Go Golang - structs, methods, embedded types, interfaces example

Go Golang - structs, methods, embedded types, interfaces example

package main
 
import ("fmt"; "math")
 
// interfaces
type Shaper interface {
    area() float64
	perimeter() float64
}
 
// structs
type Circle struct {
    x, y, r float64
}
type Rectangle struct {
    x1, y1, x2, y2 float64
}
 
// methods
func (c *Circle) area() float64 {
    return math.Pi * c.r * c.r
}
func (c *Circle) perimeter() float64 {
	return math.Pi * 2 * c.r
}
func (r *Rectangle) area() float64 {
    l := distance(r.x1, r.y1, r.x1, r.y2)
    w := distance(r.x1, r.y1, r.x2, r.y1)
    return l * w
}
func (r *Rectangle) perimeter() float64 {
	return 2 * (r.x2 - r.x1) + 2* (r.y2 - r.y1)
}
 
// functions
func distance(x1, y1, x2, y2 float64) float64 {
	a := x2 - x1
	b := y2 - y1
    return math.Sqrt(a*a + b*b)
}
func totalArea(shapes ... Shaper) float64 {
    var area float64
    for _, s := range shapes {
        area += s.area()
    }
    return area
}
func totalPerimeter(shapes ... Shaper) float64 {
    var perimeter float64
    for _, s := range shapes {
        perimeter += s.perimeter()
    }
    return perimeter
}
 
func main() {
	c := Circle{0, 0, 5}
	r := Rectangle{0, 0, 10, 10}
	
	fmt.Println("Area of circle is",c.area())
	fmt.Println("Area of rectangle is",r.area())
	fmt.Println("Total area of shapes is",totalArea(&c, &r))
	
	fmt.Println("Perimeter of circle is",c.perimeter())
	fmt.Println("Perimeter of rectangle is",r.perimeter())
	fmt.Println("Total perimeter of shapes is",totalPerimeter(&c, &r))
}