main.go

package main

import "somedwarf"
import "fmt"

type Sleepy struct {}

type IsHappy interface {
  Happy() bool
}

func (s Sleepy) Happy() bool {
  return true
}

func main() {
  g:=somedwarf.Grumpy{}
  s:=Sleepy{}
  PrintHappy(g)
  PrintHappy(s)
}

func PrintHappy(h IsHappy)  {
  if h.Happy() {
    fmt.Printf("dwarf is happy\n")
  } else {
    fmt.Printf("dwarf is sad\n")
  }
}