Is thare in STL or BOOST map like container with find and pop operation?

I want my map to be searchable and I want to be capable to kick out from it elements that were inserted into it longest 开发者_运维知识库time ago (with api like map.remove(map.get_iterator_to_oldest_inserted_element()) ) like mix of queqe and map.. Is there any such container in STL or Boost?

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You can use boost::multi_index using the ordered_unique and sequence indices, as in this example.

#include <iostream>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/sequenced_index.hpp>
#include <boost/multi_index/member.hpp>

// Element type to store in container
struct Element
{
    std::string key;
    int value;

    Element(const std::string& key, int value) : key(key), value(value) {}
};

namespace bmi = boost::multi_index;

// Boost multi_index container
typedef bmi::multi_index_container<
    Element,
    bmi::indexed_by<
        bmi::ordered_unique< bmi::member<Element,std::string,&Element::key> >,
        bmi::sequenced<> >
    >
    MyContainer;

typedef MyContainer::nth_index<1>::type BySequence;

// Helper function that returns a sequence view of the container.
BySequence& bySequence(MyContainer& container) {return container.get<1>();}

int main()
{
    MyContainer container;

    // Access container by sequence. Push back elements.
    BySequence& sequence = bySequence(container);
    sequence.push_back(Element("one", 1));
    sequence.push_back(Element("two", 2));
    sequence.push_back(Element("three", 3));

    // Access container by key. Find an element.
    // By default the container is accessed as nth_index<0>
    MyContainer::const_iterator it = container.find("two");
    if (it != container.end())
        std::cout << it->value << "\n";

    // Access container by sequence. Pop elements in a FIFO manner,
    while (!sequence.empty())
    {
        std::cout << sequence.front().value << "\n";
        sequence.pop_front();
    }
}

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You can set up a boost multi-index container to do this.

However, I have trouble understanding multi-index containers. I think it would be easier to roll my own class that has as members a std::queue and a std::map, and manage it myself.

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There is nothing like that in boost and stl, but you can make a hybrid one yourself:

map<Key, Value> Map;
deque<Key> Queue;

void insert(const Key &k, const Value &v)
{
    Map[k] = v;
    Queue.push_back(k);
}
void pop_front()
{
    const Key &k = Queue.front();
    Map.erase(k);
    Queue.pop_front();
}

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If you only ever want to find the oldest (or newest -- or more generally the least/greatest by some specified criteria, and be able to remove that element), then a priority_queue will do the job.

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Boost::bimap can be used to create a unidirectionnal map using a list-based relation set.

typedef bimap<set_of<A>, unconstrained_set_of<B>, list_of_relation> custom_map_type;

custom_map_type map;

map.push_back(custom_map_type::value_type(A(), B()));

// delete the front of the list (the first inserted element if only using push_back)
map.pop_front(); 

// otherwise, set.right behave a lot like a std::map<A,B>, with minor changes.