: sig end
This module provides some facilities for creating references (and hash tables) which can easily be snapshoted and restored to an arbitrary version.
It is used throughout the frontend (read: typechecker), to register all (well, hopefully) the global state. Thus making it easy for tools like Merlin to go back and forth typechecking different files.
val s_ref : 'a -> 'a ref
Similar to ref , except the allocated reference is registered into the store.
val s_table : ('a -> 'b) -> 'a -> 'b ref
Used to register hash tables. Those also need to be placed into refs to be easily swapped out, but one can't just "snapshot" the initial value to create fresh instances, so instead an initializer is required.
Use it like this:
let my_table = s_table Hashtbl.create 42
Note: all the following functions are currently unused inside the compiler codebase. Merlin is their only user at the moment.
val fresh : unit -> store
Returns a fresh instance of the store.
The first time this function is called, it snapshots the value of all the registered references, later calls to fresh will return instances initialized to those values.
val with_store : store -> (unit -> 'a) -> 'a
with_scope s f resets all the registered references to the value they have in s for the run of f . If f updates any of the registered refs, s is updated to remember those changes.
val reset : unit -> unit
Resets all the references to the initial snapshot (i.e. to the same values that new instances start with).
val is_bound : unit -> bool
Returns true when a scope is active (i.e. when called from the callback passed to with_scope ), false otherwise.