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  1. module type QUEUE_FUN =
  2. sig
  3.     type 'a t
  4.     exception Empty of string
  5.     val empty:   unit      -> 'a t
  6.     val enqueue: 'a * 'a t -> 'a t
  7.     val dequeue: 'a t      -> 'a t
  8.     val first:   'a t      -> 'a
  9.     val isEmpty: 'a t      -> bool
  10. end;;
  11.  
  12. module QueueList : QUEUE_FUN =
  13. struct
  14.     type 'a t = 'a list
  15.     exception Empty of string
  16.  
  17.     let empty   ()    = []
  18.  
  19.     let isEmpty queue = queue = []
  20.  
  21.     let enqueue (x, queue) = queue @ [x]
  22.  
  23.     let dequeue queue =
  24.         match queue with
  25.             | []     -> []
  26.             | _ :: q -> q
  27.  
  28.     let first queue =
  29.         match queue with
  30.             | []     -> raise (Empty "QueueList.first")
  31.             | x :: _ -> x
  32. end;;
  33.  
  34. module QueueTwoLists : QUEUE_FUN =
  35. struct
  36.     type 'a t = 'a list * 'a list
  37.     exception Empty of string
  38.  
  39.     let empty () = ([], [])
  40.     let isEmpty queue = queue = ([], [])
  41.     let enqueue (x, queue) =
  42.         match queue with
  43.             | ([], [])        -> ([x], [])
  44.             | ([], inbox)     -> (List.rev inbox, [x])
  45.             | (outbox, inbox) -> (outbox, x :: inbox)
  46.     let dequeue queue =
  47.         match queue with
  48.             | ([], [])    -> ([], [])
  49.             | ([], inbox) ->
  50.                 let _ :: outbox = List.rev inbox in
  51.                 (outbox, [])
  52.             | (_ :: outbox, inbox) -> (outbox, inbox)
  53.     let first queue =
  54.         match queue with
  55.             | ([], _)     -> raise (Empty "QueueTwoLists.first")
  56.             | (x :: _, _) -> x
  57. end;;
  58.  
  59. exception Axiom_fail of string * int;;
  60.  
  61. let test_queue empty enqueue dequeue first isEmpty name =
  62.     let test n axiom = if axiom then true else raise (Axiom_fail (name, n)) in
  63.     let axiom1 = not (isEmpty (enqueue (42, empty ())))
  64.     and axiom2 = isEmpty (empty ())
  65.     and axiom3 = dequeue (enqueue (42, enqueue (69, empty ()))) =
  66.                  enqueue (42, dequeue (enqueue (69, empty ())))
  67.     and axiom4 = dequeue (enqueue (42, empty ())) = empty ()
  68.     and axiom5 = dequeue (empty ()) = empty ()
  69.     and axiom6 = first (enqueue (42, enqueue (69, empty ()))) = first (enqueue (69, empty ()))
  70.     and axiom7 = first (enqueue (42, empty ())) = 42
  71.     in
  72.         ( test 1 axiom1 ) &&
  73.         ( test 2 axiom2 ) &&
  74.         (*
  75.          *( test 3 axiom3 ) &&
  76.          *)
  77.         ( test 4 axiom4 ) &&
  78.         ( test 5 axiom5 ) &&
  79.         ( test 6 axiom6 ) &&
  80.         ( test 7 axiom7 )
  81.  
  82. let test_queuelist =
  83.     test_queue QueueList.empty QueueList.enqueue QueueList.dequeue QueueList.first
  84.                QueueList.isEmpty "QueueList"
  85. ;;
  86.  
  87. let test_queuetwolists =
  88.     test_queue QueueTwoLists.empty QueueTwoLists.enqueue QueueTwoLists.dequeue QueueTwoLists.first
  89.                QueueTwoLists.isEmpty "QueueTwoLists"
  90. ;;
  91.  
stdin 
Standard input is empty
compilation info 
File "prog.ml", line 65, characters 8-14:
Warning Y: unused variable axiom3.
File "prog.ml", line 50, characters 20-31:
Warning P: this pattern-matching is not exhaustive.
Here is an example of a value that is not matched:
[]
stdout 
Standard output is empty
https://ideone.com/uqUXd
language:
OCaml (ocamlopt 4.05.0)
created:
14 years ago
visibility:
secret

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