Is there no good way to write \not\iff?

Question

It always comes out funky, and I'd like to avoid \nLeftrightarrow. Is there any good way to negate the longer \iff double implication arrow?

Answer 1

You can adapt the solutions form \Rightarrow vs. \implies, and "does not imply" symbol:

Code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{centernot}

\newcommand{\notiff}{%
  \mathrel{{\ooalign{\hidewidth$\not\phantom{"}$\hidewidth\cr$\iff$}}}}

\begin{document}
$A \notiff B$

$A \centernot\iff B$
\end{document}