cstack.cls

是一个VB类,相当于vbscript中的eval函数,是用堆栈实现

VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
END
Attribute VB_Name = "CStack"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = True
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = False
'CStack - Stack class for Visual Basic 5
'Copyright (c) 1995-97 SoftCircuits Programming (R)
'Redistributed by Permission.
'
'This is a generic stack class that can be used by any algorithm
'that uses a stack. Items are stored on the stack as variants. This
'allows storage of virtually any data type.
'
'This program may be distributed on the condition that it is
'distributed in full and unchanged, and that no fee is charged for
'such distribution with the exception of reasonable shipping and media
'charged. In addition, the code in this program may be incorporated
'into your own programs and the resulting programs may be distributed
'without payment of royalties.
'
'This example program was provided by:
' SoftCircuits Programming
' http://www.softcircuits.com
' P.O. Box 16262
' Irvine, CA 92623
Option Explicit

Private m_StackArray() As Variant
Private m_nStackSize As Integer
Private m_nCurrPos As Integer

'Granularity for growing stack
Private Const INC_SIZE = 10

'Read-only property returns the number of items on the stack
Public Property Get StackSize() As Integer
    StackSize = m_nCurrPos
End Property

'Pushes a value onto the stack.
'The stack is made bigger if required.
Public Sub Push(Value As Variant)
    m_nCurrPos = m_nCurrPos + 1
    If m_nCurrPos > m_nStackSize Then
        m_nStackSize = m_nStackSize + INC_SIZE
        ReDim Preserve m_StackArray(1 To m_nStackSize)
    End If
    m_StackArray(m_nCurrPos) = Value
End Sub

'Returns the value on the top of the stack and removes it
'from the stack. A run-time error is raised if the stack is empty.
Public Function Pop() As Variant
    If m_nCurrPos > 0 Then
        Pop = m_StackArray(m_nCurrPos)
        m_nCurrPos = m_nCurrPos - 1
    Else
        Err.Raise vbObjectError + 1011, , "Pop method invoked on empty stack"
    End If
End Function

'Returns the value on top of the stack without removing it
'from the stack. A run-time error is raised if the stack is empty.
Public Function GetPopValue() As Variant
    If m_nCurrPos > 0 Then
        GetPopValue = m_StackArray(m_nCurrPos)
    Else
        Err.Raise vbObjectError + 1012, , "GetPopValue method invoked on empty stack"
    End If
End Function

'Initialization routine
Private Sub Class_Initialize()
    m_nStackSize = 0
    m_nCurrPos = 0
End Sub