; Thu, 25 Mar 2004 07:58:02 -0500 In-Reply-To: Lines: 55 References: Return-Path: X-OriginalArrivalTime: 25 Mar 2004 13:19:38.0324 (UTC) FILETIME=[D2F44140:01C4126B] User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3.50 X-Scanned-By: MIMEDefang 2.28 (www . roaringpenguin . com / mimedefang) X-Spam-Score: 0 () Content-class: urn:content-classes:message Subject: Re: TeX units Date: Thu, 25 Mar 2004 14:02:44 +0100 Message-ID: A X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: TeX units Thread-Index: AcQSa9MRaFWYI/s+TBCVe7lH/7ZonA== From: "David Kastrup" Sender: "Mailing list for the LaTeX3 project" To: Reply-To: "Mailing list for the LaTeX3 project" Status: R X-Status: X-Keywords: X-UID: 4774 This is a multi-part message in MIME format. ------_=_NextPart_001_01C4126B.D2C2D100 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ulrich Dirr writes: > I've looked into TeX.web where I found the following definitions: > in :=3D set_conversion(7227)(100) > pc :=3D set_conversion(12)(1) > cm :=3D set_conversion(7227)(254) > mm :=3D set_conversion(7227)(2540) > bp :=3D set_conversion(7227)(7200) > dd :=3D set_conversion(1238)(1157) > cc :=3D set_conversion(14856)(1157) > > On occasion I need to trace TeX's page building via \tracingpages=3D2. > Assume you have a \textheight of 39 \baselineskip + \topskip, and one > \baselineskip is 13bp. Then \textheight is 507bp+10pt. No, it isn't. Disregarding the topskip (which has an exact representation): \dimen0=3D13bp \dimen0=3D39\dimen0 \showthe\dimen0 \dimen0=3D507bp \showthe\dimen0 This is TeXk, Version 3.141592 (Web2C 7.5.2) %&-line parsing enabled. (/usr/local/TeX/texmf/web2c/cp8bit.tcx) ** * *> 508.90073pt. <*> \showthe\dimen0 ? * *> 508.90125pt. <*> \showthe\dimen0 ? ! Emergency stop. <*> \showthe\dimen0 No pages of output. Transcript written on texput.log. > Maybe someone could explain this behavior to me? 507bp is calculated as 507*7227/7200, which is different from 39*(13*7227/7200), since we are talking about arithmetic without associative law. This is common in floating point arithmetic, and it is of course also relevant in TeX's fixed point arithmetic. Since units are implemented as scaling ratios rather than fixed values, you get the results you experience. -- David Kastrup, Kriemhildstr. 15, 44793 Bochum ------_=_NextPart_001_01C4126B.D2C2D100 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: TeX units

Ulrich Dirr <ud@ART-SATZ.DE> writes:

> I've looked into TeX.web where I found the = following definitions:
> in :=3D set_conversion(7227)(100)
> pc :=3D set_conversion(12)(1)
> cm :=3D set_conversion(7227)(254)
> mm :=3D set_conversion(7227)(2540)
> bp :=3D set_conversion(7227)(7200)
> dd :=3D set_conversion(1238)(1157)
> cc :=3D set_conversion(14856)(1157)
>
> On occasion I need to trace TeX's page building = via \tracingpages=3D2.
> Assume you have a \textheight of 39 = \baselineskip + \topskip, and one
> \baselineskip is 13bp. Then \textheight is = 507bp+10pt.

No, it isn't.  Disregarding the topskip (which = has an exact
representation):

\dimen0=3D13bp
\dimen0=3D39\dimen0
\showthe\dimen0

\dimen0=3D507bp
\showthe\dimen0
This is TeXk, Version 3.141592 (Web2C 7.5.2)
 %&-line parsing enabled.
 (/usr/local/TeX/texmf/web2c/cp8bit.tcx)
**
*
*> 508.90073pt.
<*> \showthe\dimen0

?
*
*> 508.90125pt.
<*> \showthe\dimen0

?
! Emergency stop.
<*> \showthe\dimen0

No pages of output.
Transcript written on texput.log.

> Maybe someone could explain this behavior to = me?

507bp is calculated as 507*7227/7200, which is = different from
39*(13*7227/7200), since we are talking about = arithmetic without
associative law.  This is common in floating = point arithmetic, and it
is of course also relevant in TeX's fixed point = arithmetic.  Since
units are implemented as scaling ratios rather than = fixed values, you
get the results you experience.

--
David Kastrup, Kriemhildstr. 15, 44793 Bochum

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