Why doesn't \nolinebreak work in this case?

Question

When I have something like:

(Some-)Thing

at the end of the line, LaTeX always breaks after the '-', even when I use:

(Some-\nolinebreak)Thing

I do know about solutions like using \mbox{}, but I ask for an explanation, not a way to work around, but if there's a "better" way to do this, I'm grateful for any recommondations!

I also tried \nolinebreak[4] which although should be the same.

Answer 1

If you use babel in German, you can use "~ that produces exactly what you want:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}

\begin{document}

\parbox{0pt}{\hspace{0pt}(Some"~)Thing}

\end{document}

The \parbox{0pt} is for inviting TeX to break wherever possible, but if you try you'll see that no break at all is taken.

What "~ does is, basically, issuing \mbox{-}.

If you don't use ngerman, but still use babel, you could import the German shorthands (see Babel: two languages, active shorthands) or, more simply, define a macro:

\newcommand{\ppref}[1]{(#1\mbox{-})} % Parenthesized PREFix

and input the text as

\ppref{Some}Thing

---

The reason why \nolinebreak is ineffective is that - in normal text inserts a discretionary break after it, so typing

(Some-\nolinebreak)Thing

is the same as typing

(Some-\discretionary{}{}{}\nolinebreak)Thing

and TeX is allowed to break lines at discretionaries. The penalty that follows cannot change this. There is no \undiscretionary similar to \unskip or \unpenalty.

The \nobreakdash macro of amsmath just encloses in an \mbox the -, -- or --- that follows, so typing

(Some\nobreakdash-)Thing

is exactly the same as typing

(Some\mbox{-})Thing

Answer 2

If you use the amsmath package, you could type

(Some\nobreakdash-)Thing

A full MWE (minimum working example):

\documentclass{article}
\usepackage{amsmath}  % for '\nobreakdash' macro
\usepackage[textwidth=1mm]{geometry} % set a very narrow measure
\begin{document}
\hspace{0pt}(Some-)Thing  % this will produce a line break

\hspace{0pt}(Some\nobreakdash-)Thing % no linebreak here...
\end{document}