are almost acceptable at normal size if the surrounding text is cmr10 (the position of the vertical bar can be affected by the surrounding font). However, they are not part of a proper maths font, and do not work in sub- and superscripts. As we’ve seen, there are plenty of alternatives: that mythical “lazy” person can inevitably do better than the macros, or anything similar using capital ‘I’ (which looks even worse!). Voluntary (La)TeX effort has redefined the meaning of laziness (in this respect!).\newcommand{\R}{{\textsf{R}\hspace*{-0.9ex}% \rule{0.15ex}{1.5ex}\hspace*{0.9ex}}} \newcommand{\N}{{\textsf{N}\hspace*{-1.0ex}% \rule{0.15ex}{1.3ex}\hspace*{1.0ex}}} \newcommand{\Q}{{\textsf{Q}\hspace*{-1.1ex}% \rule{0.15ex}{1.5ex}\hspace*{1.1ex}}} \newcommand{\C}{{\textsf{C}\hspace*{-0.9ex}% \rule{0.15ex}{1.3ex}\hspace*{0.9ex}}}
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=numbersets