Dynamic nested arrays in C++ resulting in cannot convert brace-enclosed initializer list to int

Question

I have written a function that takes in a dynamic length array but with fixed inner array size, the second parameter in the function is the length of the parent array. When I try to access the nested values however, I get the issue mentioned above.

void myFunc(int arrOfArr, int arrOfArrLen) {
  // try to access
  arrOfArr[0][1]; // expect val2
}

example usage

myFunc(
  {
    {val1, val2},
    {val3, val4}
  },
  2
);

edit: I realize "contextually" obviously an integer has no indexes, but that's how you declare an array it seems...(truthfully in Arduino context) but apparently it's still C++

Here's a runable demo of above from the first sandbox Google returned

http://cpp.sh/5sp3o

update

I did find a solution, it's ugly but it works:

instead of passing in a "raw" nested array as a param, I set it as a variable first eg:

int arrOfArr[][3] = {
  {val1, val2},
  {val3, val4}
}

Then in the function I do the same thing

void myFunc(int arrOfArr[][3], int arrOfLen) {
  // access
}

Call it

myFunc(arrOfArr, 2);

As I said it's ugly but works for me, this is a passing project thing not a low-level dev, maybe will learn it fully later on but not needed in day job.

edit: apparently the thing I was trying to do initially eg. embed an initializer list as a param does not work.

Answer 1

if you want to pass a nested array, the declaration may be:

template<size_t N>
void myFunc(int const arrOfArr[][N], int arrOfArrLen) {
  // ...
}

and you can remove the template argument if N is already decided.

const size_t N = 3;
void myFunc(int const arrOfArr[][N], int arrOfArrLen) {
  // ...
}

but it doesn't work if you pass a brace-enclosed initializer, you can add a overloaded function:

template<size_t M, size_t N>
void myFunc(int const (&arrOfArr)[M][N], int arrOfArrLen){
  // attention: int *const*
  // ...
}