On Tue, Jul 10, 2012 at 3:06 PM, Sönke Hahn <email@example.com...> wrote: > I've attached the code. The code does not make direct use of > unsafePerformIO. It uses QuickCheck, but I don't think, this is a > QuickCheck bug. The used Eq-instance is the one for Float. > > I've only managed to reproduce this bug on 32-bit-linux with ghc-7.4.2 > when compiling with -O2. > It's expected behaviour with floats. Calculations in FPU are done in maximul precision available. If one evaluation result is kept in registers and another has been moved to memory and rounded and move back to registers number will be not the same indeed.
In short. Never compare floating point number for equality unless you really know what are you doing.