As I know some is used for positive sentences and any for negative as well as question forms. But what about negative questions?
Why didn't you buy any cheese?
or
Why didn't you buy some cheese?
As I know some is used for positive sentences and any for negative as well as question forms. But what about negative questions?
Why didn't you buy any cheese?
or
Why didn't you buy some cheese?
What I would like to mention is based on standard English and I'm not talking about any other specific dialect.
We use some in questions when we expect or encourage the answer "yes" e.g. you see your friend rubbing his eye. You say,
What's wrong? Have you got something in your eye?
The same reasoning can be used for requests, or offers since we expect the person to give a "yes" answer as in
would you like some tea?
In other cases, we use any. So if I see this question in a grammar test, I'd go with 'any' not because it's a negative question but because it's a question that doesn't expect an affirmative answer.
We can have a negative question that expects a positive answer as in
Wouldn't you like some cookies?
some - an amount or number of something that is not stated or not known
any - even the smallest amount or number of
Insert these definitions into the sentences, we get:
Why didn't you buy any cheese?
Why didn't you buy even the smallest amount of cheese?
and
Why didn't you buy some cheese?
Why didn't you by an unstated amount of cheese?
The expanded some version makes sense, but the meaning of the any version is exactly right.