Why it's not possible to create a pair object in the following way:
pair<int,int> p1 = {0,42}
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1Why do you think it's not possible? – sbi Aug 16 '12 at 09:37
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If you are compiling under Linux, try linking with -std=c++11. Provided you've included the semi colon etc, it should work fine. – Owl Mar 29 '16 at 16:15
2 Answers
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in C++03 you should use
std::make_pair(0, 42);
since pair is not simple data-structure. or by calling constructor of pair i.e.
std::pair<int, int> p1(0, 42);
in C++11
pair<int, int> p1 = {0, 42}
is okay.
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Initializer list syntax is not allowed in C++03 because std::pair is not an aggregate, therefore the valid way of initializing is a constructor call.
Formal definition from the C++ standard (C++03 8.5.1 §1):
An aggregate is an array or a class (clause 9) with no user-declared constructors (12.1), no private or protected non-static data members (clause 11), no base classes (clause 10), and no virtual functions (10.3).
Please read FAQ for a detailed explanation.
Things are changed in C++11 by introduction of std::initializer_list.
