id,summary,reporter,owner,description,type,status,milestone,resolution,keywords,cc,section,state
115,Complex arithmetic misbehaves in boundary cases,guest,ijones,"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",task,new,,,,,,