std::basic_istream<CharT,Traits>::unget
Min standard notice:
Makes the most recently extracted character available again.
# Declarations
basic_istream& unget();
# Return value
*this
# Example
#include <iostream>
#include <sstream>
int main()
{
std::istringstream s1("Hello, world.");
char c1 = s1.get();
if (s1.unget())
{
char c2 = s1.get();
std::cout << "Got: '" << c1 << "'. Got again: '" << c2 << "'.\n";
}
}