Re: Round-off errors in metrics & fontinst/finst status...

[Rebecca and Rowland <rebecca@astrid.u-net.com>]

>At 06:25 AM 97/12/18 +0000, Rebecca and Rowland wrote:
>
>>And it can be less if the rounding is less than 0.5 - this 0.15mm is
>>more-or-less worst-case.  The rms rounding error is something like 0.3, so
>>the typical error with a repeated character will be nearer 0.05%, or 75
>>microns in 150mm; typical error with random characters will be nearer 7.5
>>microns.  I'm not inclined to fret over errors of less than 0.1mm across a
>>page.
>
>Ah, but even if noticable error only occurs in fixed width fonts and when
>using the same character repetedtly, doesn't it bother you to spoil the
>incredible accuracy that TeX has, just because of some unneeded sloppyness
>in making fonts, or in making metric tables?

Yes, that does bother me.  But I like to get things *right*, even down to
error estimates.  (What am I saying?  *Especially* error estimates - comes
of having a physics degree.  I make no apologies for this.)

On the same track: is it only me who gets tremendously irritated by
LaTeX2e's habit of truncating dimensions to the nearest point?  Is there
any reason for this anti-social behaviour?

>I might also mention that some DVI processors switch between relative
>and absolute positioning.  This means accumulated errors can produce
>a discontinuity at a transtion, not just at the end of the line.  This often
>happens were a superscript appears.  In this case even a small error
>may be noticeable (0.15mm is 0.5pt)

0.15mm is likely to be noticeable; it's nearer 0.4pt.  This is about twice
1/300 inch, so quite clearly resolvable even using a medium resolution
inkjet like my DW520.

[snip]

Rowland.