workbench/libs/mathtrans/spacos.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunSoft, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17 #include "mathtrans_intern.h"
  18
  19 /*****************************************************************************
  20
  21     NAME */
  22
  23         AROS_LH1(float, SPAcos,
  24
  25 /*  SYNOPSIS */
  26         AROS_LHA(float, fnum1, D0),
  27
  28 /*  LOCATION */
  29         struct Library *, MathTransBase, 20, MathTrans)
  30
  31 /*  FUNCTION
  32         Calculate arcuscos of the given number
  33
  34     INPUTS
  35
  36     RESULT
  37         Motorola fast floating point number
  38
  39         flags:
  40         zero     : Result is zero
  41         negative : 0 (not possible)
  42         overflow : fnum < -1  or  fnum > 1
  43
  44     BUGS
  45
  46     INTERNALS
  47
  48     HISTORY
  49
  50 *****************************************************************************/
  51 {
  52     AROS_LIBFUNC_INIT
  53
  54     /* 1> |x| >= 0.5 */
  55     LONG z,p,q,r,w,s,c,ix,df;
  56     ix = fnum1 & (FFPMantisse_Mask | FFPExponent_Mask); /* ix = |fnum|  */
  57
  58     z = SPCmp(ix,one);
  59
  60     if (1==z) /* |fnum1| > 1 */
  61     {
  62         SetSR(Overflow_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
  63         return -1;
  64     }
  65
  66     if (0==z) /* |fnum1| = 1 */
  67     {
  68         if (fnum1 & FFPSign_Mask) /* |fnum| = -1 */ return pi;
  69         SetSR(Zero_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
  70         return 0;
  71     }
  72
  73     /* error: 1 ulp (unit in the last place) */
  74     if (-1 == SPCmp(ix,onehalf)) /* |fnum1| < 0.5 */
  75     {
  76         z = SPMul(fnum1, fnum1);
  77         p = SPMul(z, SPAdd(pS0,
  78             SPMul(z, SPAdd(pS1,
  79             SPMul(z, SPAdd(pS2,
  80             SPMul(z, SPAdd(pS3,
  81             SPMul(z, SPAdd(pS4,
  82             SPMul(z, pS5)))))))))));
  83         q = SPAdd(one,
  84             SPMul(z, SPAdd(qS1,
  85             SPMul(z, SPAdd(qS2,
  86             SPMul(z, SPAdd(qS3,
  87             SPMul(z, qS4))))))));
  88         r = SPDiv(q, p);
  89         return (SPSub(SPAdd(fnum1,SPMul(fnum1,r)),pio2));
  90     }
  91
  92     /* error: 1 ulp */
  93     if (fnum1 & FFPSign_Mask) /* fnum1 < -0.5 */
  94     {
  95         z = SPMul(onehalf, SPAdd(one, fnum1));
  96         p = SPMul(z, SPAdd(pS0,
  97             SPMul(z, SPAdd(pS1,
  98             SPMul(z, SPAdd(pS2,
  99             SPMul(z, SPAdd(pS3,
 100             SPMul(z, SPAdd(pS4,
 101             SPMul(z, pS5)))))))))));
 102         q = SPAdd(one,
 103             SPMul(z, SPAdd(qS1,
 104             SPMul(z, SPAdd(qS2,
 105             SPMul(z, SPAdd(qS3,
 106             SPMul(z, qS4))))))));
 107         s = SPSqrt(z);
 108         r = SPDiv(q,p); /* r = p/q; */
 109         w = SPMul(r,s);
 110         return SPSub(SPMul(two, SPAdd(s, w)) ,pi);
 111     }
 112
 113     /* error: 8 ulp (this is bad !!!!) */
 114     /* fnum1 > 0.5 */
 115     z = SPMul(onehalf, SPSub(fnum1, one));
 116     s = SPSqrt(z);
 117     df = s;
 118     df = df & 0xfff000ff;
 119     c = SPDiv(SPAdd(df,s),  SPSub( SPMul(df,df), z));
 120     p = SPMul(z, SPAdd(pS0,
 121         SPMul(z, SPAdd(pS1,
 122         SPMul(z, SPAdd(pS2,
 123         SPMul(z, SPAdd(pS3,
 124         SPMul(z, SPAdd(pS4,
 125         SPMul(z, pS5)))))))))));
 126     q = SPAdd(one,
 127         SPMul(z, SPAdd(qS1,
 128         SPMul(z, SPAdd(qS2,
 129         SPMul(z, SPAdd(qS3,
 130         SPMul(z, qS4))))))));
 131     r = SPDiv(q, p);
 132     w = SPAdd(c, SPMul(r,s));
 133
 134     return SPAdd(SPMul(two, SPAdd(df,w)),0x800000a9);
 135
 136     AROS_LIBFUNC_EXIT
 137 }