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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
|
/* 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
)