Ifndef
如果未定义
🗣️ 情景例句
I have a client in the garment business, on Seventh Avenue.
我有个客户在Seventh Avenue从事成衣生意。
I can only try to justify what I did.
我唯有坚持自己所做的事是正确的。
Yes, it's empty. Look!
是的，你看，是空的。