[NTG-pdftex] [Dev-luatex] What is the unit "nc" supposed to be?

David Kastrup dak at gnu.org
Tue Apr 3 12:03:21 CEST 2007

Taco Hoekwater <taco at elvenkind.com> writes:

> David Kastrup wrote:
>> But I consider it more likely that nc should be changed to 1370:107
> And also, I applied this change to luatex.web (and fixed the
> documentation sting back). TeX's conversions are approximations
> anyway, I see little point in changing the conversion arithmetic.

Well, but I would find a change rendering "1in"="72.27pt" attractive.
I'll propose one shortly.  Anyway, those fractions carry _way_ more
precision than TeX's general arithmetic anyway, and TeX's truncation
(which this was all about in the first place) introduces more bias
than this particular fraction does.  One could argue that 32163:2512
will be a nicer fraction since it overshoots, and TeX forgets to round
the final result, so we err on different sides.

But I'd rather have the closest ratio and fix TeX's, excuse me
(hopefully Knuth didn't hear), LuaTeX's arithmetic on units by letting
it round properly.

David Kastrup

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