Module Hashhe

module Hashhe: sig .. end

Hash tables and hash functions (extension of standard library module)

Hash tables are hashed association tables, with in-place modification.

Modified by B. Jeannet: functions map, copy and print.

type ('a, 'b) hashtbl

type 'a compare = {

	`hash :'a -> int;`
	`equal :'a -> 'a -> bool;`

}

Generic interface

type ('a, 'b) t = ('a, 'b) hashtbl

The type of hash tables from type 'a to type 'b.

val create : int -> ('a, 'b) t

create n creates a new, empty hash table, with initial size n. For best results, n should be on the order of the expected number of elements that will be in the table. The table grows as needed, so n is just an initial guess.

val clear : ('a, 'b) t -> unit

Empty a hash table.

val add : ('a, 'b) t -> 'a -> 'b -> unit

add tbl x y adds a binding of x to y in table tbl. Previous bindings for x are not removed, but simply hidden. That is, after performing Hashhe.remove tbl x, the previous binding for x, if any, is restored. (Same behavior as with association lists.)

val copy : ('a, 'b) t -> ('a, 'b) t

Return a copy of the given hashtable.

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

find tbl x returns the current binding of x in tbl, or raises Not_found if no such binding exists.

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

find_all tbl x returns the list of all data associated with x in tbl. The current binding is returned first, then the previous bindings, in reverse order of introduction in the table.

val mem : ('a, 'b) t -> 'a -> bool

mem tbl x checks if x is bound in tbl.

val remove : ('a, 'b) t -> 'a -> unit

remove tbl x removes the current binding of x in tbl, restoring the previous binding if it exists. It does nothing if x is not bound in tbl.

val replace : ('a, 'b) t -> 'a -> 'b -> unit

replace tbl x y replaces the current binding of x in tbl by a binding of x to y. If x is unbound in tbl, a binding of x to y is added to tbl. This is functionally equivalent to Hashhe.remove tbl x followed by Hashhe.add tbl x y.

val iter : ('a -> 'b -> unit) -> ('a, 'b) t -> unit

iter f tbl applies f to all bindings in table tbl. f receives the key as first argument, and the associated value as second argument. Each binding is presented exactly once to f. The order in which the bindings are passed to f is unspecified. However, if the table contains several bindings for the same key, they are passed to f in reverse order of introduction, that is, the most recent binding is passed first.

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

fold f tbl init computes (f kN dN ... (f k1 d1 init)...), where k1 ... kN are the keys of all bindings in tbl, and d1 ... dN are the associated values. Each binding is presented exactly once to f. The order in which the bindings are passed to f is unspecified. However, if the table contains several bindings for the same key, they are passed to f in reverse order of introduction, that is, the most recent binding is passed first.

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

map f tbl applies f to all bindings in table tbl and creates a new hashtable associating the results of f to the same key type. f receives the key as first argument, and the associated value as second argument. Each binding is presented exactly once to f. The order in which the bindings are passed to f is unspecified. However, if the table contains several bindings for the same key, they are passed to f in reverse order of introduction, that is, the most recent binding is passed first.

val length : ('a, 'b) t -> int

length tbl returns the number of bindings in tbl. Multiple bindings are counted multiply, so length gives the number of times iter calls it first argument.

val print : ?first:(unit, Format.formatter, unit) Pervasives.format ->
       ?sep:(unit, Format.formatter, unit) Pervasives.format ->
       ?last:(unit, Format.formatter, unit) Pervasives.format ->
       ?firstbind:(unit, Format.formatter, unit) Pervasives.format ->
       ?sepbind:(unit, Format.formatter, unit) Pervasives.format ->
       ?lastbind:(unit, Format.formatter, unit) Pervasives.format ->
       (Format.formatter -> 'a -> unit) ->
       (Format.formatter -> 'b -> unit) ->
       Format.formatter -> ('a, 'b) t -> unit

Functorial interface

module type HashedType = sig .. end

The input signature of the functor Hashhe.Make.

module type S = sig .. end

The output signature of the functor Hashhe.Make.

module Make: functor (H : HashedType) -> S  with type key = H.t

Functor building an implementation of the hashtable structure.

The polymorphic hash primitive

val hash : 'a -> int

hash x associates a positive integer to any value of any type. It is guaranteed that if x = y or Pervasives.compare x y = 0, then hash x = hash y. Moreover, hash always terminates, even on cyclic structures.

val hash_param : int -> int -> 'a -> int

hash_param n m x computes a hash value for x, with the same properties as for hash. The two extra parameters n and m give more precise control over hashing. Hashing performs a depth-first, right-to-left traversal of the structure x, stopping after n meaningful nodes were encountered, or m nodes, meaningful or not, were encountered. Meaningful nodes are: integers; floating-point numbers; strings; characters; booleans; and constant constructors. Larger values of m and n means that more nodes are taken into account to compute the final hash value, and therefore collisions are less likely to happen. However, hashing takes longer. The parameters m and n govern the tradeoff between accuracy and speed.

val stdcompare : 'a compare

module Compare: sig .. end