On: 0.30000000000000004

[tzs]

Apple's Calculator app used to have an odd floating point rounding behavior (I filed a bug report and they fixed it):

    14479.14 
    - 
    152.36 
    = 
    (result is 14326.78) 
    1143 
    / 
    78 
    = 
    (result is 14.6538461538461) 
    14479.14 
    - 
    152.36 
    = 
    (result is 14326.7799999999884)

Note that the first and third calculations are the same, yet they resulted in different displayed results!

I never understood this bug. I understand floating point, so understand that some numbers are not exactly representable. However, it should at least still be consistent! The same calculation should give the same results every time.

[hxa7241 → tzs]

I suppose it depends how exact you are in defining 'same calculation' -- two possible causes of inconsistency are:

* FP means the rules of algebra do not hold, so if the calculation is done in a different equivalent form, you can get a different result.

* With Intel's old FPU unit, if a value is written to memory rather than staying in registers you can get a different result.