workbench/libs/mathieeesingtrans/ieeespacos.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunSoft, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #include "mathieeesingtrans_intern.h"
  17
  18 /*****************************************************************************
  19
  20     NAME */
  21
  22         AROS_LH1(float, IEEESPAcos,
  23
  24 /*  SYNOPSIS */
  25         AROS_LHA(float, y, D0),
  26
  27 /*  LOCATION */
  28         struct Library *, MathIeeeSingTransBase, 20, MathIeeeSingTrans)
  29
  30 /*  FUNCTION
  31         Calculate arcuscos of the given number
  32
  33     INPUTS
  34
  35     RESULT
  36         IEEE single precision floating point number
  37
  38         flags:
  39         zero     : result is zero
  40         negative : 0 (not possible)
  41         overflow : y < -1  or  y > 1
  42
  43     BUGS
  44
  45     INTERNALS
  46
  47 *****************************************************************************/
  48 {
  49     AROS_LIBFUNC_INIT
  50
  51     /* 1> |x| >= 0.5 */
  52     LONG z,p,q,r,w,s,c,ix,df;
  53     ix = y & (IEEESPMantisse_Mask | IEEESPExponent_Mask); /* ix = |y|  */
  54
  55     z = IEEESPCmp(ix,one);
  56
  57     if (1==z) /* |y| > 1 */
  58     {
  59         SetSR(Overflow_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
  60         return 0x7fffffff;
  61     }
  62
  63     if (0==z) /* |y| = 1 */
  64     {
  65         if (y & IEEESPSign_Mask) /* y = -1 */ return pi;
  66         SetSR(Zero_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
  67         return 0;
  68     }
  69
  70     /* error: 1 ulp (unit in the last place) */
  71     if (-1 == IEEESPCmp(ix,onehalf)) /* |fnum1| < 0.5 */
  72     {
  73         z = IEEESPMul(y, y);
  74         p = IEEESPMul(z, IEEESPAdd(pS0,
  75             IEEESPMul(z, IEEESPAdd(pS1,
  76             IEEESPMul(z, IEEESPAdd(pS2,
  77             IEEESPMul(z, IEEESPAdd(pS3,
  78             IEEESPMul(z, IEEESPAdd(pS4,
  79             IEEESPMul(z, pS5)))))))))));
  80         q = IEEESPAdd(one,
  81             IEEESPMul(z, IEEESPAdd(qS1,
  82             IEEESPMul(z, IEEESPAdd(qS2,
  83             IEEESPMul(z, IEEESPAdd(qS3,
  84             IEEESPMul(z, qS4))))))));
  85         r = IEEESPDiv(p, q);
  86
  87         return (IEEESPSub(pio2,IEEESPAdd(y,IEEESPMul(y,r))));
  88     }
  89
  90     /* error: 1 ulp */
  91     if (y & IEEESPSign_Mask) /* y < -0.5 */
  92     {
  93         z = IEEESPMul(onehalf, IEEESPAdd(one, y));
  94         p = IEEESPMul(z, IEEESPAdd(pS0,
  95             IEEESPMul(z, IEEESPAdd(pS1,
  96             IEEESPMul(z, IEEESPAdd(pS2,
  97             IEEESPMul(z, IEEESPAdd(pS3,
  98             IEEESPMul(z, IEEESPAdd(pS4,
  99             IEEESPMul(z, pS5)))))))))));
 100         q = IEEESPAdd(one,
 101             IEEESPMul(z, IEEESPAdd(qS1,
 102             IEEESPMul(z, IEEESPAdd(qS2,
 103             IEEESPMul(z, IEEESPAdd(qS3,
 104             IEEESPMul(z, qS4))))))));
 105         s = IEEESPSqrt(z);
 106         r = IEEESPDiv(p,q); /* r = p/q; */
 107         w = IEEESPMul(r,s);
 108
 109         return IEEESPSub(pi, IEEESPMul(two, IEEESPAdd(s, w)));
 110     }
 111
 112     /* fnum1 > 0.5 */
 113     /* error : 1 ulp */
 114     z = IEEESPMul(onehalf, IEEESPSub(one, y));
 115     s = IEEESPSqrt(z);
 116     df = s;
 117     //df = df & 0xfff000ff;
 118     c = IEEESPDiv(IEEESPSub(z, IEEESPMul(df,df)), IEEESPAdd(df,s) );
 119     p = IEEESPMul(z, IEEESPAdd(pS0,
 120         IEEESPMul(z, IEEESPAdd(pS1,
 121         IEEESPMul(z, IEEESPAdd(pS2,
 122         IEEESPMul(z, IEEESPAdd(pS3,
 123         IEEESPMul(z, IEEESPAdd(pS4,
 124         IEEESPMul(z, pS5)))))))))));
 125     q = IEEESPAdd(one,
 126         IEEESPMul(z, IEEESPAdd(qS1,
 127         IEEESPMul(z, IEEESPAdd(qS2,
 128         IEEESPMul(z, IEEESPAdd(qS3,
 129         IEEESPMul(z, qS4))))))));
 130     r = IEEESPDiv(p, q);
 131     w = IEEESPAdd(c, IEEESPMul(r,s));
 132
 133     return IEEESPMul(two, IEEESPAdd(df,w));
 134
 135     AROS_LIBFUNC_EXIT
 136 }