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C ++ digital

Usually, when we need to use numbers, we use the original data types, such as int, short, long, float, and double, and so on. These data types for numbers, its possible values ​​and range of values, we have already discussed in C ++ data type chapter.

C ++ custom number

We have chapters in various instances before the defined number. Here is a C ++ define the various types of digital integrated example:

#include <iostream>
using namespace std;
 
int main ()
{
   // 数字定义
   short  s;
   int    i;
   long   l;
   float  f;
   double d;
   
   // 数字赋值
   s = 10;      
   i = 1000;    
   l = 1000000; 
   f = 230.47;  
   d = 30949.374;
   
   // 数字输出
   cout << "short  s :" << s << endl;
   cout << "int    i :" << i << endl;
   cout << "long   l :" << l << endl;
   cout << "float  f :" << f << endl;
   cout << "double d :" << d << endl;
 
   return 0;
}

When the above code is compiled and executed, it produces the following results:

short  s :10
int    i :1000
long   l :1000000
float  f :230.47
double d :30949.4

C ++ math

In C ++, you can create a variety of functions in addition, also contains a variety of useful functions for you to use. These functions are written in standard C and C ++ libraries, calledbuilt-in functions.You can refer to these functions in the program.

C ++ built a wealth of mathematical functions can be performed on a variety of digital computing. The following table lists the C ++ some useful built-in mathematical functions.

To use these functions, you need to refer to mathematic header<cmath>.

序号函数 & 描述
1double cos(double);
该函数返回弧度角(double 型)的余弦。
2double sin(double);
该函数返回弧度角(double 型)的正弦。
3double tan(double);
该函数返回弧度角(double 型)的正切。
4double log(double);
该函数返回参数的自然对数。
5double pow(double, double);
假设第一个参数为 x,第二个参数为 y,则该函数返回 x 的 y 次方。
6double hypot(double, double);
该函数返回两个参数的平方总和的平方根,也就是说,参数为一个直角三角形的两个直角边,函数会返回斜边的长度。
7double sqrt(double);
该函数返回参数的平方根。
8int abs(int);
该函数返回整数的绝对值。
9double fabs(double);
该函数返回任意一个十进制数的绝对值。
10double floor(double);
该函数返回一个小于或等于传入参数的最大整数。

Here is a simple example of mathematical operations:

#include <iostream>
#include <cmath>
using namespace std;
 
int main ()
{
   // 数字定义
   short  s = 10;
   int    i = -1000;
   long   l = 100000;
   float  f = 230.47;
   double d = 200.374;

   // 数学运算
   cout << "sin(d) :" << sin(d) << endl;
   cout << "abs(i)  :" << abs(i) << endl;
   cout << "floor(d) :" << floor(d) << endl;
   cout << "sqrt(f) :" << sqrt(f) << endl;
   cout << "pow( d, 2) :" << pow(d, 2) << endl;
 
   return 0;
}

When the above code is compiled and executed, it produces the following results:

sign(d) :-0.634939
abs(i)  :1000
floor(d) :200
sqrt(f) :15.1812
pow( d, 2 ) :40149.7

C ++ Random Number

In many cases, we need to generate a random number. Random number generator, there are two related functions. One is therand (), the function only returns a pseudo-random number.You must callsrand () function before generating a random number.

Here is a simple example of generating random numbers. Examples of the use oftime () function to obtain the number of seconds the system time, function to generate a random number by calling the rand ():

#include <iostream>
#include <ctime>
#include <cstdlib>

using namespace std;
 
int main ()
{
   int i,j;
 
   // 设置种子
   srand( (unsigned)time( NULL ) );

   /* 生成 10 个随机数 */
   for( i = 0; i < 10; i++ )
   {
      // 生成实际的随机数
      j= rand();
      cout <<"随机数: " << j << endl;
   }

   return 0;
}

When the above code is compiled and executed, it produces the following results:

随机数: 1748144778
随机数: 630873888
随机数: 2134540646
随机数: 219404170
随机数: 902129458
随机数: 920445370
随机数: 1319072661
随机数: 257938873
随机数: 1256201101
随机数: 580322989