On Sat, Aug 22 2015, Michael Orlitzky wrote: > On 08/22/2015 09:42 AM, R0b0t1 wrote: >> https://en.wikipedia.org/wiki/Round-off_error >> https://en.wikipedia.org/wiki/Machine_epsilon >> >> Either add a tolerance (a - b <= t) or compare them as strings as >> you've been doing. >> > > You probably want |a - b| <= t there =) > > But... that can cause problems too. If your numbers are small enough, > you can wind up with infinity or NaN (not a number) and then your > comparisons will go berserk. > > Floating point addition isn't even commutative: > > > 0.1 + 0.2 + 0.3 > 0.6000000000000001 > > 0.1 + (0.2 + 0.3) > 0.6
That demonstrates non-associativity. I believe floating point is commutative: a+b = b+a > Better to avoid that quagmire entirely if you can. Use fixed point > arithmetic, arbitrary precision, or even rational numbers if you can get > away with it. Agreed. allan
