/**
Generate NaN.
@return Floating-point representation of NaN.
*/
TRIO_PUBLIC double
trio_nan(void)
{
/* Cache the result */
static double result = 0.0;
if (result == 0.0) {
#if defined(TRIO_COMPILER_SUPPORTS_C99)
result = nan(NULL);
#elif defined(NAN) && defined(__STDC_IEC_559__)
result = (double)NAN;
#elif defined(USE_IEEE_754)
result = trio_make_double(ieee_754_qnan_array);
#else
/*
* There are several ways to generate NaN. The one used here is
* to divide infinity by infinity. I would have preferred to add
* negative infinity to positive infinity, but that yields wrong
* result (infinity) on FreeBSD.
*
* This may fail if the hardware does not support NaN, or if
* the Invalid Operation floating-point exception is unmasked.
*/
# if defined(TRIO_PLATFORM_UNIX)
void (*signal_handler)(int) = signal(SIGFPE, SIG_IGN);
# endif
result = trio_pinf() / trio_pinf();
# if defined(TRIO_PLATFORM_UNIX)
signal(SIGFPE, signal_handler);
# endif
#endif
}
return result;
}
/*************************************************************************
* trio_ninf
*/
TRIO_PUBLIC double
trio_ninf(void)
{
static double result = 0.0;
if (result == 0.0) {
/*
* Negative infinity is calculated by negating positive infinity,
* which can be done because it is legal to do calculations on
* infinity (for example, 1 / infinity == 0).
*/
result = -trio_pinf();
}
return result;
}
int main(void)
{
double my_nan;
double my_pinf;
double my_ninf;
# if defined(TRIO_PLATFORM_UNIX)
void (*signal_handler)(int);
# endif
my_nan = trio_nan();
my_pinf = trio_pinf();
my_ninf = trio_ninf();
printf("NaN : %4g 0x%02x%02x%02x%02x%02x%02x%02x%02x (%2d, %2d)\n",
my_nan,
((unsigned char *)&my_nan)[0],
((unsigned char *)&my_nan)[1],
((unsigned char *)&my_nan)[2],
((unsigned char *)&my_nan)[3],
((unsigned char *)&my_nan)[4],
((unsigned char *)&my_nan)[5],
((unsigned char *)&my_nan)[6],
((unsigned char *)&my_nan)[7],
trio_isnan(my_nan), trio_isinf(my_nan));
printf("PInf: %4g 0x%02x%02x%02x%02x%02x%02x%02x%02x (%2d, %2d)\n",
my_pinf,
((unsigned char *)&my_pinf)[0],
((unsigned char *)&my_pinf)[1],
((unsigned char *)&my_pinf)[2],
((unsigned char *)&my_pinf)[3],
((unsigned char *)&my_pinf)[4],
((unsigned char *)&my_pinf)[5],
((unsigned char *)&my_pinf)[6],
((unsigned char *)&my_pinf)[7],
trio_isnan(my_pinf), trio_isinf(my_pinf));
printf("NInf: %4g 0x%02x%02x%02x%02x%02x%02x%02x%02x (%2d, %2d)\n",
my_ninf,
((unsigned char *)&my_ninf)[0],
((unsigned char *)&my_ninf)[1],
((unsigned char *)&my_ninf)[2],
((unsigned char *)&my_ninf)[3],
((unsigned char *)&my_ninf)[4],
((unsigned char *)&my_ninf)[5],
((unsigned char *)&my_ninf)[6],
((unsigned char *)&my_ninf)[7],
trio_isnan(my_ninf), trio_isinf(my_ninf));
# if defined(TRIO_PLATFORM_UNIX)
signal_handler = signal(SIGFPE, SIG_IGN);
# endif
my_pinf = DBL_MAX + DBL_MAX;
my_ninf = -my_pinf;
my_nan = my_pinf / my_pinf;
# if defined(TRIO_PLATFORM_UNIX)
signal(SIGFPE, signal_handler);
# endif
printf("NaN : %4g 0x%02x%02x%02x%02x%02x%02x%02x%02x (%2d, %2d)\n",
my_nan,
((unsigned char *)&my_nan)[0],
((unsigned char *)&my_nan)[1],
((unsigned char *)&my_nan)[2],
((unsigned char *)&my_nan)[3],
((unsigned char *)&my_nan)[4],
((unsigned char *)&my_nan)[5],
((unsigned char *)&my_nan)[6],
((unsigned char *)&my_nan)[7],
trio_isnan(my_nan), trio_isinf(my_nan));
printf("PInf: %4g 0x%02x%02x%02x%02x%02x%02x%02x%02x (%2d, %2d)\n",
my_pinf,
((unsigned char *)&my_pinf)[0],
((unsigned char *)&my_pinf)[1],
((unsigned char *)&my_pinf)[2],
((unsigned char *)&my_pinf)[3],
((unsigned char *)&my_pinf)[4],
((unsigned char *)&my_pinf)[5],
((unsigned char *)&my_pinf)[6],
((unsigned char *)&my_pinf)[7],
trio_isnan(my_pinf), trio_isinf(my_pinf));
printf("NInf: %4g 0x%02x%02x%02x%02x%02x%02x%02x%02x (%2d, %2d)\n",
my_ninf,
((unsigned char *)&my_ninf)[0],
((unsigned char *)&my_ninf)[1],
((unsigned char *)&my_ninf)[2],
((unsigned char *)&my_ninf)[3],
((unsigned char *)&my_ninf)[4],
((unsigned char *)&my_ninf)[5],
((unsigned char *)&my_ninf)[6],
((unsigned char *)&my_ninf)[7],
trio_isnan(my_ninf), trio_isinf(my_ninf));
return 0;
}
/*************************************************************************
* trio_isinf
*/
TRIO_PUBLIC int
trio_isinf(TRIO_VOLATILE double number)
{
#if defined(TRIO_COMPILER_DECC)
/*
* DECC has an isinf() macro, but it works differently than that
* of C99, so we use the fp_class() function instead.
*/
return ((fp_class(number) == FP_POS_INF)
? 1
: ((fp_class(number) == FP_NEG_INF) ? -1 : 0));
#elif defined(isinf)
/*
* C99 defines isinf() as a macro.
*/
return isinf(number);
#elif defined(TRIO_COMPILER_MSVC)
/*
* MSVC has an _fpclass() function that can be used to detect infinity.
*/
return ((_fpclass(number) == _FPCLASS_PINF)
? 1
: ((_fpclass(number) == _FPCLASS_NINF) ? -1 : 0));
#elif defined(USE_IEEE_754)
/*
* Examine IEEE 754 bit-pattern. Infinity must have a special exponent
* pattern, and an empty mantissa.
*/
int has_mantissa;
int is_special_quantity;
is_special_quantity = trio_is_special_quantity(number, &has_mantissa);
return (is_special_quantity && !has_mantissa)
? ((number < 0.0) ? -1 : 1)
: 0;
#else
/*
* Fallback solution.
*/
int status;
# if defined(TRIO_PLATFORM_UNIX)
void (*signal_handler)(int) = signal(SIGFPE, SIG_IGN);
# endif
double infinity = trio_pinf();
status = ((number == infinity)
? 1
: ((number == -infinity) ? -1 : 0));
# if defined(TRIO_PLATFORM_UNIX)
signal(SIGFPE, signal_handler);
# endif
return status;
#endif
}
