How can I loop through all the elements in a two pair STL set<pair<t1,t2>,pair<t1,t2>>?

Question

Here is the data type I am using.

  set< std::pair<string,string>,std::pair<string,string>> foo;

Here is my failed attempt at looping over it

for(auto &e: foo){
    cout << e.first << " " << e.second // this is where I am having an issue.
}

Is it possible to use auto this way? e.g

e.first, e.second // some c++ magic (i realize -> is wrong)  In pseudo -> //  e.third ...

I would love to use auto, but if not how would I write an iterator for the data type I am using?

Answer 1

You are doing something utterly weird.

The signature of set is:

template<
    class Key,
    class Compare = std::less<Key>,
    class Allocator = std::allocator<Key>
> class set;

So you are using std::pair<std::string, std::string> as comparator. It will fail to compile as soon as you try to insert something.

But I am pretty sure that's not what you want.

You probably either want

map<pair<string, string>, pair<string, string>>;

or

set<pair<pair<string, string>, pair<string<string>>>;

or maybe

set<tuple<string, string, string, string>>;