def gregory(dtype=float):
"""
Return partial sums of the Gregory series converging to atan(1) == pi/4.
Yield 1 - 1/3 + 1/5 - 1/7 + ... computed with the given type.
:param dtype:
:return:
"""
return sequence(dtype(1), step=2) >> StreamMap(lambda x: 1 / x) >> alt_sign >> StreamFold(operator.add)
def main():
# should be X(t) = mu * t + sigma * W(t)
print(cstream.sequence() >> wiener(1.) >> cstream.StreamTake(100) >> list)
