blob: 88d8563036a0b2e3e64e2f5511c385d4ef199e08 (
plain)
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
85
86
87
88
89
90
91
92
93
94
|
module type T = sig
type 'a t
val iter : ('a -> unit) -> 'a t -> unit
val map : ('a -> 'b) -> 'a t -> 'b t
val bind : 'a t -> ('a -> 'b t) -> 'b t
end
module DefaultIter (T : sig
type 'a t
val map : ('a -> 'b) -> 'a t -> 'b t
end) =
struct
let iter f v = ignore (T.map f v)
end
module type MONAD = sig
type 'a t
val map : ('a -> 'b) -> 'a t -> 'b t
val return : 'a -> 'a t
val bind : 'a t -> ('a -> 'b t) -> 'b t
end
module Binding (T : T) = struct
(* Create the let binding operators for a module.
- let* is the binding operator we can find in a monad.
- let/ is the map operator
- let- is the operator which reduce to unit. (I wanted to use . as symbol
like in caqti, but this is not allowed )
The list of the symbols used is describe here :
https://v2.ocaml.org/manual/bindingops.html#start-section
*)
let ( let* ) : 'a T.t -> ('a -> 'b T.t) -> 'b T.t = T.bind
let ( let+ ) : 'a T.t -> ('a -> 'b) -> 'b T.t = fun t f -> T.map f t
let ( let- ) : 'a T.t -> ('a -> unit) -> unit = fun t f -> T.iter f t
end
module type Traversable = sig
type 'a t
(**
Build the traversable module.
[>] means that the parameter is not wrapped in the MONAD
[**] means that the function is returning both a MONAD and the type
[*] means that the function binding into a new MONAD
The name is choosen in order to make sense in the successive binding. You
should have the first binding using [let>…] form, then [let_], and finally
just [let]
*)
module Make (T : MONAD) : sig
val ( let>** ) : 'a t -> ('a -> 'b t T.t) -> 'b t T.t
val ( let>* ) : 'a t -> ('a -> 'b T.t) -> 'b t T.t
val ( let** ) : 'a t T.t -> ('a -> 'b t T.t) -> 'b t T.t
val ( let* ) : 'a t T.t -> ('a -> 'b T.t) -> 'b t T.t
end
end
module TraversableResult : Traversable with type 'a t = ('a, string) result =
struct
type 'a t = ('a, string) result
module Make (T : MONAD) = struct
let traverse : 'a t -> ('a -> 'b T.t) -> 'b t T.t =
fun v f ->
match v with
| Ok x -> T.map (fun x -> Ok x) (f x)
| Error e -> T.return (Error e)
let ( let>* ) : 'a t -> ('a -> 'b T.t) -> 'b t T.t = traverse
let ( let>** ) : 'a t -> ('a -> 'b t T.t) -> 'b t T.t =
fun v f ->
let result = traverse v (fun v -> f v) in
T.map Result.join result
let ( let* ) : 'a t T.t -> ('a -> 'b T.t) -> 'b t T.t =
fun v f -> T.bind v (fun v -> traverse v f)
let ( let** ) : 'a t T.t -> ('a -> 'b t T.t) -> 'b t T.t =
fun v f ->
T.bind v (fun v ->
let result = traverse v (fun v -> f v) in
T.map Result.join result)
end
end
|
