Source file cps_monad.ml
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type 'a effect_ = ..
module Make
(M : Intf.Core)
(R : sig
type 'a t
end) =
struct
type ('r, 'a) cont =
{ cont : 'b. ('a -> 'r -> 'b R.t -> 'b M.t) -> 'r -> 'b R.t -> 'b M.t }
[@@unboxed]
type ('r, 'a) m = handler:'r handler -> ('r, 'a M.t) cont
and 'r handler =
{ handler :
'a 'b.
'a effect_ ->
('a M.t -> 'r -> 'b R.t -> 'b M.t) ->
'r ->
'b R.t ->
'b M.t
}
[@@unboxed]
let return : type a r. a -> (r, a) m =
fun x ~handler:_ -> { cont = (fun k w s -> k (M.return x) w s) }
let if_ cond body ~handler =
{ cont =
(fun k w s ->
(cond ~handler).cont
(fun cond w s -> M.if_ cond (fun c -> (body c ~handler).cont k w s))
w
s)
}
let map (type a b r) (m : (r, a) m) (f : a -> b) : (r, b) m =
fun ~handler ->
{ cont =
(fun k w s -> (m ~handler).cont (fun m w s -> k (M.map m f) w s) w s)
}
let map2 (type a b c r) (m : (r, a) m) (m' : (r, b) m) (f : a -> b -> c) :
(r, c) m =
fun ~handler ->
{ cont =
(fun k w s ->
(m ~handler).cont
(fun m w s ->
(m' ~handler).cont (fun m' w s -> k (M.map2 m m' f) w s) w s)
w
s)
}
let map_array (type a b r) (m : (r, a) m array) (f : a array -> b) : (r, b) m
=
fun ~handler ->
{ cont =
(fun k w s ->
Array.fold_left
(fun k (m : (r, a) m) (acc, w) ->
(m ~handler).cont (fun m w -> k (m :: acc, w)) w)
(fun (l, w) -> k (M.map_array (Array.of_list l) f) w)
m
([], w)
s)
}
let bind (m : ('r, 'a) m) (f : 'a -> ('r, 'b) m) : ('r, 'b) m =
fun ~handler ->
{ cont =
(fun k w s ->
(m ~handler).cont
(fun m w s -> M.bind m (fun m -> (f m ~handler).cont k w s))
w
s)
}
let handle effect_ ~handler = { cont = (fun k -> handler.handler effect_ k) }
module Infix = struct
let ( let* ) = bind
let ( let+ ) = map
let ( and+ ) m m' = map2 m m' (fun x y -> (x, y))
let ( >|= ) = map
let ( >>= ) = bind
let return = return
end
end
[@@inline]