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Plain Tex defines \quad so:


Why is the \relax there? It's usually used as a token that can't be expanded, serving as a "do nothing" operation after macro expansion is finished. But that use seems redundant, because it follows a command, namely \hskip.

The macro is defined alongside \enskip and \qquad in plain.tex, and in Latex in ltspace.dtx.

An idle question, but I guess the reason for it will be worth knowing.

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up vote 25 down vote accepted

So that \quad doesn't eat following text while assembling the argument of \hskip:



\quad plus 1em text


\quad plus 1em text
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This is a general feature of TeX skips: see also how LaTeX defines a number of wrappers so that 'escape' does not take place. – Joseph Wright Sep 14 '10 at 13:10
Thank you. I guess this highlights the risks associated with designing robust macros. – Charles Stewart Sep 14 '10 at 13:28
Welcome to my world :-) – Joseph Wright Sep 14 '10 at 17:12
Very nice example. Thank you. – Todd Lehman Dec 29 '11 at 15:00
Fischer's explanation above can also be seen on the dangerous bend in pg. 71 of Knuth's The TeXbook. – Mafra Dec 2 '12 at 1:32

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