The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference
by Nicolai M. Josuttis, Addison-Wesley, 1999
© Copyright Nicolai M. Josuttis 1999
#include <iostream>
#include <algorithm>
#include <iterator>
using namespace std;
bool bothSpaces (char elem1, char elem2)
{
return elem1 == ' ' && elem2 == ' ';
}
int main()
{
// don't skip leading whitespaces by default
cin.unsetf(ios::skipws);
/* copy standard input to standard output
* - while compressing spaces
*/
unique_copy(istream_iterator<char>(cin), // beginning of source: cin
istream_iterator<char>(), // end of source: end-of-file
ostream_iterator<char>(cout), // destination: cout
bothSpaces); // duplicate criterion
}