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

["Berthold K.P. Horn" <bkph@ai.mit.edu>]

At 06:44 AM 12/19/97 +0000, Rebecca and Rowland wrote:

>>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.)

If you read my original post you will see quite clearly that I point out
that in the typical case these errors tend to cancel out.  I didn't bother
to calculate the result in this case since it is so obvious.  I focused
on the worst case, when the same error is repeated many time over.

Someone else mentioned the issue of limited tables in TFM file creating
their own rounding problems.  Fortunately this is not a real issue, since
there is enough space in the case of advance width: every one of the
256 character can potentially have a difference width.  Same goes for
kerning.  The only place any rounding may be required is in height,
depth and italic correction, where it matters much less.

Regards, Berthold.


Berthold K.P. Horn
MIT AI Laboratory
mailto: bkph@ai.mit.edu