#!/usr/bin/env ruby
# This code comes from http://ruby-it.org/pages/Inizializzazione+Condizionale
# Check the page for copyright notice and explanations



 >> a=10
 => 10
 >> a= a || 20
 => 10
 >> b= b || 20
 => 20

 >> a ||= 20
 => 10
 >> b ||= 30
 => 20
 >> c ||= 40
 => 40
 >> [a,b,c]
 => [10, 20, 40]

 >> pippo
 NameError: undefined local variable or method `pippo' for main:Object
 >> if not defined? pippo
 >>  pippo=30
 >> end
 => 30
 >> pippo
 => 30

begin pippo rescue pippo = 30 end