+++ /dev/null
-(*
- * Trie: maps over lists.
- * Copyright (C) 2000 Jean-Christophe FILLIATRE
- *
- * This software is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Library General Public
- * License version 2, as published by the Free Software Foundation.
- *
- * This software is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- *
- * See the GNU Library General Public License version 2 for more details
- * (enclosed in the file LGPL).
- *)
-
-(* $Id$ *)
-
-(*s A trie is a tree-like structure to implement dictionaries over
- keys which have list-like structures. The idea is that each node
- branches on an element of the list and stores the value associated
- to the path from the root, if any. Therefore, a trie can be
- defined as soon as a map over the elements of the list is
- given. *)
-
-
-module Make (M : Map.S) = struct
-
-(*s Then a trie is just a tree-like structure, where a possible
- information is stored at the node (['a option]) and where the sons
- are given by a map from type [key] to sub-tries, so of type
- ['a t M.t]. The empty trie is just the empty map. *)
-
- type key = M.key list
-
- type 'a t = Node of 'a option * 'a t M.t
-
- let empty = Node (None, M.empty)
-
-(*s To find a mapping in a trie is easy: when all the elements of the
- key have been read, we just inspect the optional info at the
- current node; otherwise, we descend in the appropriate sub-trie
- using [M.find]. *)
-
- let rec find l t = match (l,t) with
- | [], Node (None,_) -> raise Not_found
- | [], Node (Some v,_) -> v
- | x::r, Node (_,m) -> find r (M.find x m)
-
- let rec mem l t = match (l,t) with
- | [], Node (None,_) -> false
- | [], Node (Some _,_) -> true
- | x::r, Node (_,m) -> try mem r (M.find x m) with Not_found -> false
-
-(*s Insertion is more subtle. When the final node is reached, we just
- put the information ([Some v]). Otherwise, we have to insert the
- binding in the appropriate sub-trie [t']. But it may not exists,
- and in that case [t'] is bound to an empty trie. Then we get a new
- sub-trie [t''] by a recursive insertion and we modify the
- branching, so that it now points to [t''], with [M.add]. *)
-
- let add l v t =
- let rec ins = function
- | [], Node (_,m) -> Node (Some v,m)
- | x::r, Node (v,m) ->
- let t' = try M.find x m with Not_found -> empty in
- let t'' = ins (r,t') in
- Node (v, M.add x t'' m)
- in
- ins (l,t)
-
-(*s When removing a binding, we take care of not leaving bindings to empty
- sub-tries in the nodes. Therefore, we test wether the result [t'] of
- the recursive call is the empty trie [empty]: if so, we just remove
- the branching with [M.remove]; otherwise, we modify it with [M.add]. *)
-
- let rec remove l t = match (l,t) with
- | [], Node (_,m) -> Node (None,m)
- | x::r, Node (v,m) ->
- try
- let t' = remove r (M.find x m) in
- Node (v, if t' = empty then M.remove x m else M.add x t' m)
- with Not_found ->
- t
-
-(*s The iterators [map], [mapi], [iter] and [fold] are implemented in
- a straigthforward way using the corresponding iterators [M.map],
- [M.mapi], [M.iter] and [M.fold]. For the last three of them,
- we have to remember the path from the root, as an extra argument
- [revp]. Since elements are pushed in reverse order in [revp],
- we have to reverse it with [List.rev] when the actual binding
- has to be passed to function [f]. *)
-
- let rec map f = function
- | Node (None,m) -> Node (None, M.map (map f) m)
- | Node (Some v,m) -> Node (Some (f v), M.map (map f) m)
-
- let mapi f t =
- let rec maprec revp = function
- | Node (None,m) ->
- Node (None, M.mapi (fun x -> maprec (x::revp)) m)
- | Node (Some v,m) ->
- Node (Some (f (List.rev revp) v), M.mapi (fun x -> maprec (x::revp)) m)
- in
- maprec [] t
-
- let iter f t =
- let rec traverse revp = function
- | Node (None,m) ->
- M.iter (fun x -> traverse (x::revp)) m
- | Node (Some v,m) ->
- f (List.rev revp) v; M.iter (fun x t -> traverse (x::revp) t) m
- in
- traverse [] t
-
- let rec fold f t acc =
- let rec traverse revp t acc = match t with
- | Node (None,m) ->
- M.fold (fun x -> traverse (x::revp)) m acc
- | Node (Some v,m) ->
- f (List.rev revp) v (M.fold (fun x -> traverse (x::revp)) m acc)
- in
- traverse [] t acc
-
- let compare cmp a b =
- let rec comp a b = match a,b with
- | Node (Some _, _), Node (None, _) -> 1
- | Node (None, _), Node (Some _, _) -> -1
- | Node (None, m1), Node (None, m2) ->
- M.compare comp m1 m2
- | Node (Some a, m1), Node (Some b, m2) ->
- let c = cmp a b in
- if c <> 0 then c else M.compare comp m1 m2
- in
- comp a b
-
- let equal eq a b =
- let rec comp a b = match a,b with
- | Node (None, m1), Node (None, m2) ->
- M.equal comp m1 m2
- | Node (Some a, m1), Node (Some b, m2) ->
- eq a b && M.equal comp m1 m2
- | _ ->
- false
- in
- comp a b
-
- (* The base case is rather stupid, but constructable *)
- let is_empty = function
- | Node (None, m1) -> M.is_empty m1
- | _ -> false
-
-end
projects / helm.git / blobdiff