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(*
Copyright © 2011 MLstate
This file is part of OPA.
OPA is free software: you can redistribute it and/or modify it under the
terms of the GNU Affero General Public License, version 3, as published by
the Free Software Foundation.
OPA is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for
more details.
You should have received a copy of the GNU Affero General Public License
along with OPA. If not, see <http://www.gnu.org/licenses/>.
*)
(*
@author Jérémie Lumbroso
@author François-Régis Sinot
**)
exception Id_overflow
(**
Name creation, with namespaces.
Use this generator if you wish to turn various occurrences of, say, ["x"] and ["y"] into
["x0"], ["x1"], ["x2"], ["y0"], ["y1"], ...
Generate a new unique name.
Usage: [let fresh ... = let f = fresh_named_factory ?init_size transf in f ...].
[transf] is any transformer from triple (name, description, index), typically a custom printer
{b Note} Names produced are guaranteed unique only with respect to each other,
and only if your [transf] is consistent with the way you generate new items.
In other words, the first name you will obtain by calling [fresh "x" "foo"] is
always e.g. ["x_0___AS_foo"].
*)
type stamp = int
type name = string
type descr = string
type t_fresh = stamp * int * name * descr
let compare ((l1,_,_,_):t_fresh) (r1,_,_,_) =
compare l1 r1 (* the stamp is unique *)
let equal ((l1,_,_,_):t_fresh) (r1,_,_,_) =
l1 = r1
let hash ((i,_,_,_):t_fresh) = Hashtbl.hash i
let default_print (_,index,name,descr) =
Printf.sprintf "%s_%d_%s" name index descr
let inner_fresh_named_factory ?(init_size=32) transf =
let counter = ref (1 : stamp) in
let new_stamp () =
let stamp = !counter in
if stamp < max_int && 0 - stamp > min_int then
begin
incr counter;
stamp
end
else
raise Id_overflow
in
let table = Hashtbl.create init_size in
let rev_table = Hashtbl.create init_size in
let next = fun ?(name="") ?(descr="") () ->
let key = (name, descr) in
let index =
try
Hashtbl.find table key
with
Not_found -> (-1)
in
let index = if index < max_int then index + 1 else raise Id_overflow in
Hashtbl.replace table key index;
transf (new_stamp (), index, name, descr) in
(* for the specification, see the comment about [compare] in [FRESH] *)
let prev ?(name="") ?(descr="") () =
let key = (name, descr) in
let index =
try
Hashtbl.find rev_table key
with
Not_found -> 0 (* don't start at 1 or else you can create collisions
* with the names generated by next *)
in
let index = if index > min_int then index - 1 else raise Id_overflow in
Hashtbl.replace rev_table key index;
transf (0 - new_stamp (), index, name, descr) in
next, prev
let fresh_named_factory ?(init_size=32) transf =
let (next, _) = inner_fresh_named_factory ~init_size transf in
next
let default_fresh_named_factory () =
fresh_named_factory default_print
module type FRESH =
sig
type t
val next : ?name:string -> ?descr:string -> unit -> t
val prev : ?name:string -> ?descr:string -> unit -> t
val compare : t -> t -> int
(**
values with the same name and descr are guaranteed to be
generated in increasing order by [next] and decreasing order by [prev]
ie calling [next ~name ~descr] will give you the greatest value with the
given name and descr (until you call [next] again) and [prev] will give you
the lowest value (until the you [prev] again)
*)
val equal : t -> t -> bool
val to_string : t -> string
val to_int : t -> int
val hash : t -> int
(**
export just the name, e.g. for manual printing
This is used for errors messages, we try to print types with
the name of type variables as there where in the source code.
*)
val name : t -> string
(**
This is like a next, but with the property that the name and the description
of the fresh is taken from the given fresh.
This is used in order not to loose the original names of TypeVariables.
*)
val refresh : t -> t
end
module type BRAND =
sig
val printer : t_fresh -> string
end
module DefaultBrand : BRAND =
struct
let printer (_, id, _, _) =
let rec aux count =
let count = count / 26
and charc = 97 + count mod 26 in
let char = String.make 1 (Char.chr charc) in
if count = 0 then char
else aux (count - 1) ^ char
in
"'" ^ aux id
end
module FreshGen (Brand : BRAND) : FRESH =
struct
type t = t_fresh
let name (_, _, name, _) = name
let next, prev = inner_fresh_named_factory (fun t -> t) (* hidden be signature *)
let refresh (_, _, name, descr) = next ~name ~descr ()
let hash = hash
let compare = compare
let equal = equal
let to_string = Brand.printer
let to_int (stamp, _index, _name, _descr) = stamp
end
(**
Some simpler fresh generators without names.
*)
let fresh_factory (transf : int -> 'a) : (unit -> 'a) =
let index = ref (-1) in
fun () ->
if !index < max_int then incr index else raise Id_overflow;
transf !index
(** Example *)
(** let get_stringint_fresh = fresh_factory (fun t -> Printf.sprintf "_%010d" t);; *)
module Int =
struct
(* global int counter -- better use local, specialized versions rather than this *)
let get = fresh_factory (fun t -> t);;
end
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