# examples of generators
#
# Matt Bishop, ECS 36A, Winter 2019
#
# first, our version of range
myrange = (x for x in range(5))
print("call #1 to range(5) generator, next(myrange): ", next(myrange))
print("call #2 to range(5) generator, next(myrange): ", next(myrange))
print("call #3 to range(5) generator, next(myrange): ", next(myrange))
print("call #4 to range(5) generator, next(myrange): ", next(myrange))
print("call #5 to range(5) generator, next(myrange): ", next(myrange))
try:
    print("call #6 to range(5) generator, next(myrange): ", next(myrange))
except StopIteration:
    print("In call #6, we went too far, so got a StopIteration exception")

# now we use this to compute the sum of the first 100 numbers
print("The sum of the first 100 integers is", sum(x for x in range(101)))

# another version of range, as a full function
def genmyrange(n):
    for i in range(n):
        yield i

# and here's how we use it
for i in genmyrange(10):
    print(i)
print(genmyrange(10))

# and now our version of range without using range
def genmyrange2(n):
    # start here
    i = 0
    # loop until you put out the last number (n-1
    while i < n:
        # yield here normally returns None
        # you can use the send() method to have
        # yield return a different value, and
        # that value becomes the new value of
        # the counter
        value = (yield i)
        if value is not None:
            i = value
        else:
            i += 1

# and here's how we use it
print("-----")
for i in genmyrange2(10):
    print(i)