Programming Ruby 3 - New topics

• RSpec: write rspec first, then implement code
  
• Organize project: top/ ./bin ./lib/top ./test
  
• Use setup.rb for distributing project
  
• RubyGems: open rdoc for library: open $gemdoc/builder/.../rdoc/index.html
  
• Encoding: # encoding: utf-8/ over 7bit characters assume the source file encoding
  
• Input Output Encoding: File.open("filename", "r:iso-8859-1:utf-8:")
  
• irb: load "your ruby file with classes or methods" : you use the classes in irb session. also can edit the file after loaded.
  
• irb: use tab completion alot
  
• irb: use irb in irb to make a subsession: jobs, fg 0, kill 1
  
• irb: use irb with specific class: irb "wombat"
  
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• Constant: Constant can define from the outside.
  
• Module: module_function: makes instance method module method also.
  
• Exception: rescue modifier: ["1","2.3",/pattern/].map {|v| Integer(v) rescue Float(v) rescue String(v)}
  
• Exception: retry can be used in rescue clause.
  
• methods(false): just show methods in the object; exclude superclasses'
  
• Duck typing: if you need check types: use obj#respond_to?
  
• type conversion: method coersion: 1.coerce(2.3) -> [2.3,1.0];define coerce method in your class correctly, you get arithmetic func with numbers.
  
• metaprogramming:module:ruby makes anonymous super class for a class, in which module is mixed in.
  
• metaprogramming:extend: when use extend to a obj, the module is included to an anonymous class of the obj.
  
• metaprogramming:extend: when use extend in a class, the module method become its class method. that means extend makes singleton method