def applyChanges(data):
stream.apply(data)
def alt_sign(s):
"""Alternate the sign of numbers of the input stream by multiply it with
the unit alternating series 1, -1, ...
"""
return zip(s, gseq(-1, initval=1)) >> apply(operator.mul)
#!/usr/bin/env python import operator from random import choice from stream import repeatcall, apply, fold, takei, takewhile, drop, item vectoradd = lambda u, v: zip(u, v) >> apply(operator.add) >> list Origin = [0, 0] Directions = [[1,0], [0,1], [-1,0], [0,-1]] randwalk = lambda: repeatcall(choice, Directions) >> fold(vectoradd, initval=Origin) def returned(n): """Generate a random walk and return True if the walker has returned to the origin after taking `n` steps. """ ## `takei` yield lazily so we can short-circuit and avoid computing the rest of the walk for pos in randwalk() >> drop(1) >> takei(xrange(n-1)): if pos == Origin: return True return False def first_return(): """Generate a random walk and return its length upto the moment that the walker first returns to the origin. It is mathematically provable that the walker will eventually return, meaning that the function call will halt, although it may take
def alt_sign(s): """Alternate the sign of numbers of the input stream by multiply it with the unit alternating series 1, -1, ... """ return zip(s, gseq(-1, initval=1)) >> apply(operator.mul)
