
Module Weakmodule Weak:
Arrays of weak pointers and hash tables of weak pointers.
type
The type of arrays of weak pointers (weak arrays). A weak
pointer is a value that the garbage collector may erase at
any time.
A weak pointer is said to be full if it points to a value,
empty if the value was erased by the GC.
val create : Weak.create n returns a new weak array of length n .
All the pointers are initially empty. Raise Invalid_argument
if n is negative or greater than Sys.max_array_length 1 .val length : Weak.length ar returns the length (number of elements) of
ar .val set : Weak.set ar n (Some el) sets the n th cell of ar to be a
(full) pointer to el ; Weak.set ar n None sets the n th
cell of ar to empty.
Raise Invalid_argument "Weak.set" if n is not in the range
0 to Weak.length a  1 .val get : Weak.get ar n returns None if the n th cell of ar is
empty, Some x (where x is the value) if it is full.
Raise Invalid_argument "Weak.get" if n is not in the range
0 to Weak.length a  1 .val get_copy : Weak.get_copy ar n returns None if the n th cell of ar is
empty, Some x (where x is a (shallow) copy of the value) if
it is full.
In addition to pitfalls with mutable values, the interesting
difference with get is that get_copy does not prevent
the incremental GC from erasing the value in its current cycle
(get may delay the erasure to the next GC cycle).
Raise Invalid_argument "Weak.get" if n is not in the range
0 to Weak.length a  1 .val check : Weak.check ar n returns true if the n th cell of ar is
full, false if it is empty. Note that even if Weak.check ar n
returns true , a subsequent Weak.get ar n can return None .val fill : Weak.fill ar ofs len el sets to el all pointers of ar from
ofs to ofs + len  1 . Raise Invalid_argument "Weak.fill"
if ofs and len do not designate a valid subarray of a .val blit : Weak.blit ar1 off1 ar2 off2 len copies len weak pointers
from ar1 (starting at off1 ) to ar2 (starting at off2 ).
It works correctly even if ar1 and ar2 are the same.
Raise Invalid_argument "Weak.blit" if off1 and len do
not designate a valid subarray of ar1 , or if off2 and len
do not designate a valid subarray of ar2 .
A weak hash table is a hashed set of values. Each value may magically disappear from the set when it is not used by the rest of the program any more. This is normally used to share data structures without inducing memory leaks. Weak hash tables are defined on values from a Hashtbl.HashedType
module; the equal relation and hash function are taken from that
module. We will say that v is an instance of x if equal x v
is true .
The module type S =
The output signature of the functor
Weak.Make .
module Make:
Functor building an implementation of the weak hash table structure.
