[Tex/LaTex] The \bar and \overline commands

stacking-symbols

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?

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
\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}