c – 重载的postincrement运算符在不实例化运算符的情况下对复数进行平方值

概述这是输出： First Complex Number:Enter real part of complex number: 3Enter imaginary part of complex number: 6Second Complex Number:Enter real part of complex number: 5Enter imaginary part of complex 这是输出：

First Complex Number:Enter real part of complex number: 3Enter imaginary part of complex number: 6Second Complex Number:Enter real part of complex number: 5Enter imaginary part of complex number: -5a == (-27.00+36.00i)b == (5.00-5.00i)a+b == (-22.00+31.00i)a-b == (-32.00+41.00i)a*b == (45.00+315.00i)a*a == (-567.00-1944.00i)b*b == (0.00-50.00i)a*a (using postincrement) ==(-27.00+36.00i)

正如你所看到的,并非所有涉及a的都是错误的,因为它取一个(一个复数)的平方作为a.所以,虽然答案“a * a(使用后增量)==( – 27.00 36.00i)是正确的答案…它所说的”a ==( – 27.00 36.00i)“的部分是不正确的,因为它应该是==(3 6i).我相信错误在于我的代码的重载和朋友方面,但我不知道如何解决它因为我没有给出任何错误…这是一个问题我的代码中的逻辑.

这是我的代码：

#include<iostream>#include<iomanip>using namespace std;class Complexnum{public:    Complexnum(float = 0.0,float = 0.0); //default constructor that uses default arg. in case no init. are in main    Complexnum& getComplexnum(); //get real and imaginary numbers from keyboard    Complexnum& sum(Complexnum a,Complexnum b); //method to add two Complexnum numbers together    Complexnum& diff(Complexnum a,Complexnum b); //method to find the difference of two complex numbers    Complexnum& prod(Complexnum a,Complexnum b); //method to find the product of two complex numbers    Complexnum& square(Complexnum a); //method to find square using pre/post increment operators    //overloaded operators    Complexnum& operator =  (const Complexnum& that) = default;    Complexnum& operator += (const Complexnum& that) { return sum(*this,that); }    Complexnum& operator -= (const Complexnum& that) { return diff(*this,that); }    Complexnum& operator *= (const Complexnum& that) { return prod(*this,that); }    Complexnum& operator ++() { return square(*this); } //called for ++num    Complexnum& operator ++(int) { return square(*this); } //called for num++    ostream& print(ostream& stm = cout) const;private:    float real; //float data member for real number (to be entered in by user)    float imaginary; //float data member for imaginary number (to be entered in by user)    //non-member overloaded operators    //a is passed by value    frIEnd Complexnum operator+ (Complexnum a,const Complexnum& b) { return a += b; }    frIEnd Complexnum operator- (Complexnum a,const Complexnum& b) { return a -= b; }    frIEnd Complexnum operator* (Complexnum a,const Complexnum& b) { return a *= b; }    frIEnd Complexnum operator++(Complexnum a) { return a++; }    frIEnd ostream& operator<< (ostream& stm,const Complexnum& c) { return c.print(stm); }};Complexnum::Complexnum(float a,float b){    real = a;    imaginary = b;}Complexnum& Complexnum::getComplexnum(){    Complexnum keyboard;    cout << "Enter real part of complex number: ";    cin >> real;    cout << "Enter imaginary part of complex number: ";    cin >> imaginary;    return keyboard; }Complexnum& Complexnum::square(Complexnum a){    this->real = (a.real * a.real) - (a.imaginary * a.imaginary);    this->imaginary = (2 * (a.real * a.imaginary));    return *this;}Complexnum& Complexnum::sum(Complexnum a,Complexnum b){    this->real = a.real + b.real;    this->imaginary = a.imaginary + b.imaginary;    return *this;}Complexnum& Complexnum::diff(Complexnum a,Complexnum b){    this->real = a.real - b.real;    this->imaginary = a.imaginary - b.imaginary;    return *this;}Complexnum& Complexnum::prod(Complexnum a,Complexnum b){    this->real = (a.real * b.real) - (a.imaginary * b.imaginary);    this->imaginary = (a.real * b.imaginary) + (b.real * a.imaginary);    return *this;}ostream& Complexnum::print(ostream& stm) const{    return stm << "(" << noshowpos << real << showpos << imaginary << "i)";}int main(){    Complexnum a,b;    cout << "First Complex Number:" << endl;    a.getComplexnum();    cout << endl;    cout << "Second Complex Number:" << endl;    b.getComplexnum();    cout << endl;    cout << fixed << setprecision(2)        << "a == " << a << '\n'        << "b == " << b << '\n'        << "a+b == " << a + b << '\n'        << "a-b == " << a - b << '\n'        << "a*b == " << a*b << '\n'        << "a*a == " << a*a << '\n'        << "b*b == " << b*b << '\n'        << "a*a (using postincrement) ==" << a++ << '\n';        cout << endl;    system("PAUSE");}

