code:

---

function BWTDecode($s, $o)
   dim $i,$j,$m
   $m = len($s)
   dim $[$m]
   for $i = 1 to $m
      $j=$i
      while substr($s,$i,1) < substr($s,$[$j-1],1)
         $[$j] = $[$j-1]
         $j=$j-1
      loop
      $[$j]=$i
   next
   for $j=1 to $m
      $BWTDecode = $BWTDecode + substr($s,$o+1,1)
      $o=$[$o+1]-1
   next
endfunction

---