c++ - Stream insertion combined with postfix operators

Question

Say I was reading data in which the indexing starts at 1. I want my indexing to be 0 based.

Why is it not acceptable to use postfix increment/decrement operators after a stream insertion operator?

int a;
std::cin >> a--;

Answer 1

后自增运算符的结果是一个临时对象，即使仅在表达式末尾严格应用自增。要读取一个值，需要一个左值，但临时对象不是左值：它们必然会消失。请注意，您还将将该值读入临时文件，在a.

Answer 2

operator>>有一个需要 a 的重载int&。的结果a--是右值，您不能将非常量引用绑定到右值。