🚀 go-pugleaf

robertw@informix.com (Robert Weinberg) writes:

   Manhole covers are manufactured in circular shape, rather than oval or square, to  
   satisfy one paramount condition.

   What is the condition ...

The cover can't fall down the hole.

   ... and why does a circular shape satisfy it?

Because: DIAMETER_HOLE <= DIAMETER_COVER
for all possible values of DIAMETER_HOLE and DIAMETER_COVER.

   What other shapes would also satisfy the condition?

Given the above, for any fully convex shape, I don't _think_ there are
any others.

Probably if I was clever enough (and/or had more time) perhaps I could
come up with some more complicated shape.

(Implicit in the above is the assumption that what's really keeping
the lid from dropping is a narrow lip around the edge of the hole.  If
we could play with the width of the lip, we could surely get other
allowable shapes, but the problem would quickly become uninteresting.)

N