Minecraft comparator logic, described as programming logic

// Maintain (wires: rear, front)
$output = $rear;


// Compare (wires: rear, side(s), front)
if (($rear > $left) or ($rear > $right))
{
	$output = true;
} else {
	$output = false;
}

// Subtract (wires: rear, side(s), front. Mode 2(right-click on it to change))
if ($left > $right)
{
	$output = $rear - $left;
} else {
	$output = $rear - $right;
}