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batReturn.ml
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batReturn.ml
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(*
* Return -- fast return in OCaml
* Copyright (C) 2008 David Teller
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version,
* with the special exception on linking described in file LICENSE.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*)
type 'a t = 'a -> exn
let return label value =
raise (label value)
let label (type u) (f : u t -> u) : u =
let module M = struct exception Return of u end in
try f (fun x -> M.Return x)
with M.Return u -> u
let with_label = label
(* testing nesting with_labels *)
(*$T with_label
with_label (fun label1 -> \
with_label (fun _label2 -> ignore (return label1 1)); 2 \
) = 1
*)