C++ 浮点运算

与整数一样，C++11 引入了一些基本的内置函数，用于处理日常编程和竞争性编程所需的浮点数的简单数学计算。这些函数属于头文件。本文讨论了一些介绍的功能。

1. fmod() ：此函数用于返回其参数中提到的 2 个浮点数的余数（模数） 。计算的商被截断。

句法：

fmod(a,b);  // a, b are 2 floating point numbers

例子：

C++

// C++ code to demonstrate working of fmod()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
  
    double a, b, c;
  
    // Initializing values
    a = 9.6;
    b = 3.5;
  
    // using fmod() to compute the remainder
    // computes 2 as quotient (truncated)
    // returns 2.6 as remainder
    c = fmod(a, b);
  
    cout << "The remainder computed using fmod() is : "
         << c;
    cout << endl;
}

输出

The remainder computed using fmod() is : 2.6

2. 余数（） ：此函数还用于返回其参数中提到的 2 个浮点数的余数（模数） 。计算的商是四舍五入的。

句法：

remainder(a,b);  // a, b are 2 floating point numbers

例子：

C++

// C++ code to demonstrate working of remainder()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
  
    double a, b, c;
  
    // Initializing values
    a = 9.6;
    b = 3.5;
  
    // using remainder() to compute the remainder
    // computes 3 as quotient (rounded)
    // returns -0.9 as remainder
    c = remainder(a, b);
  
    cout << "The remainder computed using remainder() is : "
         << c;
    cout << endl;
}

输出

The remainder computed using remainder() is : -0.9

3. remquo() ：此函数返回余数并将余数存储在作为参数传递的变量引用中。此函数接受 3 个参数，分子、分母和必须存储商的变量的引用。

句法：

remquo(a,b,&quo); // a, b and c are three arguments

例子：

CPP

// C++ code to demonstrate working of remquo()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
  
    double a, b, f;
    int g;
  
    // Initializing values
    a = 9.6;
    b = 3.5;
  
    // using remquo() to return quotient and remainder
    // quotient stored in g
    f = remquo(a, b, &g);
  
    cout << "The remainder part of " << a << "/" << b
         << " is : " << f;
    cout << endl;
    cout << "The quotient part of " << a << "/" << b
         << " is : " << g;
    cout << endl;
}

输出

The remainder part of 9.6/3.5 is : -0.9
The quotient part of 9.6/3.5 is : 3

4. copysign() ：此函数返回一个数字，其中第一个参数的大小和第二个参数的符号。

句法：

copysign(a, b);  // a and b are arguments

例子：

C++

// C++ code to demonstrate working of copysign()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
    double a, b;
  
    // Initializing values
    a = 9.6;
    b = -3.5;
  
    // using copysign()
    cout << "The value returned after copysigning is : ";
    cout << copysign(a, b);
  
    cout << endl;
}

输出

The value returned after copysigning is : -9.6

5. nextafter() ：此函数计算第一个参数在第二个参数方向上的下一个可表示值。

句法：

nextafter(a, b);  // a and b are arguments

例子：

CPP

// C++ code to demonstrate working of nextafter()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
    double a, b;
  
    // Initializing values
  
    a = -3.5;
    b = 0.0;
  
    // using nextafter() to compute next approximated value
    cout << "The next value approximated is : ";
    cout << nextafter(a, b);
}

输出

The next value approximated is : -3.5

6. fmin() ：返回两个参数中最小的一个。

句法：

fmin(a, b);  // a and b are arguments

例子：

C++

// C++ code to demonstrate working of fmin()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
    double a, b;
  
    // initializing values
    a = 2.5;
    b = 2.0;
  
    // using fmin() to compute smallest of two numbers
    cout << "The smallest of 2 numbers is : ";
    cout << fmin(a, b);
  
    cout << endl;
}

输出

The smallest of 2 numbers is : 2

7. fmax() ：返回两个参数中的最大值。

句法：

fmax(a, b);  // a and b are arguments

例子：

C++

// C++ code to demonstrate working of fmax()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
    double a, b;
  
    // initializing values
    a = 2.5;
    b = 2.0;
  
    // using fmax() to compute maximum of two numbers
    cout << "The largest of 2 numbers is : ";
    cout << fmax(a, b);
  
    cout << endl;
}

输出

The largest of 2 numbers is : 2.5

8. fdim() ：返回作为参数传递的数字的正差。

句法：

fdim(a, b);  // a and b are arguments

例子：

C++

// C++ code to demonstrate working of fdim()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
    double a, b;
  
    // initializing values
    a = 2.5;
    b = 2.0;
  
    // using fdim() to compute positive difference of two
    // numbers
    cout << "The positive difference of 2 numbers is : ";
    cout << fdim(a, b);
  
    cout << endl;
}

输出

The positive difference of 2 numbers is : 0.5

9. fma() ：该函数接受3 个参数并在计算后返回乘加“ x*y+z ”值。

句法：

fma(a, b, c);  // a, b and c are arguments

例子：

CPP

// C++ code to demonstrate working of fma()
#include 
#include 
using namespace std;
  
// Driver Code
int main()
{
    double a, b, c;
  
    // initializing values
    a = 2.5;
    b = 2.0;
    c = 2.5;
  
    // using fma() to compute multiply-add
    cout << "The multiply-add of 3 numbers is : ";
    cout << fma(a, b, c);
}

输出

The multiply-add of 3 numbers is : 7.5