add english version

en/code/src/apps/ch.2.5/attach_methods_to_struct/main.go

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+// Example code from Chapter 2.5
+// Attach method to struct.
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+type Rectangle struct {
+	width, height float64
+}
+
+type Circle struct {
+	radius float64
+}
+
+func (r Rectangle) area() float64 {
+	return r.width * r.height
+}
+
+func (c Circle) area() float64 {
+	return c.radius * c.radius * math.Pi
+}
+
+func main() {
+	r1 := Rectangle{12, 2}
+	r2 := Rectangle{9, 4}
+	c1 := Circle{10}
+	c2 := Circle{25}
+
+	fmt.Println("Area of r1 is: ", r1.area())
+	fmt.Println("Area of r2 is: ", r2.area())
+	fmt.Println("Area of c1 is: ", c1.area())
+	fmt.Println("Area of c2 is: ", c2.area())
+}

en/code/src/apps/ch.2.5/box_example/main.go

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+package main
+
+import "fmt"
+
+const (
+	WHITE = iota
+	BLACK
+	BLUE
+	RED
+	YELLOW
+)
+
+type Color byte
+
+type Box struct {
+	width, height, depth float64
+	color                Color
+}
+
+type BoxList []Box //a slice of boxes
+
+func (b Box) Volume() float64 {
+	return b.width * b.height * b.depth
+}
+
+func (b *Box) SetColor(c Color) {
+	b.color = c
+}
+
+func (bl BoxList) BiggestsColor() Color {
+	v := 0.00
+	k := Color(WHITE)
+	for _, b := range bl {
+		if b.Volume() > v {
+			v = b.Volume()
+			k = b.color
+		}
+	}
+	return k
+}
+
+func (bl BoxList) PaintItBlack() {
+	for i, _ := range bl {
+		bl[i].SetColor(BLACK)
+	}
+}
+
+func (c Color) String() string {
+	strings := []string{"WHITE", "BLACK", "BLUE", "RED", "YELLOW"}
+	return strings[c]
+}
+
+func main() {
+	boxes := BoxList{
+		Box{4, 4, 4, RED},
+		Box{10, 10, 1, YELLOW},
+		Box{1, 1, 20, BLACK},
+		Box{10, 10, 1, BLUE},
+		Box{10, 30, 1, WHITE},
+		Box{20, 20, 20, YELLOW},
+	}
+
+	fmt.Printf("We have %d boxes in our set\n", len(boxes))
+	fmt.Println("The volume of the first one is", boxes[0].Volume(), "cm³")
+	fmt.Println("The color of the last one is", boxes[len(boxes)-1].color.String())
+	fmt.Println("The biggest one is", boxes.BiggestsColor().String())
+
+	fmt.Println("Let's paint them all black")
+	boxes.PaintItBlack()
+	fmt.Println("The color of the second one is", boxes[1].color.String())
+
+	fmt.Println("Obviously, now, the biggest one is", boxes.BiggestsColor().String())
+}

en/code/src/apps/ch.2.5/embedded_method/main.go

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+package main
+import "fmt"
+
+type Human struct {
+    name string
+    age int
+    phone string
+}
+
+type Student struct {
+    Human // anonymous field
+    school string
+}
+
+type Employee struct {
+    Human 
+    company string
+}
+
+// define a method in Human
+func (h *Human) SayHi() {
+    fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
+}
+
+func main() {
+    mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
+    sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
+
+    mark.SayHi()
+    sam.SayHi()
+}

en/code/src/apps/ch.2.5/method_overload/main.go

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+package main
+
+import "fmt"
+
+type Human struct {
+	name  string
+	age   int
+	phone string
+}
+
+type Student struct {
+	Human
+	school string
+}
+
+type Employee struct {
+	Human
+	company string
+}
+
+func (h *Human) SayHi() {
+	fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
+}
+
+func (e *Employee) SayHi() {
+	fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,
+		e.company, e.phone) //Yes you can split into 2 lines here.
+}
+
+func main() {
+	mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
+	sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
+
+	mark.SayHi()
+	sam.SayHi()
+}

en/code/src/apps/ch.2.5/pass_struct_to_method/main.go

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+package main
+
+import "fmt"
+
+type Rectangle struct {
+	width, height float64
+}
+
+func area(r Rectangle) float64 {
+	return r.width * r.height
+}
+
+func main() {
+	r1 := Rectangle{12, 2}
+	r2 := Rectangle{9, 4}
+	fmt.Println("Area of r1 is: ", area(r1))
+	fmt.Println("Area of r2 is: ", area(r2))
+}