为什么复制构造函数参数是常量? [英] Why is the copy-constructor argument const?

问题描述

 Vector(const Vector& other) // Copy constructor 
 {
    x = other.x;
    y = other.y;

为什么参数是常量?

推荐答案

你得到的答案提到确保 ctor 不能改变正在复制的内容——他们是对的，把 const 放在那里确实有效果.

You've gotten answers that mention ensuring that the ctor can't change what's being copied -- and they're right, putting the const there does have that effect.

然而，更重要的是临时对象不能绑定到非常量引用.复制构造函数必须引用 const 对象才能复制临时对象.

More important, however, is that a temporary object cannot bind to a non-const reference. The copy ctor must take a reference to a const object to be able to make copies of temporary objects.

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