Why Can\'t I Initialize a 2D std::array Like a Regular 2D Array?

The reason for limited initialization of 2D std::array

Although std::array is a very concise container, it There are certain restrictions when initializing 2D arrays. Let's explore why a simple initialization like the following doesn't work:

std::array<std::array<int, 3>, 2> a {
    {1, 2, 3},
    {4, 5, 6}
};

Error: too many initializers for 'std::array, 2u>'

The key to understanding this error is that std::array is essentially a data structure containing a C array. Therefore, to initialize a 2D std::array, additional curly braces are required:

std::array<std::array<int, 3>, 2> a {
    {{1, 2, 3}},   // 内层花括号用于初始化 C 数组
    {{4, 5, 6}}
};

This extra curly brace nesting allows the compiler to correctly assign initialization data to C array members. Therefore, even though std::array is a C class, its initialization syntax is similar to that of a C array.

The above is the detailed content of Why Can\'t I Initialize a 2D std::array Like a Regular 2D Array?. For more information, please follow other related articles on the PHP Chinese website!