Make builds an implementation of watch helpers.
type key = K.t
The type for store keys.
type value = V.t
The type for store values.
val stats : t -> int * int
stats t is a tuple
(k,a) represeting watch stats.
k is the number of single key watchers for the store
a the number of global watchers for
Notify all listeners in the given watch state that a key has changed, with the new value associated to this key.
None means the key has been removed.
val v : unit -> t
Create a watch state.
Watch a given key for changes. More efficient than
Add a watch handler. To watch a specific key, use
watch_key which is more efficient.