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 - http://www.flickr.com/photos/ipom/5862768190/. Licensed under Creative Commons Attribution-Share Alike 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Yukihiro_Matsumoto_EuRuKo_2011.jpg#mediaviewer/File:Yukihiro_Matsumoto_EuRuKo_2011.jpg

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 with @ 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 Quotes Single Quotes

The code sample: “The time is #{Time.now}”

Prints out:The time is 2014-05-23 07:26:12 +0000

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: http://rubylearning.com/satishtalim/ruby_symbols.html

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 and Logical 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): http://sandbox.mc.edu/~bennet/ruby/code/index.html