SCRIPTING IN RUBY By Amber Bennett “Ruby is simple in appearance, but is very complex inside, just like our human body.” --Yukihiro Matsumoto

HISTORY  Created by Yukihiro Matsumoto  Initial release in 1995  Matsumoto desired a scripting language with object-oriented support Photo Credit: "Yukihiro Matsumoto EuRuKo 2011" by Mathias Meyer - Licensed under Creative Commons Attribution-Share Alike 2.0 via Wikimedia Commons -

NAMES, BINDINGS, AND SCOPES  Variable names can start with numbers, letters, and any combination of the two  They must start with a letter or an underscore  Variable names are descriptive  Case sensitivity:  Class names must be capitalized  Variable names are begun with lowercase letters

 Class variables  Exist in the scope of a class  Instance variables  Unique to a given instance of a class  Constants  Do not change throughout execution of a program  Can be reassigned, but interpreter will give a warning

DATA TYPES  Dynamically typed  Class variables start with  Instance variables start  Constants begin with a capital letter  String type  Number type  Symbols  Arrays and Hashes  Abstract Data Types  Provided through classes in Ruby

STRINGS: THE DIFFERENCE BETWEEN SINGLE AND DOUBLE QUOTES Double QuotesSingle Quotes  The code sample: “The time is #{Time.now}”  Prints out: The time is :26:  The code sample: ‘The time is #{Time.now};  Prints out: The time is \#{Time.now}

SYMBOLS 1. # p039xysymbol.rb 2. know_ruby = :yes 3. if know_ruby == :yes 4. puts 'You are a Rubyist' 5. else 6. puts 'Start learning Ruby' 7. end Source:

ARRAYS AND HASHES  Common among other languages  0 indexed  Arrays are defined by []  Hashes are defined by curly braces in the format: hash_name = { :key1 => “value1”, :key2 => “value2” }

EXPRESSIONS AND ASSIGNMENT STATEMENTS  Operators  [] []=Assignment  * / % + **Arithmetic  Comparison .. …Range  & ^ |AND, XOR, regular OR (bitwise)  || && not or andLogical operators  Ternary operator:  expression ? value_if_true : value_if_false

STATEMENT-LEVEL CONTROL STRUCTURES  If-statements  Then, else, end  Case Expressions  Blocks 1. if sum == 0 then 2. if count == 0 then 3. result = 0 4. end 5. else 6. result = 1 7. end

CASE EXPRESSIONS

OBJECT-ORIENTED SUPPORT  Matsumoto created Ruby with object-oriented support in mind  A lot of functionality when dealing with files  Matsumoto “wanted a scripting language that was more powerful than Perl, and more object-oriented than Python.” Video!

CONCURRENCY AND EXCEPTION AND EVENT HANDLING  Logical concurrency  Global Interpreter Lock (GIL)  Exceptions can be caught using “rescue”

SOURCES  Code samples taken from (unless otherwise specified): 