c++中<?=是什么操作？

Question

在翻COCI的题解代码的时候发现的，在g++上编译不过，但网上有成功编译的例子。
这是什么操作?
附图：

Answer 1

https://stackoverflow.com/q/5...

It's a GCC extension that was removed in GCC version 4.2 and later.

It's removed from g++ and should be replaced with max (or min for <?=)