CompareFunc returns a generic comparator suitable for use in a Range based on the order of values in the range, i.e., when order is desc then the first value is larger than the last value and Before is true for larger values while After is true for smaller values, etc.

Create a new Range from generic range of zed.Values according to lower and upper.

Span represents the closed interval [first, last] where first is "less than" last with respect to the Span's order.Which.