3

I have the expression

\sup_a \left\{ \inf_b f(a,b) \right\}

which renders as

enter image description here

If the braces \left\{ and \right\} were not part of the expression, I could use \adjustlimits to ensure that the arguments in the supremum and infimum shared the same vertical position.

Is there a way to achieve the desired effect in this case?

3
  • 1
    just use \{ and \} not \left\{ and \right\} the over-sized braces are not helping here – David Carlisle Dec 11 '16 at 21:01
  • @DavidCarlisle: Thanks for the comment. If you're suggesting \adjustlimits \sup_a \{ \inf_b f(a,b) \}, this also does not compile. If you're suggesting removing \adjustlimits altogether, that does not produce the desired effect. – user31162 Dec 11 '16 at 21:07
  • No the {} comment was more of a side issue. I'm sure we have questions/answers on equalising the limits on operators with and without a descender, I'll see if I can find... – David Carlisle Dec 11 '16 at 21:47
3

There's no hope of making \adjustlimits to work in this case.

The problem is twofold: “sup” has a descender, “inf” doesn't; “b” has an ascender, “a” hasn't.

So I give two solutions: in the first one I use a special “inf” with an artificial descender; in the second solution, I use a special “sup” with a smashed “p”.

\documentclass{article}

\usepackage{amsmath}

\makeatletter
\DeclareMathOperator*{\infd}{inf\vphantom{\operator@font p}} % inf with descender
\DeclareMathOperator*{\supx}{su\smash{\operator@font p}} % sup without descender
\makeatother

\begin{document}

\[
\sup_{a\vphantom{b}}\bigl\{\infd_{b} f(a,b)\bigr\}
\]

\[
\supx_{a\vphantom{b}}\bigl\{\inf_{b} f(a,b)\bigr\}
\]

\end{document}

enter image description here

1
  • oh yes b isn't the same shape as a I forgot that:-) – David Carlisle Dec 11 '16 at 22:44

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