Functor Piecewise_linear.Make_invertible

module Make_invertible: 
functor (Key : Piecewise_linear_intf.Float_like) -> 
functor (Value : Piecewise_linear_intf.Float_like) -> S_invertible 
  with type key = Key.t 
  with type value = Value.t

include Piecewise_linear_intf.S

create enforces that the x (key) values are strictly increasing. It also enforces that the y (value) values are either strictly increasing or strictly decreasing. These two properties give us invertibility.

It also enforces certain finiteness conditions: the x and y values must be finite (non-nan, and non-infinite), and differences of consecutive x values and consecutive y values must be finite.

(Conceivably, one might have a case where one wants to loosen the conditions on x and y values to non-strict monotonicity, so that one does not have true invertibility, but only a sort of formal invertibility. If that use case arises, a separate functor like Make_formally_invertible could be added, so that Make_invertible maintains its stricter semantics.)

val get_inverse : t -> value -> key

get_inverse t value is the inverse operation of get t key.