nomaddo

(* これは通らない *)
let f x =
  let (g:'a) = fun y -> y
  g 1; g "str"

(* これは通る *)
let f x =
  let g = fun y -> y
  g 1; g "str"

nomaddo

fun f x = let ... x :: nil ...  
              ... Array.update(a, i, x) ...  
          in (x, x) end  
fun g y = f (y, 3.14)  
 
(* f : 'a -> 'a * 'a  *)  
(* g : 'b -> (b * real) * ('b * real) *)  

nomaddo

# type t = :: of int * float;;
type t = :: of int * float
# 1 :: 1.1;;
- : t = :: (1, 1.1)

# 1 :: [];;
Characters 5-7:
  1 :: [];;
       ^^
Error: This expression has type 'a list

nomaddo

# type t = () of unit;;
type t = () of unit
# () ();;
- : t = () ()

nomaddo

# type 'a t = () of 'a;;
type 'a t = () of 'a
# () 12;;
- : int t = () 12
# () ();;
Characters 3-5:
  () ();;
     ^^
Error: The constructor () expects 1 argument(s),
       but is applied here to 0 argument(s)

nomaddo

# module M = struct type t = () end;;;;;
module M : sig type t = () end
# M.();;
Characters 3-4:
  M.();;
     ^
Error: Syntax error: operator expected.
# M.(());;
- : M.t = M.()

nomaddo

# type t = :: of int * float;;
type t = :: of int * float
# 1 :: 1.1;;
- : t = :: (1, 1.1)
 
# 1 :: [];;
Characters 5-7:
  1 :: [];;
       ^^
Error: This expression has type 'a list

nomaddo

# type 'a t = :: of 'a t * 'a t | Leaf of 'a;;
type 'a t = :: of 'a t * 'a t | Leaf of 'a
 
# Leaf 1 :: Leaf 2 :: Leaf 3;;
- : int t = :: (Leaf 1, :: (Leaf 2, Leaf 3))

nomaddo

# List.(map succ [1;2;3]);;
- : int list = [2; 3; 4]
# List.(M.(()));;
- : M.t = M.()

nomaddo

# type t = true of bool;;
type t = true of bool
# true true;;
- : t = true true
# type 'a t = true of 'a
  ;;
type 'a t = true of 'a
# true true;;
Characters 5-9:
  true true;;