[texhax] dash spacing

[Barbara Beeton]

tom sgouros asks about dashes and spacing
around them.  (hi, tom.)

william adams answers,
    
    I had thought there's a certain amount of spacing built into the \dash
    and \Dash macros which are used in TUGboat.

yes, you're right, because i don't like
the em-dash crashing into the words on
either side.

    Looking at ltugboat.cls maybe I'm wrong?

    \def\dash{\d at sh\nobreak\endash}
    \def\Dash{\d at sh\nobreak\emdash}

but you didn't look at the definition of
\d at sh:

  \def\d at sh#1#2{\unskip#1\thinskip#2\thinskip\ignorespaces}

\thinskip *is* breakable, hence the \nobreak
following the first one.  could have used
\, there, but this was first created for
plain tex, where \, was math only, and,
besides, having a command that "reads" the
same on both sides is more easily understood
by the next poor macro writer.

    Usually when I mislike a full em dash enough to find it distasteful
    where's a 3/4 em dash available in the font which is spaced more
    openly. (em dashes are usually tight for those instances when multiples
    are combined)

i don't have bringhurst available to check,
but i seem to remember he advocates using
an en dash will full space on either side.

the latest chicago doesn't say anything
about spacing explicitly, but there is a
small but visible space (a little more than
a hairline, but less than a thin space) on
either side of the em-dashes in examples.

by the way, for tugboat, authors sometimes
use \dash between numbers.  wrong!  in that
situation, an unspaced en-dash is what's
wanted.

as for breaking after an em-dash, i have
no problem with that.  it appears thus in
fowler, so i feel justified (sorry 'bout
that; it *is* april 1).
						-- bb