This is an intuitive explanation, but the mathematics of IEEE floating points seem to be designed so that 0.0 represents a "really small positive number" and -0.0 represents "exact zero" or at least "an even smaller really small negative number"; hence -0.0 + 0.0 = 0.0. I never understood this either.
On Saturday, July 9, 2016 at 7:40:58 AM UTC-4, Tom Breloff wrote: > > Yes. They are different numbers. In a way, negative zero represents "a > really small negative number" that can't be represented exactly using > floating point. > > On Saturday, July 9, 2016, Davide Lasagna <lasagn...@gmail.com > <javascript:>> wrote: > >> Hi, >> >> I have just been bitten by a function hashing a custom type containing a >> vector of floats. It turns out that hashing positive and negative floating >> point zeros returns different hashes. >> >> Demo: >> julia> hash(-0.0) >> 0x3be7d0f7780de548 >> >> julia> hash(0.0) >> 0x77cfa1eef01bca90 >> >> julia> hash(0) >> 0x77cfa1eef01bca90 >> >> Is this expected behaviour? >> >>
