Source file `limit.ml`

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
(*****************************************************************************)
(*                                                                           *)
(* Open Source License                                                       *)
(* Copyright (c) 2021 Nomadic Labs, <contact@nomadic-labs.com>               *)
(*                                                                           *)
(* Permission is hereby granted, free of charge, to any person obtaining a   *)
(* copy of this software and associated documentation files (the "Software"),*)
(* to deal in the Software without restriction, including without limitation *)
(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
(* and/or sell copies of the Software, and to permit persons to whom the     *)
(* Software is furnished to do so, subject to the following conditions:      *)
(*                                                                           *)
(* The above copyright notice and this permission notice shall be included   *)
(* in all copies or substantial portions of the Software.                    *)
(*                                                                           *)
(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
(* DEALINGS IN THE SOFTWARE.                                                 *)
(*                                                                           *)
(*****************************************************************************)

type 'a t = 'a option

let unknown = None

let known x = Some x

let of_option = Fun.id

let is_unknown = Option.is_none

let join (type a) ~where eq (l1 : a t) (l2 : a t) =
  match (l1, l2) with
  | None, None -> Result.return_none
  | Some x, None | None, Some x -> Result.return_some x
  | Some x, Some y ->
      if eq x y then Result.return_some x
      else error_with "Limit.join: error (%s)" where

let%expect_test "join" =
  let pp_print_err fmt = function
    | Result.Error _ -> Format.pp_print_string fmt "error"
    | Ok x ->
        Format.(
          pp_print_option
            ~none:(fun fmt () -> pp_print_string fmt "None")
            pp_print_bool)
          fmt
          x
  in
  let print x = Format.fprintf Format.std_formatter "%a" pp_print_err x in
  print (join ~where:__LOC__ Bool.equal (Some true) (Some true)) ;
  [%expect {| true |}] ;
  print (join ~where:__LOC__ Bool.equal None None) ;
  [%expect {| None |}] ;
  print (join ~where:__LOC__ Bool.equal None (Some true)) ;
  [%expect {| true |}] ;
  print (join ~where:__LOC__ Bool.equal (Some true) None) ;
  [%expect {| true |}] ;
  print (join ~where:__LOC__ Bool.equal (Some true) (Some false)) ;
  [%expect {| error |}]

let get ~when_unknown = function
  | None -> error_with "Limit.get: %s" when_unknown
  | Some x -> Ok x

let%expect_test "get" =
  let pp_print_err fmt = function
    | Result.Error _ -> Format.fprintf fmt "error"
    | Ok b -> Format.pp_print_bool fmt b
  in
  let print x = Format.fprintf Format.std_formatter "%a" pp_print_err x in
  print (get ~when_unknown:"" (Some true)) ;
  [%expect {| true |}] ;
  print (get ~when_unknown:"" None) ;
  [%expect {| error |}]

let fold ~unknown ~known x = match x with None -> unknown | Some x -> known x

let value ~when_unknown = function None -> when_unknown | Some x -> x