nan, nanf, nanl
From cppreference.com
| Defined in header <math.h>
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| float nanf( const char* arg ); |
(since C99) | |
| double nan( const char* arg ); |
(since C99) | |
| long double nanl( const char* arg ); |
(since C99) | |
Converts the implementation-defined character string arg into the corresponding quiet NaN value, as if by calling strtof, strtod, or strtold, respectively, as follows:
The call nan("string") is equivalent to the call strtod("NAN(string)", (char**)NULL);.
The call nan("") is equivalent to the call strtod("NAN()", (char**)NULL);.
The call nan(NULL) is equivalent to the call strtod("NAN", (char**)NULL);.
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.