The \bar and \overline commands

Question

I want to represent, say, the closure of a set or the extended reals, e.g., $\bar{\mathbb{R}}$ but unfortunately this creates a bar that is much too small (horizontally) and can barely be seen. On the other hand, $\overline{\mathbb{R}}$ creates a line that is too long. I need something that's just right, in between the bar and the overline. What would be my best choice?

Answer 1

Here is a command \xoverline[width percent]{symb} that will do it. Note that it will not scale inside sub or superscripts. If you need that, everthing has to go through a \mathchoice resulting in a lot more complex code.

\documentclass{article}
\usepackage{amsmath,amssymb}
\makeatletter
\newsavebox\myboxA
\newsavebox\myboxB
\newlength\mylenA

\newcommand*\xoverline[2][0.75]{%
    \sbox{\myboxA}{$\m@th#2$}%
    \setbox\myboxB\null% Phantom box
    \ht\myboxB=\ht\myboxA%
    \dp\myboxB=\dp\myboxA%
    \wd\myboxB=#1\wd\myboxA% Scale phantom
    \sbox\myboxB{$\m@th\overline{\copy\myboxB}$}%  Overlined phantom
    \setlength\mylenA{\the\wd\myboxA}%   calc width diff
    \addtolength\mylenA{-\the\wd\myboxB}%
    \ifdim\wd\myboxB<\wd\myboxA%
       \rlap{\hskip 0.5\mylenA\usebox\myboxB}{\usebox\myboxA}%
    \else
        \hskip -0.5\mylenA\rlap{\usebox\myboxA}{\hskip 0.5\mylenA\usebox\myboxB}%
    \fi}
\makeatother
\begin{document}

$|\xoverline{W}|~~
 |\xoverline{i}|~~
 |\xoverline[3.0]{i}|$

\bigskip

$\bar{\mathbb{R}}~~\overline{\mathbb{R}}~~\xoverline{\mathbb{R}}$

\end{document}

Answer 2

I usually define a command \overbar, which reduced the width of \overline by 1.5mu on each side.

\documentclass{article}

\usepackage{amsfonts}

\newcommand{\overbar}[1]{\mkern 1.5mu\overline{\mkern-1.5mu#1\mkern-1.5mu}\mkern 1.5mu}

\begin{document}
$\bar{\mathbb{R}}$ $\overbar{\mathbb{R}}$ $\overline{\mathbb{R}}$
\end{document}

Answer 3

It took me a while to get a command that puts a nice overline over any field name, independent if its the reals, rationals, a finite field, or just a single literal. Based on this and that, I wrote the command \closure that uses \olsi for the overline if the argument is just a single literal, and \ols otherwise. The following table gives a comparison of these commands.

As a small bonus it also does not require any additional packages to be loaded.

\documentclass{standalone}

\usepackage{amssymb}

%command for alg-closure that automatically adapts its 'bar' to the arg based on the args length (including '\')
\newcommand{\ols}[1]{\mskip.5\thinmuskip\overline{\mskip-.5\thinmuskip {#1} \mskip-.5\thinmuskip}\mskip.5\thinmuskip} % overline short
\newcommand{\olsi}[1]{\,\overline{\!{#1}}} % overline short italic
\makeatletter
\newcommand\closure[1]{
  \tctestifnum{\count@stringtoks{#1}>1} %checks if number of chars in arg > 1 (including '\')
  {\ols{#1}} %if arg is longer than just one char, e.g. \mathbb{Q}, \mathbb{F},...
  {\olsi{#1}} %if arg is just one char, e.g. K, L,...
}
% FROM TOKCYCLE:
\long\def\count@stringtoks#1{\tc@earg\count@toks{\string#1}}
\long\def\count@toks#1{\the\numexpr-1\count@@toks#1.\tc@endcnt}
\long\def\count@@toks#1#2\tc@endcnt{+1\tc@ifempty{#2}{\relax}{\count@@toks#2\tc@endcnt}}
\def\tc@ifempty#1{\tc@testxifx{\expandafter\relax\detokenize{#1}\relax}}
\long\def\tc@earg#1#2{\expandafter#1\expandafter{#2}}
\long\def\tctestifnum#1{\tctestifcon{\ifnum#1\relax}}
\long\def\tctestifcon#1{#1\expandafter\tc@exfirst\else\expandafter\tc@exsecond\fi}
\long\def\tc@testxifx{\tc@earg\tctestifx}
\long\def\tctestifx#1{\tctestifcon{\ifx#1}}
\long\def\tc@exfirst#1#2{#1}
\long\def\tc@exsecond#1#2{#2}
\makeatother


