VB课件VB7章节幻灯片.PPTVIP

* 练习1 Dim a As Integer, b As Integer 模块级变量 Private Sub Form_click() Dim x As Integer, y As Integer a = 5: b = 3 x = x + a: y = y + b Print fun1(x, y) Print fun1(x, y) End Sub Private Function fun1(m As Integer, n As Integer) As Integer Static k As Integer 静态变量 Dim a As Integer, b As Integer 同名的过程级变量 a = a + m: b = b - n m=m+1：n=n-1 k = k + a + b fun1 = k End Function 写程序运行结果： * 7.7 程序示例 例 7-5 ★ 例 7-7 ★ 例 7-8 ★ 例 7-9 ★ 例 7-14 * 分析： 若用穷举法则涉及到的循环次数是三个数的乘积，循环次数可能很大。 可利用以下算法完成： 1、编写求两个数的最小公倍数的函数LCM； 2、调用LCM求出任意两个数的最小公倍数，然后再次调用LCM，求出前次计算结果与第三个数的最小公倍数 注：实现时使用函数的嵌套调用。 例7-5 求三个正整数的最小公倍数(P152) * Private Sub Command1_Click() Dim A As Integer, B As Integer Dim L As Integer, C As Integer A = Text1 B = Text2 C = Text3 L = LCM(LCM(A, B), C) Text4 = L End Sub Private Function LCM(ByVal X As Integer, ByVal Y As Integer) As Integer Dim M As Long, Flg As Boolean Flg = False Do Until Flg M = M + X ‘从x开始逐倍增加，看是否是y的倍数 If M Mod Y = 0 Then Flg = True End If Loop LCM = M End Function * 例7-7 利用级数法编程求反正弦函数值（P155） [分析]：求解这一类累加和的题目，关键是两点：一是通项的表示，二是求解的精度，即当通项小于等于给定的误差值时，就停止累加。 [一般形式]如下两种： Do … t=… s=s+t n=n+1 Loop While teps Do … t=… if t =eps then exit do s=s+t n=n+1 Loop [形式二] [形式一] t是通项 * Private Function afun(ByVal x As Single, ByVal n As Integer) As Single Dim i As Integer, p As Single p = 1 For i = 1 To n p = p * (2 * i - 1) / (2 * i) Next i afun = p * x ^ (2 * n + 1) / (2 * n + 1)　 　 End Function n=1,2,3… ② ① 定义函数求通项 ① ② * Private Sub Command1_Click() Dim x As Single, n As Integer, eps As Single Dim s As Single, a As Single, temp As String temp = InputBox(“请输入一个绝对值小于等于1的数与允许误差:” , “求函数值” , “0.5, 1e-5“ ) temp = Trim(temp) ‘调用函数，删除前