Eric Fernandez wrote:
> I have a question regarding the conversion of double to int. Considering
> this little program:
>
>
> #include <iostream>
> using namespace std;
>
> int main()
> {
> double a = 50.0;
> double b = 48.7;
>
> double c = a - b;
>
> cout << c << endl;
> cout << c * 10 << endl;
> cout << static_cast<int>(c * 10) << endl;
>
> return 0;
> }
>
>
> I get this result:
> 1.3
> 13
> 12 <--- why not 13?
>
> 1) I am aware I may touch here the problem of floating point
> representation and that the 1.3 value - result of a subtraction - is not
> exactly this one, but maybe 1.2999999... Is this the reason why the int
> conversion transforms the "double" 13 into a "int" equal to 12 ?
Yes.
> 2) How to avoid this problem ? I'd like to be sure to round this number
> correctly (with a precision of 1/10th, 1/100th, etc...).
>
> I have tried to find relevant information regarding this issue but did
> not find a clear answer,
Use the round() function before static_cast<int>.
Andrew.
