simon/ocaml-containers
1
0
Fork 0
mirror of https://github.com/c-cube/ocaml-containers.git synced 2025-12-06 19:25:28 -05:00
Code Issues Projects Releases Packages Wiki Activity Actions

CCArray.lookup for divide-and-conquer search

Browse source
This commit is contained in:
Simon Cruanes 2014-07-03 15:08:59 +02:00
parent 9595ac688c
commit 4102f3b95d
2 changed files with 67 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

58
core/CCArray.ml
View file

@ -68,6 +68,15 @@ module type S = sig
(** [find f a] returns [Some y] if there is an element [x] such
that [f x = Some y], else it returns [None] *)
val lookup : ?cmp:'a ord -> 'a -> 'a t -> int option
(** Lookup the index of some value in a sorted array.
@return [None] if the key is not present, or
[Some i] ([i] the index of the key) otherwise *)
val lookup_exn : ?cmp:'a ord -> 'a -> 'a t -> int
(** Same as {!lookup_exn}, but
@raise Not_found if the key is not present *)
val for_all : ('a -> bool) -> 'a t -> bool
val for_all2 : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
@ -155,6 +164,31 @@ let rec _find f a i j =
| Some _ as res -> res
| None -> _find f a (i+1) j
let rec _lookup_rec ~cmp k a i j =
if i>j then raise Not_found
else if i=j
then if cmp k a.(i) = 0
then i
else raise Not_found
else
let middle = (j+i)/2 in
match cmp k a.(middle) with
| 0 -> middle
| n when n<0 -> _lookup_rec ~cmp k a i (middle-1)
| _ -> _lookup_rec ~cmp k a (middle+1) j
let _lookup_exn ~cmp k a i j =
if i>j then raise Not_found;
match cmp k a.(i) with
| 0 -> i
| n when n<0 -> raise Not_found (* too low *)
| _ when i=j -> raise Not_found (* too high *)
| _ ->
match cmp k a.(j) with
| 0 -> j
| n when n<0 -> _lookup_rec ~cmp k a (i+1) (j-1)
| _ -> raise Not_found (* too high *)
let rec _for_all p a i j =
i = j || (p a.(i) && _for_all p a (i+1) j)
@ -307,6 +341,23 @@ let flat_map f a =
a' = [| 1; 2; 3; 4; 5; 6 |]
*)
let lookup_exn ?(cmp=Pervasives.compare) k a =
_lookup_exn ~cmp k a 0 (Array.length a-1)
let lookup ?(cmp=Pervasives.compare) k a =
try Some (_lookup_exn ~cmp k a 0 (Array.length a-1))
with Not_found -> None
(*$T
lookup 2 [|0;1;2;3;4;5|] = Some 2
lookup 4 [|0;1;2;3;4;5|] = Some 4
lookup 0 [|1;2;3;4;5|] = None
lookup 6 [|1;2;3;4;5|] = None
lookup 3 [| |] = None
lookup 1 [| 1 |] = Some 0
lookup 2 [| 1 |] = None
*)
let (>>=) a f = flat_map f a
let for_all p a = _for_all p a 0 (Array.length a)
@ -445,6 +496,13 @@ module Sub = struct
let find f a = _find f a.arr a.i a.j
let lookup_exn ?(cmp=Pervasives.compare) k a =
_lookup_exn ~cmp k a.arr a.i (a.j-1)
let lookup ?(cmp=Pervasives.compare) k a =
try Some (_lookup_exn ~cmp k a.arr a.i (a.j-1))
with Not_found -> None
let for_all p a = _for_all p a.arr a.i a.j
let exists p a = _exists p a.arr a.i a.j

9
core/CCArray.mli
View file

@ -70,6 +70,15 @@ module type S = sig
(** [find f a] returns [Some y] if there is an element [x] such
that [f x = Some y], else it returns [None] *)
val lookup : ?cmp:'a ord -> 'a -> 'a t -> int option
(** Lookup the index of some value in a sorted array.
@return [None] if the key is not present, or
[Some i] ([i] the index of the key) otherwise *)
val lookup_exn : ?cmp:'a ord -> 'a -> 'a t -> int
(** Same as {!lookup_exn}, but
@raise Not_found if the key is not present *)
val for_all : ('a -> bool) -> 'a t -> bool
val for_all2 : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool