' FB 1.05.0
#Macro Declare_Swap(T)
Sub Swap_##T(ByRef t1 As T, ByRef t2 As T)
  Dim temp As T = t2
  t2 = t1
  t1 = temp
End Sub
#EndMacro

Dim As Integer i, j
i = 1 : j = 2

Declare_Swap(Integer) ' expands the macro
Swap_Integer(i, j)
Print i, j

Dim As String s, t
s = "Hello" : t = "World"

Declare_Swap(String)
Swap_String(s, t)
Print s, t

Print
Print "Press any key to exit"
Sleep