It is an introduction to Ruby Programming Language.

1. Ruby
Programming Language
Introduction
28 Jun 2015
Kwangshin Oh
kwangshin@gmail.com
http://kwangshin.pe.kr

2. Seven Languages in Seven Weeks
A Pragmatic
Guide to
Learning
Programming
Languages
By Bruce A. Tate

3. Why New Programming Language?
“Learning a new programming language will show you
new ways of thinking, and new approaches to problem solving
that will help you be a better programmer in any language.”
- Pragmatic Bookshelf
“Ultimately, programming is about understanding, and
understanding is about ideas. So, exposure to new ideas is essential
to a deeper understanding of what programming is all about.”
- Foreword By Joe Armstrong, creator of Erlang

4. Agenda
 Ruby is…
 History & Why?
 With a Spoonful of Sugar
 So, Ruby is…
 Ruby: Interpreted Language
 Ruby: Interpreted Language – Example
 Compare: Compiled Language - Java
 Ruby: Object-Oriented Language
 Ruby: Pure Object-Oriented Language
 Ruby: Dynamically Typed Language
 What is Duck Typing?
 Ruby: Duck Typing Code Example
 Download & Installation
 Ruby Code
 Reference

5. Ruby is…
 Programming Language!
Dynamic
Open Source
 Focus on…
Simplicity
Productivity
 Has an elegant syntax
Natural to read
Easy to write
Image Source: Ruby Programming Language

6. History & Why?
 Ruby’s Creator
Yukihiro “Matz” Matsumoto
 Created in about 1993
 Motivation
The primary motivation was to amuse himself!
Just a hobby at the beginning
New object-oriented language that combines
characteristics from Lisp, Smalltalk and Perl
To enhance programmers’ productivity
“Ruby is simple in appearance, but is very complex inside, just like our human body.”
- Matz, speaking on the Ruby-Talk mailing list, May 12th, 2000.
Image Source: Ruby Everywhere

7. With a Spoonful of Sugar
 Ruby with more syntactic sugar
Makes code easier to read and write
 Focus on the efficiency of the
programmers
“A spoonful of sugar makes the medicine go down.”
Mary Poppins
Image Source: Disney Wiki – A Spoonful of Sugar

8. So, Ruby is…
 Interpreted Language
Ruby code is executed by an interpreter
 Object-Oriented Language
Encapsulation
Inheritance
Polymorphism
 Dynamically Typed Language
Types are bound at execution time
Image Source: Skillcrush - Ruby

9. Interactive
Console
Ruby File
(*.rb)
Ruby: Interpreted Language
Image Source: http://www.iconsdb.com, http://dryicons.com and http://findicons.com
Ruby
Interpreter

10. Interactive
Console
Ruby File
(Ha.rb)
Ruby: Interpreted Language - Example
D:Ruby22bin>type Ha.rb
3.Times do
print “Ha “
end
D:Ruby22bin>ruby Ha.rb
Ha Ha Ha
D:Ruby22bin>
D:Ruby22bin>ruby
3.Times do
print “Ha “
end
^D
Ha Ha Ha
D:Ruby22bin>

11. Compare: Compiled Language - Java
Java Source File
(*.java)
Java
Compiler
Java Class File
(*.class)
JRE
(Java Runtime Environment)

12. Ruby: Object-Oriented Language
 Encapsulation
[State & Behavior] : Packaged together
 Inheritance
[Class Tree] : Object types are organized
 Polymorphism
[Many Forms]
: Objects can be shown
Image Source: What Is an Object?
Image Source: What Is Inheritance?Image Source: Object-Oriented Concepts

13. Ruby: Pure Object-Oriented Language
 Ruby Programming Language
Everything is an object!
 Compare: Java Programming Language
Primitive types (int, char, ……) are not objects!
D:Ruby22bin>irb
irb(main):001:0> 4
=> 4
irb(main):002:0> 4.class
=> Fixnum
irb(main):003:0> 4 + 4
=> 8
irb(main):004:0> 4.methods
=> [:to_s, :inspect, :-
@, :+, ∙∙∙∙∙∙, :__id__]
irb(main):005:0>

14. Ruby: Dynamically Typed Language
Types are bound
at execution time
Flexibility
Execution Safety
 Types are bound
at compile time
 Flexibility
 Execution Safety
Dynamically Typed
Statically Typed
Java

