Shrink space after colon without shrinking space after period

Question

When a colon is used to separate clauses in a sentence (rather than preceding a list), current typographic practice, and my preference, is to follow it with the same space as after a semicolon.

The LaTeX default \nonfrenchspacing violates that, making the space after a colon the same as after a period.

But \frenchspacing,while shrinking the space after a colon, unfortunately also shrinks the space after a period, which I do not want to do.

See this example:

\documentclass[12pt]{article}
\begin{document}

\nonfrenchspacing
\emph{nonfrenchspacing}
\smallskip

Spacing after; semicolon.

Spacing after: colon.

Spacing after. period

\bigskip

\frenchspacing
\emph{frenchspacing}
\smallskip

Spacing after; semicolon.

Spacing after: colon.

Spacing after. period

\end{document}

How can I get all the following:

space after a colon separating clauses the same as that after a semicolon; and
space after a colon before a list retains the larger spacing from \nonfrenchspacing; and
space after a period retains the larger spacing from \nonfrenchspacing?

The traditional (manual) approach is Spacing after:\@ colon. with the use of \@. — Steven B. Segletes, Apr 03 '20 at 19:37
It seems that \frenchspacing doesn't respect the traditional French spacing before a colon or a semicolon (thin unbreakable space)… — Bernard, Apr 03 '20 at 19:47
@Bernard The names are a bit odd, to be honest. They only refer to the spacing after punctuation. — egreg, Apr 03 '20 at 19:47
@StevenB.Segletes -- I believe that "\" (slash-space) is preferable. See What is the proper use of @ (i.e., backslash-at)? — barbara beeton, Apr 03 '20 at 20:37
@barbarabeeton Thank you for that link. Learned something new. — Steven B. Segletes, Apr 03 '20 at 22:24

egreg · Accepted Answer · 2020-04-03T19:47:07.583

If you want that the space after a colon is the same as after a semicolon, tell TeX that the space factor codes of both are the same.

\documentclass[12pt]{article}
\begin{document}

\nonfrenchspacing\sfcode`:=\sfcode`;
\emph{nonfrenchspacing}
\smallskip

Spacing after; semicolon.

Spacing after: colon.

Spacing after. period

\bigskip

\frenchspacing
\emph{frenchspacing}
\smallskip

Spacing after; semicolon.

Spacing after: colon.

Spacing after. period

\end{document}

Since you won't be changing between “French spacing” and “non French spacing” (would you?), you can simply state

\sfcode`:=\sfcode`;

before \begin{document}.

\documentclass[12pt]{article}

\sfcode`:=\sfcode`;

\begin{document}

Spacing after; x

Spacing after: x

Spacing after. x

\end{document}

TeXnical note. The space factors of semicolon, colon and period under \nonfrenchspacing are, respectively, 1500, 2000 and 3000. So it's a bit inaccurate to say that the space after a colon is the same as after a period.

But then how would I (temporarily) revert to my preferred wider space when a colon precedes a list? — murray, Apr 03 '20 at 21:11
@murray Does this make sense? Anyway, do \newcommand{\colonlist}{:\spacefactor2000\relax\space\ignorespaces} and use \colonlist in front of a list. — egreg, Apr 03 '20 at 21:14

Shrink space after colon without shrinking space after period

1 Answers1