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Annotation of src/lib/libm/src/s_copysign.c, Revision 1.3

1.1       jtc         1: /* @(#)s_copysign.c 5.1 93/09/24 */
                      2: /*
                      3:  * ====================================================
                      4:  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
                      5:  *
                      6:  * Developed at SunPro, a Sun Microsystems, Inc. business.
                      7:  * Permission to use, copy, modify, and distribute this
                      8:  * software is freely granted, provided that this notice
                      9:  * is preserved.
                     10:  * ====================================================
                     11:  */
1.3     ! jtc        12:
        !            13: #ifndef lint
        !            14: static char rcsid[] = "$Id: $";
        !            15: #endif
1.1       jtc        16:
                     17: /*
                     18:  * copysign(double x, double y)
                     19:  * copysign(x,y) returns a value with the magnitude of x and
                     20:  * with the sign bit of y.
                     21:  */
                     22:
1.2       jtc        23: #include <math.h>
1.1       jtc        24:
                     25: #ifdef __STDC__
                     26: static const double one = 1.0;
                     27: #else
                     28: static double one = 1.0;
                     29: #endif
                     30:
                     31: #ifdef __STDC__
                     32:        double copysign(double x, double y)
                     33: #else
                     34:        double copysign(x,y)
                     35:        double x,y;
                     36: #endif
                     37: {
                     38:        int     n0;
                     39:        n0 = ((*(int*)&one)>>29)^1;     /* high word index */
                     40:        *(n0+(unsigned*)&x) =
                     41:        (*(n0+(unsigned*)&x)&0x7fffffff)|(*(n0+(unsigned*)&y)&0x80000000);
                     42:         return x;
                     43: }