An arithmetic sequence generator.  Works with any type with + defined.

	>>> seq(1, 0.25) >> item[:10]
	[1, 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25]

def seq(start=0, step=1):
	"""An arithmetic sequence generator.  Works with any type with + defined.

	>>> seq(1, 0.25) >> item[:10]
	[1, 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25]
	"""
	def seq(a, d):
		while 1:
			yield a
			a += d
	return seq(start, step)