C + + Primer version Fifth exercise 7.7

Exercise 7.7: Use these new functions to rewrite the transaction handlers in the 7.1.2 practice session

Sales.data.h#ifndef sales_data_h#define sales_data_h#include <iostream> #include   &LT;STRING&GT;STRUCT&NBSP;SALES_DATA{&NBSP;&NBSP;&NBSP;&NBSP;STD::STRING&NBSP;ISBN ()  const{return  Bookno;}     double avg_price ()  const;    Sales_data&  Combine (const sales_data&);    unsigned units_sold=0;     std::string bookno;    double revenue=0.0;    double  price=0.0;}; Double sales_data::avg_price ()  const{    if (units_sold)          return revenue/units_sold;    else         return 0;} Sales_data& sales_data::combine (CONST&NBSP;SALES_DATA&NBSP;&AMP;RHS) {    units_ sold+=rhs.units_sold;    revenue+=rhs.revenue;    return *this;} Std::istream& read (std::istream &is,sales_data &item) {    is >>item.bookno>>item.units_sold>>item.price;    item.revenue=item.units_ Sold*item.price;    return is;} Std::ostream& print (Std::ostream &os,const sales_data &item) {   &NBSP;&NBSP;OS&LT;&LT;ITEM.ISBN () << " " <<item.units_sold<< " " <<item.revenue << " " <<item.avg_price ();     return os;} Sales_data add (CONST&NBSP;SALES_DATA&NBSP;&AMP;LHS,CONST&NBSP;SALES_DATA&NBSP;&AMP;RHS) {     sales_data sum=lhs;    sum.combine (RHS);     return  sum;} #endif  // sales_data_h

main.cpp#include  "Sales_data.h" Int main (INT&NBSP;ARGC,CONST&NBSP;CHAR&NBSP;**ARGV) {     sales_data total;    if (Read (std::cin,total))     {         Sales_data trans;         while (Read (Std::cin,trans))         {             if (TOTAL.ISBN () ==TRANS.ISBN ())              {                 total=add (Total,trans);             }            else             {             &nbsP;   print (std::cout,total) <<std::endl;                 total=trans;             }        }         print (std::cout,total);    }    else     {        std::cerr<< "No data?" <<std::endl;    }}

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C + + Primer version Fifth exercise 7.7