update lesson8

Author: jincheng9

workspace/lesson8/func_advance.go

@@ -0,0 +1,40 @@
+package main
+
+import "fmt"
+import "math"
+
+// define function getSquareRoot1
+func getSquareRoot1(x float64) float64 {
+	return math.Sqrt(x)
+}
+
+// deffine a function variable
+var getSquareRoot2 = func(x float64) float64 {
+	return math.Sqrt(x)
+}
+
+// define a function type
+type callback_func func(int) int
+
+
+func calValue(x int, cb callback_func) int{
+	fmt.Println("[func|calValue]")
+	return cb(x)
+}
+
+func realFunc(x int) int {
+	fmt.Println("[func|realFunc]callback function")
+	return x*x
+}
+
+func main() {
+	num := 100.00
+	result1 := getSquareRoot1(num)
+	result2 := getSquareRoot2(num)
+	fmt.Println("result1=", result1)
+	fmt.Println("result2=", result2)
+
+	value := 81
+	result3 := calValue(value, realFunc)
+	fmt.Println("result3=", result3)
+}

workspace/lesson8/method.go

@@ -0,0 +1,38 @@
+package main
+
+import "fmt"
+
+type Circle struct {
+	radius float64
+}
+
+func (c Circle) getArea() float64 {
+	return 3.14 * c.radius * c.radius
+}
+
+func (c Circle) changeRadius(radius float64) {
+	c.radius = radius
+}
+
+func (c *Circle) changeRadius2(radius float64) {
+	c.radius = radius
+}
+
+func (c Circle) addRadius(x float64) float64{
+	return c.radius + x
+}
+
+func main() {
+	var c Circle
+	c.radius = 10
+	fmt.Println("radius=", c.radius, "area=", c.getArea())		
+
+	c.changeRadius(20)
+	fmt.Println("radius=", c.radius, "area=", c.getArea())		
+
+	c.changeRadius2(20)
+	fmt.Println("radius=", c.radius, "area=", c.getArea())	
+
+	result := c.addRadius(3.6)
+	fmt.Println("radius=", c.radius, "result=", result)
+}

workspace/lesson8/readme.md

@@ -145,6 +145,110 @@
 
 * 函数高级用法
 
-  * 函数作为另一个函数的实参：函数定义后可以作为另一个函数的实参
+  * 函数作为其它函数的实参：函数定义后可以作为另一个函数的实参，比如下例的函数realFunc作为函数calValue的实参
+
+    ```go
+    package main
+    
+    import "fmt"
+    import "math"
+    
+    // define function getSquareRoot1
+    func getSquareRoot1(x float64) float64 {
+    	return math.Sqrt(x)
+    }
+    
+    // deffine a function variable
+    var getSquareRoot2 = func(x float64) float64 {
+    	return math.Sqrt(x)
+    }
+    
+    // define a function type
+    type callback_func func(int) int
+    
+    
+    // function calValue accepts a function variable cb as its second argument
+    func calValue(x int, cb callback_func) int{
+    	fmt.Println("[func|calValue]")
+    	return cb(x)
+    }
+    
+    func realFunc(x int) int {
+    	fmt.Println("[func|realFunc]callback function")
+    	return x*x
+    }
+    
+    func main() {
+    	num := 100.00
+    	result1 := getSquareRoot1(num)
+    	result2 := getSquareRoot2(num)
+    	fmt.Println("result1=", result1)
+    	fmt.Println("result2=", result2)
+    
+    	value := 81
+    	result3 := calValue(value, realFunc) // use function realFunc as argument of calValue
+    	fmt.Println("result3=", result3)
+    }
+    ```
+
   * 闭包
-  * 方法
+
+  * 方法：类似C++ class里的方法，只是go没有class的概念。
+
+    * 定义：function_name是类型var_data_type的实例的方法
+
+      ```go
+      func (var_name var_data_type) function_name([parameter_list])[return type] {
+        do sth
+      }
+      ```
+
+      
+
+    * 示例：getArea是Circle的方法，Circle的实例可以调用该方法
+
+    ```go
+    package main
+    
+    import "fmt"
+    
+    type Circle struct {
+    	radius float64
+    }
+    
+    func (c Circle) getArea() float64 {
+    	return 3.14 * c.radius * c.radius
+    }
+    
+    /*
+    changeRadius和changeRadius2的区别是后者可以改变变量c的成员radius的值，前者不能改变
+    */
+    func (c Circle) changeRadius(radius float64) {
+    	c.radius = radius
+    }
+    
+    func (c *Circle) changeRadius2(radius float64) {
+    	c.radius = radius
+    }
+    
+    func (c Circle) addRadius(x float64) float64{
+    	return c.radius + x
+    }
+    
+    func main() {
+    	var c Circle
+    	c.radius = 10
+    	fmt.Println("radius=", c.radius, "area=", c.getArea())	//10, 314
+    
+    	c.changeRadius(20)
+    	fmt.Println("radius=", c.radius, "area=", c.getArea())	//10, 314	
+    
+    	c.changeRadius2(20)
+    	fmt.Println("radius=", c.radius, "area=", c.getArea())	//20, 1256
+    
+    	result := c.addRadius(3.6)
+    	fmt.Println("radius=", c.radius, "result=", result) // 20, 23.6
+    }
+    ```
+
+