gistfile1.txt

# correct
def func1(num):
    x, y = (1, 0)
    h = 0.1
    for n in xrange(num):
        x_n = x
        y_n = y
        x = x_n + h
        y = y_n + h * (x_n - y_n**2)
        yield (x,y)

# incorrect
def func2(num):
    x, y = (1, 0)
    h = 0.1
    for n in xrange(num):
        x = x + h
        y = y + h * (x - y**2)
        yield (x,y)