# Real numbers symbol in XeTeX

How can I get the 'real number' sign (something like \mathbb{R} with the amssymb package in LaTeX) in XeTeX?

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Can you add the essential part of your preamble, particularly the font setting? –  egreg Mar 25 at 21:24
well I have no preamble since I'm on XeTeX ;-) –  lvaneesbeeck Mar 25 at 21:48
@ivaneesbeeck, i don't understand your answer. –  jpayansomet Mar 25 at 21:51
@Ivaneesbeeck Please add the username in your comment to respond properly (as I did here), otherwise the person will not be notified of your message. It would still be interesting to see your font setup. \font\1="Linux Libertine O"\1 ℝ\bye works great for me. –  Qrrbrbirlbel Mar 25 at 22:36
I see; nothing prevents you from using the msbm10 font with XeTeX. In any case, if you don't set fonts, you're basically using the same setting as normal TeX. –  egreg Mar 25 at 22:39

1. Using the default Computer Modern -font (which, as you've already found out, can be extended with the amssym to have access to BlackBoardBold.)
2. Using Unicode OpenType math fonts. Now this is a bit tricky because the glyph locations need to be (re-)told to TeX. This step can further be split into two different approaches, depending on how to use the limited number of \families:
1. Use just one family and change the active range by re-telling TeX the glyph positions every time the style changes (i.e. script, fraktur, etc. This is the way I've understood the unicode-math -package does it, please correct me if I have misunderstood!) I am not aware of anyone having done this for plain-xetex.
2. Fix the styles to their own \families using mapping-files created with teckit_compile from SIL. This is a bit hackish overall, see: Changing math font to OTF in XeTeX using plaintex-format. If memory serves, someone told me in a comment somewhere that this was the "old" way, so I wouldn't recommend this approach.
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\documentclass{article}
\usepackage{amssymb}
\begin{document}
\begin{tabular}{ll}
Plain-\TeX{}:   & ${\rm I\!R}$\\
amssymb:        & $\mathbb{R}$
\end{tabular}
\end{document}


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In a mathematical view (if you mean the symbol for real numbers) the second symbol is wrong ... –  Kurt Mar 26 at 3:30
@Kurt Please explain what you mean by "wrong". It's a matter of convention, isn't it? This Wikipedia article reports the Blackboard-Bold R as acceptable for denoting the set of real numbers. What symbol do you usually use for that set? –  Jubobs Mar 26 at 11:45
My English is not so good, but in the exact correct way you have only one doubled rule, usual the longest one, if there are two longest one only the first. So the letter R should be IR ... You can try \usepackage{txfonts} and then  $\varmathbb{ABCDEFGHIJKLMNOPQRSTUVWXYZ}$. In my opinion they fit better the usual writing by hand. (Or you use a mathematical trick: I define that IIR is set of real numbers or something else ...) BTW: which symbol has D.E. Knuth used? –  Kurt Mar 26 at 14:37
@Kurt I agree that \varmathbb{R} is closer to what I use in handwriting than \mathbb{R} and I'm actually considering using it instead in the future. However, saying that \mathbb{R} is "wrong" seems excessive to me. It's just a matter of taste, eh? –  Jubobs Mar 26 at 14:43
Well, perhaps is wrong a little bit too hard, but "in a mathematial view wrong" was ment to say, that there are usually special signs for the sets of real numbers, all numbers, numbers like 1, 2, 3 (German ganze Zahlen, don't know in English), irrational numbers: I,N,Q,R,Z. They should only used for this purpose. The typographical view is with which font can I set the mathematical sign needed here? Which font does fit best what is needed? Now it is a matter of taste ... Or a matter of definition, for example in a section "typhographical remarks". Too excact? Remember - I'm a German :-) –  Kurt Mar 26 at 15:40

You should put your symbol format definitions in another TeX file; publications tend to have their own styles, and some may use bold Roman for fields like R instead of blackboard bold. You can swap nams.tex with aom.tex. I know, this is more common with LaTeX, but the principle still applies.

For example:

% paper.tex
\input nams.tex
$\realnumbers$ is connected.

% nams.tex
\def\realnumbers{\mathbb{R}}
% more definitions for the Notices.

% aom.tex
\def\realnumbers{\mathbf{R}}
% more definitions for the Annals.


Just change one line in paper.tex to submit to the Annals instead of the Notices.

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Welcome to TeX.sx!. May be an example/illustration would help to support the answer. –  texenthusiast Mar 26 at 3:07

With lualatex

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{Latin Modern Math}
\begin{document}
$ℝ$
\end{document}


(not sure how to make it work with XeLaTeX or XeTeX)

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    \input amssym.tex
${\Bbb R}$

Did you mean \input amssymb.tex? –  Jubobs Apr 21 at 16:37