.TH "Local_store" 3 2024-05-31 OCamldoc "OCaml library"
.SH NAME
Local_store \- This module provides some facilities for creating references (and hash tables) which can easily be snapshoted and restored to an arbitrary version.
.SH Module
Module   Local_store
.SH Documentation
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Module
.BI "Local_store"
 : 
.B sig end

.sp
This module provides some facilities for creating references (and hash
tables) which can easily be snapshoted and restored to an arbitrary version\&.
.sp
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\&.

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.sp
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.PP
.SS Creators

.PP

.I val s_ref 
: 
.B 'a -> 'a ref
.sp
Similar to 
.ft B
ref
.ft R
, except the allocated reference is registered
into the store\&.

.sp

.I val s_table 
: 
.B ('a -> 'b) -> 'a -> 'b ref
.sp
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\&.
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Use it like this:
.EX
.ft B
.br
\&      let my_table = s_table Hashtbl\&.create 42
.br
\&    
.ft R
.EE

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.PP
.SS State management
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Note: all the following functions are currently unused inside the compiler
codebase\&. Merlin is their only user at the moment\&.
.PP
.I type store 

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.sp

.I val fresh 
: 
.B unit -> store
.sp
Returns a fresh instance of the store\&.
.sp
The first time this function is called, it snapshots the value of all the
registered references, later calls to 
.ft B
fresh
.ft R
will return instances
initialized to those values\&.

.sp

.I val with_store 
: 
.B store -> (unit -> 'a) -> 'a
.sp

.ft B
with_store s f
.ft R
resets all the registered references to the value they have
in 
.ft B
s
.ft R
for the run of 
.ft B
f
.ft R
\&.
If 
.ft B
f
.ft R
updates any of the registered refs, 
.ft B
s
.ft R
is updated to remember those
changes\&.

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.I val reset 
: 
.B unit -> unit
.sp
Resets all the references to the initial snapshot (i\&.e\&. to the same values
that new instances start with)\&.

.sp

.I val is_bound 
: 
.B unit -> bool
.sp
Returns 
.ft B
true
.ft R
when a store is active (i\&.e\&. when called from the callback
passed to 
.ft B
Local_store\&.with_store
.ft R
), 
.ft B
false
.ft R
otherwise\&.

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