“与"运算符是什么意思?在一个类和一个变量之间是什么意思? [英] What does "ampersand operator" mean between a class and a variable?

问题描述

我看到了下面的代码，非常困惑:

I saw the following code in plumed and am quite confused:

void ActionAtomistic::makeWhole() {
for(unsigned j=0; j<positions.size()-1; ++j) {
    const Vector & first (positions[j]);
    Vector & second (positions[j+1]);
    second=first+pbcDistance(first,second);
  }
}

谁能告诉我什么是&"用于这里吗?我用Google搜索类和变量之间的C ++连字符"，但没有找到答案.

Could anyone tell me what "&" is used for here? I googled "c++ ampersand between class and variable" but did not find the answer.

已更新:我知道引用是什么，但认为Vector和&"之间不应有任何空格.谢谢大家的澄清.

Updated: I know what reference is but thought there should not be any space between Vector and "&". Thank you guys for clarifying that.

推荐答案

这意味着 first 是引用(在本例中为 const 引用)指向类型为 Vector 的对象，而不是类型为 Vector 的对象.

This means that first is a reference (in this case, a const reference) to an object of type Vector, rather than an object of type Vector.

在此处中了解更多有关引用的信息.

Read more about references here.

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