Question

How to format floating point (double) in cout in C++

Answer 1

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
	double pi = 3.14159;

	cout << "pi = " << setprecision(1) << pi << endl;
	cout << "pi = " << setprecision(2) << pi << endl;
	cout << "pi = " << setprecision(3) << pi << endl;
	cout << endl;
	cout << "pi = " << fixed << setprecision(1) << pi << endl;
	cout << "pi = " << fixed << setprecision(2) << pi << endl;
	cout << "pi = " << fixed << setprecision(3) << pi << endl;

	return 0;
}

/*
run:

pi = 3
pi = 3.1
pi = 3.14

pi = 3.1
pi = 3.14
pi = 3.142

*/

 

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Answer 2

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
	double pi = 3.14159;

	cout << "pi = " << setprecision(4) << pi << endl;
	cout << "pi = " << setprecision(5) << pi << endl;
	cout << "pi = " << setprecision(9) << pi << endl;
	cout << endl;
	cout << "pi = " << fixed << setprecision(4) << pi << endl;
	cout << "pi = " << fixed << setprecision(5) << pi << endl;
	cout << "pi = " << fixed << setprecision(9) << pi << endl;

	return 0;
}

/*
run: 

pi = 3.142
pi = 3.1416
pi = 3.14159

pi = 3.1416
pi = 3.14159
pi = 3.141590000

*/

 

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