--- gforth/fft.fs	2005/09/27 13:50:43	1.1
+++ gforth/fft.fs	2007/10/17 15:50:01	1.4
@@ -1,3 +1,23 @@
+\ fast fourier transform
+
+\ Copyright (C) 2005 Free Software Foundation, Inc.
+
+\ This file is part of Gforth.
+
+\ Gforth 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, USA.
+
 \           *** Fast Fourier Transformation ***        15may93py
 
 require complex.fs
@@ -50,9 +70,13 @@ Carray expix
   BEGIN  2dup >  WHILE  dup 2* swap fft-step
   REPEAT  2drop drop ;
 
-: normalize ( -- )  #points dup s>f 1/f
-  0 DO  I values dup z@ 2 fpick zscale z!  LOOP  fdrop ;
+: fftscale ( r -- )
+  #points 0 DO  I values dup z@ 2 fpick zscale z!  LOOP  fdrop ;
+: normalize ( -- )  #points s>f 1/f  fftscale ;
 
 : fft  ( -- )  #points  true (fft ;
 : rfft ( -- )  #points false (fft ;
 
+: hamming ( -- )  #points 0 DO
+	I values dup z@ pi I #points fm*/ fsin f**2 f2* zscale z!
+    LOOP ;
\ No newline at end of file