Exercise 8

Primality test

Write a function that determines whether a given number is a prime number. Remember, a prime number is a (natural) number greater than 1 that is only divisible (with zero remainder) by the number 1, and itself. The first few prime numbers are 2,3,5,7,11,13,17,19,23,29, …

For now you don't have to implement a fancy algorithm for testing primeness (e.g. Sieve of Eratosthenes). For now, it's ok to implement a brute force method.

Hint: you will probably want to use the modulo operator to test whether the remainder is zero after dividing a number n by another number m. In Python the modulo operator is (n % m). In MATLAB/Octave, modulo is achieved using a function mod(n, m). In R the modulo operator is (n %% m) and in C the modulo operator looks like this: (n % m).

So for example we can test whether the number 5 is prime by testing whether (5 % m) equals 0 for m=2,3,4.


Paul Gribble | fall 2014
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