Most of this code is adapated from the OCaml Standard library's implementation of Hashtbl. It is just adapted for polymorphic types. I.E. a 'b t hashtabl binding 'a key to ('a,'b) value (note that 'a is quantified existantially here).

Integer ranges (0..n or lo..high), for quick iteration. Inspired by python's range used in for loop, but with a more functional approach.