Const Max_rn = 20
  

  Const Anz_ln = 25
  

  Const Pi = 3.1415926435  'PI
  

  

  Dim Axiom As String  '公理
  

  Dim a(Anz_ln) As String '被替换字符
  

  Dim x(Anz_ln) As String '替换字符串
  

  Dim Ke_en As String '生成字符串
  

  Dim Ke_lt As String '生成字符串
  

  Dim abc(Anz_ln) As String '每次替换的字符串
  

  

  Dim Delta As Single '生长角度
  

  Dim xPos(Max_rn) As Single '节点x坐标
  

  Dim yPos(Max_rn) As Single '节点y坐标
  

  Dim Delt(Max_rn) As Single '节点方向角
  

  

  Dim Kl_er As Integer '字符串中字符的位置
  

  Dim n As Integer '字符串替换次数
  

  Dim i As Long
  

  Dim j As Integer
  

  

  '替换减少
  

  Private Sub Command2_Click()
  

  

  Picture1.Cls
  

  n = n - 1
  

  If n < 1 Then n = 1
  

  Ke_en = abc(n - 1)
  

  Text1.Text = Ke_en
  

  Call lsystem
  

  If n = 1 Then Ke_en = Axiom
  

  

  End Sub
  

  

  '退出
  

  Private Sub Command3_Click()
  

  End
  

  End Sub
  

  

  '字符串初始信息
  

  Private Sub Form_Load()
  

  

  Axiom = "F"
  

  a(0) = "F": x(0) = "F[-F+F]F[-F]F"
  

  

  Delta = 90
  

  Ke_en = Axiom
  

  n = 1
  

  

  End Sub
  

  

  '字符串替换过程，替换增加
  

  Private Sub Command1_Click()
  

  

  Ke_lt = Ke_en
  

  Ke_en = ""
  

  

  For i = 1 To Len(Ke_lt)
  

  

  For j = 0 To Anz_ln
  

  If a(j) = Mid(Ke_lt, i, 1) Then
  

  Ke_en = Ke_en & x(j)
  

  GoTo 1
  

  End If
  

  Next j
  

  

  Ke_en = Ke_en & Mid(Ke_lt, i, 1)
  

  

  1 Next i
  

  

  abc(n) = Ke_en
  

  Text1.Text = Ke_en
  

  Open "F:\fortran\antisnow_str.txt" For Output As #1
  

  Print #1, Text1.Text
  

  Close #1
  

  Picture1.Cls
  

  Call lsystem
  

  n = n + 1
  

  

  End Sub
  

  

  '字符串中字符的作用
  

  Private Sub lsystem()
  

  

  xPos(0) = 0
  

  yPos(0) = 0
  

  Delt(0) = 0
  

  Open "f:\fortran\antisnow_axis.txt" For Output As 2
  

  For i = 1 To Len(Ke_en)
  

  

  Select Case Mid(Ke_en, i, 1)
  

  

  Case "["
  

  Kl_er = Kl_er + 1
  

  xPos(Kl_er) = xPos(Kl_er - 1)
  

  yPos(Kl_er) = yPos(Kl_er - 1)
  

  Delt(Kl_er) = Delt(Kl_er - 1)
  

  

  Case "]"
  

  Kl_er = Kl_er - 1
  

  

  Case "+"
  

  Delt(Kl_er) = Delt(Kl_er) + Delta * Pi / 180
  

  

  Case "-"
  

  Delt(Kl_er) = Delt(Kl_er) - Delta * Pi / 180
  

  

  Case "F"
  

  

  Picture1.PSet (3000 + xPos(Kl_er), 8000 - yPos(Kl_er)), RGB(0, 0, 0)
  

  xPos(Kl_er) = xPos(Kl_er) + Cos(Delt(Kl_er)) * 100
  

  yPos(Kl_er) = yPos(Kl_er) - Sin(Delt(Kl_er)) * 100
  

  Picture1.Line -(3000 + xPos(Kl_er), 8000 - yPos(Kl_er)), RGB(0, 0, 0)
  

  Print #2, xPos(Kl_er) / 100; "        "; yPos(Kl_er) / 100
  

  End Select
  

  Next i
  

  Close
  

  End Sub