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I want to use \middle| inside of brackets like this.

\documentclass{article}
\begin{document}

\begin{equation}
  \left\{\frac{1}{n} \middle| n>0\right\}
\end{equation}

\end{document}

\end{document}

But this examples lacks space before and after the mid |. I don't want to write every time:

left\{\frac{1}{n} \;\middle|\; n>0\right\}

How can I redefine the \middle| command to mean \;\middle|\;? I tried

\edef{\middle|}{\,\middle|\,}

and

\let\originalmiddle\middle
\renewcommand{\middle}{\;\originalmiddle\;}

but neither works. What is the difference between both commands and why do they not work with \middle?

share|improve this question
    
Maybe you just want \mid? Though, that won't scale vertically. –  morbusg Jul 23 at 16:28
    
I want the middle command to scale vertically like \middle| does. –  Marco Breitig Jul 23 at 16:31
2  
See tex.stackexchange.com/q/5502 to get \middle| to behave exactly as \mid –  Philippe Goutet Jul 23 at 16:48
    
Thx for hint, I used your suggestion. –  Marco Breitig Jul 24 at 7:52

1 Answer 1

up vote 9 down vote accepted

The symbol needs to come after the \middle so

\let\originalmiddle\middle
\renewcommand{\middle}[1]{\;\originalmiddle#1\;}

Although redefining primitives always breaks something, somewhere so I would suggest instead

\newcommand{\xmiddle}[1]{\;\middle#1\;}

and use \xmiddle (or any other name you wish)

share|improve this answer
    
Wow thx, that was fast! I tried to play around with a parameter but somehow did not manage to get things right. –  Marco Breitig Jul 23 at 16:33
    
Just out of curiosity, do you know how would one do that with a \(U)delcode or \(U)delimiter? (i.e., without \middle?) –  morbusg Jul 23 at 16:35
    
@morbusg If I understand your comment correctly, I don't think you can –  David Carlisle Jul 23 at 16:36
1  
@morbusg \bigm|? –  Manuel Jul 23 at 16:45
1  
\newcommand{\relmiddle}{\nonscript\;\middle\nonscript\;} –  egreg Jul 23 at 17:29

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