4.22.5 abstraction

 1package main
 2
 3import "fmt"
 4
 5// Shape is an interface that defines the basic methods for a shape.
 6type Shape interface {
 7	Area() float64
 8	Perimeter() float64
 9}
10
11// Rectangle is a struct that implements the Shape interface.
12type Rectangle struct {
13	width, height float64
14}
15
16// Area returns the area of the rectangle.
17func (r Rectangle) Area() float64 {
18	return r.width * r.height
19}
20
21// Perimeter returns the perimeter of the rectangle.
22func (r Rectangle) Perimeter() float64 {
23	return 2 * (r.width + r.height)
24}
25
26// Circle is a struct that implements the Shape interface.
27type Circle struct {
28	radius float64
29}
30
31// Area returns the area of the circle.
32func (c Circle) Area() float64 {
33	return 3.14 * c.radius * c.radius
34}
35
36// Perimeter returns the perimeter of the circle.
37func (c Circle) Perimeter() float64 {
38	return 2 * 3.14 * c.radius
39}
40
41func main() {
42	// Create a rectangle and a circle.
43	r := Rectangle{width: 10, height: 20}
44	c := Circle{radius: 5}
45
46	// Declare a slice of Shape interfaces.
47	shapes := []Shape{r, c}
48
49	// Iterate over the shapes and print their area and perimeter.
50	for _, shape := range shapes {
51		fmt.Println("Area:", shape.Area())
52		fmt.Println("Perimeter:", shape.Perimeter())
53		fmt.Println("")
54	}
55}

1$ go run main.go
2Area: 200
3Perimeter: 60
4
5Area: 78.5
6Perimeter: 31.400000000000002