III. Friday problems on while and for loops
 A. Another for loop example
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                     FOR YOU TO DO

Using a for loop, write a function product(lst), of
  type: list(number) -> number
 that returns the product of all the numbers in lst.
The following are examples:

    assert product([]) == 1
    assert product([2,3]) == 6
    assert product([1,2,3,4]) == 1 * 2 * 3 * 4
    assert product([10,5,1]) == 50
    assert product([3,2,2,3]) == 9 * 4
    assert product([10] + [3,2,2,3]) == 10*9*4










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 B. An example where continue may be used in a for loop
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                          FOR YOU TO DO

Using a for loop and continue, write a function
sumReciprocals(lst) of
   type: list(number) -> float
that returns the sum of the numbers 1/x for all
x in lst that are not zero.
The following are examples:

    from math import isclose
    assert isclose(sumReciprocals([]), 0.0)
    assert isclose(sumReciprocals([0]), 0.0)
    assert isclose(sumReciprocals([1,0]), 1.0)
    assert isclose(sumReciprocals([1,2,0]), 1/1 + 1/2)
    assert isclose(sumReciprocals([3,2,2,3]), 1/3 + 1/2 + 1/2 + 1/3)
    assert isclose(sumReciprocals([3,0,2,0,0,2,0,3,0]), 1/3 + 1/2 + 1/2 + 1/3)









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 C. An example with less direction
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                      FOR YOU TO DO

Without using the ** operator of Python or recusrion,
write a function exp(n, pow) of
  type: (int, int) -> int
where pow >= 0, so that the result is n**pow.

For example,

     assert exp(5,0) == 1
    assert exp(2,3) == 2*2*2
    assert exp(2,2) == 4
    assert exp(2,1) == 2
    assert exp(5,3) == 5*5*5
    assert exp(10,4) == 10*10*10*10
    assert exp(9,5) == 9*9*9*9*9
    assert (-3,3) == -3 * -3 * -3











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