Function A($)
   Dim $l,$i,$b,$c,$x,$d
   $l = ($^);Len($)
   $d = Left($,1)
   ;If($d = 3 And $l = 15) Or ( $d > 3 And $d < 7 And $l = 16 )
   If($d = 3 & $l = 15) | ( $d > 3 & $d < 7 & $l = 16 ); use Bitwise Operators to do the same tasks as 'And' and 'Or'
      $x = 0
      For $i = $l-1 to 0 Step-1
         $b = SubStr($,$i+1,1)
         If($l-$i) mod 2 = 0
            $c = 2*$b
            ;$b = IIf($c > 9,0+Left($c,1)+Right($c,1),$c)
            $b = IIf($c > 9,$c / 10 + $c - 10,$c); use a calulator to see that Kix drops the decimal for $c
         EndIf
         $x = $x + $b
      Next
      $d = IIf($x mod 10,0,$d)
   Else
      $d = 0
   EndIf
   $A = $d
EndFunction