【C++Primer求助】multiset容器的自定义比较函数问题

[albb318]

#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>

#ifndef MYHEAD_H
#define MYHEAD_H

using namespace std;

class Base
{
private:
string Isbn;
protected:
double Price;
public:
virtual double GetPrice(size_t Num) const
{
return Price*Num;
}
const string &GetName() const
{
return Isbn;
}
Base(string isbn="",double price=0):Isbn(Isbn),Price(price){};
virtual Base *Clone() const
{
return new Base(*this);
}
virtual ~Base(){};
};

class Bulk:public Base
{
private:
double Discount;
size_t Limit;
public:
double GetPrice(size_t Num) const
{
return Num>=Limit?(Base::GetPrice(Num)*Discount):(Base::GetPrice(Num));
}
Bulk(string isbn="",double price=0,double discount=0,size_t limit=0)
:Base(isbn,price),Discount(discount),Limit(limit){};
Bulk *Clone() const
{
return new Bulk(*this);
}
};

class Sales_item
{
private:
Base *BaseP;
size_t* Use;
public:
Sales_item(const Base &org):BaseP(org.Clone()),Use(new size_t(1)){};
Sales_item(const Sales_item &org):BaseP(org.BaseP),Use(org.Use){++*Use;};
Base *operator->() const
{
return BaseP;
}
Base &operator*() const
{
return *BaseP;
}
Sales_item &operator=(const Sales_item &right)
{
++*(right.Use);
this->~Sales_item();
BaseP=right.BaseP;
Use=right.Use;
}

~Sales_item()
{
if(--*Use==0)
{
delete BaseP;
delete Use;
}
}

};

inline bool compare(const Sales_item &left,const Sales_item &right)
{
return (left->GetName())<(right->GetName());
}

typedef bool (*Comp)(const Sales_item &left,const Sales_item &right);
typedef multiset<Sales_item,Comp> Items;


class Basket
{
private:
multiset<Sales_item,Comp> BookList;;
public:
Basket():BookList(compare){};
void AddOne(const Sales_item &item)
{
BookList.insert(item);
}
double GetPrice()
{
double Price=0;
for(Items::const_iterator Scan=BookList.begin();
Scan!=BookList.end();
Scan=upper_bound(BookList.begin(),BookList.end(),*Scan))
Price+=(*Scan)->GetPrice(count(BookList.begin(),BookList.end(),*Scan));
return Price;
}
};

