whileM' : (Monad m, Monad f, Alternative f) => (a -> Bool) -> m a -> m (f a)
whileM' p f = go
    where go = do
            x <- f
            if p x
                then do
                        xs <- go
                        pure (pure x <|> xs)
                else pure empty

whileM : Monad m => (a -> Bool) -> m a -> m (List a)
whileM = whileM'     

strcpy(to, from, count)
register char *to, *from;
register count;
{
    register n = (count + 7) / 8;
    if (!count) return;
    switch (count % 8) {
    case 0: do { *to = *from++;
    case 7:      *to = *from++;
    case 6:      *to = *from++;
    case 5:      *to = *from++;
    case 4:      *to = *from++;
    case 3:      *to = *from++;
    case 2:      *to = *from++;
    case 1:      *to = *from++;
               } while (--n > 0);
    }
}