14.1.Basic Concepts

//14.1. Basic Concepts//Exercises Section 14.1//Exercise 14.1: In what ways does an overloaded operator differ from a//built - in operator ? In what ways are overloaded operators the same as the//built - in operators ?//We can call an overloaded operator function directly.//An overloaded operator function must either be a member of a class or have at least one parameter of class type.//A few operators guarantee the order in which operands are evaluated.These overloaded versions of these operators do not preserve order of evaluation and/or short - circuit evaluation, it is usually a bad idea to overload them.//An overloaded operator has the same precedence and associativity as the corresponding built - in operator.//Exercise 14.2 : Write declarations for the overloaded input, output, addition,//and compound - assignment operators for Sales_data./*#include <iostream>#include <string>using namespace std;class Sales_data {friend istream &operator>>(istream &, Sales_data &);friend ostream &operator<<(ostream &, const Sales_data &);friend Sales_data operator+(const Sales_data &, const Sales_data &);public:Sales_data(const string &s, unsigned n, double p) :bookNo(s), units_sold(n), revenue(p) { }Sales_data() : Sales_data("", 0, 0.0) { }Sales_data(const string &s) : Sales_data(s, 0, 0.0) { }Sales_data(istream &is);Sales_data &operator += (const Sales_data &);string isbn() const { return bookNo; }private:inline double avg_price() const;string bookNo;unsigned units_sold = 0;double revenue = 0.0;};istream &operator>>(istream &, Sales_data &);ostream &operator<<(ostream &, const Sales_data &);Sales_data operator+(const Sales_data &, const Sales_data &);inline double Sales_data::avg_price() const{return units_sold ? revenue / units_sold : 0;}#include "ChenHC.h"using namespace std;Sales_data::Sales_data(istream &is) : Sales_data() {is >> *this;}Sales_data &Sales_data::operator+=(const Sales_data &rhs){units_sold += rhs.units_sold;revenue += rhs.revenue;return *this;}istream &operator>>(istream &is, Sales_data &item){double price = 0.0;is >> item.bookNo >> item.units_sold >> price;if (is)item.revenue = price * item.units_sold;else item = Sales_data();return is;}ostream &operator<<(ostream &os, const Sales_data &item){os << item.isbn() << " " << item.units_sold << " " << item.revenue << " " << item.avg_price();return os;}Sales_data operator+(const Sales_data &lhs, const Sales_data &rhs){Sales_data sum = lhs;sum += rhs;return sum;}*///Exercise 14.3 : Both string and vector define an overloaded == that can//be used to compare objects of those types.Assuming svec1 and svec2 are//vectors that hold strings, identify which version of == is applied in each//of the following expressions :(a) "cobble" == "stone"//neither, it matches (char *, char *) better than (const string, const string) version.(b)svec1[0] == svec2[0]//string(c) svec1 == svec2//vector(d) svec1[0] == "stone" //string//Exercise 14.4: Explain how to decide whether the following should be class//members :(a) % //symmetric, non-member (b) %=//change the objects, member(c) ++//change the objects, member(d) ->//=()[]->must be member(e) <<//non-member  ?(f) &&//symetric, non-member(g) ==//sysmetric, non-member(h)()//as (d)//Exercise 14.5: In exercise 7.40 from § 7.5.1 (p. 291) you wrote a sketch of//one of the following classes.Decide what, if any, overloaded operators your//class should provide.(a)Book(b) Date(c) Employee(d) Vehicle(e) Object(f) Tree#include <iostream>#include <string>using namespace std;class Book {friend istream& operator>>(istream &, Book &);friend ostream& operator<<(ostream &, const Book &);friend bool operator==(const Book &, const Book &);friend bool operator!=(const Book &, const Book &);public:Book() = default;Book(unsigned no, string name, string author, string pubdate) :no_(no), name_(name), author_(author), pubdate_(pubdate) { }Book(istream &in) { in >> *this; }private:unsigned no_;string name_;string author_;string pubdate_;};istream &operator>>(istream &, Book &);ostream &operator<<(ostream &, const Book &);bool operator==(const Book &, const Book &);bool operator!=(const Book &, const Book &);#include <iostream>#include <string>#include "ChenHC.h"using namespace std;istream &operator>>(istream &in, Book &book){in >> book.no_ >> book.name_ >> book.author_ >> book.pubdate_;return in;}ostream &operator<<(ostream &out, const Book &book){out << book.no_ << " " << book.name_ << " " << book.author_ << " " << book.pubdate_;return out;}bool operator==(const Book &lhs, const Book &rhs){return lhs.no_ == rhs.no_;}bool operator!=(const Book &lhs, const Book &rhs){return !(lhs.no_ == rhs.no_);}int main() {Book book1(123, "aaa", "bbb", "2016");Book book2(123, "aaa", "bbb", "2016");if (book1 == book2) cout << book1 << endl;return 0;}