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101 lines
2.7 KiB
OCaml
101 lines
2.7 KiB
OCaml
(*
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Copyright (c) 2013, Simon Cruanes
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer. Redistributions in binary
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form must reproduce the above copyright notice, this list of conditions and the
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following disclaimer in the documentation and/or other materials provided with
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the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*)
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(** {1 Functional queues (fifo)} *)
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type 'a t = {
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hd : 'a list;
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tl : 'a list;
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} (** Queue containing elements of type 'a *)
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let empty = {
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hd = [];
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tl = [];
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}
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(* invariant: if hd=[], then tl=[] *)
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let _make hd tl = match hd with
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| [] -> {hd=List.rev tl; tl=[] }
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| _::_ -> {hd; tl; }
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let is_empty q = q.hd = []
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let push x q = {q with tl = x :: q.tl; }
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let snoc q x = push x q
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let peek_exn q =
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match q.hd with
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| [] -> assert (q.tl = []); raise (Invalid_argument "Queue.peek")
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| x::_ -> x
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let peek q = match q.hd with
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| [] -> None
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| x::_ -> Some x
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let pop_exn q =
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match q.hd with
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| [] -> assert (q.tl = []); raise (Invalid_argument "Queue.peek")
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| x::hd' ->
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let q' = _make hd' q.tl in
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x, q'
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let pop q =
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try Some (pop_exn q)
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with Invalid_argument _ -> None
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let junk q =
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try
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let _, q' = pop_exn q in
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q'
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with Invalid_argument _ -> q
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(** Append two queues. Elements from the second one come
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after elements of the first one *)
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let append q1 q2 =
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{ hd=q1.hd;
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tl=q2.tl @ (List.rev_append q2.hd q1.tl);
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}
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let map f q = { hd=List.map f q.hd; tl=List.map f q.tl; }
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let size q = List.length q.hd + List.length q.tl
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let (>|=) q f = map f q
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let fold f acc q =
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let acc' = List.fold_left f acc q.hd in
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List.fold_right (fun x acc -> f acc x) q.tl acc'
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let iter f q = fold (fun () x -> f x) () q
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type 'a sequence = ('a -> unit) -> unit
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let to_seq q = fun k -> iter k q
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let of_seq seq =
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let q = ref empty in
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seq (fun x -> q := push x !q);
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!q
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