Comment by zerd

The general problem is much harder than that. You need to understand double negatives, when do they invert the meaning and when do they underline it? "Ain't nobody got time for that" can be interpreted in different ways. And then you need to understand sarcasm. Then a later sentence can invert the meaning of an earlier one. E.g. "This is the best movie ever. Said no one". Using word-pairs as features is easy, but there are just so many exceptions and ambiguity it's a very difficult problem to solve well.