I'm looking to create a lookup table of coordinates, something like:

```
int a[n][2] = {{0,1},{2,3}, ... }

```

For a given `n`, to be created at compile time. I started looking into `constexpr`, but is seems like a function returning a `constexpr std::vector<std::array <int, 2> >` isn't an option, as I get:

```
invalid return type 'std::vector<std::array<int, 2ul> >' of constexpr function

```

How can create such a compile time array?