LaTeX symbol for "\leftrightarrow" with "\triangleq"

Question

In LaTeX, does it exist any symbol for

enter image description here

score 6 · Answer 1 · edited Apr 13 '17 at 12:34

6

There is no ready made symbol per se, but you can definitely create a new one.

Simply define a new macro using either \mathbin or \mathrel. I think that you will need the later one, since an arrow usually shows a relation.

Please see here two understand the subtle differences between the two solutions.

You use the \overset command to stack up your operators.

Anyway here is your solution.

\documentclass{article}

\usepackage{amsmath}

\usepackage{amssymb}

\newcommand{\leftrightarrowtriangleqbin}{\mathbin{\overset\triangleq\leftrightarrow}}

\newcommand{\leftrightarrowtriangleqrel}{\mathrel{\overset\triangleq\leftrightarrow}}


\begin{document}

$S \leftrightarrowtriangleqbin T$

$S \leftrightarrowtriangleqrel T$

\end{document}

And here is a sample output.

enter image description here

See the subtle spacing difference between the two?

Actually, for the second one \mathrel around the construction is redundant. As pointed out by egreg below, \overset will keep the binary relation nature of its second argument.

edited Apr 13 '17 at 12:34

Community

1

answered Dec 29 '13 at 16:25

Masroor

17,842

2

\DeclareMathOperator? Just a new command with \mathrel enclosing the code… – Manuel Dec 29 '13 at 16:30
@Manuel Yes, may be. Depends on the context the symbols will be used. – Masroor Dec 29 '13 at 16:35
It has nothing to do with \DeclareMathOperator which is not suited for this situation. By the way, an arrow usually shows a relation. Like (almost?) all the arrows defined in Latex, I would use \newcommand\leftrightarrowtriangleq{\mathrel{\overset\triangleq\leftrightarrow}}. – Manuel Dec 29 '13 at 16:41
@Manuel I get your point and understand the mistake. Please post your solution for the OP. I am going to delete mine. – Masroor Dec 29 '13 at 16:47
1

You can edit your answer if you think my comment is right. It was written as a suggestion to your answer, not as an answer to the original question. – Manuel Dec 29 '13 at 16:50
@Manuel Okay, I will – Masroor Dec 29 '13 at 16:51
3

@Manuel \overset{\triangleeq}{\leftrightarrow} is sufficient, because \overset will keep the "binary relation" nature of its second argument. So \mathrel around the construction is redundant. – egreg Dec 29 '13 at 16:53
Posted updated answer. – Masroor Dec 29 '13 at 17:01
@egreg Great. I didn't remember that. That's the way to go. – Manuel Dec 29 '13 at 18:35

score 6 · Accepted Answer · answered Dec 29 '13 at 23:58

Here are two possible alternatives. In both cases (\symA and \symB), I use both a left and right arrow joined in order to get a wider arrow. The \mkern can be increased negatively, if you want the width narrower. The \symA uses the \triangleq component from amssymb, but the vertical gap can be controlled with the optional argument to \stackon. The \symB does not require amssymb, but tries to mimic the tapered equal sign you showed in your figure, by using stacked \rules. Again, the vertical spacings are adjustable.

\documentclass{article}
\usepackage[usestackEOL]{stackengine}
\usepackage{amssymb}
\def\symA{\mathrel{\stackon[-0.8pt]{\leftarrow\mkern-6mu\rightarrow}%
  {\scriptstyle\triangleq}}}
\def\symB{\mathrel{\stackon[.7pt]{\leftarrow\mkern-6mu\rightarrow}%
  {\setstackgap{S}{0pt}\Shortstack{%
  \scriptscriptstyle\triangle\\\rule[.8pt]{6pt}{0.25pt}\\\rule{8pt}{.25pt}}}}}
\stackMath
\begin{document}
$A \symA B \symB C$
\end{document}

enter image description here

LaTeX symbol for "\leftrightarrow" with "\triangleq"

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