关于操作符重载的问题

[discory]

#include <iostream>
using std::cout;
using std::cin;
using std::endl;
using std::ostream;
using std::istream;

#include <iomanip>
using std::setw;

class PhoneNumber
{
	friend ostream &operator <<( ostream&, const PhoneNumber & );
	friend istream &operator >>( istream&, const PhoneNumber & );

private:
	char areaCode[ 4 ];		//3-digit area code and null
	char exchange[ 4 ];		//3-digit exchange and null
	char line[ 5 ];			//4-dighit line and null
};

//Overloaded stram-insertion operator( cannot be 
//a member function if we would like to invoke it with 
//cout << somePhoneNumber; )
ostream &operator <<( ostream &output, const PhoneNumber &num )
{
	output << "(" << num.areaCode << ")"
		<< num.exchange << "-" << num.line;
	return output;		//enables cout << a << b << c;
}

istream &operator >>( istream &input, const PhoneNumber &num )
{
	input.ignore();				//skip (
	input >> setw( 4 ) >> num.areaCode;		//这里报错
	input.ignore( 2 );			//skip )
	input >> setw( 4 ) >> num.exchange;		//这里报错
	input.ignore();				//skip dash (-)
	input >> setw( 5 ) >> num.line;			//这里报错
	return input;				//enables cin >> a >> b >> c;
}

int main()
{
	PhoneNumber phone;		//create object phone

	cout << "Enter phone number in the form [phone]: \n";

	//cin >> phone invokes operator >> function by
	//issuing the call operator >>( cin, phone ).
	cin >> phone;

	//cout << phone invokes operator << function by 
	//issuing the call operator <<( cout, phone ).
	cout << "The phone number entered was: " << phone << endl;
	system("pause");
	return 0;
}

提示说操作符重载未匹配，不明白
input >> setw( 4 ) >> num.areaCode; //input area code
IntelliSense: 没有与这些操作数匹配的 ">>" 运算符
操作数类型为: std::basic_istream<char, std::char_traits<char>> >> const char [4] d:\ex\25\main.cpp 37 21 25

[rocktyt]

istream没有提供从流输入字符数组的重载，可以考虑scanf，当然，要注意缓冲区大小，还有PhoneNumber 里面的字符数组需要初始化一下 scanf("(%3c)%3c-%4c", num.areaCode, num.exchange, num.line); 顺便 friend istream &operator >>( istream&, PhoneNumber & ); const了怎么修改内容？

[昵称很不好取]

friend istream &operator >>( istream&, const PhoneNumber & ); 被const打败了

[discory]

哦，明白了，感谢2位大虾