Question

Dim n, front, rear As Integer
Dim x As Integer
Dim arr() As Integer

Public Function init()
  n = InputBox("Enter size :")
  ReDim arr(n) As Integer
  front = 0
  rear = -1
End Function

Public Function insert(x As Integer)
  If rear = n-1 Then
    MsgBox "queue FULL !!!", vbOKOnly, "QUEUE"
  Else
    rear = rear + 1
    arr(rear) = x
    MsgBox x, vbOKOnly, "INSERTED"
  End If
End Function

Public Function delete() As Integer
  If rear + 1 = front Then
    MsgBox "queue Empty !!!", vbOKOnly, "QUEUE"
  Else
    x = arr(front)
    front = front + 1
    Return x
  End If
End Function

Private Sub inser_Click()
  If rear < n Then
    x = InputBox("Enter element :")
    Call insert(x)
  Else
    MsgBox "queue FULL !!!", vbOKOnly, "QUEUE"
  End If
End Sub

Private Sub del_Click()
  x = delete()
  MsgBox x, vbOKOnly, "DELETED"
End Sub

Private Sub Exit_Click()
  End
End Sub

Private Sub Form_Load()
  Call init
End Sub

This is my code in VB6.
I am getting an error in insert function in Return x line where it says “complier error Expected : End of statement”

One more error is that whenever I try to delete the elements of the queue it shows “0 DELETED”

Answer 1

You’re attempting to return a value from a Function by using a Return statement, which is not valid in VB6. In VB6 you return a Function’s value by assigning the return value to the Function’s name.

So for your delete Function you would write this:

Public Function delete() As Integer
    If rear + 1 = front Then
        MsgBox "queue Empty !!!", vbOKOnly, "QUEUE"
    Else
        x = arr(front)
        front = front + 1
        delete = x    ' <-- returning x here.
    End If
End Function

Take a look at your other Functions, they’re not explictly returning values at all.

It might help to take a look at this, which provides an overview of how Subs and Functions work in VB6.