python code for prototyping

fft.py

@@ -0,0 +1,26 @@
+#!/usr/local/bin/python2.3
+import math
+
+def T(n,i):
+    return math.e ** complex( 0,-2*math.pi*i/n )
+
+def fft(f):
+    n=len(f)
+    if n%2 == 0:
+        np = n/2
+        fe=[0 ] * np
+        fo=[0 ] * np
+        for i in range(np):
+            fe[i] = f[i] + f[i+np]
+            fo[i] = (f[i] - f[i+np]) * T(n,i)
+        Fe=fft(fe)
+        Fo=fft(fo)
+        F=[0 ] * n
+        F[::2] = Fe
+        F[1::2] = Fo
+    elif n==1:
+        F=f
+    else:
+        raise exceptions.Exception('cannot factor %d by 2' % n)
+    return F
+