\begin{document}

\begin{tabular}{r|ccccccc}
  \texttt{\textbackslash overline} & $\overline{\mathbb{R}}$ & $\overline{\mathbb{Q}}$ & $\overline{\mathbb{F}_p}$ & $\overline{K}$ & $\overline{L}$ & $\overline{L_1}$ & $\mathcal{Z}_{\overline{K}}$\\
  \texttt{\textbackslash bar} & $\bar{\mathbb{R}}$ & $\bar{\mathbb{Q}}$ & $\bar{\mathbb{F}_p}$ & $\bar{K}$ & $\bar{L}$ & $\bar{L_1}$ & $\mathcal{Z}_{\bar{K}}$\\[4pt]
  \texttt{\textbackslash ols} & $\ols{\mathbb{R}}$ & $\ols{\mathbb{Q}}$ & $\ols{\mathbb{F}_p}$ & $\ols{K}$ & $\ols{L}$ & $\ols{L_1}$ & $\mathcal{Z}_{\ols{K}}$\\
  \texttt{\textbackslash olsi} & $\olsi{\mathbb{R}}$ & $\olsi{\mathbb{Q}}$ & $\olsi{\mathbb{F}_p}$ & $\olsi{K}$ & $\olsi{L}$ & $\olsi{L_1}$ & $\mathcal{Z}_{\olsi{K}}$\\[4pt]
  \texttt{\textbackslash closure} & $\closure{\mathbb{R}}$ & $\closure{\mathbb{Q}}$ & $\closure{\mathbb{F}_p}$ & $\closure{K}$ & $\closure{L}$ & $\closure{L_1}$ & $\mathcal{Z}_{\closure{K}}$\\
\end{tabular}

\end{document}

Answer 4

I need a bit shorter overlines for variables in boolean algebra to make clear that variables are separately inverted. I defined the following command:

\newcommand{\olsi}[1]{\,\overline{\!{#1}}} % overline short italic

It is special designed for variables that are typeset in italic, so it is not only above but rather above right. So upright characters need a different definition:

\newcommand{\ols}[1]{\mskip.5\thinmuskip\overline{\mskip-.5\thinmuskip {#1} \mskip-.5\thinmuskip}\mskip.5\thinmuskip} % overline short

Similar definitions for underlines:

\newcommand{\ulsi}[1]{\!\overline{\,{#1}}} % underline short italic
\newcommand{\uls}[1]{\mskip.5\thinmuskip\underline{\mskip-.5\thinmuskip {#1} \mskip-.5\thinmuskip}\mskip.5\thinmuskip} % underline short

Example:

$ \olsi{x+y} = \olsi{x}\olsi{y} $

is rendered as

I hope that helps.

Answer 5

I'm not a Latex expert, but I've made a code that allows you to control the length and position of the top bar in another answer. Maybe that helps someone.

---

See the complete answer to see all the examples and drawbacks.

---

Here is its summary:

\mybar{<scale factor>}{<right shift>}{<math expression>}

\usepackage{mathtools}  % <----- for '\mathrlap' command (necessary)

\newcommand{\mybar}[3]{%
    \mathrlap{\hspace{#2}\overline{\scalebox{#1}[1]{\phantom{\ensuremath{#3}}}}}\ensuremath{#3}
}

Example of use:

$\mybar{0.6}{3pt}{A}$

---

If you are planning to use this command more often for a specific mathematical expression, you can use the following code to make things cleaner.

\mybar[<scale factor>][<right shift>]{<math expression>}

\usepackage{mathtools}  % <----- for '\mathrlap' command (necessary)
\usepackage{xparse}     % <----- for '\NewDocumentCommand' command (necessary)

\NewDocumentCommand{\mybar}{ O{0.60} O{3pt} m }{%  <---- Set the default values here
    \mathrlap{\hspace{#2}\overline{\scalebox{#1}[1]{\phantom{\ensuremath{#3}}}}}\ensuremath{#3}
}

Example of use:

$\mybar{A}$
$\mybar{V}$            % <---- bad result
$\mybar[0.6][2pt]{V}$  % <---- set manually

Answer 6

I am using the unicode-math package, and evidently it modifies the placement of the overline accent just slightly such that none of the above solutions felt good to me, and similarly I don't like the accents widerbar and wideoverbar that unicode-math provides (as mentioned in this post) as they are too thin for my taste. Thus, I cooked up a fairly simple solution using calc, which I humbly submit should anyone else find themselves in a similar situation to myself.

