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the check sign



In response to Barbara and Justin's request:

It's obvious that TeX users working in different fields and subfields will
have different requirements and expectations.  For example, we could draw a
distinction between those who require multi-letter identifiers in math mode
(theoretical computer scientists) and those who like their math characters
spaced (mathematicians).  Furthermore, the Euler fonts are regarded as
essential by a third of our department (Numerical Analysis and Mathematical
Modelling) but irrelevant by the other two thirds (Programming Research
Group, Requirements Engineering).

To place my remarks about symbol usage in context, I should point out that
almost everything I set using TeX is "theoretical computer science".  The
check symbol is used in Communicating Sequential Processes, a notation for
describing the behaviour of distributed systems.  I will admit that it
rarely appears as a script symbol outside CSP.  But it's very useful as a
decoration: A^\tick or A_\tick do not carry the same connotations as A^*,
A^+ and can thus be used in the theory of your choice without people saying
"ah, closure".

That said, I'm not too bothered about "special interest" symbols like
check, I was merely pointing out that I use them.  I'm more interested in
symbols like \lefttriangle and \righttriangle, which are very widely used
(and lhd and rhd are dreadful kludges, so God bless the AMSfonts), and --
above all -- the provision of ARROWS.  I've just read Alan's document, and
I would like to stand right behind him.  I've got to set a chapter on timed
transition systems this month, and I'm not happy about the current arrow
provision (it's not much better in Lucidaworld, sadly).

While we're at it, the world is full of people bemoaning the lack of a big
square cap.  And also the following emphatic brackets:

        [|        |] -- semantic brackets (almost universal)

        (|        |) -- relational image (in Z)

        {|        |} -- bag symbol (some dialects of CSP)

        <|        |> -- bindings (in Z)

I'm sure that these four are used elsewhere with different meanings, they
are pleasing to the eye (and obvious choices for new delimiters).  I don't
have an opinion upon extensibility of these (Alan?).

If anyone wants references, perhaps the best reference for CSP symbols (a
superset of the current collection) is my "Specification and Proof in
Real-time CSP", Cambridge University Press 1993 (ISBN 0 521 45055 1).  This
was all TeX/LaTeX (I didn't have CorelDraw then), using the two AMS fonts,
a special purpose CSP font, a couple of hacked sansserif text fonts, and
the usual collection of LaTeX/TeX families.  Decent paper, 1200dpi.

Oh, alright.  So you're unlikely to respond to such an obvious plug.  But I
couldn't resist it.  Here's a more reasonable suggestion: use the ftp
server here (ftp.comlab.ox.ac.uk, IP 192.76.25.2) to grab the file
CSP/Papers/history.ps (300dpi dvips output) and check it out.

That's enough about me, I think.  :^)

Jim