#+begin_src elisp tangle: no :results none :exports none
(setq pwd (file-name-directory buffer-file-name))
(setq name (file-name-nondirectory (substring buffer-file-name 0 -4)))
(setq lib (concat pwd "lib/"))
(setq testdir (concat pwd "test/"))
(setq mli (concat lib name ".mli"))
(setq ml  (concat lib name ".ml"))
(setq test-ml  (concat testdir name ".ml"))
(org-babel-tangle)
#+end_src 

* Non-negative float 
  :PROPERTIES:
  :header-args: :noweb yes :comments both
  :END:

** Type

   #+begin_src ocaml :tangle (eval mli)
type t = private float
   #+end_src

   #+begin_src ocaml :tangle (eval ml) :exports none
type t = float 
   #+end_src

** Conversions

    #+begin_src ocaml :tangle (eval mli)
val of_float        : float -> t
val unsafe_of_float : float -> t
val to_float        : t -> float

val of_string       : string -> t
val to_string       : t -> string
    #+end_src

    The ~of_float~ function checks that the float is non-negative.
    The unsafe variant doesn't do this check.
    
    #+begin_src ocaml :tangle (eval ml) :exports none
let of_float x =
  if x < 0. then invalid_arg (__FILE__^": of_float");
  x

external to_float        : t -> float = "%identity"
external unsafe_of_float : float -> t = "%identity"

let to_string x =
  let f = to_float x in string_of_float f

let of_string x =
 let f = float_of_string x in of_float f
    #+end_src