C++11 in uniform initialization and initializer_list

The concept of uniform initialization appears in C++11:

 int  a1 = {1 };// ok  int  a2 = {1.0 }; //  error, must shrink convert  int  array1[] = {1 , 2 , 3 , 4 }; // ok  int  arrya2[] = {1.0 , 2.0 , 3.0 , 4.0 };// ok  

Note The A2 initialization error and the correct contrast of the array2. On the one hand uniform initialization require the type of initialization to be consistent, but the new C + + standard must be compatible with c++98, and array2 initialization in c++98 is legal.

The new C++11 standard also adds a std::initializer_list<> class that can be passed in the constructor for this parameter type

#include <iostream>classa{A (int,int) {Std::cout<<"Int,int"<<Std::endl;} A (Std::initializer_list<int>)//note is not a reference! {Std::cout<<"initializer_list<int>"<<Std::endl;}};intMain () {A A1 (1,1);//int intA a2{1,1};//initializer_list<int>A A3 = {1,1};//initializer_list<int>return 0;}

Notice that A3 is calling the initializer_list<int> version of the constructor.

#include <iostream>classa{ExplicitAint,int) {Std::cout<<"Int,int"<<Std::endl;} A (Std::initializer_list<int>)//Note not a reference! {std::cout<<"initializer_list<int>"<<Std::endl;}};classb{B (int,int) {Std::cout<<"Int,int"<<Std::endl;} ExplicitB (std::initializer_list<int>)//Note not a reference! {std::cout<<"initializer_list<int>"<<Std::endl;}};classc{ExplicitCint,int) {Std::cout<<"Int,int"<<Std::endl;} ExplicitC (std::initializer_list<int>)//Note not a reference! {std::cout<<"initializer_list<int>"<<Std::endl;}};intMain () {a A= {1,1};//initializer_list<int>b b = {1,1};//Int,intc C = {1,1};//error: cannot be from initializer_list to Creturn 0;}

The constructor for B above because the Initializer_list version is set to explicit and the constructor becomes the version of B (Int,int), we can infer:

1.initializer_list priority is higher than the constructor for the specified parameter

2.uniform initialization actually passed a Initializer_list object to the constructor, and a series of implicit conversions occurred. (the error message can be judged by the constructor of Class C)

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Reference: "C + + standard library-self-study tutorials and reference manual" Nicolai M.josuttis second Edition

C++11 in uniform initialization and initializer_list