view Lib/fftw-3.2.1/genfft/monads.ml @ 1:e86e9c111b29

Updates stuff that potentially fixes the memory leak and also makes it work on Windows and Linux (Need to test). Still have to fix fftw include for linux in Jucer.

(*
 * Copyright (c) 1997-1999 Massachusetts Institute of Technology
 * Copyright (c) 2003, 2007-8 Matteo Frigo
 * Copyright (c) 2003, 2007-8 Massachusetts Institute of Technology
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *)

(*************************************************************
 *   Monads
 *************************************************************)

(*
 * Phil Wadler has many well written papers about monads.  See
 * http://cm.bell-labs.com/cm/cs/who/wadler/ 
 *)
(* vanilla state monad *)
module StateMonad = struct
  let returnM x = fun s -> (x, s)

  let (>>=) = fun m k -> 
    fun s ->
      let (a', s') = m s
      in let (a'', s'') = k a' s'
      in (a'', s'')

  let (>>) = fun m k ->
    m >>= fun _ -> k

  let rec mapM f = function
      [] -> returnM []
    | a :: b ->
	f a >>= fun a' ->
	  mapM f b >>= fun b' ->
	    returnM (a' :: b')

  let runM m x initial_state =
    let (a, _) = m x initial_state
    in a

  let fetchState =
    fun s -> s, s

  let storeState newState =
    fun _ -> (), newState
end

(* monad with built-in memoizing capabilities *)
module MemoMonad =
  struct
    open StateMonad

    let memoizing lookupM insertM f k =
      lookupM k >>= fun vMaybe ->
	match vMaybe with
	  Some value -> returnM value
	| None ->
	    f k >>= fun value ->
	      insertM k value >> returnM value

    let runM initial_state m x  = StateMonad.runM m x initial_state
end