Converting string to double keeps rounding to the whole number

Question

I am trying to convert a string decimal number into a double, however when I use the atof() function, my number ends up rounding to the whole number.

#include<iostream>
#include<cstdlib>
using namespace std;
int main()
{
string num = "135427.7000";
double r = atof(num.c_str());
cout << r << endl;
}

The output is:

135428

I want:

135427.7

Answer 1

cout does that, not atof().

More precisely, operator<<, which inserts the formated data into the std::ostream.

You can use std::setprecision() from the <iomanip> standard library to print the decimals:

cout << setprecision(7) << r << endl;

or

cout << fixed << setprecision(1) << r << endl;

If you want to print the whole 135427.7000:

cout << fixed << setprecision(4) << r << endl;