Function query efficiency and optimization

Hi.

Assuming I have a function like:

CREATE FUNCTION f () RETURNS SETOF INTEGER LANGUAGE PLPgSQL AS
$$
BEGIN
RETURN QUERY SELECT * FROM t;
END;
$$;

And I call:

SELECT * FROM f LIMIT 10;

Is Postgres smart enough to ensure that the function won't do a full scan of the table and then discard all but ten results?

I'm trying to work out if i can structure things so that i can reuse most of the functions for different queries by progressively layering limits, offsets, etc.