execute (BVal s1 : BVal s2 : ss) (And     : xs) = execute (s'     : ss) xs where s' = BVal (s1 && s2)
execute (BVal s1 : BVal s2 : ss) (And     : xs) = execute (s'     : ss) xs where s' = BVal (s1 && s2)
execute (BVal s1 : BVal s2 : ss) (And     : xs) = execute (s'     : ss) xs where s' = BVal (s1 && s2)