get a double out a string c++ -

i'm searching efficient way double out of string in c++. cstring double function, can not use because string following format:

double - space - rest of string need save. 

the problem double can of different sizes, how can double efficiently , still able save rest of string.

use istringstream read double value, ignore 1 character (space expected), , read rest of line.

string s = "1.11 string";  double d; string rest;  istringstream iss(s); iss >> d; iss.ignore(); // ignore 1 character, space expected. getline(iss, rest, '\0');