interfaces.go

package main

import (
        "fmt"
)

type Square struct {
        side float64
}

func (s Square) area() float64 {
        return s.side * s.side
}

type Circle struct {
        radius float64
}

func (c Circle) area() float64 {
        return 2 * 3.1416 * c.radius * c.radius
}

type Shape interface {
        area() float64
}

func info(s Shape) {
        fmt.Println(s)
        fmt.Println(s.area())
}

func main() {
        s := Square{10}
        c := Circle{10}
        info(s)
        info(c)
}