15. What is Duck Typing?
Quacks
like a duck
Swims
like a duck
Walks
like a duck
Call it
a duck
“When I see a bird that walks like a duck and
swims like a duck and quacks like a duck,
I call that bird a duck.” - James Whitcomb Riley
Image Source: https://www.iconfinder.com and http://www.vectors4all.net/

16. Ruby: Duck Typing Code Example
D:Ruby22bin>irb
irb(main):001:0> i = 0
=> 0
irb(main):002:0> a = ['100', 100.0]
=> ["100", 100.0]
irb(main):003:0> while i < 2
irb(main):004:1> puts a[i].to_i
irb(main):005:1> i = i + 1
irb(main):006:1> end
100
100
=> nil
irb(main):007:0>
We consider this to_i method as quack!
Duck typing doesn’t care
what the underlying type might be
(whether string or float).
string
float

17. Download & Installation
 Current Stable Version
 Ruby 2.2.2 (As of 28 Jun 2015)
 Windows
 RubyInstaller - http://rubyinstaller.org/downloads/
 OS X
 Homebrew - http://brew.sh/
 Debian GNU/Linux and Ubuntu
 apt – command : $ sudo apt-get install ruby-full
 CentOS, Fedora, and RHEL
 yum – command :$ sudo yum install ruby

18. Ruby: Sample Code
D:Ruby22bin>ruby
properties = ['object oriented', 'duck typed', 'productive', 'fun']
properties.each {|property| puts "Ruby is #{property}."}
^D
Ruby is object oriented.
Ruby is duck typed.
Ruby is productive.
Ruby is fun.
D:Ruby22bin>

19. Ruby Code: Hello World!
D:Ruby22bin>irb
irb(main):001:0> puts 'Hello World!'
Hello World!
=> nil
irb(main):002:0> language = 'Ruby'
=> "Ruby"
irb(main):003:0> puts "Hello, #{language}"
Hello, Ruby
=> nil
irb(main):004:0> language = 'my Ruby'
=> "my Ruby"
irb(main):005:0> puts "Hello, #{language}"
Hello, my Ruby
=> nil
irb(main):006:0>
Ruby’s Interactive Console
<One Quote String>
Interpreted Literally
<Two Quotes String>
String Evaluation

20. Ruby Code: Comparison Operators
D:Ruby22bin>irb
irb(main):001:0> x = 4
=> 4
irb(main):002:0> x < 5
=> true
irb(main):003:0> x > 4
=> false
irb(main):004:0> false.class
=> FalseClass
irb(main):005:0> true.class
=> TrueClass
irb(main):006:0> puts 'X value is equal to 4.' if x == 4
X value is equal to 4.
=> nil
irb(main):007:0>
Everything is an object
in Ruby!

21. Ruby Code: Loops – until & while
D:Ruby22bin>irb
irb(main):001:0> x = 5
=> 5
irb(main):002:0> x = x - 1 until x == 1
=> nil
irb(main):003:0> x
=> 1
irb(main):004:0> while x < 5
irb(main):005:1> x = x + 1
irb(main):006:1> puts x
irb(main):007:1> end
2
3
4
5
=> nil

22. Ruby Code: Expressions - true & false
D:Ruby22bin>irb
irb(main):001:0> puts '1 is true in Ruby' if 1
1 is true in Ruby
=> nil
irb(main):002:0> puts 'String is true in Ruby' if 'Kwangshin Oh'
(irb):2: warning: string literal in condition
String is true in Ruby
=> nil
irb(main):003:0> puts '0 is also true in Ruby' if 0
0 is also true in Ruby
=> nil
irb(main):004:0> puts 'The false is false in Ruby' if false
=> nil
irb(main):005:0> puts 'The nil is false in Ruby' if nil
=> nil
irb(main):006:0>
Everything
( but nil and false )
evaluate to true!

23. Reference
 Seven Languages in Seven Weeks: A Pragmatic Guide to Learning Programming Language
by Bruce A. Tate
 https://pragprog.com/book/btlang/seven-languages-in-seven-weeks
 Ruby Programming Language
 https://www.ruby-lang.org/
 Ruby-Talk mailing list, May 12th, 2000
 http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/2773
 Disney Wiki – A Spoonful of Sugar
 http://disney.wikia.com/wiki/A_Spoonful_of_Sugar
 Matzにっき (Matz Diary)
 http://www.rubyist.net/~matz/
 The Java™ Tutorials - Object-Oriented Programming Concepts
 https://docs.oracle.com/javase/tutorial/java/concepts/index.html
 Duck typing
 https://en.wikipedia.org/wiki/Duck_typing