[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?

Best Answer

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.

enter image description here

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

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