值得思考的问题下面的代码有没有区别？为什么？void code(){ int i = 0; i++; // i 的值作为返回值， i 自增 1 ++i; // i 自增 1， i 作为返回值}编程实验： 真的有区别吗？#include <iostream>using namespace std;int main(){ int i = 0; i++; ++i; return 0;}vc++ 2010 汇编 int i = 0;0127136E mov dword ptr [i],0 i++;01271375 mov eax,dword ptr [i] 01271378 add eax,1 0127137B mov dword ptr [i],eax ++i;0127137E mov eax,dword ptr [i] 01271381 add eax,1 01271384 mov dword ptr [i],eax g++ 汇编14 int i = 0;0804869d: movl $0x0,0x1c(%esp)16 i++;080486a5: addl $0x1,0x1c(%esp)18 ++i;080486aa: addl $0x1,0x1c(%esp)对于基础数据类型，在工程上没有任何区别。由于实例中没有使用返回值，经过编译器优化后，生成相同的汇编代码。意想不到的事实现代编译器产品会对代码进行优化优化使得最终的二进制程序更高效优化后的二进制程序失去了 C/C++ 的原生语义不可能从编译后的二进制程序完全还原 C/C++ 程序C/C++ 开发的软件无法完全反编译思考：++ 操作符可以重载吗？如何区分前置 ++ 和后置 ++？++ 操作符重载++ 操作符可以被重载全局函数和成员函数均可进行重载【推荐成员函数】重载前置 ++ 操作符不需要额外的参数重载后置 ++ 操作符需要一个 int 类型的占位参数编程实验： ++ 操作符的重载#include <iostream>using namespace std;class Test{private: int mValue;public: Test(int i) { mValue = i; } int value() { return mValue; } Test& operator ++ () { mValue = mValue + 1; return *this; } Test operator ++ (int) // 返回值而不是引用 { Test ret(mValue); mValue = mValue + 1; return ret; }};int main(){ Test t1(0); Test t2(0); Test tt1 = t1++; cout << t1.value() << endl; cout << tt1.value() << endl; Test tt2 = ++t2; cout << t2.value() << endl; cout << tt2.value() << endl; return 0;}输出：1011后置 ++ 操作符重载分析：Test operator ++ (int){ Test ret(mValue); mValue = mValue + 1; return ret;}在栈空间创建对象调用构造函数调用析构函数真正的区别对于基础类型的变量前置 ++ 的效率与后置 ++ 的效率基本相同根据项目组编码规范进行选择对于类类型的对象前置 ++ 的效率高于后置 ++尽量使用前置 ++ 操作符提高程序效率编程实验： 复数类的进一步完善Complex.h#ifndef COMPLEX_H#define _COMPLEX_H_class Complex{private: double a; double b;public: Complex(int a = 0, int b = 0); int getA(); int getB(); int getModulus(); Complex operator + (const Complex& c); Complex operator - (const Complex& c); Complex operator * (const Complex& c); Complex operator / (const Complex& c); bool operator == (const Complex& c); bool operator != (const Complex& c); Complex& operator = (const Complex& c); Complex& operator ++ (); Complex operator ++ (int); Complex& operator – (); Complex operator – (int);};#endifComplex.cpp#include “Complex.h”#include <math.h>Complex::Complex(int a, int b){ this->a = a; this->b = b;}int Complex::getA(){ return a;}int Complex::getB(){ return b;}int Complex::getModulus(){ return sqrt(a * a + b * b);}Complex Complex::operator + (const Complex& c){ double na = a + c.a; double nb = b + c.a; Complex ret(na, nb); return ret;}Complex Complex::operator - (const Complex& c){ double na = a - c.a; double nb = b - c.b; Complex ret(na, nb); return ret;}Complex Complex::operator * (const Complex& c){ double na = a * c.a - b * c.b; double nb = a * c.b + b * c.a; Complex ret(na, nb); return ret;}Complex Complex::operator / (const Complex& c){ double nm = c.a * c.a + c.b * c.b; double na = (a * c.a + b * c.b) / nm; double nb = (b * c.a - a * c.b) / nm; Complex ret(na, nb); return ret;}bool Complex::operator == (const Complex& c){ return (a == c.a) && (b == c.b);}bool Complex::operator != (const Complex& c){ return !(*this == c);}// 为了实现循环赋值，将自身引用返回Complex& Complex::operator = (const Complex& c){ // 若意图自己给自己赋值，则跳过 if( this != &c ) { a = c.a; b = c.b; } return *this;}Complex& Complex::operator ++ (){ a = a + 1; b = b + 1; return *this;}Complex Complex::operator ++ (int){ Complex ret(a, b); a = a + 1; b = b + 1; return ret;}Complex& Complex::operator – (){ a = a - 1; b = b - 1; return *this;}Complex Complex::operator – (int){ Complex ret(a, b); a = a - 1; b = b - 1; return ret;}main.cpp#include <iostream>#include “Complex.h"using namespace std;int main(){ Complex c1(0, 0); Complex c2(0, 0); Complex c3 = c1++; cout << c3.getA() << endl; cout << c3.getB() << endl; Complex c4 = ++c2; cout << c4.getA() << endl; cout << c4.getB() << endl; return 0;}输出：0011小结编译优化使得最终的可执行程序更加高效前置 ++ 操作符和后置 ++ 操作符都可以被重载++ 操作符的重载必须符合原生语义对于基础类型， 前置 ++ 与 后置 ++ 的效率几乎相同对于类类型，前置 ++ 的效率高于后置 ++以上内容参考狄泰软件学院系列课程，请大家保护原创！