[metapost] MetaFont: Unexpected behavior of intersections times

[laurent at math.toronto.edu]

Hi all

Me> One helpful sufficient condition for one or more genuine
> intersections of the two paths p and q is this
> criterion:
> ($) existence of a quadrilateral Q [...]

Jacko> Is it possible to construct such a quadrilateral
 > efficiently?

For nice transversal intersestions I believe it is. The idea is that
near the intersection the curve pair looks like an X.  But I would
want to review Knuth's algorithm(s) to be confident of good
performance.  So I won't venture a specific construction
until I find some leisure time to play around.

One biproduct should be a very sharp determination of the
transverse intersection point. MP is somewhat sloppy.

Cheers,

Laurent S.