What is the purpose of std::make_pair vs the constructor of std::pair?

c++ stl std-pair
user542687 picture user542687 · Feb 14, 2012 · Viewed 90k times · Source

What is the purpose of std::make_pair?

Why not just do std::pair<int, char>(0, 'a')?

Is there any difference between the two methods?

Answer

Tor Valamo picture Tor Valamo · Feb 14, 2012

The difference is that with std::pair you need to specify the types of both elements, whereas std::make_pair will create a pair with the type of the elements that are passed to it, without you needing to tell it. That's what I could gather from various docs anyways.

See this example from http://www.cplusplus.com/reference/std/utility/make_pair/

pair <int,int> one;
pair <int,int> two;

one = make_pair (10,20);
two = make_pair (10.5,'A'); // ok: implicit conversion from pair<double,char>

Aside from the implicit conversion bonus of it, if you didn't use make_pair you'd have to do

one = pair<int,int>(10,20)

every time you assigned to one, which would be annoying over time...

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