This is a Ruby gem to investigate prime numbers. The PrimeNumberInvestigator class has one method prime_sifting which will find all the prime numbers up to a given number, and aother called nth_prime that will find a quantity of prime numbers (for example, the first 5 primes are 2, 3, 5, 7, 11.)
The first version was written by myself and Christian Danielsen while we were in school at Epicodus. It was an exercise in practicing Test Driven Development by writing tests to lead us through the problem using RSpec.
More recently, for practice I expanded on the tests, converted it to a class with methods instead of two separate functions, then I bundled it up as a gem and published it to rubygems.org.
- You need Ruby for this. Here are the installation instructions, and an easy installer for Windows
- You also need rspec to run the included Behavior Driven Development tests. Run this from the command line:
gem install rspec. If you get permissions errors on a Mac you can runsudo gem install rspec. - Clone or download this project and in your command line, change directory into the top level of the project folder.
- Run the tests with the command
rspec.
- Install the gem:
gem install prime_number_investigator(again, usesudo gem install prime_number_investigatorif you have permissions errors) - To try it out, let's use the ruby shell. From the command line type:
irb - Then, we require the gem and make a new instance of the PrimeNumberInvestigator class.
require 'prime_number_investigator'
@prime_playground = PrimeNumberInvestigator.new
- To print out all the prime numbers up to 10, run the following method:
@prime_playground.prime_sifting(10)
=> [2, 3, 5, 7]
- To print out the first 10 prime numbers (instead of primes less than a value of 10), run this method:
@prime_playground.nth_prime(10)
=> [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
- Ruby
- RSpec
- Command line
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