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  1.  
  2. module Pair :
  3.   sig
  4.     type t
  5.     val of_int : int -> t
  6.     val ( = ) : t -> t -> bool
  7.   end
  8.   =
  9.   struct
  10.  
  11.     type t = { x : int ; y : int }
  12.  
  13.     let of_int i = { x = i ; y = i }
  14.  
  15.     let ( = ) a b =
  16.       a.x = b.x && a.y = b.y
  17.  
  18.   end
  19.  
  20. module Ext = struct
  21.  
  22.   module Pair =
  23.     struct
  24.       include Pair
  25.  
  26.       let ( <> ) a b =
  27.         not (a = b)
  28.  
  29.     end
  30.  
  31. end
  32.  
  33.  
  34.  
  35. let main_std () =
  36.   let a = Pair.of_int 1
  37.   and b = Pair.of_int 1
  38.   and c = Pair.of_int 2 in
  39.   Printf.printf "%B %B\n" (a = b) (a = c)
  40.  
  41. let main_ext () =
  42.   let open Ext in
  43.  
  44.   (* same part *)
  45.   let a = Pair.of_int 1
  46.   and b = Pair.of_int 1
  47.   and c = Pair.of_int 2 in
  48.   Printf.printf "%B %B\n" (a = b) (a = c)
  49.   (* same part end *)
  50.  
  51.   ; Printf.printf "%B %B\n" (a <> b) (a <> c)
  52.  
  53. let _ =
  54.   main_std () ;
  55.   main_ext ()
  56.  
  57.  
  58.  
  59. (* type compatibility *)
  60.  
  61. let std_pair x =
  62.   Pair.of_int x
  63.  
  64. let ext_pair x =
  65.   let open Ext in
  66.   Pair.of_int x
  67.  
  68. let _ =
  69.   let a = std_pair 1
  70.   and b = ext_pair 1 in
  71.   Printf.printf "%B\n" (a = b) (* compiled *)
  72.  
Success #stdin #stdout 0s 5500KB
comments (?)
stdin
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Standard input is empty
stdout
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true false
true false
false true
true
https://ideone.com/zhhody
language:
OCaml (ocamlopt 4.05.0)
created:
5 years ago
visibility:
public

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