Lesson 37. Capstone: Building a prime-number library

 

This capstone covers

  • Building a new project by using stack
  • Writing basic library functions for working with prime numbers
  • Using stack test and QuickCheck to check for bugs as you go
  • Refactoring code to fix errors
  • Adding new functions and tests to your project as you go

So far in this unit, you’ve focused on one problem: creating a program for working with palindromes. For this capstone, you’ll be reiterating over all the work you’ve done creating modules and learning about stack with a new problem. This time you’ll be working on creating a library to work with prime numbers. You’ll focus on three essential problems:

  • Listing out primes less than a specified number
  • Determining whether a given number is prime
  • Breaking a number into its prime factors

The first thing that you’ll need is a way to create a list of prime numbers. Here’s the type signature for that list:

primes :: [Int]

You’ll achieve this by using a prime sieve, which works by filtering out the prime numbers. In terms of types, this will require you to take an [Int] of possible primes and then return an [Int] of just primes. The function that will perform this work is sieve: 

sieve :: [Int] -> [Int]

37.1. Starting your new project

37.2. Modifying the default files

37.3. Writing your core library functions

37.4. Writing tests for your code

37.5. Adding code to factor numbers

Summary