Programming Ruby 3rd

New topics -p118

• Hash new idiom: { cell: 'string', clarinet: 'woodwind'}
  
• require_relative
  
• be capable Comparable: def <=>(other)
  
• be capable Enumerable: def each
  
• unit test
  
• parameters to a block are always local to a block
  
• [1,2,3].each {|value; square| square} #square is local
  
• inject(:+)
  
• external iterator: [1,2,3].to_enum.next
  
• enumerator makes objects enumerable
  
• enumerator stops loop
  
• -> { puts 'hello'}, -> arg, *ary, &block { |e| ... }
  
• 3 + 4.im
  
• string encoding
  
• Song = Struct.new(:title, :name, :length); Song.new('hello', 'John', 3.14)