Defined in header <cmath> | ||
---|---|---|
#define FP_NORMAL /*implementation defined*/ | (since C++11) | |
#define FP_SUBNORMAL /*implementation defined*/ | (since C++11) | |
#define FP_ZERO /*implementation defined*/ | (since C++11) | |
#define FP_INFINITE /*implementation defined*/ | (since C++11) | |
#define FP_NAN /*implementation defined*/ | (since C++11) |
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) |
Example
#include <iostream> #include <cmath> #include <cfloat> const char* show_classification(double x) { switch(std::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() { std::cout << "1.0/0.0 is " << show_classification(1/0.0) << '\n' << "0.0/0.0 is " << show_classification(0.0/0.0) << '\n' << "DBL_MIN/2 is " << show_classification(DBL_MIN/2) << '\n' << "-0.0 is " << show_classification(-0.0) << '\n' << "1.0 is " << show_classification(1.0) << '\n'; }
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
See also
(C++11) | categorizes the given floating point value (function) |
C documentation for FP_categories |
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