# Relation symbol used by Conway in On Numbers and Games

I'm trying to find a nice way to typeset a relation used in combinatorial game theory. It's supposed to be a combination of < and || symbols (with the first vertical line connected to the <), though preferably with similar heights.

I've had some luck with joining the existing symbols \lhd and \shortmid, but I can never get the spacing correct; while in some cases it looks perfect, in others there is too much or too little spacing between.

Also, in normal text, where the symbol is mentioned, spaces - essential in math mode since this is a relation, but messy in text - will always appear; how can I get around this?

• Hi Mike, can you link to an image of the symbol? – Loop Space Dec 17 '10 at 10:56
• Most likely the book On numbers and games. MR1803095 for those with Math Reviews access. – Harald Hanche-Olsen Dec 17 '10 at 12:39
• @Mike: I added a picture with the symbol (if you want to edit your question again before you have 10 rep you will have to remove it and the link -- but I hope you will get the remaining 4 rep soon). – Caramdir Dec 17 '10 at 13:02
• Oh, OK. I found it on Google Books The symbol looks like ⧏, U029CF, "TRIANGLE LEFT BESIDE VERTICAL BAR" I don't see it in the comprehensive symbol list, though. It it were there I think it would be in Tables 76, 77, or 78. – Matthew Leingang Dec 17 '10 at 13:11
• No-one's mentioned Detexify yet, so I'll mention it and say that it didn't come up with anything for me (though that could be my rubbish drawing). – Loop Space Dec 17 '10 at 14:03

Edit: Following TH's advice, this would be a better command to use:

\newcommand{\trel}{\mathrel{\mathsurround=0pt \mbox{\raisebox{1.2pt}{\tiny \textbf{\textbar }}$\rhd$}}}


(I decided to explicitly say \mathsurround=0pt rather than just calling \m@th because that way, if Mike wants to paste this into the top of his document, he won't have to call \makeatletter)

Original: I don't know what built-in symbols would correspond to the one you're describing, but if you're just trying to get something done you could use this:

\newcommand{\trel}{\mbox{\raisebox{1.2pt}{\tiny \bf \textbar }$\rhd$}}


(and then use \trel every time you want to use this relation).

It's a huge hack, but, like I said, it might be enough to get you by.

• I think you'd want to surround that with \mathrel. You shouldn't be using \bf as that's only defined by some document classes. I'd also add a \m@th before \rhd. – TH. Dec 18 '10 at 9:11
• Thanks! I've used your code for the symbol, though for script and scriptscript a simpler command works. In case anybody else is interested in using this symbol, I found that your code for \trel (from the edit) works best in display and text mode, while \triangleleft\shortmid (or the opposite-sided equivalent) works for script cases. – Mike Dec 19 '10 at 13:09

Here is one way to do it: use XeTeX and type UTF-8 into your .tex file.

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage{fontspec}
\setromanfont{DejaVu Sans}

\begin{document}
Assume that χ ⧐ 0, then \ldots
\end{document}


What I have done here is to use an editor (gedit) which allows me to type and save UTF-8. I've used Character Map in GNOME, which is a program that lets you see each Unicode code point, search for particular code points, and show them in different fonts that are installed on your system. There are similar programs for Mac and Windows, I presume. Once I found the right code point (U+29D0, VERTICAL BAR BESIDE RIGHT TRIANGLE), I copied it to the clipboard and pasted it into gedit. I also copied another character just for fun, as you can see.

Running xelatex foo.tex on this gives the output (in foo.pdf).

You can choose another font – but if the glyphs are missing then you will get blanks instead of the desired characters. The downside is that you can't use the default LaTeX font Computer Modern because it doesn't have the ⧐ character. But with XeTeX, you have all system fonts at your disposal so the problem is now reduced to finding (and possibly installing) a font that you like and that has the right glyphs. Of course, you could change the font for only this one character, possibly defining a new command for it. Then you would just need to select a font where this glyph works well with the Computer Modern glyphs.