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129 lines
4.1 KiB
OCaml
129 lines
4.1 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 Levenshtein distance}
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We take inspiration from
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http://blog.notdot.net/2010/07/Damn-Cool-Algorithms-Levenshtein-Automata
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for the main algorithm and ideas. However some parts are adapted *)
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(** {2 Abstraction over Strings} *)
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module type STRING = sig
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type char_
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type t
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val of_list : char_ list -> t
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val get : t -> int -> char_
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val length : t -> int
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val compare_char : char_ -> char_ -> int
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end
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(** {2 Continuation list} *)
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type 'a klist =
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[
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| `Nil
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| `Cons of 'a * (unit -> 'a klist)
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]
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val klist_to_list : 'a klist -> 'a list
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(** Helper. *)
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(** {2 Signature}
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We abstract over the type of characters and strings, so that we
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can deal with several encodings, string representations, etc. *)
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module type S = sig
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type char_
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type string_
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(** {6 Edit Distance} *)
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val edit_distance : string_ -> string_ -> int
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(** Edition distance between two strings. This satisfies the classical
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distance axioms: it is always positive, symmetric, and satisfies
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the formula [distance a b + distance b c >= distance a c] *)
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(** {6 Automaton}
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An automaton, built from a string [s] and a limit [n], that accepts
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every string that is at distance at most [n] from [s]. *)
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type automaton
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(** Levenshtein automaton *)
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val of_string : limit:int -> string_ -> automaton
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(** Build an automaton from an array, with a maximal distance [limit] *)
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val of_list : limit:int -> char_ list -> automaton
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(** Build an automaton from a list, with a maximal distance [limit] *)
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val debug_print : (out_channel -> char_ -> unit) ->
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out_channel -> automaton -> unit
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(** Output the automaton on the given channel. *)
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val match_with : automaton -> string_ -> bool
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(** [match_with a s] matches the string [s] against [a], and returns
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[true] if the distance from [s] to the word represented by [a] is smaller
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than the limit used to build [a] *)
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(** {6 Index for one-to-many matching} *)
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module Index : sig
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type 'b t
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(** Index that maps strings to values of type 'b. Internally it is
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based on a trie. *)
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val empty : 'b t
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(** Empty index *)
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val is_empty : _ t -> bool
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val add : 'b t -> string_ -> 'b -> 'b t
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(** Add a char array to the index. If a value was already present
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for this array it is replaced. *)
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val remove : 'b t -> string_ -> 'b -> 'b t
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(** Remove a string from the index. *)
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val retrieve : limit:int -> 'b t -> string_ -> 'b klist
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(** Lazy list of objects associated to strings close to the query string *)
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val of_list : (string_ * 'b) list -> 'b t
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val to_list : 'b t -> (string_ * 'b) list
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(* TODO sequence/iteration functions *)
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end
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end
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module Make(Str : STRING) : S
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with type string_ = Str.t
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and type char_ = Str.char_
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include S with type char_ = char and type string_ = string
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val debug_print : out_channel -> automaton -> unit
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