【发布时间】：2017-06-30 19:59:17
【问题描述】：
这是输出：
First Complex Number:
Enter real part of complex number: 3
Enter imaginary part of complex number: 6
Second Complex Number:
Enter real part of complex number: 5
Enter imaginary part of complex number: -5
a == (-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)
如您所见，并非所有涉及a 的内容都是错误的，因为它将a（一个复数）的平方作为a。所以，虽然“a*a (using postincrement) == (-27.00+36.00i)”的答案是正确的答案......它说“a == (-27.00+36.00i)”的部分是不正确的，因为它应该是a==(3+6i)。我相信错误在于重载和朋友方面我的代码，但我不知道如何修复它，因为我没有给出任何错误......这是我代码中的逻辑问题。
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");
}
【问题讨论】：
-
ComplexNum& getComplexNum();-- 这个函数在哪里？ -
使用
a++会破坏输出中a的所有其他用法。 -
@gary - 对
cout（很多！）的参数评估顺序未指定，因此您无法判断增量何时发生。 -
@garyoak 正如前面的评论所指出的，你在
getComplexNum()中确实有一个错误。您正在返回对局部变量的引用，这是未定义的行为。所以基本上，你得到的任何输出都是假的，即使你修复了++问题。只需按值而不是引用返回ComplexNum。 -
Prefix-++ 应该通过引用返回，而 postfix-++ 应该按值返回（你搞砸了两次）
标签： c++ operator-overloading post-increment