isnan函数 c语言

C ++ isnan()函数 (C++ isnan() function)

isnan() function is a library function of cmath header, it is used to check whether the given value is a NaN (Not-A-Number). It accepts a value (float, double or long double) and returns 1 if the given value is NaN; 0, otherwise.

isnan()函数是cmath标头的库函数，用于检查给定的值是否为NaN(非数字)。 它接受一个值( float ， double或long double )，如果给定值为NaN，则返回1；否则，返回1。 0，否则。

Syntax of isnan() function:

isnan()函数的语法：

In C99, it has been implemented as a macro,

在C99中，它已实现为宏，

    macro isnan(x)

In C++11, it has been implemented as a function,

在C ++ 11中，它已作为函数实现，

    bool isnan (float x);
    bool isnan (double x);
    bool isnan (long double x);

Parameter(s):

参数：

• x – represents a value to be checked as a NaN.

  x –表示要检查为NaN的值。

Return value:

返回值：

The returns type of this function is bool, it returns 1 if the x is NaN; 0, otherwise.

该函数的返回类型为bool ，如果x为NaN，则返回1；否则，返回1。 0，否则。

Example:

例：

    Input:
    float x = 0.0f/0.0f;
    
    Function call:
    isnan(x);    
    
    Output:
    1

    Input:
    float x = sqrt(-1.0f);
    
    Function call:
    isnan(x);    
    
    Output:
    1

    Input:
    float x = 10.0f;
    
    Function call:
    isnan(x);    
    
    Output:
    0

C ++代码演示isnan()函数的示例 (C++ code to demonstrate the example of isnan() function)

// C++ code to demonstrate the example of
// isnan() function

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    cout << "isnan(sqrt(-10.0f)): " << isnan(sqrt(-10.0f)) << endl;
    cout << "isnan(0.0f/0.0f): " << isnan(0.0f / 0.0f) << endl;
    cout << "isnan(0.0f/1.0f): " << isnan(0.0f / 1.0f) << endl;
    cout << "isnan(1.0f/0.0f): " << isnan(1.0f / 0.0f) << endl;

    float x = sqrt(-1.0f);

    // checking using the condition
    if (isnan(x)) {
        cout << x << " is a NaN." << endl;
    }
    else {
        cout << x << " is not a NaN." << endl;
    }

    x = sqrt(2);

    if (isnan(x)) {
        cout << x << " is a NaN." << endl;
    }
    else {
        cout << x << " is not a NaN." << endl;
    }

    return 0;
}

Output

输出量

isnan(sqrt(-10.0f)): 1
isnan(0.0f/0.0f): 1
isnan(0.0f/1.0f): 0
isnan(1.0f/0.0f): 0
-nan is a NaN.
1.41421 is not a NaN.

Reference: C++ isnan() function

参考： C ++ isnan()函数

翻译自: https://www.includehelp.com/cpp-tutorial/isnan-function-with-example.aspx

isnan函数 c语言