Source file state.ml
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module StateFunc = struct
module type S = sig
type s
type 'a m = s -> s * 'a
val return : 'a -> s -> s * 'a
val bind : (s -> 'a * 'b) -> ('b -> 'a -> 'c) -> s -> 'c
val read : s -> s * s
val write : 'a -> s -> 'a * unit
val run : (s -> 'a) -> s -> 'a
val eval : (s -> 'a * 'b) -> s -> 'b
val modify : (s -> 'a) -> s -> 'a * unit
module Infix :
sig val ( >>= ) : (s -> 'a * 'b) -> ('b -> 'a -> 'c) -> s -> 'c
end
end
module Make (T : sig type s end) = struct
type s = T.s
type 'a m = T.s -> (T.s * 'a)
let return x (s: T.s) = (s, x)
let bind xf f (s: T.s) =
let s',x = xf s in f x s'
let read (s: T.s) = (s,s)
let write x (_: T.s) = (x,())
let run x (s: T.s) = x s
let eval x (s: T.s) = snd (x s)
let modify f = bind read (fun s -> write (f s))
module Infix = struct
let (>>=) = bind
end
end
end
module State = struct
type ('s, 'a) m = 's -> 's * 'a
let return x s = (s, x)
let bind xf f s = let s',x = xf s in f x s'
let read s = (s,s)
let write x _ = (x,())
let run x s = x s
let eval x s = snd (x s)
let modify f = bind read (fun s -> write (f s))
module Infix = struct
let ( >>= ) = bind
end
end