Function A($)
Dim $s,$f
$a = 0
If $ > 3&$ < 7&($^)+($ < 4) = 16
   While $
      $a = Right($,1)
      $s = $s+$f*(-9*(4 < $a)+$a)+$a
      $ = Left($,-1)
      $f = 1-$f
      If $s mod 10 $a = 0
EndFunction