More than
once, when
somebody has
learnt that I
study Linguistics, they've recited this
witty little
tale:
Once upon a time, a teacher was telling her class that, while two negatives make a positive, two positives never make a negative.
And a little voice from the back of the room pipes up: "yeah, yeah".
This is wrong on so many levels. First of all, two negatives don't make a positive, often they just make a really strong negative. Furthermore, your average Linguistics student cares little, if at all, for grammar Nazi-ism. That's kind of the point of the subject. But also, and back to the topic of this writeup, "yeah, yeah" doesn't, in fact, mean no, or anything approaching no. It means "I probably disagree, but I definitely don't care enough to argue". Pretty much like whatever in that regard.
No, if you're looking for two positives that make a negative, what you want is "aye, right".