Note that neither the unicode-math package nor the fontspec package is required for this, it is simply to demonstrate the outcome using my font scheme of choice.

\documentclass{article}

\usepackage{fontspec}
\usepackage{amsmath}
\usepackage{calc}
\usepackage{unicode-math}

\setmainfont{Inter}
\setmathfont{Asana-Math}
\setmathfont{XITSMath-Regular.otf}[range=cal,StylisticSet=1]

% \varbar: 4 parameter auxiliary macro for forming a wide bar accent
%  #1: linear offset from the right of the entire post-accent symbol (morally intended to compensate for total horizontal space lost or gained due to the following two offset parameters)
%  #2: spacing scale factor introducing a linear offset proportional to the width of the to-be-accented symbol placed before the symbol under the \overline, typically used for negative space (to "push the left-end of the \overline to the right")
%  #3: same as argument #2 except that the scale factor is for space appended after to-be-accented symbol underneath the overline (to "pull the right-end of the \overline to the right")
%  #4: to-be-accented symbol, of which the scale factor parameters #2 & #3 correspond to
\newcommand{\varbar}[4]{\hspace{#1}\overline{\hspace{\widthof{#4}*\real{#2}}#4\hspace{\widthof{#4}*\real{#3}}}}
% \widebar: 1-optional 1-mandatory parameter macro to define a wide bar accent; the particular constants employed are "magic numbers" found experimentally via fine adjustment in my font scheme of choice, notably each such constant corresponds directly to a linear offset (outside or inside the \overline), the total scale of which sums to 0 such that total symbol space is preserved (as seen in the examples below with all characters aligning from the plain to the \widebar test rows)
%  #1: optional parameter fixing the outer-linear offset parameter #1 as proportional to the to-be-accented symbol, defaults to .075
%  #2: parameter for the to-be-accented symbol
\newcommand{\widebar}[2][.075]{\varbar{\widthof{\ensuremath{#2}}*\real{#1}}{-.115}{.04}{\ensuremath{#2}}}

\newcommand{\test}[1]{#1{A}, #1{M}, #1{W}, #1{g}, #1{\mathcal{A}}, #1{\symbb{A}}, #1{A}^g, #1{A}_q, #1{A^g_q}, #1{Ae}, #1{\beta}, #1{\Omega}, \int\limits_z^{#1{z}} f(z) \text{d} z, #1{\sin(z)}, \min_{#1{U}}|f|}
\newcommand{\run}[1]{\hspace{0pt-\widthof{#1}}#1: }

\begin{document}
    \phantom{a} \linebreak
    \run{InL normal}\(\test{}\) \linebreak
    \run{InL \texttt{widebar}}\(\test{\widebar}\) \linebreak
    \run{InL \texttt{bar}}\(\test{\bar}\) \linebreak
    \run{InL \texttt{overline}}\(\test{\overline}\) \linebreak
    \run{InL \texttt{overbar}}\(\test{\overbar}\) \linebreak
    \run{InL \texttt{wideoverbar}}\(\test{\wideoverbar}\) \linebreak

    \begin{gather*}
        \text{\run{Dsp Plain}}\test{} \\
        \text{\run{Dsp \texttt{widebar}}}\test{\widebar} \\
        \text{\run{Dsp \texttt{bar}}}\test{\bar} \\
        \text{\run{Dsp \texttt{overline}}}\test{\overline} \\
        \text{\run{Dsp \texttt{overbar}}}\test{\overbar} \\
        \text{\run{Dsp \texttt{wideoverbar}}}\test{\wideoverbar} \\
    \end{gather*}
\end{document}

Here is the inline portion:

Likewise, here is the display test:

Notice that my widebar does not play perfectly happily with very large expressions which include parentheses, such as the first-to-last item of the test list, but in these situations I feel overline does well. I note that the final item on the test list in the inline section is what caused my ire originally: an inline operator with a subscript which needed a bar accent. All other options hurt my eyes when reading between various zoom levels, and (tragically), given the spacing woes I discovered were caused by unicode-math, none of the above solutions made this better; that said, I feel that I've found a solution which doesn't hurt the eyes when looking at it at various zoom levels, so I'm satisfied.