# How to get the covering relation symbol?

I want    to denote the covering relation. I can't find this symbol in my standard sources for this sort of thing. Detextify has also failed in this. How can I get this relational symbol?

• Isn't it a \prec symbol? – Malipivo Mar 24 '15 at 13:41
• @Malipivo No. The one I ask about has only straight lines. – Git Gud Mar 24 '15 at 13:43
• Very well, in case we wouldn't find that symbol, we could draw our own symbol, e.g. in TikZ. – Malipivo Mar 24 '15 at 13:46
• Is a symbol like in this picture good enough? – egreg Mar 24 '15 at 13:46
• @egreg No, but the second option in your answer is looking good. Thanks. – Git Gud Mar 24 '15 at 19:12

## 2 Answers

If you can't use unicode-math, here you find a couple of possibilities:

\documentclass{article}
\usepackage{amsmath}
\usepackage{pict2e,picture}

\newcommand{\coveringA}{%
\mathrel{-\mkern-4mu}<%
}
\newcommand{\coveringB}{\mathrel{\text{$\vcenter{\hbox{\pictcoveringB}}$}}}

\newcommand{\pictcoveringB}{%
\begin{picture}(1em,.5em)
\roundcap
\put(0,.25em){\line(1,0){.6em}}
\put(.6em,.25em){\line(3,1){.4em}}
\put(.6em,.25em){\line(3,-1){.4em}}
\end{picture}%
}

\begin{document}

$x\coveringA y_{\coveringA}$

$x\coveringB y_{\coveringB}$

\end{document}


If you're sure that you won't use the symbol in subscripts or superscripts, then

\newcommand{\coveringB}{\mathrel{\vcenter{\hbox{\pictcoveringB}}}}


is more efficient. You can play with the parameters as you wish, in the second solution.

• I'm sure that I won't use it in subscripts or superscripts. So how exactly do I incorporate \newcommand{\coveringB}{\mathrel{\vcenter{\hbox{\pictcoveringB}}}} into your proposed solution? – Git Gud Mar 24 '15 at 21:44
• @GitGud Just use the second proposed definition in place of the original one. Of course you don't need to define \coveringA and maybe give \coveringB a better name. – egreg Mar 24 '15 at 21:47

The symbol you are looking for is U+2919. You could use unicode-math in order to get it. It is already defined as \mathrel here.

% arara: lualatex

\documentclass{article}
\usepackage{unicode-math}

\begin{document}
\setmathfont{XITS Math}
$\righttail\lefttail$
\setmathfont{Cambria Math}
$\righttail\lefttail$
\setmathfont{Asana Math}
$\righttail\lefttail$
\end{document}


Or you choose any font you like and do:

% arara: lualatex

\documentclass{article}
\usepackage{fontspec}
\usepackage{mathtools}
\newcommand*{\lefttail}[1]{\mathrel{\fontspec{#1}\text{\symbol{"2919}}}}

\begin{document}
$x\lefttail{code2000.ttf} y$
$x\lefttail{quivira.otf} y$
$x\lefttail{stix-regular.otf} y$
$x\lefttail{symbola.ttf} y$
\end{document}


Some of them will need some vertical adjustment, though.

You may also want to take a look on :

% arara: pdflatex

\documentclass{article}
\usepackage{tikz-cd}

\begin{document}
$\begin{tikzcd}[column sep=4mm] x & y\arrow[no head, tail]{l} \end{tikzcd}$
\end{document}