\overbrace and \underbrace with square bracket

Question

I'm trying to put a nice square bracket over a complex text, it should look like an \overline but with ending like \ulcorner and \urcorner. The presence of \overrightarrow and \overleftarrow makes me believe that is possible to decorate the end of the \overline bar.

I know the existence of \overbrace, but I need a square bracket; moreover, \overbrace takes too much vertical space

Answer 1

Try \mathtools's \underbracket and \overbracket:

\documentclass{article}
\usepackage{mathtools}% http://ctan.org/pkg/mathtools
\begin{document}
\[
  \overbrace{a+b+c}^{d} \quad \overbracket{a+b+c}^{d} \quad
  \underbrace{a+b+c}_{d} \quad \underbracket{a+b+c}_{d}
\]
\end{document}

You can adjust the rule width and bracket height/depth via optional arguments. From the mathtools documentation (section 3.3.2 Braces and brackets, p. 14):

\underbracket[<rule thickness>][<bracket height>]{<arg>}
\overbracket[<rule thickness>][<bracket height>]{<arg>}

---

Or, a more subtle approach with abraces:

\documentclass{article}
\usepackage{abraces}% http://ctan.org/pkg/abraces
\begin{document}
\[
  \overbrace{a+b+c}^{d} \quad \aoverbrace[L1R]{a+b+c}^{d} \quad
  \underbrace{a+b+c}_{d} \quad \aunderbrace[l1r]{a+b+c}_{d}
\]
\end{document}

The usage requires a brace specification <spec> as an optional argument to \aoverbrace and \aunderbrace (see the abraces documentation):

Answer 2

The "standard LaTeX" underbraces and overbraces quickly become straight lines with only minor bumps as soon as the material being embraced (pun intended) is of more than minimal length. To add some visual interest and pizzazz, one may want to consider using the \undercbrace and \overcbrace macros of the MathTime Professional 2 package. Note that the full mtpro2 package isn't free of charge; however, its "lite" subset, which is all that's required to generate the curly braces shown below, is indeed available free of charge.

\documentclass{article}
\usepackage[lite]{mtpro2}%
\begin{document}
Curly over- and underbraces of the \texttt{mtpro2} package:
\[
   \overcbrace{a+b+c+d+e+f}^{ghi} \quad 
  \undercbrace{a+b+c+d+e+f}_{ghi}
\]

``Standard \LaTeX'' over- and underbraces:
\[
   \overbrace{a+b+c+d+e+f}^{ghi} \quad 
  \underbrace{a+b+c+d+e+f}_{ghi}
\]
\end{document}

Answer 3

When Unicode math font is loaded then \overbracket and \underbracket are standard horizontally scalable math objects. For example in OpTeX:

\fontfam[lmfonts]

$\overbracket{a+b+c}$

\bye