运行代码：

//向量与sort()
#include"std_lib_facilities.h"
//声明Item类
struct Item
{
	string name;
	int iid;
	double value;
	
	friend istream& operator>>(istream& is, Item& ii);
	friend ostream& operator<<(ostream& os, const Item& ii);
};

//------------------------------------------------------------
//重载Item类的输入和输出操作符
istream& operator>>(istream& is, Item& ii)
{
	is >> ii.name >> ii.iid >> ii.value;
	return is;
}

ostream& operator<<(ostream& os, const Item& ii)
{
	os << ii.name << " " << ii.iid << " " << ii.value;
	return os;
}

//----------------------------------------------------------
//定义根据name进行排序的函数（字典序）
bool sort_by_name(Item& ii1,Item& ii2)
{
	return ii1.name < ii2.name;
}

//------------------------------------------------------------
//定义根据iid进行排序的函数（升序）
bool sort_by_iid(Item& ii1, Item& ii2)
{
	return ii1.iid < ii2.iid;
}

//------------------------------------------------------------
//定义根据value进行排序的函数（降序）
bool sort_by_value(Item& ii1, Item& ii2)
{
	return ii1.value > ii2.value;
}

//-------------------------------------------------------------
int main()
try
{
	cout << "输入读取文件名： ";
	string from_file;
	cin >> from_file;

	ifstream is(from_file.c_str());
	if (!is)error("can't open ", from_file);

	istream_iterator<Item>ii(is);
	istream_iterator<Item>eos;
	ostream_iterator<Item>oo(cout, "\n");

	vector<Item>vi(ii, eos);
	sort(vi.begin(),vi.end(), sort_by_value);
	copy(vi.begin(), vi.end(), oo);

	return 0;
}
catch (exception& e) {
	cerr << "error:" << e.what() << '\n';
	keep_window_open();
	return 1;
}
catch (...) {
	cerr << "Oops:unknown exception!\n";
	keep_window_open();
	return 2;
}

读取文件：Item_file.txt

Max 2 43.2
Jane 3 34.2
Tom 3 32.4
Mary 8 23.0
Peter 5 32.5
Max 2 43.2
Jane 3 34.2
Tom 3 32.4
Mary 8 23.0
Peter 5 32.5

运行结果：