74 lines
1.6 KiB
OCaml
74 lines
1.6 KiB
OCaml
(* camlp4r *)
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(* $Id$ *)
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(* Copyright 2001 INRIA *)
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type t 'a = { count : int; data : Lazy.t (data 'a) }
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and data 'a =
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[ Nil
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| Cons of 'a and t 'a
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| App of t 'a and t 'a ]
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;
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value from f =
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loop 0 where rec loop i =
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{count = 0;
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data =
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lazy
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(match f i with
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[ Some x -> Cons x (loop (i + 1))
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| None -> Nil ])}
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;
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value rec next s =
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let count = s.count + 1 in
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match Lazy.force s.data with
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[ Nil -> None
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| Cons a s -> Some (a, {count = count; data = s.data})
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| App s1 s2 ->
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match next s1 with
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[ Some (a, s1) -> Some (a, {count = count; data = lazy (App s1 s2)})
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| None ->
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match next s2 with
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[ Some (a, s2) -> Some (a, {count = count; data = s2.data})
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| None -> None ] ] ]
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;
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value empty s =
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match next s with
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[ Some _ -> None
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| None -> Some ((), s) ]
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;
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value nil () = {count = 0; data = ref (Lazy.Value Nil)};
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value cons a s = Cons a s;
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value app s1 s2 = App s1 s2;
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value flazy f = {count = 0; data = ref (Lazy.Delayed f)};
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value of_list l =
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List.fold_right (fun x s -> flazy (fun () -> cons x s)) l (nil ())
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;
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value of_string s =
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from (fun c -> if c < String.length s then Some s.[c] else None)
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;
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value of_channel ic =
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from (fun _ -> try Some (input_char ic) with [ End_of_file -> None ])
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;
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value iter f =
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do_rec where rec do_rec strm =
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match next strm with
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[ Some (a, strm) -> let _ = f a in do_rec strm
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| None -> () ]
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;
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value count s = s.count;
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value count_unfrozen s =
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loop 0 s where rec loop cnt s =
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match s.data.val with
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[ Lazy.Value (Cons _ s) -> loop (cnt + 1) s
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| _ -> cnt ]
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;
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