Option Explicit


'Note: can use "Exit Sub" or "Exit Function" to terminate process




Sub Main()

    Dim a As Integer, b As Integer, ret As Integer
    a = 1
    b = 2
    
    'call function with reference variable
    Call add(a, b, ret)
    Debug.Print "add sum = " & ret
    
    'call function by value
    ret = add2(a, b)
    Debug.Print "add2 sum = " & ret
    
    'call sub produce, reference variable
    Call minus(a, b, ret)
    Debug.Print "minus : " & ret
End Sub

'sub produce, reference variable
Sub minus(a As Integer, b As Integer, sum As Integer)
    sum = a - b
End Sub


'function with reference variable
Function add(a As Integer, b As Integer, sum As Integer) As Boolean
    sum = a + b
    add = True
End Function


'function by value
Function add2(ByVal a As Integer, ByVal b As Integer) As Integer
    add2 = a + b
End Function