let plus (a:int8) (b:int8) = let (a1,a2,a3,a4,a5,a6,a7,a8) = a in let (b1,b2,b3,b4,b5,b6,b7,b8) = b in (a1+b1,a2+b2,a3+b3,a4+b4,a5+b5,a6+b6,a7+b7,a8+b8)