C++核心準則C.160:定義運算符主要是為了模仿習慣用法

C.160: Define operators primarily to mimic conventional usage

C.160:定義運算符主要是為了模仿習慣用法

Reason(原因)

Minimize surprises.

讓程序看起來更自然。

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.

這里，賦值，相等比較的習慣語義得以保持。

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.

非成員運算符應(yīng)該要么是友元函數(shù)，要么和操作對象定義在一起。二進制運算符應(yīng)該同等對待操作對象。

Enforcement(實施建議)

Possibly impossible.

可能無法做到。

原文鏈接：

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

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