How do I get the dimensions (nestedness) of a nested vector (NOT the size)?

January 1, 2024 by Tarik

Something on these lines:

template<class Y> 
struct s
{
    enum {dims = 0};
};

template<class Y>
struct s<std::vector<Y>>
{
    enum {dims = s<Y>::dims + 1};
};

Then for example,

std::vector<std::vector<double> > x;
int n = s<decltype(x)>::dims; /*n will be 2 in this case*/

Has the attractive property that all the evaluations are at compile time.