It is recommended to place a non-breaking space before \cite, \ref, inline math and perhaps at few other locations.

The question is whether you can design an improved version of \cite (say) which would gobble all the preceding spaces, insert a non-breaking space, and then proceed to calling the original \cite?

  • 2
    @Yossi: Why did you tag your question with {tex-core}?
    – lockstep
    Feb 20, 2011 at 23:50
  • Oh, because I thought it had to do with the way TeX consumes characters. If it ain't so, I will gladly fix the tagging.
    – Yossi Gil
    Feb 21, 2011 at 0:09
  • Well, I tried fixing that, but could not change the tags. Perhaps the high ranking members of this friendly and wise community have more privileges than I do?
    – Yossi Gil
    Feb 21, 2011 at 6:26
  • @Yossi: Fixed for you.
    – lockstep
    Feb 21, 2011 at 6:43
  • 1
    @Yossi: And once you have 500 rep (shouldn't be too long now), you may retag questions yourself.
    – lockstep
    Feb 21, 2011 at 6:49

2 Answers 2


Yes you can. The varioref package does this already. Have a look at the source code of it. For example:

    More parsing. . .
596 \def\@vpageref[#1]{\@ifnextchar[%
    The default for the second optional argument is a space which is prexed by
    \unskip to get rid of any leading space inserted already.
597 {\@@vpageref{#1}}{\@@vpageref{#1}[\unskip\vref@space]}}

You should be able to define:


or save \cite away using \let:

  • Neat! Thanks. I did not think this would be as easy, since I thought TeX has consumed the preceding spaces already. I think this would be useful to many. I will surely start using this right away.
    – Yossi Gil
    Feb 21, 2011 at 0:15
  • @YossiGil: Well TeX has consumed the space indeed, but stored it as a skip which can be removed using the \unskip. Jan 26, 2012 at 13:41

Combining Martin's answer with this redefinition of \cite answer, I was able to use the following in my preamble, without needing the varioref package:


A good explanation of what's going on with \let and \renewcommand was found in the Make your own style section of a LaTeX tutorial:

We interfere with LaTeX using the \let command which defines a pointer to the current definition of another command; thus


defines \LaTeXtitle to point to the original LaTeX definition of \title. Follow this with


to define a new version of \title that colours it magenta and puts it into a sans serif font. Neat!

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    Another way is to say \robustify\cite\preto\cite{\unskip~} after having loaded the etoolbox package; \robustify is needed because \cite is defined with \DeclareRobustCommand. Otherwise the more obscure \expandafter\preto\csname cite \endcsname{\unskip~} is needed (there's a space between cite and \endcsname).
    – egreg
    Jun 4, 2011 at 16:11
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    Of course one has to be very careful not to start a sentence with \cite, so I prefer always to put a ~ before \cite so that I can delete it in troublesome cases; and the ~ is probably wrong when an author-date system is used.
    – egreg
    Jun 4, 2011 at 17:06
  • Done this way: \let\originalcite\cite \def\cite{\unskip~\originalcite}, it works with the optional argument too, e.g., \cite[p. 10]{Foo}. Want to edit your answer?
    – andrew
    Jun 20, 2012 at 22:33

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