function a($x)
    dim $v, $b, $
    while $x
        $ = left($x,1)
        $x = right($x,~)
        if $>!
            $v = ($=X)*10 + $ + ($="/")*(10-$v)
            $a = $a + ($b+($b<2))*$v
            $b = ($b>1) + instr("/X",$)*($x<!)
endfunction

function a($x)
    dim $v, $b, $
    while $x
        $ = left($x,1)
        $x = right($x,~)
        if $>!
            $v = ($=X)*10 + $ + ($="/")*(10-$v)
            $a = $a + ($b+($b<2))*$v
            $b = instr("/X",$)*($x<!) + $b/2
endfunction

pseudo:
$a = $a + 30 - overly complicated calculations

function a($x)
   dim $v, $b, $
   while $x
       $ = left($x,1)
       $x = right($x,~)
       if $>!
           $v = ($=X^$="/")*10 + $ - ($="/")*$v
           $a = $a + ($b+($b<2))*$v
           $b = instr("/X",$)*($x<!) + $b/2
endfunction

function a($)
   dim $v, $b, $x, $c
   while $
       $x = left($,1)
       $ = right($,~)
       if $x>!
           $c = instr("/X",$x)
           $v = ($c>)*10 + $x - ($c=1)*$v
           $a = $a + ($b+($b<2))*$v
           $b = $c*($<!) + $b/2
endfunction