irb(main):001:0> def h
irb(main):002:1> puts "Hello"
irb(main):003:1> end
=> nil
irb(main):004:0> h
Hello
=> nil
irb(main):005:0> h()
Hello
=> nil
irb(main):006:0> def h(name)
irb(main):007:1> puts "Hello #{name}!"
irb(main):008:1> end
=> nil
irb(main):009:0> h("yang")
Hello yang!
=> nil
irb(main):010:0> def h(name = "world")
irb(main):011:1> puts "Hello #{name.capitalize}"
irb(main):012:1> end
=> nil
irb(main):013:0> h "yang"
Hello Yang
=> nil
irb(main):014:0> h
Hello World
=> nil
irb(main):015:0>