解决方法 这不是关于运算符重载,大概是 order of evaluation.

在声明中：

cout << fixed << setprecision(2)        << "a == " << a << '\n'        << "b == " << b << '\n'        << "a+b == " << a + b << '\n'        << "a-b == " << a - b << '\n'        << "a*b == " << a*b << '\n'        << "a*a == " << a*a << '\n'        << "b*b == " << b*b << '\n'        << "a*a (using postincrement) ==" << a++ << '\n';

参数将按照您的预期从左向右打印,但计算每个参数的各个步骤不必按此顺序完成.

编译器可以按任何顺序计算每个子表达式的值,只要该值在需要打印时“就绪”即可.所以它可以做这样的事情：

auto&& temp1 = a + b;auto&& temp2 = a - b;auto&& temp3 = a*b;auto&& temp4 = a*a;auto&& temp5 = b*b;auto&& temp6 = a++;cout << fixed << setprecision(2)        << "a == " << a << '\n'        << "b == " << b << '\n'        << "a+b == " << temp1 << '\n'        << "a-b == " << temp2 << '\n'        << "a*b == " << temp3 << '\n'        << "a*a == " << temp4 << '\n'        << "b*b == " << temp5 << '\n'        << "a*a (using postincrement) ==" << temp6 << '\n';

如果发生这种情况,您将获得您期望的行为,因为子表达式将按从左到右的顺序进行评估.但是当前的C标准(C 14)允许编译器重新排序评估,这可能允许它更好地优化代码,如果它需要更少的堆栈空间更少的寄存器.该声明的另一个有效执行是：

auto&& temp1 = a++;auto&& temp2 = b*b;auto&& temp3 = a*a;auto&& temp4 = a*b;auto&& temp5 = a - b;auto&& temp6 = a + b;cout << fixed << setprecision(2)        << "a == " << a << '\n'        << "b == " << b << '\n'        << "a+b == " << temp6 << '\n'        << "a-b == " << temp5 << '\n'        << "a*b == " << temp4 << '\n'        << "a*a == " << temp3 << '\n'        << "b*b == " << temp2 << '\n'        << "a*a (using postincrement) ==" << temp1 << '\n';

这次你可以看到a *** 作首先发生,因此稍后的计算将在发生之后完成.

编译器还可以选择子表达式评估的任何其他排序,例如,它可以评估a * a然后a a b等等(但实际上最常见的顺序是从左到右和从右到左)

另外,您的代码还有两个严重问题：

此函数返回对局部变量的引用：

Complexnum& Complexnum::getComplexnum(){    Complexnum keyboard;    // ...    return keyboard; }

函数返回后,该局部变量不再存在,因此任何使用该引用的尝试都将访问不存在的对象.永远不要这样做！你的编译器应该警告你这里有问题,启用编译器的警告,不要忽略它们！

其次,重载运算符是一个非常糟糕的主意,就像意味着完全不同的东西一样,就像将对象本身相乘一样.当运算符对您要执行的 *** 作有意义时,您应该只使用 *** 作符重载.增量不是平方,所以这是一个糟糕的选择.我只想为此定义一个普通(非运算符)函数.

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