Interface example in Go

interface_ex.go

package main

import (
  "fmt"
  "math"
)

type Shaper interface {
  SurfaceArea() float64
  Volume() float64
}

type Cube struct {
  side float64
}

func (c Cube) SurfaceArea() float64 {
  return 6 * math.Pow(c.side, 2)
}

func (c Cube) Volume() float64 {
  return math.Pow(c.side, 3)
}

type Sphere struct {
  radius float64
}

func (s Sphere) SurfaceArea() float64 {
  return 4 * math.Pi * math.Pow(s.radius, 2)
}

func (s Sphere) Volume() float64 {
  return (4/3) * math.Pi * math.Pow(s.radius, 3)
}

func main() {
  cube   := Cube{side : 10}
  sphere := Sphere{radius : 10}
  shapes := [...]Shaper{cube, sphere}

  for i, _ := range shapes {
    fmt.Println("Shape #", i) 
    fmt.Printf("\tSurfaceArea : %g\n", shapes[i].SurfaceArea())
    fmt.Printf("\tVolume : %g\n", shapes[i].Volume())
  }
}