Relation symbol used by Conway in On Numbers and Games

Question

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.

(Google Book search)

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?

Answer 1

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.

Answer 2

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.