Symbol for "corresponds to" (equals sign with hat) [duplicate]

Question

Recently in some LaTeX documentation I noticed that there is a special LaTeX command for the symbol meaning "corresponds to", which is similar to an equal sign with a hat on top. \hat{=} or \widehat{=} both do not give satisfying results (my personal view). Unfortunately, I cannot remember which documentation it was! Does anyone know the command or the documentation where to find it?

The symbol I am looking for:

PS: I have already tried detexify but it didn't produce anything useful! Also, browsing the comprehensive LaTeX symbol list wasn't successful.

Answer 1

Try this. Of course, the parameters can be adjusted to change vertical separation height or horizontal width of wedge relative to = sign, or aspect ratio of wedge. Note that the appearance of this is not quite the same as \hateq cited in comments above, but better conforms to the symbol illustrated by the questioner.

REVISED SOLUTION eliminated use of array to make space around \equalhat compatible with \mathrel.

\documentclass{article}
\usepackage{scalerel,stackengine,amsmath}
\newcommand\equalhat{\mathrel{\stackon[1.5pt]{=}{\stretchto{%
    \scalerel*[\widthof{=}]{\wedge}{\rule{1ex}{3ex}}}{0.5ex}}}}
\begin{document}
\[
x^2 \equalhat \ensurestackMath{\Centerstack[c]{a b c}}
\]

\begin{align}
a &\equalhat b \\
a &= b
\end{align}
\end{document}

ORIGINAL SOLUTION

\documentclass{article}
\usepackage{scalerel,amssymb}

\newcommand\equalhat{%
\let\savearraystretch\arraystretch
\renewcommand\arraystretch{0.3}
\begin{array}{c}
\stretchto{
    \scalerel*[\widthof{=}]{\wedge}
    {\rule{1ex}{3ex}}%
}{0.5ex}\\ 
=%
\end{array}
\let\arraystretch\savearraystretch
}

\begin{document}

$x^2 \equalhat \begin{array}{c}a\\b\\c\end{array}$

\end{document}