Signature Description Parameters
template<typename F, typename T, typename I = unsigned long>
struct ExpandingRollAdopter;
This functor applies functor F to the data in a rolling progression. The roll count is given to the constructor of SimpleRollAdoptor.
The result is a vector of values with same number of items as the given column. The first roll_count items, in the result, will be NAN.
          inline SimpleRollAdopter(F &&functor, size_t roll_count)
        
F: Functor type
T: Column data type
I: Index type