Ignoring the Voices: C++11 Example - decltype

decltype_useful.cpp

#include <iostream>
#include <map>
#include <string>
#include <vector>

std::map<int, std::vector<std::string>> MyFunction()
{
    std::vector<std::string> v1;
    v1.push_back("Hello");
    v1.push_back("World");
    
    std::vector<std::string> v2;
    v2.push_back("Goodbye");
    v2.push_back("World");
    
    std::map<int, decltype(v2)> m1;
    m1.insert(std::pair<int, decltype(v2)>(1, v1));
    m1.insert(std::pair<int, decltype(v2)>(2, v2));
    
    return m1;
}

auto MakeCollection() -> decltype( MyFunction() )
{
    auto val = MyFunction();
    return val;
}

int main()
{
    auto collection = MakeCollection();
    
    for (auto m = collection.begin(); m != collection.end(); ++m)
    {
        std::cout << m->first;
        for (auto s = m->second.begin(); s != m->second.end(); ++s)
        {
            std::cout << " " << *s;
        }
        std::cout << std::endl;
    }
}

Compiled as follows:

g++ -std=c++0x -Wall -Werror -o decltype_useful decltype_useful.cpp