Latex 'fat comma'

Question

I am looking for a 'blackboard-bold' style comma notation. In particular, is there a comma similar to the lower part in \fatsemi from the stmaryrd package? I tried to search 'fat comma', 'blackboard-bold comma', but did not get anything wanted. I am aware of using the approach similar to \fcmp but that looks less nice to me.

Answer 1

You can grab the glyph from the bbold font. The style is a little bit different from that of \fatsemi though:

\documentclass[12pt]{article}
\usepackage{stmaryrd, bbold}

\DeclareSymbolFont{bbsymbol}{U}{bbold}{m}{n}
\DeclareMathSymbol{\bbsemicolon}{\mathbin}{bbsymbol}{"3B}
\DeclareMathSymbol{\bbcomma}{\mathbin}{bbsymbol}{"2C}

\begin{document}
    \begin{tabular}{ll}
        \verb|\fatsemi|:        & $a\fatsemi b$ \\
        \verb|bbold| semicolon: & $a\bbsemicolon b$ \\ 
        \verb|bbold| comma:     & $a\bbcomma b$ \\ 
    \end{tabular}
\end{document}

Answer 2

You could use trimclip:

\documentclass{article}

\usepackage{stmaryrd, trimclip}

\newcommand{\fatcomma}{\mathbin{\clipbox*{0 -1ex {\width} .66ex}{$\fatsemi$}}}

\begin{document}

$a\fatsemi b$

$a\fatcomma b$

\end{document}