Initializing elements of a 2D array using std::array. c++ - c++

Question

I'm using std::array<array<float, 4,3> = . . . to in
I'm having trouble understand how to format the following code so I don't get the following error:
g++ array2d_colors.cpp -o array2dcolors.o
array2d_colors.cpp: In function ‘void arrayStart()’:
array2d_colors.cpp:36:7: error: too many initializers for
‘std::array<std::array<float, 4ul>, 3ul>’ };
^
using namespace;
array<array<float,4>,3> color = {
{ 0.0 , 0.1686 , 0.2117 },
{ 0.0274 , 0.2117 , 0.2588},
{ 0.3450 , 0.4313 , 0.4588},
{ 0.3960 , 0.4823, 0.5137}
};
This code worked in another study:
using namespace;
array<array<float, 2>, 2> a1 = {{{5,6},{7,8}}};
That is a lot of "{'s" . What if a want to create a 16x3?
I'd appreciate some help.

Answer 1

When you're doing
array<array<float,4>,3> color
you're saying that the inner array has 4 elements and the outer one has 3. So it becomes a 4*3 matrix while you're defining a 3*4 matrix.
Try doing :
array<array<float,3>,4> color = {{
{ 0.0 , 0.1686 , 0.2117 },
{ 0.0274 , 0.2117 , 0.2588},
{ 0.3450 , 0.4313 , 0.4588},
{ 0.3960 , 0.4823, 0.5137}
}};
and remember to add {{ - two braces before defining the array of inner arrays and you'll be good to go!

Answer 2

You have the initializer arrays transposed to a 4 x 3 array. Hence, it does not match the declaration of color.
You can use:
array<array<float, 3>, 4> color =
{
{ 0.0 , 0.1686 , 0.2117 }, // 1st of four of the outer array
{ 0.0274 , 0.2117 , 0.2588},
{ 0.3450 , 0.4313 , 0.4588},
{ 0.3960 , 0.4823, 0.5137} // 4th of four of the outer array
};
If you need to have a 3 x 4 array, you have to change the initializer array.
Ex:
array<array<float, 4>, 3> color =
{
{ 0.0 , 0.1686 , 0.2117, 1 }, // 1st of three of the outer array
{ 0.0274 , 0.2117 , 0.2588, 2},
{ 0.3960 , 0.4823, 0.5137, 3} // 3rd of three of the outer array
};

Answer 3

Issue 1: Dimensions are swtitched
array<array<float,3>,4> color = {
// ^ ^
Issue 2: Explicitly mention the type of array in initializer. Compiler can't deduce it.
array<float,3>{ 0.0 , 0.1686 , 0.2117 },
// ^^^^^^^^^^^^
{ 0.0274 , 0.2117 , 0.2588},
{ 0.3450 , 0.4313 , 0.4588},
{ 0.3960 , 0.4823, 0.5137}