Harlin wrote:

What good is the modulus operator? What would I ever need it for?

* A quick way of testing whether an integer is even and odd
* For that matter, a quick way of testing whether a the variable is a
factor of any other arbitrary number.
* In some programs (a weight control program I worked on comes to mind)
it's necessary to get a remainder so that you can get the results of a
leftover evenly divisible number.

Also, it's a good way to ensure that some number is in a specified range, and "wraps around" to the beginning if it goes out of that range. For a quick & cheesy example, let's say we want to count time for music:


import time
def beats = ['one', 'two', 'three', 'four']

n = 0
while True:
    print beats[n]
    n = (n+1) % 4
    time.sleep(0.5)

By using '% 4', I ensure that n is always in the interval [0...4) (including 0 but not including 4).

Modulus is useful for all sorts of periodic behavior.

Jeff Shannon
Technician/Programmer
Credit International

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