Implementing Eratosthenes Sieve

In this recipe, we will look at a prime number calculator called Eratosthenes Sieve. It is an old algorithm for finding prime numbers. The prime numbers are found by crossing out composite numbers. The sieve works as follows: 

1. Start with 2, a known prime. Strike out all the numbers that are multiples of 2.
2. Start with the next unmarked number, which will be the next prime (since it is not divided by any prime before). Repeat the procedure of marking all the multiples.
3. Repeat the procedure.

For more information, visit https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes.

Getting ready

Create a new project, eratosthenes, using the simple Stack template. Change into the project directory and build it:

      stack new eratosthenes simple
      stack build

How to do it...

1. Open src/Main.hs; we will add our prime number generator here.
2. We will start with 2 as the initial prime number and continue with only odd numbers; this will remove all the factors of 2.
3. We will assume that...