scipy/base/src/_isnan.c


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/* Adapted from cephes */

static int 
isnan(double x)
{
	union
	{
		double d;
		unsigned short s[4];
		unsigned int i[2];
	} u;
	
	u.d = x;

#if SIZEOF_INT == 4

#ifdef WORDS_BIGENDIAN /* defined in pyconfig.h */
        if( ((u.i[0] & 0x7ff00000) == 0x7ff00000)
            && (((u.i[0] & 0x000fffff) != 0) || (u.i[1] != 0)))
                return 1;
#else
        if( ((u.i[1] & 0x7ff00000) == 0x7ff00000)
            && (((u.i[1] & 0x000fffff) != 0) || (u.i[0] != 0)))
                return 1;
#endif

#else  /* SIZEOF_INT != 4 */

#ifdef WORDS_BIGENDIAN
        if( (u.s[0] & 0x7ff0) == 0x7ff0)
                {
                if( ((u.s[0] & 0x000f) | u.s[1] | u.s[2] | u.s[3]) != 0 )
                        return 1;
                }
#else
       if( (u.s[3] & 0x7ff0) == 0x7ff0)
                {
                if( ((u.s[3] & 0x000f) | u.s[2] | u.s[1] | u.s[0]) != 0 )
                        return 1;
                }
#endif
       
#endif  /* SIZEOF_INT */
       
       return 0;
}