I would like to obtain a number from stringstream and set it to 5 significant figures. How do I do this? So far, this is what I have managed to come up with:
double a = 34.34566535
std::stringstream precisionValue;
precisionValue.precision(6) << a << std::endl;
However, this is not compiling. Thanks.
It doesn't compile because ios_base::precision() returns streamsize (it's an integral type).
You can use stream manipulators:
precisionValue << std::setprecision(6) << a << std::endl;
You'll need to include <iomanip>.
std::stringstream::precision() returns a streamsize, not a reference to the stream itself, which is required if you want to sequence << operators. This should work:
double a = 34.34566535;
std::stringstream precisionValue;
precisionValue.precision(6);
precisionValue << a << std::endl;
The precision member function returns current precision, not a reference to the stringstream, so you cannot chain the calls as you've done in the snippet.
precisionValue.precision(6);
precisionValue << a;
std::cout << precisionValue.str() << std::endl;
Or use the setprecision IO manipulator to chain the calls:
precisionValue << setprecision(6) << a;
std::cout << precisionValue.str() << std::endl;
You can use std::setprecision from header <iomanip>
#include <string>
#include <sstream>
#include <iomanip>
#include <iostream>
int main()
{
double a = 34.34566535;
std::stringstream precisionValue;
precisionValue << std::setprecision(6);
precisionValue << a << std::endl;
std::cout << precisionValue.str();
}
