macro/function
<cmath> <ctgmath>
fpclassify
| function | int fpclassify (float x);int fpclassify (double x);int fpclassify (long double x); |
|---|
Classify floating-point value
Returns a value of type int that matches one of the classification macro constants, depending on the value of x:
| value | description |
|---|
| FP_INFINITE | Positive or negative infinity (overflow) |
| FP_NAN | Not-A-Number |
| FP_ZERO | Value of zero |
| FP_SUBNORMAL | Sub-normal value (underflow) |
| FP_NORMAL | Normal value (none of the above) |
Note that each value pertains to a single category: zero is not a normal value.
These macro constants of type int are defined in header <cmath> (<math.h>).
In C, this is implemented as a macro, but the type of x shall be float, double or long double.
Parameters
- x
The value to classify.
Return value
One of the followoing int values: FP_INFINITE, FP_NAN, FP_ZERO, FP_SUBNORMAL or FP_NORMAL.
Example
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| /* fpclassify example */ #include <stdio.h> /* printf */ #include <math.h> /* fpclassify, signbit, FP_* */ int main() { double d = 1.0 / 0.0; switch (fpclassify(d)) { case FP_INFINITE: printf ("infinite"); break; case FP_NAN: printf ("NaN"); break; case FP_ZERO: printf ("zero"); break; case FP_SUBNORMAL: printf ("subnormal"); break; case FP_NORMAL: printf ("normal"); break; } if (signbit(d)) printf (" negative\n"); else printf (" positive or unsigned\n"); return 0; }
|
Output:
infinite positive or unsigned |
See also
- isfinite
- Is finite value (macro)
- isnan
- Is Not-A-Number (macro/function)
- isnormal
- Is normal (macro/function)
- signbit
- Sign bit (macro/function)