求助，关于重载运算符

[fan318]

重载运算符+,=,==,实现字符串连接，字符串的拷贝赋值，字符串的判断相等

#include <iostream.h>
#include <string.h>
class string
{
char* ptr;
public:
string();
string(char* s);
virtual ~string();
void print();
string& operator = (const string& s);
string operator + (string& s2);
bool operator == (string& s2);

};
string::string()
{

}

string::string(char* s)
{
ptr = new char[strlen(s)+1];
strcpy(ptr,s);
}

void string::print()
{
cout << ptr << endl;
}
string::~string()
{
delete ptr;
}

string& string::operator = (const string& s)
{
if ( this == &s)
{
return *this;
}
delete ptr;
ptr = new char[strlen(s.ptr)+1];
strcpy(ptr,s.ptr);
return *this;
}

string string::operator + (string& s2)
{
if (s2.ptr == NULL)
{
return *this;
}
char *p = NULL;
p = new char[strlen(ptr)+strlen(s2.ptr)+1];
while ( *ptr != '\0' )
{
*p++ = *ptr++;

}
while ( *s2.ptr != '\0' )
{
*p++ = *s2.ptr++;

}
p = '\0';
delete ptr;
ptr = new char[strlen(p)];
strcpy(ptr,p);
return *this;

}

bool string::operator == (string& s2)
{
if ( strcmp(ptr,s2.ptr) == 0 )
{
return true;
}
else
return false;
}

void main()
{
string p1("book");
{
string p2("pen");
cout << "p2 ";
p2.print();
p2 = p1;
cout << "p2 ";
p2.print();
}
cout << "p1 ";
p1.print();
string p3("china");
p3 = p3 + p1;
if ( p1 == p3 )
{
cout << "p1与p3一致" << endl;
}
else
{
cout << "p1与p3不一致" << endl;
}

}

[smaltdd]

你的问题是啥？

最好说明，难道还要去研究你的整个代码？

[fan318]

运行p3 = p3 + p1;时出错，是什么原因？？

[wanyuzhen]

在string string::operator + (string& s2)里

while ( *ptr != '\0' )
{
*p++ = *ptr++;

}
指针ptr最后为'\0'
总之可以这样：
char *temp = ptr;
while ( *temp != '\0' )
{
*p++ = *temp++;

}
temp = s2.ptr;
while ( *s2.ptr != '\0' )
{
*p++ = *temp++;

}

[fan318]

还是有问题啊！！！
是内存错误吗？？

[wanyuzhen]

错误有两个，改后的：
string &string::operator + (string& s2)
{
if (s2.ptr == NULL)
{
return *this;
}
char *p = NULL,*tempp ;
p = new char[strlen(ptr)+strlen(s2.ptr)+1];
tempp = p;
char *temp = ptr;
while ( *temp != '\0' )
{
*p++ = *temp++;

}
temp = s2.ptr;
while ((*p++ = *temp++));

delete ptr;
ptr = new char[strlen(tempp)];
strcpy(ptr,tempp);
return *this;

}
第二个是p3 = p3 +p1运行+后，应该是自身复制

[fan318]

在VC环境还是运行不过去啊！！