C + + Third day

Things to do today:

Main Line

1, reviewed the contents of yesterday while (Std::cin >> value) scan "standard input"

2. Download the sales_item.h code below online

#ifndef Salesitem_h#defineSalesitem_h#include<iostream>#include<string>classsales_item{ Public: Sales_item (ConstSTD::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 &,ConstSales_item &); Public: Sales_item&operator+=(Constsales_item&); Public: DoubleAvg_price ()Const; BOOLSAME_ISBN (ConstSales_item &AMP;RHS)Const {  returnISBN = =RHS.ISBN;} Sales_item (): Units_sold (0), Revenue (0.0){} Public: std::stringISBN; unsigned units_sold;Doublerevenue;};usingStd::istream;usingStd::ostream; Sales_itemoperator+(ConstSales_item &ConstSales_item &); inlineBOOL operator==(ConstSales_item &AMP;LHS,ConstSales_item &RHS) { returnLhs.units_sold = = Rhs.units_sold && lhs.revenue = = Rhs.revenue &&LHS.SAME_ISBN (RHS);} InlineBOOL operator!=(ConstSales_item &AMP;LHS,ConstSales_item &RHS) { return! (LHS = =RHS);} Inline Sales_item& Sales_item::operator+=(ConstSales_item &RHS) {Units_sold+=Rhs.units_sold; Revenue+=rhs.revenue;return* This;} Inline Sales_itemoperator+(ConstSales_item &AMP;LHS,ConstSales_item &RHS) {sales_item ret (LHS); RET+=RHS;returnret;} Inline IStream&operator>> (IStream &inch, Sales_item &1) { DoublePrice ;inch>> S.ISBN >> s.units_sold >>Price ;if(inch) S.revenue= S.units_sold *Price ;Elses=Sales_item ();return inch;} Inline Ostream&operator<< (Ostream & out,ConstSales_item &1) {  out<< S.ISBN <<"\ t"<<s.units_sold <<"\ t"<< s.revenue <<"\ t"<<S.avg_price ();return  out;} InlineDoubleSales_item::avg_price ()Const{ if(Units_sold)returnrevenue/Units_sold;Else  return 0;}#endif

3. Use file redirection, for example: $ prog1<input.txt>output.txt

Regional

Things to plan for tomorrow: None

Problems encountered:

1, in C++primer e5, Access to ISBN is ITEM1.ISBN (),

In the header file I downloaded, the ISBN was directly defined as public and did not write the ISDN () function. So in the code below, you access the ISDN of the object directly with ITEM1.ISDN.

2, in addition, Std::cerr << "xxx" is not affected by redirection, XXX Direct output in the CMD interface

Exercise 1.19

#include <iostream>intMain () {std::cout<<"Enter The numbers:"<<Std::endl; intV1 =0, V2 =0; Std::cin>> v1 >>v2; inttemp =0; if(V1 >v2) {Temp=v1; V1=v2; V2=temp; }     for(; V1 <= v2; + +v1) {Std::cout<< v1 <<Std::endl; }    return 0;}

Harvest: 艹

C + + Third day