insert map into map?

This is a discussion on insert map into map? within the C++ Programming forums, part of the General Programming Boards category; Im having problems inserting a map into a map, I cant manage to access the actual element and call insert() ...

  1. #1
    Registered User
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    insert map into map?

    Im having problems inserting a map into a map, I cant manage to access the actual element and call insert() on it.

    Thank you

    Code:
    #include <map>
    using namespace std;
    
    int main() {
    	map<int, multimap<int, int> > my_map;
    
    	map<int, multimap<int, int> >::iterator my_it;
    	pair<map<int, multimap<int, int> >::iterator, bool> func_pair;
     
    	my_it = my_map.find(42);
    	if(my_it == my_map.end()) {
    		func_pair = my_map.insert(make_pair(42, multimap<int, int>()));
    		(func_pair.first)->insert(make_pair(42, 42));
    	} else {
    		//
    	}
    	
    	return 0;
    }

  2. #2
    and the Hat of Guessing tabstop's Avatar
    Join Date
    Nov 2007
    Posts
    14,185
    func_pair.first is an iterator into your map. Dereferencing that iterator will give you a pair of <int, multimap>. If you are intending to insert your (42, 42) pair into that multimap, you will have to access the second element of that pair, something like (untested):
    Code:
    ((func_pair.first)->second).insert(make_pair(42, 42));

  3. #3
    Algorithm Dissector iMalc's Avatar
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    What problem are you trying to solve such that you've arrived at a map to a multimap as the best solution? That's awfully unusual.
    Or is it just a learning exercise?
    My homepage
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