Re: [Dev-luatex] What is the unit "nc" supposed to be?

3 Apr 2007


      David Kastrup wrote:
...
Taco Hoekwater  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.
this is not going to happen soon, maybe a different 'rounding' some day;

while developing we need to be able to compare pdftex output with luatex 
output/processing and implementing a different rounding model is not 
convenient at this time

nobody bothered about that for 25 years so we're not in a great hurry 
there -)

Hans  

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