The auto keyword from C++98, where it did absolutely nothing, has been repurposed in C++0x for automatic type deduction. When used in a declaration, it says "make the type of this thing the same as the type of whatever initializes it". Behold:



C:\Temp>type autocat.cpp

#include <iostream>

#include <map>

#include <ostream>

#include <regex>

#include <string>

using namespace std;

using namespace std::tr1;



int main() {

map<string, string> m;



const regex r("(\\w+) (\\w+)");



for (string s; getline(cin, s); ) {

smatch results;



if (regex_match(s, results, r)) {

m[results[1]] = results[2];

}

}



for (auto i = m.begin(); i != m.end(); ++i) {

cout << i->second << " are " << i->first << endl;

}

}



C:\Temp>cl /EHsc /nologo /W4 autocat.cpp > NUL && autocat

cute kittens

ugly puppies

evil goblins

^Z

kittens are cute

goblins are evil

puppies are ugly



map<string, string>::iterator, your decade-long reign of terror has come to an end!



(Note that m.begin() returns iterator, not const_iterator, because the map is not const. C++0x cbegin() allows you to request a const_iterator from a non-const container.)