module Hashtbl:Hash tables and hash functions.sig..end
Hash tables are hashed association tables, with in-place modification.
type ('a, 'b) t
'a to type 'b.val create : int -> ('a, 'b) tHashtbl.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 -> unitval add : ('a, 'b) t -> 'a -> 'b -> unitHashtbl.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 Hashtbl.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) tval find : ('a, 'b) t -> 'a -> 'bHashtbl.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 listHashtbl.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 -> boolHashtbl.mem tbl x checks if x is bound in tbl.val remove : ('a, 'b) t -> 'a -> unitHashtbl.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 -> unitHashtbl.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 Hashtbl.remove tbl x
followed by Hashtbl.add tbl x y.val iter : ('a -> 'b -> unit) -> ('a, 'b) t -> unitHashtbl.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 -> 'cHashtbl.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 length : ('a, 'b) t -> intHashtbl.length tbl returns the number of bindings in tbl.
Multiple bindings are counted multiply, so Hashtbl.length
gives the number of times Hashtbl.iter calls its first argument.module type HashedType =sig..end
Hashtbl.Make.
module type S =sig..end
Hashtbl.Make.
module Make:
val hash : 'a -> intHashtbl.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 -> intHashtbl.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.