How can I set the level of precision of a value obtained through static casting?

Question

I want to set the precision to max 2 or three for the variable correctAnswer. I dont want to format the output but store in the memory with max 3 precision. Both a and b are integer values.

double correctAnswer = static_cast<double>(a) / b;

Answer 1

You can't set a precision for a cast. But you can for the output

double d = 3.14159265358979;
std::cout.precision(3);
std::cout << "Pi: " << std::fixed << d << std::endl;

Answer 2

You can use integer arithmetic for that:

const int precision = 100;
double correctAnswer = precision * a / b / static_cast<double>( precision );

you need to make sure that precision * a still fits to int or use bigger type and when you compare/output correctAnswer you still need to handle double properly