如何理解 its lifetime begind with the evaluation of e 的句子

Question

int main(){
  int v = 0;
  int const& rf = v;
}

判断表达式int const& rf = v;是否为核心常量表达式，需要经过这些引号：

an id-expression that refers to a variable or data member of reference type unless the reference has a preceding initialization and either:

• it is initialized with a constant expression or
• its lifetime began within the evaluation of e;

当计算表达式int const& rf = v;时，引用类型的表达式rf将是evaluted.For这个id-expression，它有一个前置初始化，但是v不是一个常量expression.Does rf的生命周期开始于int const& rf = v;的求值范围内，我只是不知道如何理解within。我只发现关于引用的生命周期规则是这里：

The lifetime of a reference begins when its initialization is complete. The lifetime of a reference ends as if it were a scalar object.

那么，这是its lifetime began within the evaluation of e;的情况吗，如果不是，这里的关键字within怎么理解？

Answer 1

beginning of that series of statements是：

An expression e is a core constant expression unless the evaluation of e, following the rules of the abstract machine, would evaluate one of the following expressions:

int const& rf = v; 是声明，不是表达式。因此，询问它是否是一个核心常量表达式是没有意义的。你可以问 v 哪里是核心常量表达式。你可以问一下 rf 的一些 usage 是否是一个核心常量表达式。

但是你不能问一个声明是否是核心常量表达式。

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至于怎么读"within"，你就当普通英文读吧。 e 是一个表达式，上面引用的部分讲了它的求值。 "Within its evaulation" 将是其评估期间发生的事情的顺序。