[Tex/LaTex] latex symbol for “if and only if”

logicmath-operatorssymbols

In LaTeX the symbol for material implication is produced by $\to$, but for biconditional ?

Best Answer

LaTeX defines \to as \rightarrow:

\let\to\rightarrow % fontmath.ltx

The other direction is \gets:

\let\gets\leftarrow

For \leftrightarrow you can define your own command, e.g. \biconditional:

\documentclass{article}
\let\biconditional\leftrightarrow
\begin{document}
\[ A \to B \biconditional C \gets D \]

\[ A \rightarrow B \leftrightarrow C \leftarrow D \]
\[ A \longrightarrow B \longleftrightarrow C \longleftarrow D \]

\[ A \Rightarrow B \Leftrightarrow C \Leftarrow D \]
\[ A \Longrightarrow B \Longleftrightarrow C \Longleftarrow D \]
\[ B \iff C \]
\end{document}

Result

Remarks:

  • \iff adds some extra space (from fontmath.ltx):

    \DeclareRobustCommand\iff{\;\Longleftrightarrow\;}

  • The example also shows some other arrow variants.

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