递归作用域复习和实例.pptVIP

练一练:1 Private Function f (ByVal n As Integer) As Long If n = 0 Or n = 1 Then f = 1 Else f = f(n-2)+ f (n - 1) End If Print f End Function 主调程序中：x＝f(3)窗体打印几行，每行结果是什么？ 递归真题实例 Option Explicit Private Sub Form_Click() Dim a As Integer a = 2: Call sub1(a) End Sub Private Sub sub1(x As Integer) x = x * 2 + 1 If x 10 Then Call sub1(x) End If x = x * 2 + 1: Print x End Sub 7.6 变量的作用域 变量的作用域 “变量的作用域”指的是变量的“有效范围”或“作用范围”。只有在该范围内，变量才有意义。 根据说明变量的语句及说明位置，变量可分为： 过程级变量（局部变量） 模块级变量 全局变量 Option Explicit Dim TestString As String Private Sub Form_ Activate () Debug.Print 在Form_Activate 事件过程中; TestString Call ShowTestString End Sub Private Sub Form_Load() TestString = 测试变量作用域 End Sub Private Sub ShowTestString() Debug.Print 在过程ShowTestString 中; TestString End Sub 例子 教材P147 全局变量的缺点：容易造成错误 Option Explicit Public X As Integer, Y As Integer, Z As Integer Private Sub Form_Activate() Conflict_X Debug.Print X,Y 和 Z 是, X, Y, Z End Sub Private Sub Form_Load() X = 10 : Y = 20 : Z = 35 End Sub Private Sub Conflict_X() Dim X As Integer X = 135 Debug.Print X,Y 和 Z 是, X, Y, Z End Sub 同名变量 Private Sub Form_Click() Dim a As Integer, b As Integer a = 1: b = 2 Call proc1(a, b) Print a, b End Sub Private Sub proc1(c As Integer, d As Integer) Dim a As Integer, b As Integer c = a + b: d = a - b Print c, d End Sub Dim a As Integer, b As Integer Private Sub Form_Click() a = 1: b = 2 Call proc1(a, b) Print a, b End Sub Private Sub proc1(c As Integer, d As Integer) c = a + b: d = a - b Print c, d End Sub Dim x As Integer, y As Integer Private Sub Command1_Click() Dim a As Integer, b As Integer a = 5 b = 3 Call sub1(a, b) Print a, b Print x, y End Sub Option Explicit Private Sub Command1_Click() Dim K As Integer K = 5 Call Static_Variable(K) Debug.Print 第一次调用：K =; K K = 5 Call Static_Variable(K) Debug.Print 第二次调用：K =;