关于模板的 问题

[s__c__007]

#include<iostream.h>
template <class T>
class complex
{
private:
    T real;
	T imag;
public:
	complex(T r=0,T i=0)
	{
		real=r;
		imag=i;
	}
	void print();
	friend complex operator+(const complex &a,const complex &b);
	friend complex operator-(const complex &a,const complex &b);
	complex operator*(const complex &a);
	complex operator/(const complex &a);
	friend complex operator++(complex &a);
	complex operator++(int);
	friend ostream& operator<<(ostream &s,const complex &c);
	friend istream& operator>>(istream &s,complex &c);
};
template <class T>
void complex<T>::print()
{
	cout<<real;
	if(imag)
	{
		if(imag>0)cout<<"+";
		cout<<imag<<"i";
		cout<<endl;
	}
}
template <class T>
complex<T> operator+(const complex<T> &a,const complex<T> &b)
{
	complex<T> temp;
	temp.real=a.real+b.real;
	temp.imag=a.imag+b.imag;
	return temp;
}
template <class T>
complex<T> operator-(const complex<T> &a,const complex<T> &b)
{
	complex<T> temp;
	temp.real=a.real-b.real;
	temp.imag=a.imag-b.imag;
	return temp;
}
template <class T>
complex<T> complex<T>::operator*(const complex<T> &a)
{
	complex<T> temp;
	temp.real=a.real*real-a.imag*imag;
	temp.imag=a.real*imag+real*a.imag;
	return temp;
}
template <class T>
complex<T> complex<T>::operator/(const complex<T> &a)
{
	complex<T> temp;
	temp.real=(real*a.real+a.imag*imag)/(a.real*a.real+a.imag*a.imag);
	temp.imag=(real*(-a.imag)+imag*a.real)/(a.real*a.real+a.imag*a.imag);
	return temp;
}
template <class T>
complex<T> operator++(complex<T> &a)
{
	++a.real;
	++a.imag;
	return a;
}
template <class T>
complex<T> complex<T>::operator++(int)
{
	complex<T> temp(*this);
	real++;
	imag++;
	return temp;
}
/*template <class T>
ostream& operator<<(ostream &s,const complex<T> &c)
{
	s<<c.real;
	if(c.imag)
	{
		if(c.imag>0) s<<"+";
		s<<c.imag<<"i";
		s<<endl;
	}
	return s;
}*/
template <class T>
istream& operator>>(istream &s,complex<T> &c)
{
	s>>c.real;
	s>>c.imag;
	return s;
}

int main()
{
	complex <double> A1(2.3,4.6),A2(3.6,2.8);
	complex <double> A3,A4,A5,A6;
	A3=A1+A2;
	A4=A1-A2;
	A5=A1*A2;
	A6=A1/A2;
	cout<<"A1=";
	cout<<A1;
	cout<<endl<<"A2=";
	cout<<A2;
	cout<<endl<<"A3=A1+A2=";
	cout<<A3;
	cout<<endl<<"A4=A1-A2=";
	cout<<A4;
	cout<<endl<<"A5=A1*A2=";
	cout<<A5;
	cout<<endl<<"A6=A1/A2=";
	cout<<A6;
	A3=++A1;
	cout<<endl<<"after A3=++A1"<<endl;
	cout<<"A1=";
	cout<<A1;
	cout<<endl<<"A3=";
	cout<<A3;
	A4=A2++;
	cout<<endl<<"after A4=A2++"<<endl;
	cout<<"A2=";
	cout<<A2;
	cout<<endl<<"A4=";
	cout<<A4;
	return 0;
}

在注释的地方如果调用print函数该怎么写？

[mengde007]

/*template <class T>
ostream& operator<<(ostream &s,const complex<T> &c)
{
    s<<c.real;
    if(c.imag)
    {
        if(c.imag>0) s<<"+";
        s<<c.imag<<"i";
        s<<endl;
    }
    return s;
}*/

不是已经重载了cout吗、楼主想重载print吗

[「已注销」]

直接print()

[s__c__007]

在上面有对成员函数print的定义，这里向直接调用print函数啊。。。
ostream& operator<<(ostream &s,const complex<T> &c)
就是这个的函数体中直接用print函数

[猫已经找不回了]

print不是运算符号,重载也是重载函数.
为何要在模板里讨论C风格的printf?这么奇怪.

[gao125210]

/*template <class T>
ostream& operator<<(ostream &s,const complex<T> &c)
{
    s<<c.real;
    if(c.imag)
    {
        if(c.imag>0) s<<"+";
        s<<c.imag<<"i";
        s<<endl;
    }
    return s;
}*/

貌似真不好弄啊，print不会识别%T吧，呵呵

[xiaocha]

改一下 print() 函数
template <class T>
void complex<T>::print(ostream &s)
{
s << real;
if(imag)
{
if(imag>0) s << "+";
s << imag << "i";
s << endl;
}
}
然后
template <class T>
ostream& operator<<(ostream &s,const complex<T> &c)
{
c.print(s);
}

[s__c__007]

题目要求：重载operator<<函数的 代码中可以 直接调用原来已经具有输出功能的print（）成员函数

[s__c__007]

8-1.cpp
E:\学习\C++\程序\实验\8-1.cpp(34) : error C2244: 'complex<T>::print' : unable to resolve function overload
E:\学习\C++\程序\实验\8-1.cpp(35) : error C2954: template definitions cannot nest
执行 cl.exe 时出错.

