Is there any command inverse to \mathstrut?

Question

Maybe my question is a bit ridiculous but I wonder is there any command inverse to \mathstrut? I think this command would be useful for reducing unwanted size of auto delimiter such as inline \Set{}

\usepackage{braket}

\begin{document}
some text
$\Set{A\in R| A\in Q}$ %a bit bad delimiter 
\end{document}

or in \left \right math formulas.

@CarLaTeX, not horizontally, reducing vertical size. are you familiar with \mathstrut? — , Sep 13 '19 at 05:58
How to use it? e.g. \Set{\smash[b]{A\in R| A\in Q}}? but this produce some error for me!! — , Sep 13 '19 at 06:08
In a sense \smash{...} is the opposite, making its contents zero height and depth. In the braket package's command \Set you would have to \smash each half by itself. But in your example the braces are already the smallest braket will use. For me the mathtools approach to a set command is preferable. — Andrew Swann, Sep 13 '19 at 06:10
To use \smash here write \Set{\smash{A\in R}|\smash{A\in Q}} — Andrew Swann, Sep 13 '19 at 06:15
There is a non auto scaling version in the manual for the mathtools package. Having it go auto scaling by default is seldom a good idea — daleif, Sep 13 '19 at 06:18
@daleif That is partly what I meant, avoid the automatic scaling. But the mathtools documentation defines \Set with its \Set* variant which is auto scaling — Andrew Swann, Sep 13 '19 at 06:22
@AndrewSwann yes, but you have to choose the star to get auto scaling it is not the default. — daleif, Sep 13 '19 at 06:52
The simplest is not using \Set from braket. There's no reason to. — egreg, Sep 13 '19 at 08:31

Andrew Swann · Accepted Answer · 2019-09-13T07:58:55.857

You can use \smash to hide height and depth of contents. In the context of the \Set command from the braket package you need to apply this to each half of the contents separately. In your particular example you will see no difference (with standard fonts) as the braces are already at their smallest size.

\documentclass{article}

\usepackage{braket}

\begin{document}

$\Set{A\in R|A\in Q}$

$\Set{\smash{A\in R}|\smash{A\in Q}}$

$\Set{A\in R^{2}|A\in Q}$

$\Set{\smash{A\in R^{2}}|\smash{A\in Q}}$

\end{document}

In general it is best to avoid auto sizing, cf. Is it ever bad to use \left and \right? . The mathtools package documentation provides a \Set command that can be manually sized, e.g. \Set[\bigg], with an auto sizing variant \Set*. Here is the version I usually use:

\documentclass{article}

\usepackage{mathtools}

\newcommand{\with}{\SetSymbol[\delimsize]}
\newcommand{\SetSymbol}[1][]{\nonscript\:#1\vert
  \allowbreak\nonscript\:\mathopen{}}
\DeclarePairedDelimiterX{\Set}[1]{\lbrace}{\rbrace}{#1}

\begin{document}

\( \Set{A\in R \with A\in Q} \)

\( \Set{A\in R^{2} \with A\in Q} \)

\( \Set[\big]{A\in R^{2} \with A\in Q} \)

\( \Set*{A\in R^{2} \with A\in Q} \)

\end{document}

You write \with instead of the | in the braket notation. It has the advantage over braket that if you change your mind later and wish to have the separator as a colon instead of a vertical line, then you just adjust the definition of \with (or of \SetSymbol).

is this works for command defined in preamble using \left and \right? e.g. \newcommand[\norm][1]{\left\| #1\right\|} then $\norm{\smash{(A^2)^2}}$ ? — , Sep 13 '19 at 08:00
Yes, but again I would use the mathtools constraction \DeclarePairedDelimiter{\norm}{\lVert}{\rVert} which provides \norm[\big] etc. and the autoscaling \norm*. Autoscaling is really only for drafting of material. — Andrew Swann, Sep 13 '19 at 08:11
@C.F.G note for example that your norm definition is wrong if you remove the \left/right part, try removing them at do \norm{-1}, the spacing on the - is wrong. In Andrews version the spacing is correct (mainly because of the use of \lVert and \rVert (in general \| is not the correct symbol to use for norms). — daleif, Sep 13 '19 at 08:29

Is there any command inverse to \mathstrut?

1 Answers1