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|
(** {1 extra list functions dedicated to OCaml extraction} *)
module OCaml
use list.List
use list.Length
use int.Int
use mach.int.Int63
let length_defensive (l: list 'a) : int63
requires { Length.length l <= int63'maxInt }
ensures { result = Length.length l }
= let rec aux (n:int63) (l:list 'a) : int63
requires { n + Length.length l <= int63'maxInt }
variant { l }
ensures { result = n + Length.length l }
= match l with
| Nil -> n
| Cons _ rem -> aux (n+1) rem
end
in
aux 0 l
(** return the length of a list as an machine integer. in principle
this function is not realizable, but with the "Peano" implicit
assumption one can admit that nobody can ever built a list with
more than 2^63 elements
See also library `mach.peano`
*)
use mach.peano.Peano
let rec length_peano (l: list 'a) : Peano.t
variant { l }
ensures { result = Length.length l }
= match l with
| Nil -> Peano.zero
| Cons _ rem -> Peano.succ (length_peano rem)
end
use mach.peano.Int63
let partial length (l: list 'a) : int63
ensures { result = Length.length l }
= to_int63 (length_peano l)
end
|
