Need Help With Namespace!

[Alfie]

Hello

Im having a problem undrestanding a code providied by my school as a help for exam.

Here is the Code:

#include <algorithm>
#include <functional>
#include <iostream>
#include <iomanip>
#include <iterator>
#include <map>
#include <string>
#include <utility>
using namespace std;


namespace std
{
ostream& operator<<(ostream& os, const pair<string, int>& p)
{
return os << setw(8) << left << p.first << p.second;
}

ostream& operator<<(ostream& os, const pair<int, string>& p)
{
return os << setw(8) << left << p.second << p.first;
}
}

int main()
{
map<string, int> dog_names;
string name;

while (cin >> name)
{
++dog_names[name];
}

copy(dog_names.begin(), dog_names.end(),
ostream_iterator< pair<string, int> >(cout, "\n"));
cout << endl;

multimap<int, string, std::greater<int> > dog_names_ranked;

for (map<string, int>::const_iterator it = dog_names.begin();
it != dog_names.end();
++it)
{
dog_names_ranked.insert(make_pair(it->second, it->first));
}

copy(dog_names_ranked.begin(), dog_names_ranked.end(),
ostream_iterator< pair<int, string> >(cout, "\n"));

return 0;
}


Now the part I dont undrestand is:

namespace std
{
ostream& operator<<(ostream& os, const pair<string, int>& p)
{
return os << setw(8) << left << p.first << p.second;
}

ostream& operator<<(ostream& os, const pair<int, string>& p)
{
return os << setw(8) << left << p.second << p.first;
}
}

why make a namespace with the name std? we are alredy using namespaces std;

and how are we manipulating the << ? When are we using this namespace anyway??

I would apricate a answer

Thx!!

[Breadman]

You are just extending the std namespaces functionality. for example before you could say
std::cout << "hello"; and
std::cout << 5+74;

after our code you can also say cout << somepair;
i think not completely sure :/

[Alfie]

Thank you,,

it now make sense.

but if I change the namespace name to ex "bart" and then call the namespace whenever i need to use it. eg .. bart::greater<int>. But it dosent compile... So we are only extending the std namespaces.

My question Now is: What dose this do ?

ostream& operator<<(ostream& os, const pair<string, int>& p)
{
return os << setw(8) << left << p.first << p.second;
}


and espacially : ostream& operator<<(ostream& os, const pair<string, int>& p)

[Breadman]

well you need to implement cout also in bart namespace. and thats friggin hard i think

[Alfie]

thx m8 :)