How to initialize an array easily in constructor?

Question

How to initialize an array easily in the constructor? For example

class A
{
    array<array<int, 2>, 2> m;
    A(int m00, int m01, int m10, int m11)
       : m {m00, m01, m10, m11} // ??? how to list here 
    {}
};

It works as is if you fix the variable typos. – user975989 Jun 09 '16 at 21:07 — user975989, Jun 09 '16 at 21:07

score 3 · Accepted Answer · answered Jun 09 '16 at 21:05

3

class A
{
    std::array<std::array<int, 2>, 2> m;
    A(int m00, int m01, int m10, int m11)
       : m {{{m00, m01}, {m10, m11}}}
    {}
};

answered Jun 09 '16 at 21:05

Revolver_Ocelot

I intuitively understand `{m00, m01}` for inner array, and `{{...}, {...}}` for outer, but why are the outermost braces needed? – eerorika Jun 09 '16 at 21:13
I think the answer is right. but why need 3 pairs of `{}`? If it is `vector>`, need 3 sets also? – user1899020 Jun 09 '16 at 21:13
@user1899020 In short, because `array` is an aggregate. Because inner type is an aggregate itself, you actually can drop all braces, except outer ones: `m{m00, m01, m10, m11}` – Revolver_Ocelot Jun 09 '16 at 21:18
@user1899020 http://stackoverflow.com/questions/18792731/can-we-omit-the-double-braces-for-stdarray-in-c14 – Bob__ Jun 09 '16 at 21:19
Maybe `initializer_list` is better? – Yves Jun 10 '16 at 07:10

1 Answers1