Module Piecewise_linear_intf

module Piecewise_linear_intf: sig .. end

module type Float_like = sig .. end

module type S = sig .. end

module type S_invertible = sig .. end

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.

get t x evaluates the piecewise linear function t at x.

It is possible to get discontinuous functions by using repeated x-values in the knots. In that case, the function is evaluated in such a way that it is right-continuous. For example, if t has knots [(0.,0.5); (1.,1.5); (1.,10.); (2.,11.)], then get t 1. returns 10., get t 0.999 returns 1.499, and get t 1.001 returns 10.001.

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.)

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