# Multiple inference lines of single inference rule

I looked at both the semantic and mathpartir package, is is possible to insert multiple inference lines in single inference rules? Or are there better ways to do this?

The mathpartir package has a little example but it does not work very well and I can't find any better solutions.

\documentclass[12pt, notitlepage]{article}
\usepackage{mathpartir}

\begin{document}

\section{Judgement}

$$\mprset{fraction={===}} \inferrule {a = b \in A} {b = a \in A}$$

\end{document}


Here is what it produces.

• Welcome! Can you show us what you've tried? A minimal example starting with \documentclass and ending with \end{document} would make your question clearer and easier to answer. – cfr Dec 4 '15 at 0:13

\documentclass[a4paper]{article}