On Sat, Dec 28, 2019, 9:36 PM Richard Damon <rich...@damon-family.org>
wrote:

> > NaN may be an instance of the abstract type Number, but is isn't a
> mathematical number.


Yes, floating point numbers are not pure-math Reals. Not even Rationals.
They are a CS construct that is very useful for computer programs that very
approximately resemble Rationals.

One of the necessary details in that approximation is that NaN is a special
"computer number." You get it as a result of some operations where other
answers aren't possible in the system. Inf is the same way. It's not a
Rational. It's also not omega-zero in set theory. It's just a thing the
system does to be "pretty good" more of the time. They are all "numbers."

... or if you insist: no floating point number is a "number." (not a closed
field, operations not transitive, blah blah)

Also, YAML is NOT a markup language, but a data serialization format. It in
> fact started as Yet Another Markup Language, but when they realized that
> what they were designing wasn't really a mark up language...


I communicated with Clark Evans in 2001 and wrote about the format near
then. Both funny acronyms are equally old. YAML is a way of *marking up*
structured data. I create YAML much more in my text editor by hand than by
serializing in-memory objects.

You are free to have a personal definition of the loose concept "markup
language" the excludes YAML.


Also GNU isn't Unix, as Unix is a trademarked name for a specific set of
> operating systems. GNU produced Linux, which is a mostly work-alike
> operating system. Its sort of like saying Scotties isn't a Kleenex (Both
> brands of facial tissues).
>

Yes, it's like arguing at great length that Scotties isn't Kleenex. Or that
I don't make a Xerox copy on my Ricoh brand printer. Pedantically you are
correct. FWIW, I am unusual in almost never using genericized brand names,
which is party of why I sound funny to everyone else :-).
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