Nan

Defined in header <cmath>.

Description

Converts the character string arg into the corresponding quiet NaN value, as if by calling std::strtof, std::strtod, or std::strtold, respectively.

Declarations

// 1)
float nanf( const char* arg );
// 2)
double nan ( const char* arg );
// 3)
long double nanl( const char* arg );

Parameters

arg - narrow character string identifying the contents of a NaN

Return value

The quiet NaN value that corresponds to the identifying string arg or zero if the implementation does not support quiet NaNs.

If the implementation supports IEEE floating-point arithmetic (IEC 60559), it also supports quiet NaNs.

Error handling

This function is not subject to any of the error conditions specified in math_errhandling.

Examples

#include <cmath>
#include <cstdint>
#include <cstring>
#include <iostream>
 
int main()
{
    double f1 = std::nan("1");
    std::uint64_t f1n; 
    std::memcpy(&f1n, &f1, sizeof f1);
    std::cout 
        << "nan(\"1\") = " 
        << f1 << " (" 
        << std::hex << f1n << ")\n";
 
    double f2 = std::nan("2");
    std::uint64_t f2n; 
    std::memcpy(&f2n, &f2, sizeof f2);
    std::cout 
        << "nan(\"2\") = " 
        << f2 << " (" 
        << std::hex << f2n << ")\n";
}

Possible Result

nan("1") = nan (7ff0000000000001)
nan("2") = nan (7ff0000000000002)