第一章 快速入门

// 1、编写简单的C++程序 ------------------------------------------------



int main()
{
  return 0;
}


// 2、初窥输入/输出 ---------------------------------------------------


#include <iostream>
int main()
{
  std::cout << "Enter two numbers:" << std::endl; 
  int v1, v2;
  std::cin >> v1 >> v2;   
  std::cout << "The sum of " << v1 << " and " << v2
            << " is " << v1 + v2 << std::endl;
  return 0;
}


// 3、关于注释 --------------------------------------------------------------


/* Simple main function: Read two numbers and write their sum */
#include <iostream>
int main()
{
  // prompt user to enter two numbers
  std::cout << "Enter two numbers:" << std::endl; 
  int v1, v2;           //uninitialized
  std::cin >> v1 >> v2; // read input  
  return 0;
}



// 4、控制结构 -------------------------------------------------------------


// while
#include <iostream>
int main()
{
  int sum = 0, val = 1;
  // keep executing the while until val is greater than 10
  while(val <= 10)
  {
    sum += val; // assigns sum + val to sum
    ++val; // add 1 to val
  }
  std::cout << "Sum of 1 to 10 inclusive is " << sum << std::endl;
  return 0;
}


// for
#include <iostream>
int main()
{
  int sum = 0;
  // sum values from 1 up to 10 inclusive
  for(int val = 1; val <= 10; ++val)
    sum += val;
  // equivalent to sum = sum + val
  std::cout << "Sum of 1 to 10 inclusive is " << sum << std::endl;
  return 0;
}


// if
#include <iostream>
int main()
{
  std::cout << "Enter two numbers:" << std::endl;
  int v1, v2;
  std::cin >> v1 >> v2; // read input
  // use smaller number as lower bound for summation
  // and larger number as upper bound
  int lower, upper;
  if(v1 <= v2)
  {
    lower = v1;
    upper = v2;
  }
  else
  {
    lower = v2;
    upper = v1;
  }
  int sum = 0;
  // sum values from lower up to and including upper
  for(int val = lower; val <= upper; ++val)
    sum += val;
  // sum = sum + val
  std::cout << "Sum of " << lower << " to " << upper << " inclusive is " << sum
    << std::endl;
  return 0;
}


// end of file. Ctrl+z 可以模拟文件尾
#include <iostream>
int main()
{
  int sum = 0, value;
  // read till end-of-file, calculating a running total of all values read
  while(std::cin >> value)
    sum += value;
  // equivalent to sum = sum + value
  std::cout << "Sum is: " << sum << std::endl;
  return 0;
}


// 5、类的简介 ----------------------------------------------------

/*
必须将Sales_item.h文件，放在程序文件的同一目录下，
这个程序才可以运行。
Sales_item.h文件，目前不要求读者制作。
Sales_item.h文件具体内容，在最前面。
*/
#include <iostream>
#include "Sales_item.h"
int main()
{
  Sales_item book;
  // read ISBN, number of copies sold, and sales price
  std::cin >> book;
  // write ISBN, number of copies sold, total revenue, and average price
  std::cout << book << std::endl;
  return 0;
}
// input:   0-201-70353-X 4 24.99


// 对象之和
#include <iostream>
#include "Sales_item.h"
int main()
{
  Sales_item item1, item2;
  std::cin >> item1 >> item2; // read a pair of transactions
  std::cout << item1 + item2 << std::endl; // print their sum
  return 0;
}
/*

0-201-78345-X 3 20.00
0-201-78345-X 2 25.00

*/



// 成员函数
#include <iostream>
#include "Sales_item.h"
int main()
{
  Sales_item item1, item2;
  std::cin >> item1 >> item2;
  // first check that item1 and item2 represent the same book
  if(item1.same_isbn(item2))
  {
    std::cout << item1 + item2 << std::endl;
    return 0; // indicate success
  }
  else
  {
    std::cerr << "Data must refer to same ISBN" << std::endl;
    return  - 1; // indicate failure
  }
}
/*

0-201-78345-X 3 20.00
0-201-78345-X 2 25.00

0-201-78345-X 3 20.00
0-888-78345-X 2 25.00

*/



// 6、C++程序 ------------------------------------------------------

#include <iostream>
#include "Sales_item.h"
int main()
{
  //  declare variables to hold running sum and data for the next record
  Sales_item total, trans;
  //  is there data to process?
  if(std::cin >> total)
  {
    // if so, read the transaction records
    while(std::cin >> trans)
      if(total.same_isbn(trans))
    //  match: update the running total
        total = total + trans;
      else
    {
      //  no match: print & assign to total
      std::cout << total << std::endl;
      total = trans;
    }
    //  remember to print last record
    std::cout << total << std::endl;
  }
  else
  {
    //  no input!, warn the user
    std::cout << "No data?!" << std::endl;
    return  - 1; //  indicate failure
  }
  return 0;
}