有关重载友元<<的问题，麻烦各位指点一下

Beover1984 2003-10-23 10:42:06

//LinearList.h

#include<iostream>

using namespace std;

template<class T>
class LinearList{
friend ostream& operator<<( ostream &out, const LinearList<T> &x );
public:
LinearList( int Msize = 10 );
~LinearList() { delete [] _elem; }

bool isEmpty()const { return _length == 0; }
int length()const { return _length; }
bool find( int k, T &x )const;
int search( const T &x )const;

LinearList<T>& del( int k, T &x );
LinearList<T>& insert( int k, const T &x);
private:
int _length;
int _max_size;
T *_elem;
};
template<class T>
ostream& operator<<( ostream &out, const LinearList<T> &x )
{
for( int i = 0; i < _length; ++i ){
out<< _elem[i] << ",";
}
out<< endl;
return out;
};

//test.cpp

#include<stdlib.h>
#include<iostream>
#include"LinearList.h"

using namespace std;

int main()
{
try{
LinearList<int> l(5);
cout<< " length = " << l.length() << "\n"
<< " isEmpty = " << l.isEmpty() << "\n";
l.insert( 0, 2 ).insert( 0 , 6 );
cout<< " length = " << l.length() << "\n"
<< " isEmpty = " << l.isEmpty() << "\n";
int z;
l.find( 1, z );
cout<< " first element is " << z << "\n"
<< " length = " << l.length() << "\n";
l.del(1, z );
cout<< " delete element is " << z << "\n"
<< " list is " << l << endl;
}
catch(...) {
cerr<< "an exception has occurred" << endl;
}
system( "pause" );
}

编译出错：
25 D:\cpp\LinearList.h
[Warning] friend declaration `class ostream & operator <<(ostream &, const LinearList<T> &)'
还有好多warning都是和这个友元<<有关的请各位看一下，谢谢了

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ttlb 2003-10-23

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up Hot_Forever(用钱砸死我吧)

Hot_Forever 2003-10-23

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看看这段：
template<class T>
ostream& operator<<( ostream &out, const LinearList<T> &x )
{
for( int i = 0; i < _length; ++i ){
out<< _elem[i] << ",";
}
out<< endl;
return out;
}
肯定是错的，为啥？你这里的_length是哪个对象的_length?,难道是ostream的？
这里定义了一个x对象也没用到,
然后你可能会写
for(int i=0;i<x._length;++i){
out<<x._elem[i]<<",";
}
对不起，无法将类的私有变量赋给i

ttlb 2003-10-23