[Edu-sig] Basic dictionary question

[Kirby Urner]

Talk about fishing for expert help!  

Thanks Guido.

It's a pruning algorithm where I strip way pieces that don't meet up at
(x,y,z) bridge points.  Lots of symmetry about the origin so just pure
distance won't work (not unique enough).  

I think might still get away with a tuple-indexed dict (tallying for pairs,
pruning the rest) if I boil my floating points down to fixed decimals -- a
chance to play with the new decimal type perhaps.

I appreciate the quick lecture on intransitive nature of fuzzy equality and
__hash__ vs. __eq__.  Helps me think.

Kirby


> You never said what you wanted to do with these points -- are you
> looking to find which points are in fact close enough to be considered
> the same point? I suppose you could sort them by the vector length
> (sqrt(x**2 + y**2 + z**2), that sort of thing) and then you only have
> to compare points that are close together in the sorted list (as long
> as the abs values are closer than your epsilon). Or you could divide
> 3-space up into cubes with sides equal epsilon, and then you'd only
> have to look for points that end up in the same or in adjacent cubes.
> 
> --Guido