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c++stlstd-pair

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

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?

Solution

  • (This answer is only correct for C++14 and earlier standards, due to CTAD)

    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...