C ++ Nanl()函数 (C++ nanl() function)

nanl() function is a library function of cmath header, it is used to get the NaN value of type long double. It accepts an argument (which is an implementation-specific C String – to get NaN value we have to pass an empty string), it returns NaN value of type long double.

nanl()函数是cmath标头的库函数，用于获取long double类型的NaN值。 它接受一个参数(这是特定于实现的C字符串-要获取NaN值，我们必须传递一个空字符串)，它返回long double类型的NaN值。

Not-A-Number (NaN) values are used to check whether the value is an unidentified/non-representable or not? For example, the square root of a negative number is unidentified.

非数字(NaN)值用于检查该值是否为未识别/不可代表？ 例如，负数的平方根不确定。

Syntax of nanl() function:

nanl()函数的语法：

C++11:

C ++ 11：

long double nanl (const char* tagp);

Parameter(s):

参数：

• tagp – represents an implementation-specific C-String.

  tagp –表示特定于实现的C-String。

Return value:

返回值：

The return type of this method is long double, it returns NaN value.

此方法的返回类型为long double ，它返回NaN值。

Example:

例：

Function call:    nanl("");            Output:    nan

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

// C++ code to demonstrate the example of// nanl() function#include 
    
     #include 
     
      using namespace std;// main() sectionint main(){    float nanValue;    //generating generic NaN value    //by passing an empty string    nanValue = nanl("");    //printing the value    cout << "nanValue: " << nanValue << endl;    return 0;}
     
    

Output

输出量

nanValue: nan

Reference:

参考：

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