FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN
From cppreference.com
C
Concurrency support (C11)
Common mathematical functions
Functions
Basic operations
Maximum/minimum operations
(C23)
(C23)
(C23)
(C23)
(C23)
Exponential functions
Power functions
Trigonometric and hyperbolic functions
Nearest integer floating-point
Floating-point manipulation
Narrowing operations
Quantum and quantum exponent
(C23)
(C23)
(C23)
(C23)
Decimal re-encoding functions
(C23)
(C23)
(C23)
(C23)
Total order and payload functions
(C23)
(C23)
(C23)
(C23)
Classification
(C99)
(C23)
(C99)
(C99)
(C99)
(C99)
(C99)
(C23)
(C23)
(C99)
(C99)
(C99)
(C99)
(C99)
(C99)
(C23)
(C23)
Error and gamma functions
Types
(C99)(C99)
(C99)(C99)
(C23)(C23)
Macro constants
Special floating-point values
(C99)(C99)(C23)
(C99)(C23)
(C99)(C23)
Arguments and return values
(C99)(C99)
FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN
(C99)(C99)(C99)(C99)(C99)
(C23)(C23)
(C23)(C23)(C23)(C23)(C23)
Error handling
(C99)(C99)
(C99)
Fast operation indicators
(C99)(C99)
(C23)(C23)(C23)(C23)
(C23)(C23)(C23)(C23)
(C23)(C23)(C23)(C23)
(C99)(C23)
(C23)(C23)(C23)(C23)
(C23)(C23)(C23)(C23)
(C23)(C23)(C23)(C23)
Defined in header
<math.h>
#define FP_NORMAL /*implementation defined*/
(since C99)
#define FP_SUBNORMAL /*implementation defined*/
(since C99)
#define FP_ZERO /*implementation defined*/
(since C99)
#define FP_INFINITE /*implementation defined*/
(since C99)
#define FP_NAN /*implementation defined*/
(since C99)
The FP_NORMAL, FP_SUBNORMAL, FP_ZERO, FP_INFINITE, FP_NAN macros each represent a distinct category of floating-point numbers. They all expand to an integer constant expression.
Constant
Explanation
FP_NORMAL
indicates that the value is normal, i.e. not an infinity, subnormal, not-a-number or zero
FP_SUBNORMAL
indicates that the value is subnormal
FP_ZERO
indicates that the value is positive or negative zero
FP_INFINITE
indicates that the value is not representable by the underlying type (positive or negative infinity)
FP_NAN
indicates that the value is not-a-number (NaN)
[edit] Example
Run this code
#include <stdio.h> #include <math.h> #include <float.h> const char *show_classification(double x) { switch(fpclassify (x)) { case FP_INFINITE: return "Inf"; case FP_NAN: return "NaN"; case FP_NORMAL: return "normal"; case FP_SUBNORMAL: return "subnormal"; case FP_ZERO: return "zero"; default: return "unknown"; } } int main(void) { printf ("1.0/0.0 is %s\n", show_classification(1/0.0)); printf ("0.0/0.0 is %s\n", show_classification(0.0/0.0)); printf ("DBL_MIN/2 is %s\n", show_classification(DBL_MIN /2)); printf ("-0.0 is %s\n", show_classification(-0.0)); printf (" 1.0 is %s\n", show_classification(1.0)); }
Output:
1.0/0.0 is Inf 0.0/0.0 is NaN DBL_MIN/2 is subnormal -0.0 is zero 1.0 is normal
[edit] References
- C17 standard (ISO/IEC 9899:2018):
- 7.12/6 FP_NORMAL, ... (p: 169-170)
- C11 standard (ISO/IEC 9899:2011):
- 7.12/6 FP_NORMAL, ... (p: 232)
- C99 standard (ISO/IEC 9899:1999):
- 7.12/6 FP_NORMAL, ... (p: 213)
[edit] See also
C++ documentation for FP_categories