General Purpose Language General Purpose Language Ruby Ruby Kit Chan Kit Chan COMP3351 COMP3351 Programming Languages Programming Languages November 9, 2007 November 9, 2007 Outline Outline  Reference Reference  Introduction Introduction  Ruby is Ruby is  Features Features  Array Array  Loop Loop  Ruby v.s. Java Ruby v.s. Java  Duck Typing Duck Typing  Dynamic Typing Dynamic Typing  Type Tag Checking Type Tag Checking  Functional Programming Functional Programming Reference Reference  Wikipedia Wikipedia http://en.wikipedia.org/wiki/Ruby_(programming_language) http://en.wikipedia.org/wiki/Ruby_(programming_language) http://en.wikipedia.org/wiki/Comparison_of_programming_languages http://en.wikipedia.org/wiki/Comparison_of_programming_languages  Ruby Official Website Ruby Official Website http://www.ruby-lang.org/en/ http://www.ruby-lang.org/en/  Learning Ruby Learning Ruby http://www.math.umd.edu/~dcarrera/ruby/0.3/index.html http://www.math.umd.edu/~dcarrera/ruby/0.3/index.html  Duck Typing Duck Typing http://rubylearning.com/satishtalim/duck_typing.html http://rubylearning.com/satishtalim/duck_typing.html Introduction Introduction  Developed by Yukihiro “Matz” Matsumoto, in Feb, 1993 Developed by Yukihiro “Matz” Matsumoto, in Feb, 1993  First released in 1995 First released in 1995  1.8.6 Ruby 1.9 developed March, 2007 1.8.6 Ruby 1.9 developed March, 2007  Named Named  As a gemstone because of a joke with in Matsumoto’s friends alluding to As a gemstone because of a joke with in Matsumoto’s friends alluding to Perl’s name Perl’s name Ruby is Ruby is  Cross-platform Operating System Cross-platform Operating System  Combines syntax by Combines syntax by  Perl Perl  Smalltalk-like OO features Smalltalk-like OO features  Shares features with Shares features with  Lisp Lisp  Python Python  Dylan Dylan  CLU CLU Ruby is Ruby is  The interpreted scripting language for The interpreted scripting language for  Quick Quick  Easy OO programming Easy OO programming  designed for programmer productivity designed for programmer productivity  Straight-forward Straight-forward  principle of least surprise (POLS) principle of least surprise (POLS)  Ruby behaves in a way that minimizing confusion for Ruby behaves in a way that minimizing confusion for experienced users experienced users  After you learn Ruby very well After you learn Ruby very well Ruby is Ruby is  Obedient Obedient >> 'Hello World' >> 'Hello World' => "Hello World” => "Hello World”  >> 'blink ' * 4 >> 'blink ' * 4  => "blink blink blink blink " => "blink blink blink blink "  Your Calculator Your Calculator >> 1+1 >> 1+1 => 2 => 2 Or Or >> 2**2**2 >> 2**2**2 => 16 => 16 Features Features  Object-oriented Object-oriented  Four levels of variables: Four levels of variables:  Global Global $var $var  Instance Instance @var @var  Local Local [a-z] or _; var [a-z] or _; var  Constant Constant [A-Z] [A-Z]  Exception handling Exception handling  Iterators & closures Iterators & closures  Automatic garbage collecting Automatic garbage collecting  Highly portable Highly portable http://tryruby.hobix.com/ http://tryruby.hobix.com/ Array Array  >> numbers = ["zero", "one", "two", "three", "four"] >> numbers = ["zero", "one", "two", "three", "four"]  => ["zero", "one", "two", "three", "four"] => ["zero", "one", "two", "three", "four"]  => Array => Array  >> numbers[0] >> numbers[0]  => "zero" => "zero" What arrays do? What arrays do?  >> numbers[0].class >> numbers[0].class  => String => String  >> numbers[0].upcase >> numbers[0].upcase  => "ZERO" => "ZERO"  >> numbers[0].reverse >> numbers[0].reverse  => "orez" => "orez" Loop Loop  If I knew Ruby when I was in grade school……. If I knew Ruby when I was in grade school…….  >> 100.times do >> 100.times do  puts "I won't do that again" puts "I won't do that again"  end end  I won't do that again I won't do that again       => 100 => 100  My life was going to be much easier My life was going to be much easier [...]... startTime)/1000; System.out.println("It took " + difference + " seconds"); } } Ruby v.s Java  Performance   Ruby: 24 – 26 seconds Java: 1 – 2 seconds Language Paradigm Type Checking Java Imperative Static Object-oriented Generic Ruby Imperative Object-oriented Functional Aspect-oriented Dynamic (duck) Duck Typing  Ruby interpreter is happy to treat it as it were a duck   If an object walks... Paddle paddle paddle => nil => nil I am walking walking => nil irb(main):022:0> Dynamic Typing  Ruby, the data types are not wholly declared on variable  Data associated with variables are not known until the time of execution  Advantage:  flexibility  Less work for the programmer Type Tag Checking  Ruby is dynamically typed   it supports run-time dispatch on tagged data Takes place at run-time... to execute the 3rd line,  Checks the type tags integer and string  If the operation + (addition) is not defined  An error is signaled Why Ruby?  High productivity for programmers   Web Developments   Execution time is not the main concern Projects like Ruby on Rails Functional Programming  Paradigm treats computation as the evaluation of mathematical functions  Emphasize  on application of.. .Ruby v.s Java- Syntax                   begin_time = Time.now.to_i i=0 100.times do i += 1 j=0 10.times do j += 1 k=0 100.times do k += 1 puts i.to_s + " + " + j.to_s + " + " + k.to_s . General Purpose Language General Purpose Language Ruby Ruby Kit Chan Kit Chan COMP3351 COMP3351 Programming Languages Programming Languages November 9, 2007 November. Reference Reference  Wikipedia Wikipedia http://en.wikipedia.org/wiki /Ruby_ (programming _language) http://en.wikipedia.org/wiki /Ruby_ (programming _language) http://en.wikipedia.org/wiki/Comparison_of_programming_languages http://en.wikipedia.org/wiki/Comparison_of_programming_languages  Ruby Official Website Ruby Official Website http://www .ruby- lang.org/en/ http://www .ruby- lang.org/en/  Learning Ruby Learning Ruby http://www.math.umd.edu/~dcarrera /ruby/ 0.3/index.html http://www.math.umd.edu/~dcarrera /ruby/ 0.3/index.html  Duck. seconds");  }  } Ruby v.s. Java Ruby v.s. Java  Performance Performance  Ruby: 24 – 26 seconds Ruby: 24 – 26 seconds  Java: 1 – 2 seconds Java: 1 – 2 seconds Language Language Paradigm Paradigm Type