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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?

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See also this answer of mine for a \widebar command that produces a bar wider than \bar and smaller than \overline. – Hendrik Vogt May 13 '13 at 12:25
Related Question: Overline thickness. – Peter Grill Aug 23 '14 at 16:25
up vote 39 down vote accepted

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.


    \setbox\myboxB\null% Phantom box
    \wd\myboxB=#1\wd\myboxA% Scale phantom
    \sbox\myboxB{$\m@th\overline{\copy\myboxB}$}%  Overlined phantom
    \setlength\mylenA{\the\wd\myboxA}%   calc width diff
       \rlap{\hskip 0.5\mylenA\usebox\myboxB}{\usebox\myboxA}%
        \hskip -0.5\mylenA\rlap{\usebox\myboxA}{\hskip 0.5\mylenA\usebox\myboxB}%





enter image description here

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Wow, I never knew this would be so involved! Very nice answer though and thanks for your help. – 3Sphere Jul 2 '11 at 13:08
Someone should do the \mathchoice thing and package this into a package! – Mariano Suárez-Alvarez Jun 27 '14 at 5:38

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



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

$\bar{\mathbb{R}}$ $\overbar{\mathbb{R}}$ $\overline{\mathbb{R}}$


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Would this solution have the same issues regarding subscripts/superscripts as described in Danie's solution? – Anthony Mottaz Jan 24 at 21:48

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