multimap query - order in which we store keys with multiple values

Question

Possible Duplicate:
how does the stl’s multimap insert respect orderings?

I have a multimap as follows - multimap<string,string> myMultiMap;

myMultiMap[sKey] = s1;
myMultiMap[sKey] = s2;
myMultiMap[sKey] = s3;

I add s1,s2,s3 in sequence. Later on, I may pass by a value 1,2,3 and based on that get its value.

For instance, if I pass '1', I should get back s1.

If I do this - iterator = myMultiMap.equal_range(sKey); get the value of the 1st element in the iterator list.

WIll this work? Does the iterator store the values for a key (in case of multiple values) in the order in which they were inserted?

Pls advise.

thx - Anand

Answer 1

In C++11 it seems to be the case that the order of retrieval is the same as the order of insertion (see here: http://en.cppreference.com/w/cpp/container/multimap)

I tried the following short program on GCC 4.7.1, and it fulfills that expectation:

#include <iostream>
#include <map>
#include <algorithm>

using namespace std;

int main()
{
    multimap<string, string> m;
    m.insert({"a", "x"});
    m.insert({"a", "y"});
    m.insert({"a", "z"});

    auto r = m.equal_range("a");
    for_each(r.first, r.second, [] (decltype(*(r.first))& p) { cout << p.second << endl; });

    return 0;
}

P.S.: please notice, that std::multimap does not have an operator []