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
– user975989

2016-06-09 21:07:10 +00:00
Commented Jun 9, 2016 at 21:07 — user975989
– user975989, Commented Jun 9, 2016 at 21:07

Revolver_Ocelot · Accepted Answer · 2016-06-09 21:05:26Z

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 9, 2016 at 21:05

Revolver_Ocelot

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5 Comments

eerorika Over a year ago

I intuitively understand {m00, m01} for inner array, and {{...}, {...}} for outer, but why are the outermost braces needed?

user1899020 Over a year ago

I think the answer is right. but why need 3 pairs of {}? If it is vector<vector<int>>, need 3 sets also?

Revolver_Ocelot Over a year ago

@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}

Bob__ Over a year ago

@user1899020 stackoverflow.com/questions/18792731/…

Yves Over a year ago

Maybe initializer_list is better?

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