s_isnan.c

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/* @(#)s_isnan.c 1.3 95/01/18 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunSoft, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice 
 * is preserved.
 * ====================================================
 */

/*
 * isnan(x) returns 1 is x is nan, else 0;
 * no branching!
 */

#include "fdlibm.h"

#ifdef __STDC__
    int isnan(double x)
#else
    int isnan(x)
    double x;
#endif
{
    int hx,lx;
    hx = (__HI(x)&0x7fffffff);
    lx = __LO(x);
    hx |= (unsigned)(lx|(-lx))>>31; 
    hx = 0x7ff00000 - hx;
    return ((unsigned)(hx))>>31;
}