base

Full standard library replacement for OCaml
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Library base
Module type Base . Hashtbl . Accessors

Accessors

type ('a, 'b) t
type 'a key
val sexp_of_key : ( 'a, _ ) t -> 'a key -> Sexp.t
val clear : ( _, _ ) t -> unit
val copy : ( 'a, 'b ) t -> ( 'a, 'b ) t
val fold : ( 'a, 'b ) t -> init:'c -> f:( key:'a key -> data:'b -> 'c -> 'c ) -> 'c

Attempting to modify (set, remove, etc.) the hashtable during iteration (fold, iter, iter_keys, iteri) will raise an exception.

val iter_keys : ( 'a, _ ) t -> f:( 'a key -> unit ) -> unit
val iter : ( _, 'b ) t -> f:( 'b -> unit ) -> unit
val iteri : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> unit ) -> unit

Iterates over both keys and values.

Example:

      let h = Hashtbl.of_alist_exn (module Int) [(1, 4); (5, 6)] in
      Hashtbl.iteri h ~f:(fun ~key ~data ->
        print_endline (Printf.sprintf "%d-%d" key data));;
      1-4
      5-6
      - : unit = ()
val existsi : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> bool ) -> bool
val exists : ( _, 'b ) t -> f:( 'b -> bool ) -> bool
val for_alli : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> bool ) -> bool
val for_all : ( _, 'b ) t -> f:( 'b -> bool ) -> bool
val counti : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> bool ) -> int
val count : ( _, 'b ) t -> f:( 'b -> bool ) -> int
val length : ( _, _ ) t -> int
val is_empty : ( _, _ ) t -> bool
val mem : ( 'a, _ ) t -> 'a key -> bool
val remove : ( 'a, _ ) t -> 'a key -> unit
val set : ( 'a, 'b ) t -> key:'a key -> data:'b -> unit

Sets the given key to data.

val add : ( 'a, 'b ) t -> key:'a key -> data:'b -> [ `Ok | `Duplicate ]

add and add_exn leave the table unchanged if the key was already present.

val add_exn : ( 'a, 'b ) t -> key:'a key -> data:'b -> unit
val change : ( 'a, 'b ) t -> 'a key -> f:( 'b option -> 'b option ) -> unit

change t key ~f changes t's value for key to be f (find t key).

val update : ( 'a, 'b ) t -> 'a key -> f:( 'b option -> 'b ) -> unit

update t key ~f is change t key ~f:(fun o -> Some (f o)).

val map : ( 'a, 'b ) t -> f:( 'b -> 'c ) -> ( 'a, 'c ) t

map t f returns a new table with values replaced by the result of applying f to the current values.

Example:

      let h = Hashtbl.of_alist_exn (module Int) [(1, 4); (5, 6)] in
      let h' = Hashtbl.map h ~f:(fun x -> x * 2) in
      Hashtbl.to_alist h';;
      - : (int * int) list = [(5, 12); (1, 8)]
val mapi : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> 'c ) -> ( 'a, 'c ) t

Like map, but the function f takes both key and data as arguments.

val filter_map : ( 'a, 'b ) t -> f:( 'b -> 'c option ) -> ( 'a, 'c ) t

Returns a new table by filtering the given table's values by f: the keys for which f applied to the current value returns Some are kept, and those for which it returns None are discarded.

Example:

      let h = Hashtbl.of_alist_exn (module Int) [(1, 4); (5, 6)] in
      Hashtbl.filter_map h ~f:(fun x -> if x > 5 then Some x else None)
      |> Hashtbl.to_alist;;
      - : (int * int) list = [(5, 6)]
val filter_mapi : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> 'c option ) -> ( 'a, 'c ) t

Like filter_map, but the function f takes both key and data as arguments.

val filter_keys : ( 'a, 'b ) t -> f:( 'a key -> bool ) -> ( 'a, 'b ) t
val filter : ( 'a, 'b ) t -> f:( 'b -> bool ) -> ( 'a, 'b ) t
val filteri : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> bool ) -> ( 'a, 'b ) t
val partition_map : ( 'a, 'b ) t -> f:( 'b -> [ `Fst of 'c | `Snd of 'd ] ) -> ( 'a, 'c ) t * ( 'a, 'd ) t

Returns new tables with bound values partitioned by f applied to the bound values.

val partition_mapi : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> [ `Fst of 'c | `Snd of 'd ] ) -> ( 'a, 'c ) t * ( 'a, 'd ) t

Like partition_map, but the function f takes both key and data as arguments.

val partition_tf : ( 'a, 'b ) t -> f:( 'b -> bool ) -> ( 'a, 'b ) t * ( 'a, 'b ) t

Returns a pair of tables (t1, t2), where t1 contains all the elements of the initial table which satisfy the predicate f, and t2 contains the rest.

val partitioni_tf : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> bool ) -> ( 'a, 'b ) t * ( 'a, 'b ) t

Like partition_tf, but the function f takes both key and data as arguments.

val find_or_add : ( 'a, 'b ) t -> 'a key -> default:( unit -> 'b ) -> 'b

find_or_add t k ~default returns the data associated with key k if it is in the table t, and otherwise assigns k the value returned by default ().

