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 <string>
#include <deque>
#include <set>
#include <algorithm>
using namespace std;
/* class Person
*/
class Person {
private:
string fn; // first name
string ln; // last name
public:
Person() {
}
Person(const string& f, const string& n)
: fn(f), ln(n) {
}
string firstname() const;
string lastname() const;
// ...
};
inline string Person::firstname() const {
return fn;
}
inline string Person::lastname() const {
return ln;
}
ostream& operator<< (ostream& s, const Person& p)
{
s << "[" << p.firstname() << " " << p.lastname() << "]";
return s;
}
/* class for function predicate
* - operator () returns whether a person is less than another person
*/
class PersonSortCriterion {
public:
bool operator() (const Person& p1, const Person& p2) const {
/* a person is less than another person
* - if the last name is less
* - if the last name is equal and the first name is less
*/
return p1.lastname()<p2.lastname() ||
(p1.lastname()==p2.lastname() &&
p1.firstname()<p2.firstname());
}
};
int main()
{
Person p1("nicolai","josuttis");
Person p2("ulli","josuttis");
Person p3("anica","josuttis");
Person p4("lucas","josuttis");
Person p5("lucas","otto");
Person p6("lucas","arm");
Person p7("anica","holle");
// declare set type with special sorting criterion
typedef set<Person,PersonSortCriterion> PersonSet;
// create such a collection
PersonSet coll;
coll.insert(p1);
coll.insert(p2);
coll.insert(p3);
coll.insert(p4);
coll.insert(p5);
coll.insert(p6);
coll.insert(p7);
// do something with the elements
// - in this case: output them
cout << "set:" << endl;
PersonSet::iterator pos;
for (pos = coll.begin(); pos != coll.end(); ++pos) {
cout << *pos << endl;
}
}