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Comprehensive Ruby Programming

You're reading from   Comprehensive Ruby Programming From beginner to confident programmer

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Product type Paperback
Published in Jun 2017
Publisher Packt
ISBN-13 9781787280649
Length 330 pages
Edition 1st Edition
Languages
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Author (1):
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Jordan Hudgens Jordan Hudgens
Author Profile Icon Jordan Hudgens
Jordan Hudgens
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Table of Contents (20) Chapters Close

Preface 1. Introduction to the Ruby Programming Language 2. Ruby Variables FREE CHAPTER 3. Ruby Strings 4. Working with Numbers in Ruby 5. Ruby Methods 6. Ruby Iterators and Loops 7. Ruby Collections 8. Ruby Conditionals 9. Object-Oriented Programming in Ruby 10. Working with the Filesystem in Ruby 11. Error Handling in Ruby 12. Regular Expressions in Ruby 13. Searching with grep in Ruby 14. Ruby Gems 15. Ruby Metaprogramming 16. Ruby Web Frameworks 17. Working with APIs in Ruby 18. Ruby Algorithms 19. Machine Learning

Implementing a prime number counting algorithm

In this section, we are going to create an algorithm that will find all the prime numbers between zero to 2 million. Sound exciting? In traditional programming languages, this algorithm would need hundreds of lines of code, but in Ruby, we're going to see how to implement this efficiently.

To start, let's get access to the prime library, and to do this, use this code:

require 'prime' 

Next, store the prime numbers in an array with this code:

prime_array = Prime.take_while{ |p| p <2_000_000 } 

In this code, we created a variable called prime_array. In this variable, we store all the prime numbers up to 2 million.

Ruby ignores underscores with integers, which is how we were able to represent the integer of 2 million with this syntax: 2_000_000. This is helpful when it comes to writing large numbers since we can...
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