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112 lines
3.7 KiB
OCaml
112 lines
3.7 KiB
OCaml
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(*
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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 Vantage-Point Tree}
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A data structure used to store and retrieve elements that belong to a
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metric space. References are:
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{{: https://github.com/UnixJunkie/vantage_point_tree_from_codepad/blob/master/vp_tree.ml} François Berenger's implementation}
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{{: http://en.wikipedia.org/wiki/Vantage-point_tree} Wikipedia}
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*)
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module type METRIC_SPACE = sig
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type t
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(** Elements of the metric space *)
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type num
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(** Numeric type used for distances *)
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val distance : t -> t -> num
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(** Distance between two points. It must satisfy the following invariants:
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- [distance x y = distance y x]
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- [distance x y <= distance x z + distance z y]
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- [distance x y >= 0]
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- [distance x y = 0] if and only if [x] and [y] are the same point.
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*)
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val add : num -> num -> num
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(** Addition of two distances (associative, commutative) *)
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val compare : num -> num -> int
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(** Total ordering on the numeric type used for distances; must
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be compatible with {!add} *)
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end
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(** {2 Utils} *)
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type 'a sequence = ('a -> unit) -> unit
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module LazyList : sig
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type +'a t =
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| Nil
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| Cons of 'a * 'a t Lazy.t
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val take : int -> 'a t -> 'a t
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val to_list : 'a t -> 'a list
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val iter : 'a t -> ('a -> unit) -> unit
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end
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(** {2 VPTree functorial interface} *)
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module type S = sig
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module Space : METRIC_SPACE
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type key = Space.t
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type +'a t
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(** VPTree that maps to data of type 'a *)
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val member : _ t -> key -> bool
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(** Is the given key, member of the tree? *)
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val find_closest : 'a t -> key -> (key * 'a * int) LazyList.t
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(** [find_closest tree key] finds the points of [tree]
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that are the closest to [key], in increasing order. Enumerates all
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the points eventually, if the whole list is explored.
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Each tuple also contains the distance to the [key]. *)
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val of_array : (key * 'a) array -> 'a t
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(** Build a VPTree from an array of bindings. The array is modified in
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place (values are swapped).
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If a key occurs several times in the sequence, one of the value
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it maps to is chosen arbitrarily. *)
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val of_list : (key * 'a) list -> 'a t
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(** Build a VPTree from a list *)
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val of_seq : (key * 'a) sequence -> 'a t
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val of_lazy_list : (key * 'a) LazyList.t -> 'a t
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val size : _ t -> int
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(** Find the number of key/value pairs in the tree (linear time) *)
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end
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module Make(Space : METRIC_SPACE) : S with module Space = Space
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