How can you address the size of surrounding parentheses whose size is determined by \left and \right?

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How to automatically resize the vertical bar in a set comprehension?

Trying to type the formula for a conditional probability like this

\mathrm{P} \left( whatever \mid whatever \right) = ...,

I'd like to have \mid the same size as the left and right parentheses.

How can I achieve this?

score 6 · Accepted Answer · answered May 05 '11 at 15:06

6

use \middle| or for a double \middle|\middle|

\[ \left( \frac{a}{b^2}+1\middle| f(x)\right)\]

answered May 05 '11 at 15:06

1

Arg, 12sec to late ... I would have used \middle\vert, but \middle| seems to do the same. – Martin Scharrer May 05 '11 at 15:07
I was 29 seconds too late... – Gonzalo Medina May 05 '11 at 15:11
@Herbert: Thanks, works fine (I just have to adjust the spaces around the | a little)! – j.p. May 05 '11 at 15:13
@Martin: Sorry, but you could have been a little less altruistic and first answer the question before beautifying it. – j.p. May 05 '11 at 15:15
\vert is the same as \| – May 05 '11 at 15:27
1

@Herbert: \vert is the same as |, \Vert is the same as \| – egreg May 05 '11 at 16:04
sure, that's what I wanted to say ... – May 05 '11 at 16:41

score 4 · Answer 2 · answered May 05 '11 at 16:18

\middle doesn't add spaces around the symbol it produces and treats it as an ordinary symbol, like when we say \bigg| or even \bigg(. On the other hand it can't be put inside \mathrel.

The problem might arise when when \middle is used in a subscript; one can say either of

\left( something \nonscript\;\middle|\nonscript\; something \right)
\left( something \mathrel{}\middle|\mathrel{} something \right)

and the result will be the same as if we used \mid (of course if we decide that this vertical bar must be treated as a relation symbol). This is for writing macros that use the \middle feature, as in direct input one knows what space is necessary.

How can you address the size of surrounding parentheses whose size is determined by \left and \right?

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