Fall 2012 -- Ruby 1.9
--Short introduction to Ruby:
References:

• Learn to Program
• Chapter 0: Instuctions for SciTE editor and getting started
• In the "tool pull down menu" in SciTE you can select the syntax checker
  
• The Ruby Programming Language by  David Flanagan, Yukihiro Matsumoto

• Beginning Ruby: From Novice to Professional by Peter Cooper
• CHAPTER 1 Let’s Get It Started: Installing Ruby
• Introduction to Ruby
• Programming Ruby: The Pragmatic Programmer 3nd edition
  
• Little Book of Ruby

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Getting started:
Interactive scripts:

• Using your favor editor create a script and save it in a file with an extension of *.rb
• Using irb (Interactive Ruby Enviornment)
• open irb
• at prompt type

   load 'filename.rb' 

• Dir is a useful class. e.g.
• irb(main):003:0> Dir.pwd
  => "/home/eileen/Desktop/DOCUMENT/Courses/471/HW/1SOL"
  
• irb(main):012:0> Dir.glob("*")
  => ["hw1.py", "hw1_1.c", "a.out", "hw1.rb"]
  
• irb(main):017:0> Dir.chdir("1SOL")
  => 0
  

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Some important language features:

1. Multi-paradigm language
1. concurrent and object-oriented (class-based) are all supported
2. dynamically typed 
1. -- no declaration of variables
2. -- type "lives" with objects, not names
3. reference model - like smalltalk
4. line breaks are significant and taken as the end of a statement; a semicolon may be equivalently used
5. "end" terminates all blocks
6. indentation is not significant
7. "#" begins a comment until the end of line
8. && -- logical  and operator,   != logical Not equal operator
9. elsif can be used for "optional parts"

if n < 5 then
    return 10
elsif n < 20 then
    return 100
else
    return 1000

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Example code:
fib.rb

# Recursive definition of  the nth fibonacci number
module FibEx

    def fib (n)
      if (n < 2) then
        return 1
      else 
        return fib(n-1) + fib(n-2)
      end #End of "if/else"
    end #End of "function/method"
 
    def fibi (n)
        a = 1
        b = 1
        s = 1
       while (s < n)
         s += 1
         t = a + b
         a = b
         b = t
       end #End while
       return b
    end #End of fibi

  
    def fibf (n)
       a = 1
       b = 1
       for i in 2 .. n    # i assumes the values 2 to n
          t = a + b
          a = b
          b = t
        end #End of for
        return b
    end #End of fibf

    def fibl(n)
      a, b = 0, 1
      n.times do  #Even numbers are objects
        a, b = b, a+b
      end
      return a
      end  
     
end #End of Module

# To use methods in IRB we need to include this module
include FibEx
# prints out the results after running in SciTE with "GO" or after loading in irb or running the script in Ruby shell.
puts fib(8)
puts fibf(8)
puts fibl(8)