Cfrgtkky

I have two variables: vec{x} and another one which is somehow dual to the first. Therefore I would like to symbolize the second with something similar but a leftarrow on top of the x. I already tried stackrel{leftarrwo}{x} but it looks to different (too big gap between x and the arrow, and too big arrow).

Is there a way to define a cev command which does what I want?

This may not be the best way, but two reflectbox commands will do the trick:

documentclass{article}

usepackage{graphicx}

newcommand{cev}[1]{reflectbox{ensuremath{vec{reflectbox{ensuremath{#1}}}}}}

begin{document}

[

vec{a} quad cev{a} quad vec{b} quad cev{b}

]

end{document}

A cev command that seems to give good results on most letters and works correctly (apart a very small drift) in subscripts and superscripts.

documentclass{article}

usepackage{graphicx,accents}



makeatletter

DeclareRobustCommand{cev}[1]{%

  mathpalettedo@cev{#1}%

}

newcommand{do@cev}[2]{%

  fix@cev{#1}{+}%

  reflectbox{$m@th#1vec{reflectbox{$fix@cev{#1}{-}m@th#1#2fix@cev{#1}{+}$}}$}%

  fix@cev{#1}{-}%

}

newcommand{fix@cev}[2]{%

  ifx#1displaystyle

    mkern#23mu

  else

    ifx#1textstyle

      mkern#23mu

    else

      ifx#1scriptstyle

        mkern#22mu

      else

        mkern#22mu

      fi

    fi

  fi

}



makeatother



begin{document}

$Xx$



$Xcev{x}_{cev{x}_{cev{x}}}$ $cev{a}cev{b}cev{m}cev{X}$



$Xvec{x}_{vec{x}_{vec{x}}}$ $vec{a}vec{b}vec{m}vec{X}$



$cev{imath}$



$vec{imath}$

end{document}

A different implementation:

documentclass{article}

usepackage{graphicx}



makeatletter

DeclareRobustCommand{cev}[1]{%

  {mathpalettedo@cev{#1}}%

}

newcommand{do@cev}[2]{%

  vbox{offinterlineskip

    sboxz@{$m@th#1 x$}%

    ialign{##cr

      hidewidthreflectbox{$m@th#1vec{}mkern4mu$}hidewidthcr

      noalign{kern-htz@}

      $m@th#1#2$cr

    }%

  }%

}

makeatother



begin{document}

$Xx$



$Xcev{x}_{cev{x}_{cev{x}}}$ $cev{a}cev{b}cev{m}cev{X}$



$Xvec{x}_{vec{x}_{vec{x}}}$ $vec{a}vec{b}vec{m}vec{X}$



$cev{imath}$



$vec{imath}$



$cev{sigma}cev{x}$

$vec{sigma}vec{x}$

end{document}

The extensible overleftarrow might do the trick. The problem is that the arrow is bigger than the one used for vec, as shown by [overleftarrow{a}overrightarrow{a}vec{a}] . To have consistent arrows, you should redefine $vec$ :

documentclass{minimal}

renewcommandvec[1]{overrightarrow{#1}}

newcommandcev[1]{overleftarrow{#1}}



begin{document}

[cev{a}vec{a}]

end{document}

Edited to add:

Another solution is the overset command from amsmath, used with leftarrow. However, the arrow is still bigger than the one from the vec
command.

documentclass{minimal}

usepackage{amsmath}

begin{document}

[overset{leftarrow}{v}overset{rightarrow}{v}vec{v}]

end{document}

*Edited to add *
Using shortleftarrow from the stmaryrd package slightly improves the above construction.

The vec is an accent (and its own symbol; hence all leftarrow and similar constructs look different), and the default Computer Modern font doesn't have a symbol which would be its mirror.

In addition to rotating/mirroring the vec accent symbol, as shown by Ian, you could make use of one provided by, say, STIX/XITS (if you use XeTeX).
Then you could define:

defcev{XeTeXmathaccent"0"1"20D6}

% The first number ("0) denotes the math type (0=Ord,1=Op,2=Bin,3=Rel,etc.)

% The second number ("1) denotes the math family (0=Roman,1=Italic,etc.)

% The last number ("20D6) denotes the actual glyph slot

$cev a qquad vec a$

Which could look like:

I have a little to add to Frederic's solution:

usepackage{stmaryrd}



overset{shortleftarrow}{a} quad vec{a} quad overset{{}_{shortleftarrow}}{a}

Basically, the arrow in the subscript makes it smaller and reduces the vertical space between it and the variable. Unfortunately, nesting doesn't seem to work.