val findi_or_add : ( 'a, 'b ) t -> 'a key -> default:( 'a key -> 'b ) -> 'b

Like find_or_add but default takes the key as an argument.

val find : ( 'a, 'b ) t -> 'a key -> 'b option

find t k returns Some (the current binding) of k in t, or None if no such binding exists.

val find_exn : ( 'a, 'b ) t -> 'a key -> 'b

find_exn t k returns the current binding of k in t, or raises Caml.Not_found or Not_found_s if no such binding exists.

val find_and_call : ( 'a, 'b ) t -> 'a key -> if_found:( 'b -> 'c ) -> if_not_found:( 'a key -> 'c ) -> 'c

find_and_call t k ~if_found ~if_not_found

is equivalent to:

match find t k with Some v -> if_found v | None -> if_not_found k

except that it doesn't allocate the option.

val findi_and_call : ( 'a, 'b ) t -> 'a key -> if_found:( key:'a key -> data:'b -> 'c ) -> if_not_found:( 'a key -> 'c ) -> 'c
val find_and_remove : ( 'a, 'b ) t -> 'a key -> 'b option

find_and_remove t k returns Some (the current binding) of k in t and removes it, or None is no such binding exists.

val merge : ( 'k, 'a ) t -> ( 'k, 'b ) t -> f: ( key:'k key -> [ `Left of 'a | `Right of 'b | `Both of 'a * 'b ] -> 'c option ) -> ( 'k, 'c ) t

Merges two hashtables.

The result of merge f h1 h2 has as keys the set of all k in the union of the sets of keys of h1 and h2 for which d(k) is not None, where:

d(k) =

  • f ~key:k (Some d1) None if k in h1 maps to d1, and h2 does not have data for k;
  • f ~key:k None (Some d2) if k in h2 maps to d2, and h1 does not have data for k;
  • f ~key:k (Some d1) (Some d2) otherwise, where k in h1 maps to d1 and k in h2 maps to d2.

Each key k is mapped to a single piece of data x, where d(k) = Some x.

Example:

      let h1 = Hashtbl.of_alist_exn (module Int) [(1, 5); (2, 3232)] in
      let h2 = Hashtbl.of_alist_exn (module Int) [(1, 3)] in
      Hashtbl.merge h1 h2 ~f:(fun ~key:_ -> function
        | `Left x -> Some (`Left x)
        | `Right x -> Some (`Right x)
        | `Both (x, y) -> if x=y then None else Some (`Both (x,y))
      ) |> Hashtbl.to_alist;;
      - : (int * [> `Both of int * int | `Left of int | `Right of int ]) list =
      [(2, `Left 3232); (1, `Both (5, 3))]
type 'a merge_into_action =
| Remove
| Set_to of 'a

Every key in src will be removed or set in dst according to the return value of f.

val merge_into : src:( 'k, 'a ) t -> dst:( 'k, 'b ) t -> f:( key:'k key -> 'a -> 'b option -> 'b merge_into_action ) -> unit
val keys : ( 'a, _ ) t -> 'a key list

Returns the list of all keys for given hashtable.

val data : ( _, 'b ) t -> 'b list

Returns the list of all data for given hashtable.

val filter_keys_inplace : ( 'a, _ ) t -> f:( 'a key -> bool ) -> unit

filter_inplace t ~f removes all the elements from t that don't satisfy f.

val filter_inplace : ( _, 'b ) t -> f:( 'b -> bool ) -> unit
val filteri_inplace : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> bool ) -> unit
val map_inplace : ( _, 'b ) t -> f:( 'b -> 'b ) -> unit

map_inplace t ~f applies f to all elements in t, transforming them in place.

val mapi_inplace : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> 'b ) -> unit
val filter_map_inplace : ( _, 'b ) t -> f:( 'b -> 'b option ) -> unit

filter_map_inplace combines the effects of map_inplace and filter_inplace.

val filter_mapi_inplace : ( 'a, 'b ) t -> f:( key:'a key -> data:'b -> 'b option ) -> unit
val equal : ( 'a, 'b ) t -> ( 'a, 'b ) t -> ( 'b -> 'b -> bool ) -> bool

equal t1 t2 f and similar t1 t2 f both return true iff t1 and t2 have the same keys and for all keys k, f (find_exn t1 k) (find_exn t2 k). equal and similar only differ in their types.

val similar : ( 'a, 'b1 ) t -> ( 'a, 'b2 ) t -> ( 'b1 -> 'b2 -> bool ) -> bool
val to_alist : ( 'a, 'b ) t -> ('a key * 'b) list

Returns the list of all (key, data) pairs for given hashtable.

val validate : name:( 'a key -> string ) -> 'b Validate.check -> ( 'a, 'b ) t Validate.check
val incr : ?by:int -> ?remove_if_zero:bool -> ( 'a, int ) t -> 'a key -> unit

remove_if_zero's default is false.

val decr : ?by:int -> ?remove_if_zero:bool -> ( 'a, int ) t -> 'a key -> unit