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Still learning about active characters, catcodes, mathcodes, and such.

I know how to make *hello* produce bold in text mode and $x$ produce a bold $x$ in math mode. I also know how to make *{hello} produce bold in text mode and $*x$ produce a bold $x$ in math mode.

What I don't know is how to make *hello* produce bold in text mode and $*x$ produce a bold $x$ in math mode. (Note the number of asterisks.)

(I've run out of upvotes for the day, but will reward good answers tomorrow)

This I can do:

\documentclass{article} \usepackage{amsmath} \usepackage{bm} \begingroup\lccode`\~=`*\lowercase{\endgroup\def~#1~}{\ifmmode\bm{#1}\else{\bfseries #1}\fi} \mathcode`*="8000 \catcode`*=13 \begin{document} *this bold* this not $*x*$ % produces bold math % I want $*x$ to produce a bold x \end{document}

This I can do, also:

\documentclass{article} \usepackage{amsmath} \usepackage{bm} \begingroup\lccode`\~=`*\lowercase{\endgroup\def~#1}{\ifmmode\bm{#1}\else{\bfseries #1}\fi} \mathcode`*="8000 \catcode`*=13 \begin{document} *{this bold} this not $*x$ % produces bold math \end{document}
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    since you are making it globally active the \mathcode setting isn't doing anything (also you break other uses of * such as in tabular preambles. Commented Aug 20, 2016 at 20:07
  • Thank you @DavidCarlisle. I'm in the process of learning about the process, not necessarily thinking about this particular example. Commented Aug 20, 2016 at 20:09

2 Answers 2

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enter image description here

\documentclass{article} \usepackage{amsmath} \usepackage{bm} \catcode`*=13 \def*{\relax\ifmmode\expandafter\bm\else\expandafter\bstar\fi} \def\bstar#1*{\textbf{#1}} \begin{document} *this bold* this not $*x x$ % produces bold math \end{document}
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This is not very different from David's answer, but it also fixes other usages of * (for variant commands and in tabular preambles).

\documentclass{article} \usepackage{amsmath} \usepackage{bm} \makeatletter \newcommand{\jpi@active@ast}{% \relax % in case we're in a tabular \ifmmode \expandafter\jpi@active@ast@math \else \expandafter\jpi@active@ast@text \fi } \catcode`*=\active \def*{\ifincsname\string*\else\expandafter\jpi@active@ast\fi} \def\jpi@active@ast@text#1*{\textbf{#1}} \let\jpi@active@ast@math\bm % fix the kernel macros \def\@ifstar#1{\@ifnextchar *{\@firstoftwo{#1}}} % fix \@ifstar \def\@expast#1{\@xexpast #1*0x\@@} \def\@xexpast#1*#2#3#4\@@{% \edef\reserved@a{#1}% \@tempcnta#2\relax \ifnum\@tempcnta>\z@ \@whilenum\@tempcnta>\z@\do {\edef\reserved@a{\reserved@a#3}\advance\@tempcnta \m@ne}% \let\reserved@b\@xexpast \else \let\reserved@b\@xexnoop \fi \expandafter\reserved@b\reserved@a #4\@@} \makeatother \begin{document} \section*{Unnumbered} *this bold* this not $*x$ % produces bold math \begin{equation*} a=*x \end{equation*} \begin{tabular}[t]{*{2}{c}} a & bb \\ cc & d \end{tabular} \end{document}

enter image description here

Do you want to use it? No, don't. ;-)

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  • I'll have to study your answer to understand what's going on, thank you! Commented Aug 20, 2016 at 20:41
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    Did you search latex.ltx for asterisks? Commented Aug 20, 2016 at 23:03
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    @GustavoMezzetti Yes, indeed Commented Aug 21, 2016 at 7:21
  • @egreg: I had done so too, and I was delighted in seeing that I couldn’t find anything that wasn’t cared for! :-) Commented Aug 22, 2016 at 1:41

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