第二章 变量和基本类型

code:

// 第二章 变量和基本类型


// 1、基本内置类型 ----------------------------------------------


// 类型字节长
#include <iostream>
using namespace std;
int main()
{
  cout << sizeof(bool) << endl;
  cout << sizeof(char) << endl;  
  cout << sizeof(wchar_t) << endl;  
  cout << sizeof(short) << endl;  
  cout << sizeof(int) << endl;  
  cout << sizeof(long) << endl;  
  cout << sizeof(long long) << endl;  
  cout << sizeof(float) << endl;  
  cout << sizeof(double) << endl;  
  cout << sizeof(long double) << endl;
  
  return 0;
}


// 2、字面值常量 -------------------------------------------------


// 字面值常量
#include <iostream>
using namespace std;
int main()
{
  int i;
  i=20;  //decimal
  cout << i << endl;
  i=024; //octal
  cout << i << endl;
  i=0x14; // hexadecimal
  cout << i << endl;  
  return 0;
}


// concatenated long string literal
#include <iostream>
using namespace std;
int main()
{
  std::cout << "a multi-line "
    "string literal "
    "using concatenation" 
    << std::endl;
  return 0;
}



// Multi-Line Literals
#include <iostream>
using namespace std;
int main()
{
  // ok: A \ before a newline ignores the line break
  /*
  std::cou\
  t << "Hi" << std::e\
  ndl;
  */// 这样行不通，通不过编译
  //
  std::cout << "Hi" << std::endl;
  // multiline string literal
  // 在字符串中加\，可以的
  std::cout << "a multi-line \
string literal \
using a backslash"
  << std::endl;

  return 0;
}



// 3、变量 -----------------------------------------------------

#include <iostream>
int main()
{
  // a first, not very good, solution
  std::cout << "2 raised to the power of 10: ";
  std::cout << 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2;
  std::cout << std::endl;
  return 0;
}


#include <iostream>
int main()
{
  // local objects of type int
  int value = 2;
  int pow = 10;
  int result = 1;
  // repeat calculation of result until cnt is equal to pow
  for(int cnt = 0; cnt != pow; ++cnt)
    result *= value;
  // result = result * value;
  std::cout << value << " raised to the power of " << pow 
    << ": \t" << result << std::endl;
  return 0;
}



#include <iostream>
#include <string>
using namespace std;
int main()
{
  // alternative ways to initialize string from a character string literal
  string titleA = "C++ Primer, 4th Ed.";
  string titleB("C++ Primer, 4th Ed.");
  cout << titleA << endl;
  cout << titleB << endl;
  string all_nines(30,'9');
  cout << all_nines << endl;
  return 0;
}



#include <iostream>
#include <string>
using namespace std;
int main()
{
  // ok: salary defined and initialized before it is used to initialize wage
  double salary = 9999.99, wage(salary + 0.01);
  // ok: mix of initialized and uninitialized
  int interval, month = 8, day = 7, year = 1955;
  // ok: both forms of initialization syntax used
  string title("C++ Primer, 4th Ed."), publisher = "A-W";

  return 0;
}


#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;
}



#include <iostream>
#include <string>
/*  Program for illustration purposes only:
 *  It is bad style for a function to use a global variable and then
 *  define a local variable with the same name
 */
std::string s1 = "hello"; // s1 has global scope
int main()
{
  std::string s2 = "world"; // s2 has local scope
  // uses global s1; prints "hello world"
  std::cout << s1 << " " << s2 << std::endl;
  int s1 = 42; // s1 is local and hides global s1
  // uses local s1;prints "42 world"
  std::cout << s1 << " " << s2 << std::endl;
  return 0;
}



// 4、const限定符 ------------------------------------------------------

#include <iostream>
using namespace std;

int main()
{
  const int bufSize = 512;     // input buffer size
  //bufSize = 0; // error: attempt to write to const object
  
  const std::string hi = "hello!"; // ok: initialized
  //const int i, j = 0;  // error: i is uninitialized const

  return 0;
}


// 5、引用 -------------------------------------------------------------

#include <iostream>
int main()
{
  const int ival=1024;
  const int &refVal=ival;
  std::cout<<refVal;
  //
  int i=42;
  const int &r=42;
  const int &r2=r+i;
  std::cout<<' '<<r2<<std::endl;
  return 0;
}


// 6、typedef名字 -------------------------------------------------------

#include <iostream>
int main()
{
  typedef double wages; //  wages is a synonym for double
  typedef int exam_score; //  exam_score is a synonym for int
  typedef wages salary; //  indirect synonym for double
  wages hourly, weekly; // double hourly, weekly;
  exam_score test_result; // int test_result;
  return 0;
}


// 7、枚举 --------------------------------------------------------------

#include <iostream>
using namespace std;
int main()
{
  // shape is 1, sphere is 2, cylinder is 3, polygon is 4
  enum Forms
  {
    shape = 1, sphere, cylinder, polygon
  };
  // point2d is 2, point2w is 3, point3d is 3, point3w is 4
  enum Points
  {
    point2d = 2, point2w, point3d = 3, point3w
  };
  Points pt3d = point3d; //  ok: point3d is a Points enumerator
  //Points pt2w = 3; //  error: pt2w initialized with int
  //pt2w = polygon; //  error: polygon is not a Points enumerator
  Points pt2w;
  pt2w = pt3d; //  ok: both are objects of Points enum type
  //
  cout << pt3d << endl;
  cout << pt2w << endl;
  
  return 0;
}


// 8、类类型 -------------------------------------------------------------

// 类的定义
#include <iostream>
using namespace std;

int main()
{
  class Sales_item
  {
    public:
      // operations on Sales_item objects will go here
    private:
      std::string isbn;
      unsigned units_sold;
      double revenue;
  };
  struct Sales_item2
  {
    // no need for public label, members are public by default
    // operations on Sales_item objects
    private:
      std::string isbn;
      unsigned units_sold;
      double revenue;
  };
  return 0;
}



// 9、编写自己的头文件 -----------------------------------------------

#include <iostream>
using namespace std;

int main()
{
  #ifndef SALESITEM_H
  #define SALESITEM_H
  // Definition of Sales_itemclass and related functions goes here
  #endif

  return 0;
}

 

 

 

 

 

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