yield statements in ruby

yield_demo.rb

def foo
  yield 1
  yield 2
  puts "* This code is inside #foo"
  yield 3
  puts "* This code is also inside #foo"
end

foo # Exception: no block given (yield) (LocalJumpError)
    #   from yield.rb:9

foo {|val| puts "> Value #{val} was passed into block"} #=>
    # > Value 1 was passed into block
    # > Value 2 was passed into block
    # * This code is inside #foo
    # > Value 3 was passed into block
    # * This code is also inside #foo