Re: TeX (was: apostrophe etc.)

From: Markus Kuhn (
Date: Thu Aug 19 1999 - 15:57:24 EDT

Michael Everson wrote on 1999-08-19 17:37 UTC:
> >TeX goes even beyond Unicode at least for one interesting special
> >character: TeX distinguishes between normal spaces and spaces after a
> >sentence. The latter are allowed to grow a bit larger during paragraph
> >formatting (unless the \frenchspacing option is activated which
> >prohibits this), and according to at least US typewriter rules are
> >represented by a double space on typewriters (not so Europe).
> Good gods, what a horrible "solution". The _problem_ is that when they
> learned to type people (mostly North Americans) didn't learn the detail
> that there really _aren't_ supposed to be two spaces after a full stop, it
> is only TYPED there with MECHANICAL TYPEWRITERS on PAPER to help someone
> else actually set the page. In the modern world of electronic publishing,
> whether on one's own desktop or another's,

I am not entirely sure, I understood the above paragraph completely and
part of the last sentence seems to be missing. I have observed that many
mechanical typewriter users in the US write two spaces after a full-stop
at the end of a sentence. I know several pieces of software that have
algorithms hardwired into them that makes use or support this habit. The
corresponding behaviour in TeX and GNU Emacs can be deactivated by
European users with "\frenchspacing" and "(setq sentence-end-double-space
nil)" respectively. I don't know, what the various US typographical style
guides precisely recommend here. What exactly is the bad training
problem that you refer to?

TeX doesn't handle spaces just as an ordinary character. The paragraph
filling algorithms of TeX are considerably more sophisticated than
anything else I have seen in the publishing industry so far. It has a
whitespace object called "glue", which is like a rubberband that has an
adjustable elasticity associated with it. The glue after a comma
stretches at 1.25 times the rate of glue between adjacent words; the glue
after a fullstop, question/exclamation mark, or a closing quotation mark
stretches even 3 times the rate. (TeXbook, chapter 12, page 73).

More information on TeX's line-breaking algorithm can be found in

  D. Knuth, M. Plass: Breaking Paragraphs into Lines. Software
  Practice and Experience 11 (1981), pp 1119-1184.

which has been reprinted recently in

  Donald E. Knuth: Digital Typography. Cambridge University Press, 1999.
  ISBN 1-57586-010-4. <http://www-cs-staff.Stanford.EDU/~knuth/dt.html>


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: <>

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