please can some tell me why #include "Sales_item.h" #include<iostream> wouldn't compile, but #include<iostream> #include "Sales_item.h" compiles. the same, but different order.
it gave me 3 errors
1) Severity Code Description Project File Line
Error (active) linkage specification is incompatible with previous "lround" (declared at line 76 of "c:\Users\evan_2\Documents\Visual Studio 2015\Projects\ConsoleApplication1\ConsoleApplication1\Version_test.h") ConsoleApplication1 c:\Program
Files (x86)\Microsoft Visual Studio 14.0\VC\include\xtgmath.h 201
2) Severity Code Description Project File Line
Error C2375 'lround': redefinition; different linkage ConsoleApplication1 c:\program files (x86)\windows kits\10\include\10.0.10150.0\ucrt\math.h 509
3) Severity Code Description Project File Line
Error (active) linkage specification is incompatible with previous "lround" (declared at line 76 of "c:\Users\evan_2\Documents\Visual Studio 2015\Projects\ConsoleApplication1\ConsoleApplication1\Version_test.h") ConsoleApplication1 c:\Program
Files (x86)\Windows Kits\10\Include\10.0.10150.0\ucrt\math.h 509
// THIS IS THE MAIN CODE:
#include "stdafx.h"
#include "Sales_item.h"
#include<iostream>
int main()
{
Sales_item item1;
int x{}, y{}, z{};
std::string isbn1{ "0-201-78345-X" }, isbn2{ "0-201-70353-X" };
while (std::cin >> item1)
{
if (item1.isbn() == isbn1)
{
++x;
}
else if (item1.isbn() == isbn2)
{
++y;
}
else {
++z;
}
}
std::cout << "0-201-78345-X :" << x << std::endl;
std::cout << "0-201-70535-X :" << y << std::endl;
std::cout << "0-201-78645-X :" << z << std::endl;
return 0;
}
// THE SALES_ITEM.H CODE:
#pragma once
/*
* This file contains code from "C++ Primer, Fifth Edition", by Stanley B.
* Lippman, Josee Lajoie, and Barbara E. Moo, and is covered under the
* copyright and warranty notices given in that book:
*
* "Copyright (c) 2013 by Objectwrite, Inc., Josee Lajoie, and Barbara E. Moo."
*
*
* "The authors and publisher have taken care in the preparation of this book,
* but make no expressed or implied warranty of any kind and assume no
* responsibility for errors or omissions. No liability is assumed for
* incidental or consequential damages in connection with or arising out of the
* use of the information or programs contained herein."
*
* Permission is granted for this code to be used for educational purposes in
* association with the book, given proper citation if and when posted or
* reproduced.Any commercial use of this code requires the explicit written
* permission of the publisher, Addison-Wesley Professional, a division of
* Pearson Education, Inc. Send your request for permission, stating clearly
* what code you would like to use, and in what specific way, to the following
* address:
*
* Pearson Education, Inc.
* Rights and Permissions Department
* One Lake Street
* Upper Saddle River, NJ 07458
* Fax: (201) 236-3290
*/
/* This file defines the Sales_item class used in chapter 1.
* The code used in this file will be explained in
* Chapter 7 (Classes) and Chapter 14 (Overloaded Operators)
* Readers shouldn't try to understand the code in this file
* until they have read those chapters.
*/
#ifndef SALESITEM_H
// we're here only if SALESITEM_H has not yet been defined
#define SALESITEM_H
#include "Version_test.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
// THE VERSION_TEST.H CODE:
#pragma once
/*
* This file contains code from "C++ Primer, Fifth Edition", by Stanley B.
* Lippman, Josee Lajoie, and Barbara E. Moo, and is covered under the
* copyright and warranty notices given in that book:
*
* "Copyright (c) 2013 by Objectwrite, Inc., Josee Lajoie, and Barbara E. Moo."
*
*
* "The authors and publisher have taken care in the preparation of this book,
* but make no expressed or implied warranty of any kind and assume no
* responsibility for errors or omissions. No liability is assumed for
* incidental or consequential damages in connection with or arising out of the
* use of the information or programs contained herein."
*
* Permission is granted for this code to be used for educational purposes in
* association with the book, given proper citation if and when posted or
* reproduced. Any commercial use of this code requires the explicit written
* permission of the publisher, Addison-Wesley Professional, a division of
* Pearson Education, Inc. Send your request for permission, stating clearly
* what code you would like to use, and in what specific way, to the following
* address:
*
* Pearson Education, Inc.
* Rights and Permissions Department
* One Lake Street
* Upper Saddle River, NJ 07458
* Fax: (201) 236-3290
*/
#ifndef VERSION_TEST_H
#define VERSION_TEST_H
/* As of the first printing of C++ Primer, 5th Edition (July 2012),
* the Microsoft Complier did not yet support a number of C++ 11 features.
*
* The code we distribute contains both normal C++ code and
* workarounds for missing features. We use a series of CPP variables to
* determine whether a given features is implemented in a given release
* of the MS compiler. The base version we used to test the code in the book
* is Compiler Version 17.00.50522.1 for x86.
*
* When new releases are available we will update this file which will
* #define the features implemented in that release.
*/
#if _MSC_FULL_VER == 170050522 || _MSC_FULL_VER == 170050727
// base version, future releases will #define those features as they are
// implemented by Microsoft
/* Code in this delivery use the following variables to control compilation
Variable tests C++ 11 Feature
CONSTEXPR_VARS constexpr variables
CONSTEXPR_FCNS constexpr functions
CONSTEXPR_CTORS constexpr constructors and other member functions
DEFAULT_FCNS = default
DELETED_FCNS = delete
FUNC_CPP __func__ local static
FUNCTION_PTRMEM function template with pointer to member function
IN_CLASS_INITS in class initializers
INITIALIZER_LIST library initializer_list<T> template
LIST_INIT list initialization of ordinary variables
LROUND lround function in cmath
NOEXCEPT noexcept specifier and noexcept operator
SIZEOF_MEMBER sizeof class_name::member_name
TEMPLATE_FCN_DEFAULT_ARGS default template arguments for function templates
TYPE_ALIAS_DECLS type alias declarations
UNION_CLASS_MEMS unions members that have constructors or copy control
VARIADICS variadic templates
*/
#endif // ends compiler version check
#ifndef LROUND
inline long lround(double d)
{
return (d >= 0) ? long(d + 0.5) : long(d - 0.5);
}
#endif
#endif // ends header guard