I want to write following formula in Latex:
The problem is the "i" underneath "x". It is not a regular fraction. It means that value "x" will be replaced with "i". How can I write this one in Latex? Additionally, the underlines are longer than the regular one which is used by typing "_". How can I modify the lenght of the underline?
\documentclass[12pt, a4paper]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english,ngerman]{babel}
\usepackage{amsmath,amsfonts,amssymb,amstext}
\begin{document}
$\langle x\,\,\underline{\,\,\,}\rangle_{k}\,\,\langle \underline{\,\,}\,\,x \mapsto i\,\,\underline{\,\,\,}\rangle_{state}$
\end{document}
Hopefully, you can help me.
Edit:
Thanks for your help! I have copied your extension and pasted it into my align environment.
\begin{align}
\centerline{Computational rules}
\[
p[\tabbedShortunderstack{
\udash{l_1}&,&\udash{l_2}&,&\dots&,&\udash{l_n}\\
r_1 & & r_2 & & & & r_n
}]
\]
\centerline{Structural rules}
\[
p[\tabbedShortunderstack{
\uddash{l_1}&,&\uddash{l_2}&,&\dots&,&\uddash{l_n}\\
r_1 & & r_2 & & & & r_n
}]
\]
\end{align}
If I try to run it, process stops with following error:
Bad math environment delimiter. \end{align}
What does that mean?