ciabatta/test/test_math.c

77 lines
2.8 KiB
C

#include <stdio.h>
#include <math.h>
#include <float.h>
#include <fenv.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() {
printf("\n=== fpclassify === \n");
double zero = 0.0; // fucken msvc
printf("1.0/0.0 is %s\n", show_classification(1.0/zero));
printf("0.0/0.0 is %s\n", show_classification(0.0/zero));
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));
printf("\n\n=== signbit === \n");
printf("signbit(+0.0) = %d\n", signbit(+0.0));
printf("signbit(-0.0) = %d\n", signbit(-0.0));
printf("\n\n=== copysign === \n");
printf("copysign(1.0,+2.0) = %f\n", copysign(1.0,+2.0));
printf("copysign(1.0,-2.0) = %f\n", copysign(1.0,-2.0));
printf("copysign(INFINITY,-2.0) = %f\n", copysign(INFINITY,-2.0));
printf("copysign(NAN,-2.0) = %f\n", copysign(NAN,-2.0));
printf("\n\n=== rint === \n");
fesetround(FE_TONEAREST);
printf("rounding to nearest (halfway cases to even):\n"
"rint(+2.3) = %f ", rint(2.3));
printf("rint(+2.5) = %f ", rint(2.5));
printf("rint(+3.5) = %f\n", rint(3.5));
printf("rint(-2.3) = %f ", rint(-2.3));
printf("rint(-2.5) = %f ", rint(-2.5));
printf("rint(-3.5) = %f\n", rint(-3.5));
fesetround(FE_DOWNWARD);
printf("rounding down: \nrint(+2.3) = %f ", rint(2.3));
printf("rint(+2.5) = %f ", rint(2.5));
printf("rint(+3.5) = %f\n", rint(3.5));
printf("rint(-2.3) = %f ", rint(-2.3));
printf("rint(-2.5) = %f ", rint(-2.5));
printf("rint(-3.5) = %f\n", rint(-3.5));
feclearexcept(FE_ALL_EXCEPT);
printf("rint(1.1) = %f\n", rint(1.1));
if(fetestexcept(FE_INEXACT)) printf(" FE_INEXACT was raised\n");
float from1 = 0, to1 = nextafterf(from1, 1);
printf("The next representable float after %f is %f\n", from1, to1);
float from2 = 1, to2 = nextafterf(from2, 2);
printf("The next representable float after %f is %f\n", from2, to2);
{
#pragma STDC FENV_ACCESS ON
feclearexcept(FE_ALL_EXCEPT);
double from4 = DBL_MAX, to4 = nextafter(from4, INFINITY);
printf("The next representable double after %f is %f\n",
from4, to4);
if(fetestexcept(FE_OVERFLOW)) printf(" raised FE_OVERFLOW\n");
if(fetestexcept(FE_INEXACT)) printf(" raised FE_INEXACT\n");
}
float from5 = 0.0, to5 = nextafter(from5, -0.0);
printf("nextafter(+0.0, -0.0) gives %f (%f)\n", to5, to5);
return 0;
}