/*
 *
 * NaN.h -- include file to deal with IEEE NaN values
 *
 * Idea taken from fitsio2.h in the cfitsio package by William Pence (HEASARC),
 * to whom grateful acknowledgement is made.
 *
 * These functions tests whether the float value is a reserved IEEE
 * value such as a Not-a-Number (NaN), or underflow, overflow, or
 * infinity.   The functions returns 1 if the value is a NaN, overflow
 * or infinity; otherwise it returns 0.
 *
 * isnanf tests floats, isnand tests doubles.
 *
 */

#define NATIVE             0 /* generic machine using IEEE formats */
#define ULTRIX             1
#define ALPHA_OSF          2
#define VAXVMS             3
#define ALPHAVMS           4
#define IBMPC              5
#define CRAY               6

/* the following are used to determine what type machine we are running on */
 
#if defined(vax) && defined(VMS)
 
#define NAN_MACHINE VAXVMS
#define BYTESWAPPED 1
 
#elif defined(__alpha) && defined(VMS)
 
#define NAN_MACHINE ALPHAVMS
#define BYTESWAPPED 1
 
#elif defined(__alpha) && defined(unix)
 
#define NAN_MACHINE ALPHA_OSF
#define BYTESWAPPED 1
 
#elif defined(ultrix) && defined(unix)
 
#define NAN_MACHINE ULTRIX
#define BYTESWAPPED 1
 
#elif defined(__linux__) && ( defined(__i386__) || defined(__i486__) || defined(__i586__) )

/*  IBM PC running linux */
#define NAN_MACHINE IBMPC
#define BYTESWAPPED 1

#elif defined(_MSC_VER) || defined(__BORLANDC__) || defined(__TURBOC__)

/*  IBM PC running DOS or Windows */
#define NAN_MACHINE IBMPC       
#define BYTESWAPPED 1

#elif defined(_NI_mswin_)

/*  LabWindows/CVI with Windows 3.x, 95, or NT  */
#define NAN_MACHINE IBMPC       
#define BYTESWAPPED 1

#elif  defined(__EMX__)

/*  IBM PC running OS/2 */
#define NAN_MACHINE IBMPC
#define BYTESWAPPED 1

#else

/*  assume machine uses the same IEEE formats as used in FITS files */
#define NAN_MACHINE NATIVE
#define BYTESWAPPED 0
 
#endif
 
/* byte-swapping determine which short int we will mask for NaN test */
#if (BYTESWAPPED == 1)

#define FNANOFF 1
#define DNANOFF 3

#else

#define FNANOFF 0
#define DNANOFF 0

#endif

#if NAN_MACHINE == ALPHAVMS
 
#define FNANMASK   0x7F00 /* mask bits 1 - 7; all set on NaNs */
                                     /* all 0 on underflow  or 0. */
 
#define DNANMASK   0x7FE0 /* mask bits 1 - 10; all set on NaNs */
                                     /* all 0 on underflow  or 0. */
 
#else
 
#define FNANMASK   0x7F80 /* mask bits 1 - 8; all set on NaNs */
                                     /* all 0 on underflow  or 0. */
 
#define DNANMASK   0x7FF0 /* mask bits 1 - 11; all set on NaNs */
                                     /* all 0 on underflow  or 0. */
 
#endif
 
#if NAN_MACHINE == CRAY
    /*
      Cray machines:   the large negative integer corresponds
      to the 3 most sig digits set to 1.   If these
      3 bits are set in a floating point number (64 bits), then it represents
      a reserved value (i.e., a NaN)
    */
#define isnanf(L) ( (L) >= 0xE000000000000000 ? 1 : 0) )
 
#else
 
#ifndef isnanf

#define isnanf(X) ((((union { float f; short x[2]; } \
                        *)&X)->x[FNANOFF] & FNANMASK) == FNANMASK)

#endif

#ifndef isnand

#define isnand(X) ((((union { double d; short x[4]; } \
                        *)&X)->x[DNANOFF] & DNANMASK) == DNANMASK)

#endif

#endif
 
/* routines to return NaN values */
float getnanf();
double getnand();