A widebar equivalent for including a bar below letter

Question

I was wondering if there is something that similar to a \widebar when I want to put the bar below a character. I am working in the math mode and here is the relevant preamnle

\documentclass[12pt,letterpaper]{article}
\usepackage[margin=1in]{geometry}
\usepackage[english]{babel}
\usepackage{amsmath}
\usepackage{xfrac}
\usepackage{nicefrac}
\usepackage{accents}
\newcommand\munderbar[1]{%
    \underaccent{\bar}{#1}}
\newcommand*\widebar[1]{%
    \begingroup
    \def\mathaccent##1##2{%
        \rel@kern{0.8}%
        \overline{\rel@kern{-0.8}\macc@nucleus\rel@kern{0.2}}%
        \rel@kern{-0.2}%
    }%
    \macc@depth@ne
    \let\math@bgroup@empty \let\math@egroup\macc@set@skewchar
    \mathsurround\z@ \frozen@everymath{\mathgroup\macc@group\relax}%
    \macc@set@skewchar\relax
    \let\mathaccentV\macc@nested@a
    \macc@nested@a\relax111{#1}%
    \endgroup
}

I am using the accent package to put the bar below the character of M_c.

Here is the line of codes I am using \munderbar{M}_{c} < M_{c}^{1} < M_{c}^{0} < \widebar{M_{c}}$

I was wondering how make the bar below the last character, that is, M_c, wider like that of M_c with widebar appearing last.

Can this help: https://tex.stackexchange.com/a/351127/10898? or https://tex.stackexchange.com/a/133294/10898 — azetina, Mar 01 '21 at 23:12
How about \underline{...}, which comes with the amsmath package? — Steven B. Segletes, Mar 01 '21 at 23:19
@StevenB.Segletes Yes, tried \underline but the gap between the character and the underbar is too much. This is probably because of the subscript. — OGC, Mar 01 '21 at 23:22

score 2 · Accepted Answer · answered Mar 01 '21 at 23:35

The comment suggestion of \underline was rejected because of the size of the undergap in the presence of subscripts. Here, I offer \qunderline as an alternative. The stacking value of -1pt can be tuned to suit.

This 1st version only works in text and display styles.

\documentclass{article}
\usepackage{graphicx,amsmath,stackengine}
\newcommand\qunderline[1]{%
  \ensurestackMath{\stackengine{-1pt}{#1}{\underline{\hphantom{#1}}}
   {U}{c}{F}{F}{S}}%
}
\begin{document}
\[
  M
\underline{M_c} \text{\,vs\,}
\qunderline{M_c}
\qunderline{M_q}
\qunderline{M_j^2}
\]
\end{document}

Here's a version that also works in smaller math styles:

\documentclass{article}
\usepackage{graphicx,amsmath,stackengine,scalerel}
\newcommand\qunderline[1]{\ThisStyle{%
  \ensurestackMath{\stackengine{-1pt}{\SavedStyle#1}
  {\SavedStyle\underline{\hphantom{#1}}}{U}{c}{F}{F}{S}}}%
}
\begin{document}
\[
  M
\underline{M_c} \text{\,vs\,}
\qunderline{M_c}
\qunderline{M_q}
\qunderline{M_j^2}
\scriptstyle\qunderline{M_j^2}
\]
\end{document}

A widebar equivalent for including a bar below letter

1 Answers1