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  1. (*
  2.     Swift's closure
  3.         https://d...content-available-to-author-only...e.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html
  4. *)
  5.  
  6.  
  7. load "Intmap";  (* for Moscow ML *)
  8.  
  9.  
  10. fun unfoldr_string f b = case f b of
  11.       SOME (a, b') => a ^ (unfoldr_string f b')
  12.     | NONE         => ""
  13.  
  14. fun unfoldl_string f b = case f b of
  15.       SOME (a, b') => (unfoldl_string f b') ^ a
  16.     | NONE         => ""
  17.  
  18.  
  19. val digitNames = foldr
  20.     (fn ((i, s), m) => Intmap.insert (m, i, s))
  21.     (Intmap.empty ())
  22.     [
  23.         (0, "Zero"), (1, "One"), (2, "Two"),   (3, "Three"), (4, "Four"),
  24.         (5, "Five"), (6, "Six"), (7, "Seven"), (8, "Eight"), (9, "Nine")
  25.     ]
  26. val numbers = [16, 58, 510]
  27.  
  28.  
  29. val strings = map
  30.     (
  31.         fn number => unfoldl_string
  32.             (fn (num, output) =>
  33.                 if num <= 0 then
  34.                     NONE
  35.                 else
  36.                     SOME (
  37.                         Intmap.retrieve (digitNames, num mod 10) ^ output,
  38.                         (num div 10, output)
  39.                     )
  40.             )
  41.             (number, "")
  42.     )
  43.     numbers
  44.  
  45.  
  46. fun print_strings xs = (
  47.     (map (fn s => (print (s ^ "\n") ; ())) xs) ;
  48.     ()
  49. )
  50.  
  51.  
  52.  
  53. (****
  54.  
  55. $ mosml numbers-map-haskell.sml 
  56. Moscow ML version 2.01 (January 2004)
  57. Enter `quit();' to quit.
  58. [opening file "numbers-map-haskell.sml"]
  59. > val it = () : unit
  60. > val 'a unfoldr_string = fn : ('a -> (string * 'a) option) -> 'a -> string
  61.   val 'a unfoldl_string = fn : ('a -> (string * 'a) option) -> 'a -> string
  62.   val digitNames = <intmap> : string intmap
  63.   val numbers = [16, 58, 510] : int list
  64.   val strings = ["OneSix", "FiveEight", "FiveOneZero"] : string list
  65.   val print_strings = fn : string list -> unit
  66. [closing file "numbers-map-haskell.sml"]
  67. - print_strings strings;
  68. OneSix
  69. FiveEight
  70. FiveOneZero
  71. > val it = () : unit
  72. -
  73.  
  74. ****)
Compilation error #stdin compilation error #stdout 0s 0KB
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Standard input is empty
compilation info 
File "prog.ml", line 10, characters 23-24:
Syntax error
stdout
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Standard output is empty
https://ideone.com/o5JM86
language:
OCaml (ocamlopt 4.05.0)
created:
9 years ago
visibility:
public

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