好奇怪，重载"+"的参数是一个么？

[freshui]

bin_seq& operator + (const bin_seq &bs1,const bin_seq &bs2)
给出的错误提示是：
d:\Cpp_works\exam4\exam4.cpp(83) : error C2804: 二进制“operator +”的参数太多

[lann64]

你是在类内重载？类内就一个，ｔｈｉｓ是隐含的。
友元重载是两个参数

[freshui]

那return呢？return *this就行了啊？
也就是说，在类内重载 + 和重载＋＝的代码是一样的啊？

[lann64]

当然不是，+重载，一般应该生成一个局部变量，返回这个局部变量

[freshui]

请看这个重载：
bin_seq& bin_seq::operator +(const bin_seq &bs)
{
int new_length;
new_length=n+bs.getSize();
char *new_bits=new char[new_length];

for(int ix=0; ix<n; ix++)
new_bits[ix]=bits[ix];
for( ; ix<new_length; ix++)
new_bits[ix]=bs[ix-n];

delete bits;
n=new_length;

return *this;
}

这样写对不？
如果不对，这样的写法是不是重载+=的代码啊？
那真正的代码应该是啥样啊？是不是这样吗？

bin_seq& bin_seq::operator +(const bin_seq &bs)
{
int new_length;
new_length=n+bs.getSize();
char *new_bits=new char[new_length];

for(int ix=0; ix<n; ix++)
new_bits[ix]=bits[ix];
for( ; ix<new_length; ix++)
new_bits[ix]=bs[ix-n];

//delete bits;
//n=new_length;

bin_seq temp_bs(new_bits,new_length);
delete new_length;

return temp_bs;
}

[lann64]

不知道你的类怎么实现，不过+重载通常不返回引用类型，+=才返回引用

[freshui]

我把类代码全贴出来：
class bin_seq {

private:
int n;
char *bits;
public:

//----------------------------------
bin_seq(char *b=NULL, int length=0);
int getSize() const {return n;}
~bin_seq() {delete [] bits;}

bin_seq& operator + (const bin_seq &bs);
bin_seq& operator+=(const bin_seq &bs);
char operator[](int index)
{
if(index<0 || index>n)
throw "Wrong Index!";
else
return bits[index];
}
char operator[](int index) const
{
if(index<0 || index>n)
throw "Wrong Index!";
else
return bits[index];
}

};
bin_seq::bin_seq(char *b,int length)
{
if(NULL==b || length<=0)
{ bits=NULL; n=0; }
else
{
bits=new char[length];
for(int ix=0; ix<length; ix++)
bits[ix]=b[ix];
n=length;
}

}
bin_seq& bin_seq::operator +(const bin_seq &bs)
{
int new_length;
new_length=n+bs.getSize();
char *new_bits=new char[new_length];

for(int ix=0; ix<n; ix++)
new_bits[ix]=bits[ix];
for( ; ix<new_length; ix++)
new_bits[ix]=bs[ix-n];

//delete bits;
//n=new_length;

bin_seq temp_bs(new_bits,new_length);
delete [] new_bits;

return temp_bs;

}

bin_seq& bin_seq::operator +=(const bin_seq &bs)
{
int new_length;
new_length=n+bs.getSize();
char *new_bits=new char[new_length];

for(int ix=0; ix<n; ix++)
new_bits[ix]=bits[ix];
for( ; ix<new_length; ix++)
new_bits[ix]=bs[ix-n];

delete [] bits;
n=new_length;

return *this;
}
类数据就是char*
重载的+实现功能就是两串 char * 相加。

[lann64]

class bin_seq {

private:
int n;
char *bits;
public:

//----------------------------------
bin_seq(char *b=NULL, int length=0);
int getSize() const {return n;}
~bin_seq() {delete [] bits;}

bin_seq operator + (const bin_seq &bs); //----------
bin_seq& operator+=(const bin_seq &bs);
char operator[](int index)
{
if(index<0 || index>n)
throw "Wrong Index!";
else
return bits[index];
}
char operator[](int index) const
{
if(index<0 || index>n)
throw "Wrong Index!";
else
return bits[index];
}

};
bin_seq::bin_seq(char *b,int length)
{
if(NULL==b || length<=0)
{ bits=NULL; n=0; }
else
{
bits=new char[length];
for(int ix=0; ix<length; ix++)
bits[ix]=b[ix];
n=length;
}

}
bin_seq bin_seq::operator +(const bin_seq &bs) //------------
{
int new_length;
new_length=n+bs.getSize();
char *new_bits=new char[new_length];

int ix; //---------------
for(ix=0; ix<n; ix++) //----------
new_bits[ix]=bits[ix];
for( ; ix<new_length; ix++)
new_bits[ix]=bs[ix-n];

//delete bits;
//n=new_length;

bin_seq temp_bs(new_bits,new_length);
delete [] new_bits;

return temp_bs;

}

bin_seq& bin_seq::operator +=(const bin_seq &bs)
{
int new_length;
new_length=n+bs.getSize();
char *new_bits=new char[new_length];

int ix; // ---------
for(ix=0; ix<n; ix++) //----------
new_bits[ix]=bits[ix];
for( ; ix<new_length; ix++)
new_bits[ix]=bs[ix-n];

delete [] bits;
n=new_length;

return *this;
}

语法上应该可以了，逻辑上没认真看。