frmfactorial.frm

Visual Basic 6 大学教程的代码

VERSION 5.00
Begin VB.Form frmFactorial 
   Caption         =   "Fig. 6.26: Factorial Program"
   ClientHeight    =   4845
   ClientLeft      =   3120
   ClientTop       =   1155
   ClientWidth     =   4425
   LinkTopic       =   "Form1"
   PaletteMode     =   1  'UseZOrder
   ScaleHeight     =   4845
   ScaleWidth      =   4425
   Begin VB.TextBox txtInput 
      BeginProperty Font 
         Name            =   "MS Sans Serif"
         Size            =   12
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   3105
      TabIndex        =   4
      Top             =   210
      Width           =   1215
   End
   Begin VB.ListBox lstValues 
      BeginProperty Font 
         Name            =   "Courier"
         Size            =   12
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   2700
      Left            =   120
      MultiSelect     =   1  'Simple
      TabIndex        =   2
      Top             =   1935
      Width           =   4185
   End
   Begin VB.CommandButton cmdCalculate 
      Caption         =   "Calculate"
      BeginProperty Font 
         Name            =   "MS Sans Serif"
         Size            =   12
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   615
      Left            =   1365
      TabIndex        =   0
      Top             =   855
      Width           =   1695
   End
   Begin VB.Label lblValues 
      Caption         =   "Factorial Values:"
      BeginProperty Font 
         Name            =   "MS Sans Serif"
         Size            =   12
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   255
      Left            =   135
      TabIndex        =   3
      Top             =   1620
      Width           =   3855
   End
   Begin VB.Label lblInput 
      Caption         =   "Enter an integer:"
      BeginProperty Font 
         Name            =   "MS Sans Serif"
         Size            =   12
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   375
      Left            =   120
      TabIndex        =   1
      Top             =   240
      Width           =   2055
   End
End
Attribute VB_Name = "frmFactorial"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
' Fig. 6.26
' Program recursively calculates factorials
Option Explicit      ' General declaration

Private Sub cmdCalculate_Click()
   Dim x As Integer, n As Integer
   
   Call lstValues.Clear     ' Clear lstValues
   n = txtInput.Text        ' Get input
   
   ' Calculate factorial(s)
   For x = 0 To n
      lstValues.AddItem Format$(x, "@@") & "! = " & _
                        Factorial((x))  ' Call-by-value
   Next x
   
End Sub

Private Function Factorial(ByVal y As Double) As Double
   
   If y <= 1 Then
      Factorial = 1                     ' Base case
   Else
      Factorial = y * Factorial(y - 1)  ' Recursive step
   End If
   
End Function