class IndexTransformDecimationInFrequency(object):
	"""docstring for IndexTransformDecimationInFrequency"""
	def __init__(self, N):
		super(IndexTransformDecimationInFrequency, self).__init__()
		self.N = N
		self.new_k = range(self.N)
		self.build_index_vector()
		print 'new_k = ', self.new_k
		
	def reverse_order(self, sequence):
		old_sequence = sequence[:]
		for i in (range(len(sequence))):
			a = sequence[ i ];
			sequence[ i ] = old_sequence[ self.new_k[i] ]

	def build_index_vector(self):
		if self.N == 8: 							# 2^3 => 3 bits
			for indice in range(self.N):
				b = '{:03b}'.format(indice)
				b = b[::-1]
				self.new_k[indice] = int(b, 2)
		elif self.N == 16:							# 2^4 => 4 bits
			for indice in range(self.N):
				b = '{:04b}'.format(indice)
				b = b[::-1]
				self.new_k[indice] = int(b, 2)
		elif self.N == 32:							# 2^5 => 5 bits
			for indice in range(self.N):
				b = '{:05b}'.format(indice)
				b = b[::-1]
				self.new_k[indice] = int(b, 2)
		elif self.N == 256:							# 2^8 => 8 bits
			for indice in range(self.N):
				b = '{:08b}'.format(indice)
				b = b[::-1]
				self.new_k[indice] = int(b, 2)
		else:
			print'error, N = ', self.N, ' is not supported by the index_transform function'

if __name__ == "__main__":
	x = range(8)
	indexTransformDecimationInFrequency = IndexTransformDecimationInFrequency(len(x))
	print 'x ', x
	indexTransformDecimationInFrequency.reverse_order(x)
	print 'x rearranged ', x
	y = x
	indexTransformDecimationInFrequency.reverse_order(y)
	print 'y ', y
	x = range(16)
	indexTransformDecimationInFrequency = IndexTransformDecimationInFrequency(len(x))
	print 'x ', x
	indexTransformDecimationInFrequency.reverse_order(x)
	print 'x rearranged ', x
	y = x
	indexTransformDecimationInFrequency.reverse_order(y)
	print 'y ', y