Re: Too narrowly defined: DIVISION SIGN & COLON

From: Jukka K. Korpela <>
Date: Thu, 12 Jul 2012 22:03:56 +0300

2012-07-12 21:07, Asmus Freytag wrote:

> What the examples show from TeX is that colon and ratio cannot be
> substituted for each other without affecting the display.

This looks like a problem in TeX rather than character standards. If TeX
can space $a+b$ properly, what’s the issue with $a:b$? And when I tested
it, I got proper spacing, corresponding to the example in
“Detailtypographie” (which mentions that the colon, Doppelpunkt, is used
“eventuell aus didaktischen Gründen, sonst eher veraltet oder als
»verhält sic zu« verwendet”).

However, it might be argued that disambiguation is desirable, because
COLON is also used as punctuation symbol in mathematical expressions, as
in “f: A → B” and here (arguably) there should be some spacing after the
colon but not before it. Yet, there are other contexts where the meaning
of a symbol should affect is spacing in math, and yet we don’t have
specialized symbols for them. (For example, the vertical bar should
probably have different spacing when used for an absolute value, as in
|a|, and when used as a separator as in {x|x²<1}, but this must be
handled by special logic in typesetting software or, more reasonably, by
using spaces and/or formatting tools.)

> I have no opinion on ISO 80000-2, but if this example is typical, I
> don't think much of the quality of that standard.

It’s about notations, not typography, and it has some flaws, but I don’t
see an issue here.

Received on Thu Jul 12 2012 - 14:06:15 CDT

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