Re: Math literal colon

[Hans Aberg <haberg-1@telia.com>]

> On 24 Jul 2015, at 15:29, Hans Hagen <pragma@wxs.nl> wrote:
> 
> On 7/24/2015 2:32 PM, Hans Aberg wrote:
>> [Note: I use the cc to know that I have received a reply.]
>> 
>>> On 24 Jul 2015, at 10:30, Hans Hagen <pragma@wxs.nl> wrote:
>>> 
>>> On 7/20/2015 6:06 PM, Hans Aberg wrote:
>> 
>>>>> On 20 Jul 2015, at 16:40, Aditya Mahajan <adityam@umich.edu> wrote:
>>>>> 
>>>>> On Mon, 20 Jul 2015, Hans Aberg wrote:
>>>>> 
>>>>>> The LaTeX package unicode-math has an option colon=literal, which makes it behave as in math functions (as in example below). Has ConTeXt a similar option?
>>>>> 
>>>>> No. You have to use \colon.
>>>> 
>>>> It would be nice with such an option, as it helps the readability of the input files.
>>> 
>>> already for some years i'm thinking of something similar to openmath dictionaries i.e. in many cases when one writes math it is in some field that is consistent within a document, say logic or engineering
>>> 
>>> it is rather trivial to support something
>>> 
>>> \setupmathematics[domain=logic]
>>> 
>>> or so, where we automatically relate the math class with the symbols used, something that becomes more important once we start coding in unicode instead of using names
>>> 
>>> but ... in order to provide this, i need information about useful categories
>> 
>> Unicode provides one such category. The reason is all math characters are added and in that process analyzed. I worked with Taco on that in the late 1990s.
>> 
>> So one main option, which might be the simplest, to assume that the input is UTF-8. Oen can the added ASCII command names, based on the Unicode names. In addition some options for special needs and legacy.
> 
> i don't understand what you mean as the issue is not unicode or ascii but categorizing symbols in classes

Right, but that has in part already been done by Unicode. It is not really possible to classify math symbols from the the mathematical point of view, as every author in principle use their own notation.

> when we have a symbol in the input (can be a : but also something else) in some cases it is a binary but in other cases a relation or whatever

Right. When TeX was written, there was only ASCII, so Knuth set “:” to the ratio binary operator, and the function “:” to \colon.

Now, when Unicode is available, it sets the ratio binary operator to  ≔ COLON EQUALS U+2254, leaving : COLON U+003A open for other uses. So set the latter to \colon, and add a command \ratio for the former.

> this influences the spacing and the 'domain' (or dictionaries) group symbols so that we can assign the right properties
> 
> entering a utf sequence representing 0x2236 still doesn't always prescribe what mathclass it is, 0x22A5 0x22C5 0x25B3 are examples of such dual face characters
> 
> (this is actually more important in for instance xml input)

I was thinking of just having the two, \colon and \ratio. Looking into some books before electronic typesetting, the spacing of the latter can vary widely: some do not use spaces at all. So a set might look
  {x:x < a}
instead of
  {x : x < a}
But that would be a typographical issue, rather than semantic.

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