Ifndef
如果未定义
🗣️ 情景例句
All the Stewart men were big. Stewart
家的男人都很大。
The whole carton is packed with double straps, each corner of the carton consolidated with metal angles.
纸箱外加了两道箍，每个箱角都用金属角加固。
I opened the cupboard door and then stood in front of it petrified.
我打开柜门，站在柜门前一下惊呆了。