Module Base.Hashtbl

val hash : 'a -> int
val hash_param : int -> int -> 'a -> int
type ('a, 'b) t
val sexp_of_t : ('a -> Sexp.t) -> ('b -> Sexp.t) -> ('a, 'b) t -> Sexp.t

We provide a sexp_of_t but not a t_of_sexp for this type because one needs to be explicit about the hash and comparison functions used when creating a hashtable. Note that Hashtbl.Poly.t does have [@@deriving_inline sexp][@@@end], and uses OCaml's built-in polymorphic comparison and and polymorphic hashing.

type ('a, 'b) t

Creators

val create : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> ('a, 'b) t

The module you pass to create must have a type that is hashable, sexpable, and comparable.

Example:

        Hashtbl.create (module Int);;
        - : (int, '_a) Hashtbl.t = <abstr>;;
val of_alist : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> ('a * 'b) list -> [ `Ok of ('a, 'b) t | `Duplicate_key of 'a ]

Example:

         Hashtbl.of_alist (module Int) [(3, "something"); (2, "whatever")]
         - : [ `Duplicate_key of int | `Ok of (int, string) Hashtbl.t ] = `Ok <abstr>
val of_alist_report_all_dups : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> ('a * 'b) list -> [ `Ok of ('a, 'b) t | `Duplicate_keys of 'a list ]

Whereas of_alist will report Duplicate_key no matter how many dups there are in your list, of_alist_report_all_dups will report each and every duplicate entry.

For example:

        Hashtbl.of_alist (module Int) [(1, "foo"); (1, "bar"); (2, "foo"); (2, "bar")];;
        - : [ `Duplicate_key of int | `Ok of (int, string) Hashtbl.t ] = `Duplicate_key 1

        Hashtbl.of_alist_report_all_dups (module Int) [(1, "foo"); (1, "bar"); (2, "foo"); (2, "bar")];;
        - : [ `Duplicate_keys of int list | `Ok of (int, string) Hashtbl.t ] = `Duplicate_keys [1; 2]
val of_alist_or_error : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> ('a * 'b) list -> ('a, 'b) t Or_error.t
val of_alist_exn : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> ('a * 'b) list -> ('a, 'b) t
val of_alist_multi : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> ('a * 'b) list -> ('a, 'b list) t

Creates a "multi" hashtable, i.e., a hashtable where each key points to a list potentially containing multiple values. So instead of short-circuiting with a `Duplicate_key variant on duplicates, as in of_alist, of_alist_multi folds those values into a list for the given key:

      let h = Hashtbl.of_alist_multi (module Int) [(1, "a"); (1, "b"); (2, "c"); (2, "d")];;
      val h : (int, string list) Hashtbl.t = <abstr>

      Hashtbl.find_exn h 1;;
      - : string list = ["b"; "a"]
val create_mapped : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> get_key:('r -> 'a) -> get_data:('r -> 'b) -> 'r list -> [ `Ok of ('a, 'b) t | `Duplicate_keys of 'a list ]

Applies the get_key and get_data functions to the 'r list to create the initial keys and values, respectively, for the new hashtable.

create_mapped get_key get_data [x1;...;xn]
        = of_alist [get_key x1, get_data x1; ...; get_key xn, get_data xn]

Example:

        let h =
          Hashtbl.create_mapped (module Int)
            ~get_key:(fun x -> x)
            ~get_data:(fun x -> x + 1)
           [1; 2; 3];;
        val h : [ `Duplicate_keys of int list | `Ok of (int, int) Hashtbl.t ] = `Ok <abstr>

        let h =
          match h with
          | `Ok x -> x
          | `Duplicate_keys _ -> failwith ""
        in
        Hashtbl.find_exn h 1;;
        - : int = 2
val create_with_key : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> get_key:('r -> 'a) -> 'r list -> [ `Ok of ('a, 'r) t | `Duplicate_keys of 'a list ]
create_with_key ~get_key [x1;...;xn]
        = of_alist [get_key x1, x1; ...; get_key xn, xn]
val create_with_key_or_error : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> get_key:('r -> 'a) -> 'r list -> ('a, 'r) t Or_error.t
val create_with_key_exn : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> get_key:('r -> 'a) -> 'r list -> ('a, 'r) t
val group : ?⁠growth_allowed:bool -> ?⁠size:int -> (module Base__.Hashtbl_intf.Key with type t = 'a) -> get_key:('r -> 'a) -> get_data:('r -> 'b) -> combine:('b -> 'b -> 'b) -> 'r list -> ('a, 'b) t

Like create_mapped, applies the get_key and get_data functions to the 'r list to create the initial keys and values, respectively, for the new hashtable -- and then, like add_multi, folds together values belonging to the same keys. Here, though, the function used for the folding is given by combine (instead of just being a cons).

Example:

         Hashtbl.group (module Int)
           ~get_key:(fun x -> x / 2)
           ~get_data:(fun x -> x)
           ~combine:(fun x y -> x * y)
            [ 1; 2; 3; 4]
         |> Hashtbl.to_alist;;
         - : (int * int) list = [(2, 4); (1, 6); (0, 1)]
type ('a, 'b) t
type 'a key = 'a
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
type ('a, 'b) t
type 'a key
val add_multi : ('a, 'b list) t -> key:'a key -> data:'b -> unit

add_multi t ~key ~data if key is present in the table then cons data on the list, otherwise add key with a single element list.

val remove_multi : ('a, _ list) t -> 'a key -> unit

remove_multi t key updates the table, removing the head of the list bound to key. If the list has only one element (or is empty) then the binding is removed.

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

find_multi t key returns the empty list if key is not present in the table, returns t's values for key otherwise.

val hashable_s : ('key, _) t -> (module Base__.Hashtbl_intf.Key with type t = 'key)
include Invariant.S2 with type ('a, 'b) t := ('a, 'b) t
type ('a, 'b) t
val invariant : 'a Base__.Invariant_intf.inv -> 'b Base__.Invariant_intf.inv -> ('a, 'b) t Base__.Invariant_intf.inv
type nonrec ('key, 'data, 'z) create_options = ('key, 'data, 'z) Base__.Hashtbl_intf.create_options
module Creators : functor (Key : sig ... end) -> sig ... end
module Poly : S_poly with type ('a, 'b) t = ('a, 'b) t
module M : functor (K : T.T) -> sig ... end

M is meant to be used in combination with OCaml applicative functor types:

include For_deriving with type ('a, 'b) For_deriving.t := ('a, 'b) t
type ('k, 'v) t
module type Sexp_of_m = sig ... end
module type M_of_sexp = sig ... end
val sexp_of_m__t : (module Sexp_of_m with type t = 'k) -> ('v -> Sexp.t) -> ('k, 'v) t -> Sexp.t
val m__t_of_sexp : (module M_of_sexp with type t = 'k) -> (Sexp.t -> 'v) -> Sexp.t -> ('k, 'v) t