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# std::nan, std::nanf, std::nanl

From cppreference.com
< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
float nanf( const char* arg ); |  | (since C++11)
double nan( const char* arg ); |  | (since C++11)
long double nanl( const char* arg ); |  | (since C++11)

Converts the implementation-defined character string `arg` into the corresponding quiet NaN value. The call std::nan("string") is equivalent to the call std::strtod("NAN(string)", (char**)NULL);.

### [edit] Parameters

arg | - | narrow character string identifying the contents of a NaN, or an empty string

### [edit] Return value

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

### [edit] See also

isnan (C++11) | checks if the given number is NaN (function) [edit]
quiet_NaN [static] | returns a quiet NaN value of the given floating-point type (public static member function of `std::numeric_limits`) [edit]
C documentation for nanf, nan, nanl

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