[metapost] Re: MetaPost 0.891 announcement
taco at elvenkind.com
Tue Mar 22 09:27:58 CET 2005
Larry Siebenmann wrote:
> Concerning 6:
> I am not keen on introducing systematic functionality in any public
> mp version that is ab initio known to be inappropriate and impermanent.
We are not introducing functionality. turningnumber is not new.
This new implementation of turningnumber is a better than the
original, even if it is not yet perfect. A temporary solution
that make the problem have a lesser sting while at the same
time a real resolution is being sought is a valid way to deal
with bugs in software.
> A more orthodox alternative is to introduce the new primitive
No. That would be 'new functionality that is ab initio known to be
inappropriate and impermanent', since it will become obsolete as
soon as the real turningnumber is fixed.
> I have railed often against ignoring the inevitable instabilities
> of turningnumber. They should be signaled somehow. But how?
Of course I have seen your warnings about instable curves, but
warnings do not transform themselves into pascal code, and I have
not yet found a usable algorithm that finds whether or not a path
segment is well-behaved, based on its points (as opposed to its
As it stands, I've allowed myself or others six months (until the
next release) to find a definitive solution for this problem.
> Example: Consider the mirror image 'almost perfect' circles
> With your current proposal, what does mp say about their respective
> turningnumber's (ie secantturningnumber's).
both report the same, 1. (that follows from the description of the
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