Function A($)	
	$a = $^0 ;no need for long keywords like len()
	dim $i, $x, $b[$a-1],$s ;$l removed using $a instead. $s introduced as "swinger"
	
		;redim $b[$a-1] ;no need to redim if doing right in the start ;)
		for $i = $a-1 to 0 step -1
			$x = substr($,$i+1,1)
			if $s ;second for loop removed. using swinger swapper instead.
				$x = 2*$x
				$x = $x-9*($x>9)
			endif
			$b[$i] = $x
			$s=$s^1
		next

		$i = execute("$X="+join($b,'+'))

	$a = ($>3 & $<7 & $a=16-($<4) & $x mod 10=)*left($,1)
Endfunction