Math & Science ⇒ Making three delimiters having the same size (like {|})

[nagmat84]

Hello everybody,
I need a way how to make three delimiters (a left, a middle and a right one) having the same size. This situation frequently occurs when defining a set with a vertical bar (\mid) as the "such that" operator.
For example:

Code: Select all

\begin{equation}
A = \left \lbrace f \mid foo \right\rbrace
\end{equation}

If "foo" is higher than normal, the left and the right brace scales correctly to fit the content, but the middle "delimiter", i.e. the vertical bar, stays as is.
In my opinion that is really unpleasant as the vertical bar belongs to the same level as the outer braces.
Thank you for any ideas,
Matthias

[localghost]

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\begin{equation}
  A=\left\{\frac{x}{y}\middle|\frac{u}{w}\right\}
\end{equation}

Best regards and welcome to the board
Thorsten

[nagmat84]

Thank you,
the scaling works if I use the character | as delimiter, as you suggested. But than the spacing is wrong.
| is the characer for "divides", as in "p|q". Thus it uses a class 2 spacing for binary relations with no space on the left nor right.
Amsmath recommends the \mid keyword, if you need a class 3 spacing, which is correct for the "such that" semantic. For the same reason one should use "\lvert" and "\rvert", if one need a vertical bar as a left or right delimiter.
But \middle\mid does not work.
Matthias

[localghost]

Just insert additional space.

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\begin{equation}
  A=\left\{\frac{x}{y}\,\middle|\,\frac{u}{w}\right\}
\end{equation}

[nagmat84]

Thanks again,
but I found the solution myself by now. \mid does not work, because it is not an extensible character. The correct keyword is \bracevert or \arrowvert, the last one is a little bit thinner. So

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\left\lbrace foo \middle\bracevert foo \right\rbrace

does it and results into a correct class-3-spacing.

I prefer not to interfere with LaTeX spacing algorithm, as I would do, if I used \, to insert a little exta space. Latter would mean: "Use a class-2-spacing and put a fixed amount of extra space around it".