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From: Eric Sosman <esosman@comcast-dot-net.invalid>
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Subject: Re: double == double
Date: Sat, 15 Oct 2016 14:15:58 -0400
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On 10/15/2016 12:36 PM, 4ndre4 wrote:
> [...] I was
> developing a 3D geometry library in C++ a while ago. The problem I had
> was testing the library. I had to test for equality with 0.0 when
> checking whether a point belonged to a plane or a rect was the result of
> the intersection between two planes. Determining the delta to use turned
> out to be extremely difficult, if not impossible. I ended up tranforming
> my classes into templates with a generic type for the coordinate, and
> write tests using integers instead of doubles. I'd be curious to know if
> there can be a better solution.

<topicality level="marginal">

     Although it covers only the two-dimensional case, this paper

http://www.cpsc.ucalgary.ca/~marina/papers/Segment_intersection.ps

describes some techniques you might find (or might have found) useful.
In particular, it offers a method of determining *exactly* whether a
sum of floating-point values would be negative, zero, or positive if
it were carried out in perfect precision.

</topicality>

-- 
esosman@comcast-dot-net.invalid
"Everybody must get stoned."  Looks like the Swedish Academy was.