Note: Do not confuse <sstream> classes with the outdated and deprecated <strstream> family of char*-oriented stream classes, namely strstreambuf, istrstream, ostrstream, and strstream. Although both libraries offer the same functionality more or less, the newer <sstream> library is superior in many respects.

In the following example, we define a stringstream object and insert a variable of type double to it. We use the stringstream overloaded << and >> operators for insertion and extraction.

#include <sstream>
using namespace std;
int main()
{
 double d=123.45;
 stringstream s;
 s << d; // insert double into stream
}

Note that stringstream objects have a built-in memory manager that takes care of allocating memory as needed. This is a major advantage as it eliminates the drudgery of manual memory management, potential buffer overflows, and memory leaks. To extract the value stored in s to a string, use the >> operator:

string val;
s >> value;

Now val contains the string "123.45".

The opposite conversion, namely double to string, is just as simple:

string val="124.55";
stringstream s;
double d=0;
s << val; // insert string
s >> d; // d now equals 124.55