I want to define an OCaml type with constraints.

For example:

type item = Item of int * float;;

If here this float type is for price of some item, and I want to make sure

it is positive. In other words, if x = (xi, xf) of type item, 

I want to enforce, xf must >= 0.

Is there a way to define OCaml type like this?

Thanks a lot!

Angela