\
R
for the real numbers and
other standard number sets. Traditionally these were typeset in bold.
Because, in the ordinary course of events, mathematicians do not have
access to bold chalk, they invented the special symbols that are now
often used for \
R
, \
C
, etc. These symbols are known
as “blackboard bold”. Before insisting on using them, consider
whether going back to the old system of ordinary bold might not be
acceptable (it is certainly simpler).
A set of blackboard bold capitals is available in the AMS
msbm fonts (msbm is available at a range of
design sizes, with names such as msbm10). The pair of font
families (the other is called msam) have a large number of
mathematical symbols to supplement the ones in the standard TeX
distribution, and are available in Type 1 format with most modern
distributions. Support files for using the fonts, both under
Plain TeX and LaTeX (packages amssymb and
amsfonts), are available. The font shape is a rather
austere sans, which many people don’t like (though it captures the
essence of quickly-chalked writing rather well).
The bbold family is set of blackboard bold fonts written in
Metafont. This set offers blackboard bold forms of lower-case letters;
the font source directory also contains sources for a LaTeX package
that enables use of the fonts. The fonts are not available in Type 1 format.
The bbm family claims to provide
‘blackboard’ versions of most of the cm fonts ... including
the bold and bold-extended series. Again, the fonts are designed in
Metafont and are not available in Type 1 format. LaTeX macro support
comes from a package by Torsten Hilbrich.
The doublestroke family comes in just roman
and sans shapes, at a single weight, and is available both as Metafont
sources and as Type 1; the font covers the uppercase latin letters,
lowercase ‘h’ and ’k’, and the digit ‘1’.
An alternative source of Type 1 fonts with blackboard bold characters
may be found in the steadily increasing set of complete families, both
commercial and free, that have been prepared for use with (La)TeX
(see
“choice of outline fonts”).
Of the free sets, the txfonts and pxfonts families
both come with replicas of msam and msbm
(though, as noted elsewhere, there are other reasons not to use these
fonts). The mathpazo family includes a “mathematically
significant” choice of blackboard bold characters, and the
fourier fonts contain blackboard bold upper-case letters,
the digit ‘1’, and lower-case ‘k’.
The “lazy person’s” blackboard bold macros:
\newcommand{\R}{{\sf R\hspace*{-0.9ex}% \rule{0.15ex}{1.5ex}\hspace*{0.9ex}}} \newcommand{\N}{{\sf N\hspace*{-1.0ex}% \rule{0.15ex}{1.3ex}\hspace*{1.0ex}}} \newcommand{\Q}{{\sf Q\hspace*{-1.1ex}% \rule{0.15ex}{1.5ex}\hspace*{1.1ex}}} \newcommand{\C}{{\sf C\hspace*{-0.9ex}% \rule{0.15ex}{1.3ex}\hspace*{0.9ex}}}
are almost acceptable at normal size if the surrounding text is cmr10. However, they are not part of a proper maths font, and so do not work in sub- and superscripts. Moreover, the size and position of the vertical bar can be affected by the font of the surrounding text. As we’ve seen, there are plenty of alternatives: don’t try the macros, or anything similar using capital ‘I’ (which looks even worse!).
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=numbersets