Complex arithmetic misbehaves in boundary cases
Consider complex multiplication. If we have a number x+iy and multiply this number by i we get -y+ix. Let us try the same thing in Haskell with IEEE floating point: let inf = 1.0/0.0
a = 1 :+ inf
i = 0 :+ 1
in a * i This comes out as (-Infinity) :+ NaN when it should have been (-Infinity) :+ 1.0. It is not just a made up problem, see, e.g., http://www.cs.berkeley.edu/~wkahan/Curmudge.pdf
We should address this problem. I have not yet determined if testing for a real part of 0 in multiplication (and division) is sufficent, but I think it is. I will be back with more information on the fix.
-- Lennart
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| Component | HaskellPrime |
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