\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{widebar}
\RequirePackage{amsmath}
\let\save@mathaccent\mathaccent
\newcommand*\if@single[3]{
\setbox0\hbox{${\mathaccent"0362{#1}}^H$}
\setbox2\hbox{${\mathaccent"0362{\kern0pt#1}}^H$}
\ifdim\ht0=\ht2 #3\else #2\fi
}
\newcommand*\rel@kern[1]{\kern#1\dimexpr\macc@kerna}
\DeclareRobustCommand\widebar[1]{\@ifnextchar^{{\wide@bar{#1}{0}}}{\wide@bar{#1}{1}}}
\newcommand*\wide@bar[2]{\if@single{#1}{\wide@bar@{#1}{#2}{1}}{\wide@bar@{#1}{#2}{2}}}
\newcommand*\wide@bar@[3]{
\begingroup
\def\mathaccent##1##2{
\let\mathaccent\save@mathaccent
\if#32 \let\macc@nucleus\first@char \fi
\setbox\z@\hbox{$\macc@style{\macc@nucleus}_{}$}
\setbox\tw@\hbox{$\macc@style{\macc@nucleus}{}_{}$}
\dimen@\wd\tw@
\advance\dimen@-\wd\z@
\divide\dimen@ 3
\@tempdima\wd\tw@
\advance\@tempdima-\scriptspace
Avez-vous essayé la commande
\overline
?