Difference between control space and non-breaking space

Question

In my answer to Two-column layout with left column just as wide as its content I've used non-breaking spaces ~ (ties) to align monospaced text. Actually I rather meant control spaces \ , but they're less convenient to type (and read), and line breaks were not of interest anyway. Some experiments concerning line breaking are documented in the code below.

Question: Besides their line-breaking behaviour, is there any difference between \ and ~? In particular, do (or may) they by nature have a different width?

\documentclass{article}
\usepackage{lipsum}
\usepackage{parskip}

\begin{document}

\lipsum[75]

%non-breaking space
lorem lorem lorem lorem lorem lorem lorem lorem lorem 
lorem lorem lo~lo~lo~lo~lo~lo~lo~lo~ip~ip~ip~sum sum sum sum sum sum sum sum sum

lorem lorem lorem lorem lorem lorem lorem lorem lorem 
lorem lorem lo~lo~lo~lo~lo~ %input line break doesn't affect non-breaking space
lo~lo~lo~ip~ip~ip~sum sum sum sum sum sum sum sum sum

lorem lorem lorem lorem lorem lorem lorem lorem lorem 
lorem lorem lo~lo~lo~lo~lo  %breaks at input line break
lo~lo~lo~ip~ip~ip~sum sum sum sum sum sum sum sum sum

%breaks at protected space
lorem lorem lorem lorem lorem lorem lorem lorem lorem 
lorem lorem lo~lo~lo~lo~lo\ lo~lo~lo~ip~ip~ip~sum sum sum sum sum sum sum sum sum

\end{document}

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score 30 · Accepted Answer · answered Jun 09 '12 at 23:25

30

Control space \ and a tie ~ have the same width and only differ in their line-breaking behaviour. The definition of the latter, taken from latex.ltx is:

\DeclareRobustCommand{\nobreakspace}{%
   \leavevmode\nobreak\ }
\catcode `\~=13
\def~{\nobreakspace{}}

answered Jun 09 '12 at 23:25

Werner

603,163

1

I'm wondering why it's LaTeX that defines the tie. Is it not a TeX primitive? – dgs Jun 09 '12 at 23:34
@dgs: Yes, TeX actually defines it as \penalty\@M\, but LaTeX redefines it. – Werner Jun 09 '12 at 23:40
8

@Werner ~ is not a primitive in plain TeX, it is an active character with a macro definition (\penalty\@M\, as you say). – Joseph Wright Jun 10 '12 at 07:30
This answer doesn't explain the difference... What do they do different then? – Tvde1 Dec 29 '18 at 15:43
1

@Tvde1: They differ in how things happen around a line-break. ~ inserts a large penalty while \ does not. Does this example explain it better? – Werner Dec 29 '18 at 16:05
Alright, \ does not add a penalty and ~ does. Many thanks! – Tvde1 Dec 29 '18 at 17:03

Difference between control space and non-breaking space

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