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Determine if a number is finite
#include <math.h>
int isfinite ( double x );
- x
- The number you want to test.
libm
Use the -l m option to
qcc
to link against this library.
The isfinite() macro determines if x is finite.
- True (1)
- The value of x is finite.
- False (≠ 1)
- The value of x is infinity or NAN.
#include <stdio.h>
#include <errno.h>
#include <inttypes.h>
#include <math.h>
#include <fpstatus.h>
int main(int argc, char** argv)
{
double a, b, c, d;
a = 2;
b = -0.5;
c = NAN;
fp_exception_mask(_FP_EXC_DIVZERO, 1);
d = 1.0/0.0;
printf("%f is %s \n", a, (isfinite(a)) ? "finite" : "not finite");
printf("%f is %s \n", b, (isfinite(b)) ? "finite" : "not finite");
printf("%f is %s \n", c, (isfinite(c)) ? "finite" : "not finite");
printf("%f is %s \n", d, (isfinite(d)) ? "finite" : "not finite");
return(0);
}
produces the output:
2.000000 is finite
-0.500000 is finite
NAN is not finite
Inf is not finite
POSIX 1003.1
Safety: | |
Cancellation point |
No |
Interrupt handler |
No |
Signal handler |
No |
Thread |
Yes |
isinf(),
isnan()
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