Rounding value to 2 decimal place without the use of cout<<

Question

Hi im trying to convert a value to 2 decimal place. But instead of using setprecision, i want it to be from a string. Does anyone know how to round the value to 2 decimal?

double computeArea(){
     double area = 3.1415927 * pow(3,2);
     return area;
}

int main(){
  string circle;
  circle += to_string((double)area);
  cout << circle;
  return 0;
}

You could write to an `ostringstream` and output that to `cout`. — Tanveer Badar, Aug 22 '21 at 06:01
std::stringstream ss; ss << std::setprecision(2); ss << whatever; cout << ss.str(); — keith, Aug 22 '21 at 07:47

score -1 · Answer 1 · answered Aug 22 '21 at 06:12

-1

This works

double round_to_two_decimals(double value)
{
    return std::floor(100.0 * value) / 100.0;
}

int main() 
{

    double circle = 3.14159279265;

    std::cout << circle << std::endl;
    std::cout << round_to_two_decimals(circle) << std::endl;

    return 0;
}

answered Aug 22 '21 at 06:12

Pepijn Kramer

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Note that this might produce inaccurate results for some numbers – Alan Birtles Aug 22 '21 at 06:41
okay seems I still need more coffee this morning :) For starters floor should have been std::round... and yeah it was quick and dirty. And I haven't been thinking about potential other corner cases at all. – Pepijn Kramer Aug 22 '21 at 06:46
One does not do coffee on sundays! – Tanveer Badar Aug 22 '21 at 07:03

Rounding value to 2 decimal place without the use of cout<<

1 Answers1