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C++ 语法错误：C2064: 项不会计算为接受 0 个参数的函数
#include<iostream>
#include"Sales_item.h"
using namespace std;
int main() {
Sales_item total;
if (cin >> total) {
Sales_item trans;
while (cin >> trans) {
if (total.isbn() == trans.isbn())
total += trans;
else {
cout << total << endl;
total = trans;
}
}
cout << total << endl;
}
else {
cerr << "no data" << endl;
return -1;
}
return 0;
}
这个是c++ primer plus上面的程序，但是报错了，因为初学所以不太会改，谢谢。
#include"Sales_item.h"
using namespace std;
int main() {
Sales_item total;
if (cin >> total) {
Sales_item trans;
while (cin >> trans) {
if (total.isbn() == trans.isbn())
total += trans;
else {
cout << total << endl;
total = trans;
}
}
cout << total << endl;
}
else {
cerr << "no data" << endl;
return -1;
}
return 0;
}
这个是c++ primer plus上面的程序，但是报错了，因为初学所以不太会改，谢谢。
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csucxy 2019-07-25
前面那个是C++ Primer第四版的，下面这个是第五版的。差别不大（相应的成员变量名、成员函数名稍有不同)。
第四版
成员变量：std::string isbn;
成员函数：
bool same_isbn(const Sales_item& rhs) const
{
return isbn == rhs.isbn;
}
第五版
成员变量：std::string bookNo;
成员函数：
std::string isbn() const { return bookNo; }
//////////////////////////////////////////////////////////////
#ifndef SALESITEM_H
// we're here only if SALESITEM_H has not yet been defined
#define SALESITEM_H
// Definition of Sales_item class and related functions goes here
#include <iostream>
#include <string>
class Sales_item {
// these declarations are explained section 7.2.1, p. 270
// and in chapter 14, pages 557, 558, 561
friend std::istream& operator>>(std::istream&, Sales_item&);
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
friend bool operator<(const Sales_item&, const Sales_item&);
friend bool
operator==(const Sales_item&, const Sales_item&);
public:
// constructors are explained in section 7.1.4, pages 262 - 265
// default constructor needed to initialize members of built-in type
#if defined(IN_CLASS_INITS) && defined(DEFAULT_FCNS)
Sales_item() = default;
#else
Sales_item(): units_sold(0), revenue(0.0) { }
#endif
Sales_item(const std::string &book):
bookNo(book), units_sold(0), revenue(0.0) { }
Sales_item(std::istream &is) { is >> *this; }
public:
// operations on Sales_item objects
// member binary operator: left-hand operand bound to implicit this pointer
Sales_item& operator+=(const Sales_item&);
// operations on Sales_item objects
std::string isbn() const { return bookNo; }
double avg_price() const;
// private members as before
private:
std::string bookNo; // implicitly initialized to the empty string
#ifdef IN_CLASS_INITS
unsigned units_sold = 0; // explicitly initialized
double revenue = 0.0;
#else
unsigned units_sold;
double revenue;
#endif
};
// used in chapter 10
inline
bool compareIsbn(const Sales_item &lhs, const Sales_item &rhs)
{ return lhs.isbn() == rhs.isbn(); }
// nonmember binary operator: must declare a parameter for each operand
Sales_item operator+(const Sales_item&, const Sales_item&);
inline bool
operator==(const Sales_item &lhs, const Sales_item &rhs)
{
// must be made a friend of Sales_item
return lhs.units_sold == rhs.units_sold &&
lhs.revenue == rhs.revenue &&
lhs.isbn() == rhs.isbn();
}
inline bool
operator!=(const Sales_item &lhs, const Sales_item &rhs)
{
return !(lhs == rhs); // != defined in terms of operator==
}
// assumes that both objects refer to the same ISBN
Sales_item& Sales_item::operator+=(const Sales_item& rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}
// assumes that both objects refer to the same ISBN
Sales_item
operator+(const Sales_item& lhs, const Sales_item& rhs)
{
Sales_item ret(lhs); // copy (|lhs|) into a local object that we'll return
ret += rhs; // add in the contents of (|rhs|)
return ret; // return (|ret|) by value
}
std::istream&
operator>>(std::istream& in, Sales_item& s)
{
double price;
in >> s.bookNo >> s.units_sold >> price;
// check that the inputs succeeded
if (in)
s.revenue = s.units_sold * price;
else
s = Sales_item(); // input failed: reset object to default state
return in;
}
std::ostream&
operator<<(std::ostream& out, const Sales_item& s)
{
out << s.isbn() << " " << s.units_sold << " "
<< s.revenue << " " << s.avg_price();
return out;
}
double Sales_item::avg_price() const
{
if (units_sold)
return revenue/units_sold;
else
return 0;
}
#endif
csucxy 2019-07-25
这才是头文件内容吧？另外好像也不是c++ primer plus中的，好像是c++ primer中的
#ifndef SALESITEM_H
#define SALESITEM_H
// Definition of Sales_item class and related functions goes here
