Why Can\'t I Use Simple Brace Initialization for 2D `std::array`s in C ?

Why is Brace Initialization Not Possible for 2D std::arrays?

In C , you can define a simple 2D array using std::array, as seen in the example:

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

However, this initialization fails with a compiler error, stating that there are too many initializers. The reason for this discrepancy lies in the fact that std::array is an aggregate class that encapsulates a C-style array.

For proper initialization, separate braces are required for the C class and its contained C array:

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

In this corrected code:

• The outermost braces initialize the std::array class.
• The nested braces initialize the C-style arrays within the class.

By matching the brace structure between C and C syntax, you can successfully initialize multidimensional arrays using brace initialization in C .

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