#endif


C++Primer的习题，自定义了Base基类，Bulk打折派生类，用Sales_itme类句柄进行管理。
定义multiset保存句柄，但是定义比较函数时出问题了，如下：
>------ 已启动生成: 项目: Death from Above, 配置: Debug Win32 ------
1>正在编译...
1>Death from Above.cpp
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)”: 无法从“Sales_item”为“const std::_Tree<_Traits> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\xtree(1453) : 参见“std::operator ==”的声明
1> d:\program files\microsoft visual studio 9.0\vc\include\algorithm(162): 参见对正在编译的函数 模板 实例化“__w64 int std::_Count<std::_Tree<_Traits>::iterator,_Ty>(_InIt,_InIt,const _Ty &)”的引用
1> with
1> [
1> _Traits=std::_Tset_traits<Sales_item,Comp ,std::allocator<Sales_item>,true>,
1> _Ty=Sales_item,
1> _InIt=std::_Tree<std::_Tset_traits<Sales_item,Comp ,std::allocator<Sales_item>,true>>::iterator
1> ]
1> f:\课程\c\death from above\death from above\death from above\myhead.h(113): 参见对正在编译的函数 模板 实例化“__w64 int std::count<std::_Tree<_Traits>::iterator,Sales_item>(_InIt,_InIt,const _Ty &)”的引用
1> with
1> [
1> _Traits=std::_Tset_traits<Sales_item,Comp ,std::allocator<Sales_item>,true>,
1> _InIt=std::_Tree<std::_Tset_traits<Sales_item,Comp ,std::allocator<Sales_item>,true>>::iterator,
1> _Ty=Sales_item
1> ]
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::basic_string<_Elem,_Traits,_Alloc> &,const _Elem *)”: 无法从“Sales_item”为“const std::basic_string<_Elem,_Traits,_Alloc> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\string(90) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const _Elem *,const std::basic_string<_Elem,_Traits,_Alloc> &)”: 无法从“Sales_item”为“const _Elem *”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\string(80) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::basic_string<_Elem,_Traits,_Alloc> &,const std::basic_string<_Elem,_Traits,_Alloc> &)”: 无法从“Sales_item”为“const std::basic_string<_Elem,_Traits,_Alloc> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\string(70) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::vector<_Ty,_Alloc> &,const std::vector<_Ty,_Alloc> &)”: 无法从“Sales_item”为“const std::vector<_Ty,_Alloc> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\vector(1303) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::istream_iterator<_Ty,_Elem,_Traits,_Diff> &,const std::istream_iterator<_Ty,_Elem,_Traits,_Diff> &)”: 无法从“Sales_item”为“const std::istream_iterator<_Ty,_Elem,_Traits,_Diff> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\iterator(266) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::istreambuf_iterator<_Elem,_Traits> &,const std::istreambuf_iterator<_Elem,_Traits> &)”: 无法从“Sales_item”为“const std::istreambuf_iterator<_Elem,_Traits> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\streambuf(548) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::allocator<_Ty> &,const std::allocator<_Other> &) throw()”: 无法从“Sales_item”为“const std::allocator<_Ty> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\xmemory(173) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)”: 无法从“Sales_item”为“const std::reverse_iterator<_RanIt> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\xutility(2220) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)”: 无法从“Sales_item”为“const std::_Revranit<_RanIt,_Base> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\xutility(2024) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2784: “bool std::operator ==(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)”: 无法从“Sales_item”为“const std::pair<_Ty1,_Ty2> &”推导 模板 参数
1> d:\program files\microsoft visual studio 9.0\vc\include\utility(68) : 参见“std::operator ==”的声明
1>d:\program files\microsoft visual studio 9.0\vc\include\algorithm(152) : error C2676: 二进制“==”: “Sales_item”不定义该运算符或到预定义运算符可接收的类型的转换
1>生成日志保存在“file://f:\课程\C\Death From Above\Death from Above\Death from Above\Debug\BuildLog.htm”
1>Death from Above - 12 个错误，0 个警告
========== 生成: 成功 0 个，失败 1 个，最新 0 个，跳过 0 个 ==========


好像是缺少“==”的定义，但明明已经有compare函数了啊。。。
求大虾帮助~~

[nineforever]

count需要operator==

[waizqfor]

[Quote=引用楼主 albb318 的帖子:]

#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>

#ifndef MYHEAD_H
#define MYHEAD_H

using namespace std;

class Base
{
private:
string Isbn;
protected:
double Price;
public:
virtual double GetPrice(size_t Num) const
{
return Price*Num;
}
const string &GetName() const
{
return Isbn;
}
Base(string isbn="",do…
[/Quote]
重载的问题

[albb318]

[Quote=引用 1 楼 nineforever 的回复:]
count需要operator==
[/Quote]
改成这样了，可还是不行。

class Basket
{
	typedef bool (*Comp)(const Sales_item &left,const Sales_item &right);
	typedef multiset<Sales_item,Comp> Items;
public:
	Basket():BookList(compare){};
	void AddOne(const Sales_item &item)
	{
		BookList.insert(item);
	}
	double GetPrice()
	{
		double Price=0;
		for(Items::const_iterator Scan=BookList.begin();
			Scan!=BookList.end();
			Scan=upper_bound(BookList.begin(),BookList.end(),*Scan))
			Price+=(*Scan)->GetPrice(BookList.count(*Scan));
		return Price;
	}
private:
	multiset<Sales_item,Comp> BookList;
};

[nineforever]

你的Sales_item需要提供operator==，因为count会用到
另外你需要传递compare给upper_bound，因为它默认用operator<

[albb318]

