I have a question about Japanese conditionals. Recently, I had a lesson on the use of ～ば、～と and ～たら. I found the distinctions between all of these rather confusing, especially in the following sentences:
(1) ゆきさんが【×来れば ×来ると 〇来たら】、パーティーを始めましょう。= When Yuki-san comes, (I/we) will start the party.
(2) 試験が【×終われば ×終わると 〇終わったら】遊びに行きたい。 = When the exam ends, I want to go have fun.
My teacher told me that in both cases, the use of ば is wrong, because in (1) it’s used to express intention and in (2), it’s used to express a wish. However, when I consulted my “Dictionary of Basic Japanese Grammar” I found the following statement: “(in S1ばS2) S2 can be a statement of the speaker’s volition or hope.” So who’s right here? Because I really don’t know now…