isnan
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header  <math.h> | ||
| #define isnan(arg) /* implementation defined */ | (since C99) | |
Determines if the given floating point number arg is not-a-number (NaN). The macro returns an integral value.
| Contents | 
[edit] Parameters
| arg | - | floating point value | 
[edit] Return value
Nonzero integral value if arg is NaN, 0 otherwise.
[edit] Example
Run this code
#include <stdio.h> #include <math.h> #include <float.h> int main(void) { printf("isnan(NAN) = %d\n", isnan(NAN)); printf("isnan(INFINITY) = %d\n", isnan(INFINITY)); printf("isnan(0.0) = %d\n", isnan(0.0)); printf("isnan(DBL_MIN/2.0) = %d\n", isnan(DBL_MIN/2.0)); printf("isnan(1.0) = %d\n", isnan(1.0)); return 0; }
Possible output:
isnan(NAN) = 1 isnan(INFINITY) = 0 isnan(0.0) = 0 isnan(DBL_MIN/2.0) = 0 isnan(1.0) = 0
[edit] See also
| (C99) | classifies the given floating-point value (function) | 
| (C99) | checks if the given number has finite value (function) | 
| (C99) | checks if the given number is infinite (function) | 
| (C99) | checks if the given number is normal (function) | 
| (C99) | checks if two floating-point values are unordered (function) | 
| C++ documentation for isnan | |


