setprecision Help please...

[Atimes]

I have

double m=0.5;
cout<<setprecision(20);

Then the output is 0.5 but

double m=0.6;
cout<<setprecision(20);

the output is 0.59999999999999999998
What happens and how can I fix this error ?

Thanks in advance,

[transcendental]

There is nothing you can do about it. This is a issue with IEEE floating point.

IEEE floating point format is not accurate. Anyway double type have precision up to 15 decimal digits.

There is c maths library which allows any numbers up to any arbitrary digits you require. The downside of it is it is slow.

[transcendental]

Here's one library, The GNU MP Home Page

I'm sure there are more which you can google.