CODEWITHSUNDEEP
c++vectoroperator-overloadingstdmap
andres
andres

Reputation: 321

Would it be possible to overload << operator for a std::map with pair std:string and std::vector<int>?

I previously overloaded the << operator for a std::map using template for a std::map<std::string, int> 

template <typename T, typename S> 
std::ostream & operator<<(std::ostream & os, const std::map<T, S>& v) 
{ 
    for (auto it : v)  
        os << it.first << " : " << it.second << "\n"; 

    return os; 
}

How can a template be written if the map, for instance, was std::map< std::string, std::vector<int> >?

Upvotes: 1

Views: 59

Answers (2)

Aconcagua
Aconcagua

Reputation: 25526

There are several options for.

At first you could just provide a separate operator<< overload for std::vector, e. g.:

template <typename T>
std::ostream& operator<< (std::ostream& s, std::vector<T> const& v)
{ /* your generic implementation */ return s; }

It will then be called for every vector in your map:

os << it.first << " : " << it.second << "\n";
//                           ^ here...

I consider this the cleanest solution – but if it is too generic and you need something really different only for this specific map type, then you could either provide a separate overload for exclusively this type of map:

std::ostream& operator<<
        (std::ostream& s, std::map<std::string, std::vector<int>> const& m)
{ /* your specific implementation */ return s; }

or, alternatively, specialise your operator for it:

template <>
std::ostream& operator<< <std::string, std::vector<int>>
        (std::ostream& s, std::map<std::string, std::vector<int>> const& m)
{ /* your specific implementation */ return s; }

Upvotes: 2

JVApen
JVApen

Reputation: 11317

Is it possible? Yes, you could write the code.

Is it allowed? No, it's undefined behavior to extend the std namespace with your own symbols unless explicitly specified.

Looking at your current approach, I wouldn't overload the existing method. I would provide a new method for the pair.

Upvotes: 1

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