c++ - `>>>` 如何在 C++0x 中进行词法分析？

Question

>>> 的词法是 >>>。但是如果第一个 > 关闭模板参数列表会发生什么，结果应该等同于 >> > 还是 >>>？

在下面的代码中确实很重要:

template<class T> struct X { };

void operator >>(const X<int>&, int) { }

int main() {
    *new X<int>>> 1;
}

Answer 1

FDIS 的文本说

Similarly, the first non-nested >> is treated as two consecutive but distinct > tokens

它不能解除标记和 relex。所以这将是一个 >> >。请注意，C++ 实现的输入首先被转换为预处理标记，然后这些标记被转换为 C++ 标记。因此，首先您的输入是 C++ 标记 >>>，然后 C++ 解析器将这些标记更改为 >> >。

Each preprocessing token is converted into a token. (2.7). The resulting tokens are syntactically and semantically analyzed and translated as a translation unit. [ Note: The process of analyzing and translating the tokens may occasionally result in one token being replaced by a sequence of other tokens (14.2). — end note ]

您不可能合并这两个尾随 >> 标记。