C++核心准则C.160:定义运算符主要是为了模仿习惯用法

C.160: Define operators primarily to mimic conventional usage

C.160:定义运算符主要是为了模仿习惯用法

Reason(原因)

Minimize surprises.

让程序看起来更自然。

Example(示例)

class X {
public:
    // ...
    X& operator=(const X&); // member function defining assignment
    friend bool operator==(const X&, const X&); // == needs access to representation
                                                // after a = b we have a == b
    // ...
};

Here, the conventional semantics is maintained: Copies compare equal.

这里，赋值，相等比较的习惯语义得以保持。

Example, bad(反面示例)

X operator+(X a, X b) { return a.v - b.v; }   // bad: makes + subtract

Note(注意）

Nonmember operators should be either friends or defined in the same namespace as their operands. Binary operators should treat their operands equivalently.

非成员运算符应该要么是友元函数，要么和操作对象定义在一起。二进制运算符应该同等对待操作对象。

Enforcement(实施建议)

Possibly impossible.

可能无法做到。

原文链接：

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c160-define-operators-primarily-to-mimic-conventional-usage

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