# [OS X TeX] blackboard bold semicolon

Thu Jul 24 08:25:13 EDT 2008

Art Werschulz wrote:
> Hi.
>
> On Jul 24, 2008, at 4:25 AM, Ross Moore wrote:
>
>> Hi Art,
>>
>> On 24/07/2008, at 2:17 AM, Art Werschulz wrote:
>>> Hi.
>>>
>>> I am trying to produce a blackboard bold semicolon.  My test file is
>>> as follows:
>>>
>>> <testfile>
>>> \documentclass[12pt]{article}
>>> \usepackage{amsfonts}
>>>
>>> \begin{document}
>>> $R{\mathbb{;}}S$ and $R;S$ should look different (the semicolon should
>>> be blackboard bold and normal, respectively).

This seems to be the way \mathbb is defined. It uses the command
\DeclareMathAlphabet, and according to the latex font documentation,

"Only symbols of type \mathalpha will be affected by math alphabet
commands: within the argument of a math alphabet command they will
produce the character in slot <slot> of that math alphabet's font.
Symbols of other types will always produce the same symbol (within one
math version)."

The semicolon is of type \mathpunct, so it will not be affected by \mathbb.

You can define your own \bbsemi:

\newcommand\bbsemi{\mathop{\mbox{\textbb;}}}

--
Martin