Multidimensional C Arrays

Question

I have four arrays that contains some values. Another array should contain all these four arrays like shown in the code:

static const long ONE_COLOR[2] = { RGB_BLACK, RGB_WHITE };
static const long TWO_COLOR[4] = { RGB_WHITE, RGB_RED, RGB_GREEN, RGB_BLUE };
static const long THREE_COLOR[8] = { RGB_BLACK, RGB_RED, RGB_GREEN, RGB_BLUE,
    RGB_CYAN, RGB_YELLOW, RGB_MAGENTA, RGB_WHITE };
static const long FOUR_COLOR[16] = { RGB_WHITE, RGB_RED, RGB_GREEN, RGB_BLUE,
    RGB_CYAN, RGB_YELLOW, RGB_MAGENTA, RGB_DARK_RED, RGB_DARK_GREEN,
    RGB_DARK_BLUE, RGB_LIGHT_BLUE, RGB_LIGHT_GREEN, RGB_ORANGE, RGB_LIME,
    RGB_PINK, RGB_LILA };

//this array should contain all other arrays
static const long COLOR_ARRAY = {ONE_COLOR,TWO_COLOR, THREE_COLOR,
    FOUR_COLOR };

My problem is to access the values in the array. I thought I can receive the value of RGB_BLACK with COLOR_ARRAY[0][0]. I tried it with some pointer constructions, but it doesn't work neither :(

Answer 1

It sounds like you want an array of pointers to arrays.

static const long *const COLOR_ARRAY[4] = {
    ONE_COLOR, TWO_COLOR, THREE_COLOR, FOUR_COLOR
};

Both const are recommended: the first const means that this is a pointer to constant arrays, the second const means that this array of pointers is, itself, constant.

You can access the elements as you'd think, so COLOR_ARRAY[1][3] == RGB_BLUE, et cetera.

Note

I am being a little sloppy with terminology. You are not actually getting pointers to arrays but pointers to the first element in each array. For most operations, in C, an array and a pointer to the first element are interchangeable.

Answer 2

Maybe you mean

static const long COLOR_ARRAY[] = {ONE_COLOR,TWO_COLOR, THREE_COLOR, FOUR_COLOR };

You don't have [] in your version.

Answer 3

you can define COLOR_ARRAY like this:

static const long* COLOR_ARRAY[4] = {ONE_COLOR,TWO_COLOR, 
                                     THREE_COLOR,FOUR_COLOR };

now you should be able to use:

COLOR_ARRAY[0][0]

Answer 4

You can combine arrays like this:

first[3] = { 11, 17, 23 };
second[3] = { 46, 68, 82 };

combo[2][3] = {
         { 11, 17, 23 },{ 46, 68, 82 }};

I shamelessly copied this example from here: http://rapidpurple.com/blog/tutorials/c-tutorials/programming-in-c-array-of-arrays/

Check it out!

Best regards -Tom