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core.ml
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core.ml
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open Internal
exception ZarError of string
let positive_of_int (i : int) : positive =
if i < 1 then
raise (ZarError ("positive_of_int: int must be positive, got "
^ string_of_int i))
else
let rec go (j : int) : positive =
if j == 1 then
XH
else if j mod 2 == 0 then
XO (go @@ j / 2)
else
XI (go @@ j / 2)
in go i
let rec int_of_positive = function
| XH -> 1
| XO p' -> 2 * int_of_positive p'
| XI p' -> 2 * int_of_positive p' + 1
let z_of_int (i : int) : z =
if i == 0 then
Z0
else if i > 0 then
Zpos (positive_of_int i)
else
Zneg (positive_of_int (-i))
let int_of_z = function
| Z0 -> 0
| Zpos p -> int_of_positive p
| Zneg p -> - int_of_positive p
let qmake n d = { qnum = z_of_int n; qden = positive_of_int d }
(** Run an itree sampler to produce a single sample from a given
stream of bits. Returns the unconsumed rest of the stream. *)
let rec run t bs =
match observe t with
| RetF x -> x, bs
| TauF t' -> run t' bs
| VisF (_, k) ->
match Seq.uncons bs with
| None -> raise (ZarError "run: out of bits")
| Some (b, bs') -> run (k (Obj.magic b)) bs'
let rec run_forever t bs =
let x, bs' = run t bs in
(fun () -> Seq.Cons (x, run_forever t bs'))