c++ input double until Enter key is pressed -

i have code adds doubles entered user , stops when user enters negative number. want change stop when user presses enter key , doesn't enter number, possible? , if so, how?

double sum = 0, n;  cout << endl;  {     cout << "enter amount <negative quit>: ";     cin >> n;      if(n >= 0)     {         sum += n;     } }while(n >= 0);  return sum; 

use getline() below:

#include <iostream> #include <string> using namespace std; int main() {     string s;     double sum=0.0;     while (1)     {         cout<<"enter number:";         getline(cin, s);         if (s.empty())         {             cout <<"sum is: " <<sum;             return 0;         }         else         {           sum=sum+ stod( s );         }     }         return 0; } 

an example output:

  enter number:89   enter number:89.9   enter number:   sum is: 178.9