有这两个错误

[xiaocha]

void print(); 也要改改：void print(ostream &s);

[s__c__007]

依然有错

[xiaocha]

是的，两者关系反了，这样就行了：

template <class T>
void complex <T>::print(ostream &s)
{
s << *this;
}
然后
template <class T>
ostream& operator <<(ostream &s,const complex <T> &c)
{
s << real;
if(imag)
{
if(imag>0) s << "+";
s << imag << "i";
//s << endl;
}
}

[s__c__007]

这样和题目意思不就反了吗？？？
题目要求：重载operator < <函数的 代码中可以 直接调用原来已经具有输出功能的print（）成员函数

[xiaocha]

[Quote=引用 10 楼 s__c__007 的回复:]
依然有错
[/Quote]
错误提示？

[xiaocha]

11楼没细想，6楼应该没错呀，把你的代码和错误提示再贴一下

[s__c__007]

#include<iostream.h>
template <class T>
class complex
{
private:
    T real;
	T imag;
public:
	complex(T r=0,T i=0)
	{
		real=r;
		imag=i;
	}
	void print(ostream &s);
	friend complex operator+(const complex &a,const complex &b);
	friend complex operator-(const complex &a,const complex &b);
	complex operator*(const complex &a);
	complex operator/(const complex &a);
	friend complex operator++(complex &a);
	complex operator++(int);
	friend ostream& operator<<(ostream &s,const complex &c);
	friend istream& operator>>(istream &s,complex &c);
};
template <class T> 
void complex<T>::print(ostream &s) 
{ 
    s<<real; 
    if(imag) 
    { 
        if(imag>0)s<<"+"; 
        s<<imag<<"i"; 
        s<<endl; 
    } 
} 
template <class T>
complex<T> operator+(const complex<T> &a,const complex<T> &b)
{
	complex<T> temp;
	temp.real=a.real+b.real;
	temp.imag=a.imag+b.imag;
	return temp;
}
template <class T>
complex<T> operator-(const complex<T> &a,const complex<T> &b)
{
	complex<T> temp;
	temp.real=a.real-b.real;
	temp.imag=a.imag-b.imag;
	return temp;
}
template <class T>
complex<T> complex<T>::operator*(const complex<T> &a)
{
	complex<T> temp;
	temp.real=a.real*real-a.imag*imag;
	temp.imag=a.real*imag+real*a.imag;
	return temp;
}
template <class T>
complex<T> complex<T>::operator/(const complex<T> &a)
{
	complex<T> temp;
	temp.real=(real*a.real+a.imag*imag)/(a.real*a.real+a.imag*a.imag);
	temp.imag=(real*(-a.imag)+imag*a.real)/(a.real*a.real+a.imag*a.imag);
	return temp;
}
template <class T>
complex<T> operator++(complex<T> &a)
{
	++a.real;
	++a.imag;
	return a;
}
template <class T>
complex<T> complex<T>::operator++(int)
{
	complex<T> temp(*this);
	real++;
	imag++;
	return temp;
}
template <class T>
ostream& operator<<(ostream &s,const complex<T> &c)
{
	c.print(s);
}
template <class T>
istream& operator>>(istream &s,complex<T> &c)
{
	s>>c.real;
	s>>c.imag;
	return s;
}

int main()
{
	complex <double> A1(2.3,4.6),A2(3.6,2.8);
	complex <double> A3,A4,A5,A6;
	A3=A1+A2;
	A4=A1-A2;
	A5=A1*A2;
	A6=A1/A2;
	cout<<"A1=";
	cout<<A1;
	cout<<endl<<"A2=";
	cout<<A2;
	cout<<endl<<"A3=A1+A2=";
	cout<<A3;
	cout<<endl<<"A4=A1-A2=";
	cout<<A4;
	cout<<endl<<"A5=A1*A2=";
	cout<<A5;
	cout<<endl<<"A6=A1/A2=";
	cout<<A6;
	A3=++A1;
	cout<<endl<<"after A3=++A1"<<endl;
	cout<<"A1=";
	cout<<A1;
	cout<<endl<<"A3=";
	cout<<A3;
	A4=A2++;
	cout<<endl<<"after A4=A2++"<<endl;
	cout<<"A2=";
	cout<<A2;
	cout<<endl<<"A4=";
	cout<<A4;
	return 0;
}

E:\学习\C++\程序\实验\8-1.cpp(85) : error C2662: 'print' : cannot convert 'this' pointer from 'const class complex<double>' to 'class complex<double> &'
Conversion loses qualifiers
E:\学习\C++\程序\实验\8-1.cpp(104) : see reference to function template instantiation 'class ostream &__cdecl operator <<(class ostream &,const class complex<double> &)' being compiled
执行 cl.exe 时出错.

[xiaocha]

void print(ostream &s); ==> void print(ostream &s) const;

c.print(s); ==> c.print(s); return s;

[s__c__007]

谢谢 这里为什么加const啊 ？？？

[love514425]

> print不是运算符号,重载也是重载函数.
> 为何要在模板里讨论C风格的printf?
> 建议LZ好好看看 <<Effictive C++>>

[xiaocha]

[Quote=引用 17 楼 s__c__007 的回复:]
谢谢 这里为什么加const啊 ？？？
[/Quote]

加 const 表示 print 函数不会改变类的的变量,
相当于 print 内的 this 指针为 const 类型,

避免了错误:
E:\学习\C++\程序\实验\8-1.cpp(85) : error C2662: 'print' : cannot convert 'this' pointer from 'const class complex <double>' to 'class complex <double> &' Conversion loses qualifiers

让

template <class T> ostream& operator<<(ostream &s,const complex<T> &c)
{
c.print(s);
}
这种需要const complex<T>的函数可以调用