Procedure Main()
   Local k
   For k := 0 to 20
      ? "A(", k, ", 1, -1, -1, 1, 0) =", A(k, 1, -1, -1, 1, 0)
   Next
Return
 
Static Function A(k, x1, x2, x3, x4, x5)
   Local ARetVal
   Local B := {|| --k, ARetVal := A(k, B, x1, x2, x3, x4) }
   If k <= 0
      ARetVal := Evaluate(x4) + Evaluate(x5)
   Else
      B:Eval()
   Endif
Return ARetVal
 
Static Function Evaluate(x)
   Local xVal
   If ValType(x) == "B"
      xVal := x:Eval()
   Else
      xVal := x
   Endif
Return xVal