Thread: Formatting number output

One way is to use a floating point variable (double is the common choice) and set cout to print a fixed number of fractional digits with that number (precision) being 1:

Code:

#include <iostream>
#include <iomanip>
 
int main() 
{
    int millisec = 4562;
 
    // Must be floating point to have a fractional part.
    // Note that the calculation must have at least one floating point value
    // (1000.0 in this case) for the calculation to be floating point.
    double seconds = (millisec / 1000.0);
 
    // Set cout to a fixed number of fractional digits
    // In fixed mode, the precision indicates the number of fractional digits.
    std::cout << std::fixed << std::setprecision(1);
 
    std::cout << seconds << '\n';  // prints 4.6
}

Note that this rounds up.

Alternatively you can do it with just integer math:

Code:

#include <iostream>
 
int main() 
{
    int millisec = 4562;
 
    // Without rounding (prints 4.5)
    std::cout << millisec / 1000 << '.' << millisec % 1000 / 100 << '\n';
 
    // With rounding (prints 4.6)
    std::cout << millisec / 1000 << '.' << (millisec + 50) % 1000 / 100 << '\n';
}