mirror of
https://github.com/tildearrow/furnace.git
synced 2024-11-23 13:05:11 +00:00
54e93db207
not reliable yet
71 lines
2.6 KiB
OCaml
71 lines
2.6 KiB
OCaml
(*
|
|
* Copyright (c) 1997-1999 Massachusetts Institute of Technology
|
|
* Copyright (c) 2003, 2007-14 Matteo Frigo
|
|
* Copyright (c) 2003, 2007-14 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*
|
|
*)
|
|
|
|
(*
|
|
* The LittleSimplifier module implements a subset of the simplifications
|
|
* of the AlgSimp module. These simplifications can be executed
|
|
* quickly here, while they would take a long time using the heavy
|
|
* machinery of AlgSimp.
|
|
*
|
|
* For example, 0 * x is simplified to 0 tout court by the LittleSimplifier.
|
|
* On the other hand, AlgSimp would first simplify x, generating lots
|
|
* of common subexpressions, storing them in a table etc, just to
|
|
* discard all the work later. Similarly, the LittleSimplifier
|
|
* reduces the constant FFT in Rader's algorithm to a constant sequence.
|
|
*)
|
|
|
|
open Expr
|
|
|
|
let rec makeNum = function
|
|
| n -> Num n
|
|
|
|
and makeUminus = function
|
|
| Uminus a -> a
|
|
| Num a -> makeNum (Number.negate a)
|
|
| a -> Uminus a
|
|
|
|
and makeTimes = function
|
|
| (Num a, Num b) -> makeNum (Number.mul a b)
|
|
| (Num a, Times (Num b, c)) -> makeTimes (makeNum (Number.mul a b), c)
|
|
| (Num a, b) when Number.is_zero a -> makeNum (Number.zero)
|
|
| (Num a, b) when Number.is_one a -> b
|
|
| (Num a, b) when Number.is_mone a -> makeUminus b
|
|
| (Num a, Uminus b) -> Times (makeUminus (Num a), b)
|
|
| (a, (Num b as b')) -> makeTimes (b', a)
|
|
| (a, b) -> Times (a, b)
|
|
|
|
and makePlus l =
|
|
let rec reduceSum x = match x with
|
|
[] -> []
|
|
| [Num a] -> if Number.is_zero a then [] else x
|
|
| (Num a) :: (Num b) :: c ->
|
|
reduceSum ((makeNum (Number.add a b)) :: c)
|
|
| ((Num _) as a') :: b :: c -> b :: reduceSum (a' :: c)
|
|
| a :: s -> a :: reduceSum s
|
|
|
|
in match reduceSum l with
|
|
[] -> makeNum (Number.zero)
|
|
| [a] -> a
|
|
| [a; b] when a == b -> makeTimes (Num Number.two, a)
|
|
| [Times (Num a, b); Times (Num c, d)] when b == d ->
|
|
makeTimes (makePlus [Num a; Num c], b)
|
|
| a -> Plus a
|
|
|