#include <iostream>
#include <string>
class Sales_item
{
friend bool operator==(const Sales_item&, const Sales_item&);
// other members as before
public:
// added constructors to initialize from a string or an istream
Sales_item(const std::string& book) :
isbn(book), units_sold(0), revenue(0.0) { }
Sales_item(std::istream& is) { is >> *this; }
friend std::istream& operator>>(std::istream&, Sales_item&);
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
public:
// operations on Sales_item objects
// member binary operator: left-hand operand bound to implicit this pointer
Sales_item& operator+=(const Sales_item&);
// other members as before
public:
// operations on Sales_item objects
double avg_price() const;
bool same_isbn(const Sales_item& rhs) const
{
return isbn == rhs.isbn;
}
// default constructor needed to initialize members of built-in type
Sales_item() : units_sold(0), revenue(0.0) { }
// private members as before
private:
std::string isbn;
unsigned units_sold;
double revenue;
};
// nonmember binary operator: must declare a parameter for each operand
Sales_item operator+(const Sales_item&, const Sales_item&);
inline bool
operator==(const Sales_item& lhs, const Sales_item& rhs)
{
// must be made a friend of Sales_item
return lhs.units_sold == rhs.units_sold &&
lhs.revenue == rhs.revenue &&
lhs.same_isbn(rhs);
}
inline bool
operator!=(const Sales_item& lhs, const Sales_item& rhs)
{
return !(lhs == rhs); // != defined in terms of operator==
}
using std::istream; using std::ostream;
// assumes that both objects refer to the same isbn
inline
Sales_item& Sales_item::operator+=(const Sales_item& rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}
// assumes that both objects refer to the same isbn
inline
Sales_item
operator+(const Sales_item& lhs, const Sales_item& rhs)
{
Sales_item ret(lhs); // copy lhs into a local object that we'll return
ret += rhs; // add in the contents of rhs
return ret; // return ret by value
}
inline
istream&
operator>>(istream& in, Sales_item& s)
{
double price;
in >> s.isbn >> s.units_sold >> price;
// check that the inputs succeeded
if (in)
s.revenue = s.units_sold * price;
else
s = Sales_item(); // input failed: reset object to default state
return in;
}
inline
ostream&
operator<<(ostream& out, const Sales_item& s)
{
out << s.isbn << "\t" << s.units_sold << "\t"
<< s.revenue << "\t" << s.avg_price();
return out;
}
inline
double Sales_item::avg_price() const
{
if (units_sold)
return revenue / units_sold;
else
return 0;
}
#endif
月凉西厢 2019-07-24
isbn只是个成员变量，不是函数，干嘛要加括号
Italink 2019-07-24
把你的类代码也贴出来，不要贴图
ccql 2019-07-24
第五版1.6节的代码
csucxy 2019-07-24
你确定是书上的程序？
ccql 2019-07-24
这是那个Sales_item头文件
---------------------------------------
#ifndef SALESITEM_H
#define SALESITEM_H
#include <iostream>
#include <string>
class Sales_item
{
public:
Sales_item(const std::string& book) :isbn(book), units_sold(0), revenue(0.0) {}
Sales_item(std::istream& is) { is >> *this; }
friend std::istream& operator>>(std::istream&, Sales_item&);
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
public:
Sales_item& operator+=(const Sales_item&);
public:
double avg_price() const;
bool same_isbn(const Sales_item& rhs)const
{
return isbn == rhs.isbn;
}
Sales_item() :units_sold(0), revenue(0.0) {}
public:
std::string isbn;
unsigned units_sold;
double revenue;
};
using std::istream;
using std::ostream;
Sales_item operator+(const Sales_item&, const Sales_item&);
inline bool operator==(const Sales_item& lhs, const Sales_item& rhs)
{
return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs);
}
inline bool operator!=(const Sales_item& lhs, const Sales_item& rhs)
{
return !(lhs == rhs);
}
inline Sales_item& Sales_item::operator +=(const Sales_item & rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}
inline Sales_item operator+(const Sales_item & lhs, const Sales_item & rhs)
{
Sales_item ret(lhs);
ret += rhs;
return ret;
}
inline istream& operator>>(istream & in, Sales_item & s)
{
double price;
in >> s.isbn >> s.units_sold >> price;
if (in)
s.revenue = s.units_sold * price;
else
s = Sales_item();
return in;
}
inline ostream& operator<<(ostream & out, const Sales_item & s)
{
out << s.isbn << "\t" << s.units_sold << "\t" << s.revenue << "\t" << s.avg_price();
return out;
}
inline double Sales_item::avg_price() const
{
if (units_sold)
return revenue / units_sold;
else
return 0;
}
#endif
ccql 2019-07-24
........我把括号删了就对了，为什么c++ primer plus那本书上面加了括号？而且其他人的程序好像都没报错
