答案1
您可以使用包中的\overbracket
和命令。\underbracket
mathtools
\documentclass{article}
\usepackage{mathtools}
\begin{document}
\[
\underbracket{\overbracket{%
\begin{array}{ll}
\Gamma \vdash \diamond & \text{$\Gamma$ is a well-formed environment}
\end{array}
}}
\]
\[
\underbracket[0.5pt]{\overbracket[0.5pt]{%
\begin{array}{ll}
\Gamma \vdash \diamond & \text{$\Gamma$ is a well-formed environment}
\end{array}
}}
\]
\end{document}