Add name field and modify output for better understanding

Author: amirhasanpour

content/chapter 4/oop/4.23.5-abstraction.md

@@ -30,7 +30,9 @@ type Shape interface {
 
 // Rectangle is a struct that implements the Shape interface.
 type Rectangle struct {
-	width, height float64
+	name   string
+	width  float64
+	height float64
 }
 
 // Area returns the area of the rectangle.
@@ -45,6 +47,7 @@ func (r Rectangle) Perimeter() float64 {
 
 // Circle is a struct that implements the Shape interface.
 type Circle struct {
+	name   string
 	radius float64
 }
 
@@ -60,16 +63,16 @@ func (c Circle) Perimeter() float64 {
 
 func main() {
 	// Create a rectangle and a circle.
-	r := Rectangle{width: 10, height: 20}
-	c := Circle{radius: 5}
+	r := Rectangle{name: "Rectangle", width: 10, height: 20}
+	c := Circle{name: "Circle", radius: 5}
 
 	// Declare a slice of Shape interfaces.
 	shapes := []Shape{r, c}
 
 	// Iterate over the shapes and print their area and perimeter.
 	for _, shape := range shapes {
-		fmt.Println("Area:", shape.Area())
-		fmt.Println("Perimeter:", shape.Perimeter())
+		fmt.Printf("Area of shape %v is: %.2f\n", shape, shape.Area())
+		fmt.Printf("Perimeter of shape %v is: %.2f\n", shape, shape.Perimeter())
 		fmt.Println("")
 	}
 }