MMBJ Shanzhai Culture

1. R uby Talk – An Introduction to Premshree Pillai [email_address]

2. S cope of Talk What this talk is and what it isn’t Me, myself What is? Why use? How to? (a quick run through the syntax) Quick comparisons (with Perl and Python) Resources

3. P urpose What this talk is? Get you interested Get you started with Ruby What it isn’t? Not a tutorial

4. W ho am I? (or why should you listen to me) 21/male/single :) Technology consultant Freelance writer since 2001 Perl/Python/Ruby/REBOL hacker

5. H istory (Ruby’s, not mine) Created (in Japan) by Yukihiro Matsumoto, popularly called Matz Named as “Ruby” to reflect its Perl hertitage Released to the public in 1995 Licensed under GPL or Ruby terms

6. W hat the heck is Ruby? An object-oriented “scripting” language As powerful as Perl; simpler, better OO The simplicity of Python Follows the principle of “Least Surprise” – What You Expect Is What You Get

7. W here can you use Ruby? System (n/w, RegExps) Web programming (using CGI) Agents, crawlers DB programming (using DBI) GUI (Tk, RubyMagick)

8. G eneral Features High level language True OO (everything’s an object!) Interpreted Portable Low learning curve A quick scan thro’ the syntax

9. R unning Ruby From the command line: ruby file.rb Windows binary comes bundled with Scintilla

10. B asic stuff print 'Hello, world!' p 'Hello, world!' # prints with newline my_var = gets # get input

11. O perators + (addition) - (subtraction/negation) * (multiplication) / (division) % (modulus) ** (exponentiation)

12. O perators (contd.) == <=> (returns -1, 0 or 1) <, <=, >=, > =~ (matching) eql? (test of equality of type and values)

13. O perators (contd.) ++ and -- are not reserved operators Use += and +-

14. L ogical Operators and or not

15. T yping Dynamic typed Type checking at run-time Strong typed

16. B asic Data Types Integers and floats Strings Ranges Arrays Hashes

17. S trings my_str = 'whatever' my_str = "blah, blah" my_str.split(",")[0].split("")[2] * 3

18. R anges Inclusive range my_range = 1 .. 3 my_range = 'abc' .. 'abf' Non-inclusive range my_range = 1 … 5 my_range = 'abc' … 'abf'

19. A rrays my_array = [1, 2, 3] Common methods: my_array.length my_array << 4 my_array[0], etc.

20. H ashes my_hash = { 'desc' => {'color' => 'blue',}, 1 => [1, 2, 3] } print my_hash['desc']['color'] will return blue

21. H ashes (contd.) Common methods: my_hash.keys my_hash.values

22. D ata Type Conversion Converting to an Array: var_data_type .to_a Converting to an String: var_data_type .to_s More (guess!): var_data_type .to_i var_data_type .to_f

23. E verything's an Object Methods can be applied to data directly – not just on variables holding data Example: 5.to_s will return "5"

24. C ode Blocks Code blocks may use braces ( { } ) or do/end

25. C ode Blocks (contd.) Example def my_print(what) print what end You cannot use braces for function blocks

26. I f Statement if expression code block elsif ( expression ) code block else code block end

27. W hile Statement while expression code block end Example: count = 1 while count < 10 print count count += 1 end

28. F or Loop for variable_name in range code block end Example: for count in 0..2 print count end

29. I terators array_or_range = value array_or_range.each { |x| print x } Example: my_range = 1..5 my_range.each { |x| print x }

30. F unctions Functions begin with the keyword def def function_name ( [args] ) code block end Example: def print_name(name='Ruby') print name end

31. O O Ruby Classes are containers for static data members and functions Declared using the class keyword. All class names should begin with a capital letter Constructor declared using the initialize keyword Class variables precede with an “ @ ” Objects created using the new method

32. E xample class class My_class def initialize(arg1, arg2) @arg1 = arg1 @arg2 = arg1 end def print_arg1() print @arg1 end def print_foo() print " I Love Ruby! " end private def print_arg2() print @arg2 end end my_object = My_class.new(2, 3) my_object.print_arg1 my_object.print_arg2 # will cause an exception

33. I nheritance class Derived_class < My_class def initialize() @arg = "I Love Ruby!" end def print_arg() print @arg end end my_object = Derived_class.new my_object.print_foo

34. N otes on OO Ruby Access specifiers: public , protected , private Multiple inheritance not possible

35. R uby modules require 'net/http' superclass subclass

36. A dvanced topics Regular expressions Network programming MT programming GUI programming (using Tk) Web programming

37. N ow what? What you can do now? Get your hands dirty with Ruby Write simple Ruby programs What you have to do? Explore Ruby modules Find a problem, and Ruby it!

38. P erl compared to Ruby Complicated OO Cryptic code (Ruby is often called “A Better Perl”) PS: Don’t kill me!

39. P ython compared to Ruby Incomplete OO Instance variables require self. var No class method No true GC (uses ref counting) Not suitable for one-liners PS: Don’t kill me!

40. R esources Ruby Home Page http://www.ruby-lang.org/en/ Programming Ruby http://www.rubycentral.com/book/ RubyGarden http:// www.rubygarden.org /ruby Ruby Application Archive (RAA) http://raa.ruby-lang.org/

41. R esources (contd.) RubyForge http://rubyforge.org/ ruby-talk http://blade.nagaokaut.ac.jp/ruby/ruby-talk/index.shtml

42. If God did OOP, he’d probably do it in Python; He’s now considering switching to Ruby!

43. Thank you! Questions?

MMBJ Shanzhai Culture

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