Populating std::array in class' constructor initializer

Question

Is there a way to populate a std::array in a class' constructor initializer?

Right now I'm populating it the long way:

class Matrix3x3 {
//...
private:
    std::array<double, 9> _indicies;
};
//...
Matrix3x3::Matrix3x3(double m00, double m01, double m02, double m10, double m11, double m12, double m20, double m21, double m22) : _indicies() {
    _indicies[0] = m00; _indicies[1] = m01; _indicies[2] = m02;
    _indicies[3] = m10; _indicies[4] = m11; _indicies[5] = m12;
    _indicies[6] = m20; _indicies[7] = m21; _indicies[8] = m22;
}

-EDIT--

Visual Studio 2010 does not have full c++11 support (it still lists std::array as a typedef to the std::tr1::array namespace!).

Attempts include:

1. Matrix3x3::Matrix3x3(const std::initializer_list<std::array<double, 9> >& row_column_values) : _indicies(row_column_values) { }
2. Matrix3x3::Matrix3x3(double m00, double m01, double m02, double m10, double m11, double m12, double m20, double m21, double m22) : _indicies({m00, m01, m02, m10, m11, m12, m20, m21, m22}) { }

None of which work in VS2010. All of them report errors:

1. error C2664: 'std::tr1::array<_Ty,_Size>::array(const std::tr1::array<_Ty,_Size> &)' : cannot convert parameter 1 from 'const std::initializer_list<_Elem>' to 'const std::tr1::array<_Ty,_Size> &'
2. Cascading errors:
    error C2059: syntax error : ')'
    error C2143: syntax error : missing ')' before '{'
    error C2143: syntax error : missing ';' before '}'
    error C2447: '{' : missing function header (old-style formal list?)

Answer 1

In C++11 you can use a curly brace initializer, like this:

Matrix3x3::Matrix3x3(double m00, double m01, double m02, double m10, double m11, double m12, double m20, double m21, double m22)
:   _indicies({m00, m01, m02, m10, m11, m12, m20, m21, m22}) {
}

Demo on ideone.

Answer 2

This works for me:

array<int, 4> arr;
arr = {1,2,3,4};

perhaps changing your code to:

Matrix3x3::Matrix3x3(double m00, double m01, double m02, double m10, double m11, double m12, double m20, double m21, double m22) : _indicies({m00, m01, m02, m10, m11, m12, m20, m21, m22}) {}

Answer 3

Here's a generic constructor

template<typename... A>
Matrix3x3(A&&... a) : _indicies{{std::forward<A>(a)...}} { }

that will accept at most 9 initializers that are implicitly convertible to double (except narrowing), exactly like std::array<double, 9>'s aggregate-initialization.