[Quote=引用 4 楼 nineforever 的回复:]
你的Sales_item需要提供operator==，因为count会用到
另外你需要传递compare给upper_bound，因为它默认用operator <
[/Quote]
再次修改

#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>

#ifndef MYHEAD_H
#define MYHEAD_H

using namespace std;

class Base//定义基类
{
private:
	string Isbn;
protected:
	double Price;
public:
	virtual double GetPrice(size_t Num) const
	{
		return Price*Num;
	}
	string GetName() const
	{
		return Isbn;
	}
	Base(string isbn="",double price=0):Isbn(Isbn),Price(price){};
	virtual Base *Clone() const
	{
		return new Base(*this);
	}
	virtual ~Base(){};
};

class Bulk:public Base//打折类
{
private:
	double Discount;
	size_t Limit;
public:
	double GetPrice(size_t Num) const
	{
		return Num>=Limit?(Base::GetPrice(Num)*Discount):(Base::GetPrice(Num));
	}
	Bulk(string isbn="",double price=0,double discount=0,size_t limit=0)
		:Base(isbn,price),Discount(discount),Limit(limit){};
	Bulk *Clone() const
	{
		return new Bulk(*this);
	}
};

class Sales_item//句柄类
{
private:
	Base *BaseP;
	size_t* Use;
public:
	Sales_item():BaseP(0),Use(new size_t(1)){}
	Sales_item(const Base &org):BaseP(org.Clone()),Use(new size_t(1)){};
	Sales_item(const Sales_item &org):BaseP(org.BaseP),Use(org.Use){++*Use;};
	Base *operator->() const
	{
		return BaseP;
	}
	Base &operator*() const
	{
		return *BaseP;
	}
	Sales_item &operator=(const Sales_item &right)
	{
		++*(right.Use);
		this->~Sales_item();
		BaseP=right.BaseP;
		Use=right.Use;
	}

	~Sales_item()
	{
		if(--*Use==0)
		{
			delete BaseP;
			delete Use;
		}
	}

};


bool operator<(const Sales_item &left,const Sales_item &right)
{
	return	(left->GetName())<(right->GetName());
}//定义符号"<"

 bool compare(const Sales_item &left,const Sales_item &right)
{
	return (left->GetName())<(right->GetName());
}//定义一个比较函数

class Compare
{
public:
	bool operator()(const Sales_item &left,const Sales_item &right)
	{
		return	(left->GetName())<(right->GetName());
	}
};//定义一个函数对象进行比较




class Basket
{
	//typedef bool (*Comp)(const Sales_item &left,const Sales_item &right);
	typedef multiset<Sales_item,Compare> Items;//这里有个问题:
	//typedef multiset<Sales_item,Compare> Items;  OK
	//typedef multiset<Sales_item> Items; OK
	//typedef multiset<Sales_item,compare> Items; Error
	//提示说“compare”不是参数“_Pr”的有效 模板 类型变量
//为什么直接把compare函数传给multiset就出错呢？
public:
	Basket(){};
	void AddOne(const Sales_item &item)
	{
		BookList.insert(item);
	}
	double GetPrice()
	{
		double Price=0;
		for(Items::const_iterator Scan=BookList.begin();
			Scan!=BookList.end();
			Scan=upper_bound(BookList.begin(),BookList.end(),*Scan))
			Price+=(*Scan)->GetPrice(BookList.count(*Scan));
		return Price;
	}
private:
	Items BookList;
};

[nineforever]

compare是函数，multiset的模板参数要求的是类型
你需要在multiset的模板参数里指定比较函数的类型，同时在multiset的构造函数里提供比较函数本身

[WEBCONFIG]

[Quote=引用 6 楼 nineforever 的回复:]
compare是函数，multiset的模板参数要求的是类型
你需要在multiset的模板参数里指定比较函数的类型，同时在multiset的构造函数里提供比较函数本身
[/Quote]
正解啊

[taodm]

试multiset就不要把其它代码带进来干扰视线。