# [Tex/LaTex] Logical equivalence vDashv

logicsymbols

I need to create a symbol logical equivalence. Contact vDash with appropriate vertical line, but I can not find any. Can you advise?

While mathabx has some symbols that might help, using it means changing all symbol fonts and this, in general, is not desirable.

Here's a possible way to do it: superimpose a \vDash symbol to its reflected copy.

\documentclass{article}
\usepackage{amsmath,amssymb,graphicx}
\newcommand{\Dashv}{%
\mathrel{\text{\reflectbox{$\vDash$}}}%
}
\newcommand{\vDashv}{%
\mathrel{%
\text{%
\ooalign{$\vDash$\cr\reflectbox{$\vDash$}\cr}%
}%
}%
}

\begin{document}
$f\vDash g$

$f\Dashv g$

$f\vDashv g$
\end{document}


I've also defined a \Dashv command with the reflected symbol.

See \subseteq + \circ as a single symbol ("open subset") for a quick introduction to \ooalign.