Module type Hashtbl.Creators
Creators
val create : ?growth_allowed:bool -> ?size:int -> 'a Base__.Hashtbl_intf.Key.t -> ('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 -> 'a Base__.Hashtbl_intf.Key.t -> ('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 -> 'a Base__.Hashtbl_intf.Key.t -> ('a * 'b) list -> [ `Ok of ('a, 'b) t | `Duplicate_keys of 'a list ]
Whereas
of_alist
will reportDuplicate_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 -> 'a Base__.Hashtbl_intf.Key.t -> ('a * 'b) list -> ('a, 'b) t Base.Or_error.t
val of_alist_exn : ?growth_allowed:bool -> ?size:int -> 'a Base__.Hashtbl_intf.Key.t -> ('a * 'b) list -> ('a, 'b) t
val of_alist_multi : ?growth_allowed:bool -> ?size:int -> 'a Base__.Hashtbl_intf.Key.t -> ('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 inof_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 -> 'a Base__.Hashtbl_intf.Key.t -> get_key:('r -> 'a) -> get_data:('r -> 'b) -> 'r list -> [ `Ok of ('a, 'b) t | `Duplicate_keys of 'a list ]
Applies the
get_key
andget_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 -> 'a Base__.Hashtbl_intf.Key.t -> 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 -> 'a Base__.Hashtbl_intf.Key.t -> get_key:('r -> 'a) -> 'r list -> ('a, 'r) t Base.Or_error.t
val create_with_key_exn : ?growth_allowed:bool -> ?size:int -> 'a Base__.Hashtbl_intf.Key.t -> get_key:('r -> 'a) -> 'r list -> ('a, 'r) t
val group : ?growth_allowed:bool -> ?size:int -> 'a Base__.Hashtbl_intf.Key.t -> get_key:('r -> 'a) -> get_data:('r -> 'b) -> combine:('b -> 'b -> 'b) -> 'r list -> ('a, 'b) t
Like
create_mapped
, applies theget_key
andget_data
functions to the'r list
to create the initial keys and values, respectively, for the new hashtable -- and then, likeadd_multi
, folds together values belonging to the same keys. Here, though, the function used for the folding is given bycombine
(instead of just being acons
).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)]