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     FUNCTION
  21       Calculate arcuscos of the given number
  22
  23     RESULT
  24       Motorola fast floating point number
  25
  26       flags:
  27       zero     : result is zero
  28       negative : 0 (not possible)
  29       overflow : fnum &lt; -1  or  fnum &gt; 1
  30
  31     NOTES
  32
  33     EXAMPLE
  34
  35     BUGS
  36
  37     SEE ALSO
  38
  39     INTERNALS
  40
  41     HISTORY
  42 */
  43
  44 AROS_LH1(float, SPAcos,
  45     AROS_LHA(float, fnum1, D0),
  46     struct Library *, MathTransBase, 20, MathTrans
  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 = fnum1 & (FFPMantisse_Mask | FFPExponent_Mask); /* ix = |fnum|  */
  54
  55     z = SPCmp(ix,one);
  56
  57     if (1==z) /* |fnum1| > 1 */
  58     {
  59         SetSR(Overflow_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
  60         return -1;
  61     }
  62
  63     if (0==z) /* |fnum1| = 1 */
  64     {
  65         if (fnum1 & FFPSign_Mask) /* |fnum| = -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 == SPCmp(ix,onehalf)) /* |fnum1| < 0.5 */
  72     {
  73         z = SPMul(fnum1, fnum1);
  74         p = SPMul(z, SPAdd(pS0,
  75             SPMul(z, SPAdd(pS1,
  76             SPMul(z, SPAdd(pS2,
  77             SPMul(z, SPAdd(pS3,
  78             SPMul(z, SPAdd(pS4,
  79             SPMul(z, pS5)))))))))));
  80         q = SPAdd(one,
  81             SPMul(z, SPAdd(qS1,
  82             SPMul(z, SPAdd(qS2,
  83             SPMul(z, SPAdd(qS3,
  84             SPMul(z, qS4))))))));
  85         r = SPDiv(q, p);
  86         return (SPSub(SPAdd(fnum1,SPMul(fnum1,r)),pio2));
  87     }
  88
  89     /* error: 1 ulp */
  90     if (fnum1 & FFPSign_Mask) /* fnum1 < -0.5 */
  91     {
  92         z = SPMul(onehalf, SPAdd(one, fnum1));
  93         p = SPMul(z, SPAdd(pS0,
  94             SPMul(z, SPAdd(pS1,
  95             SPMul(z, SPAdd(pS2,
  96             SPMul(z, SPAdd(pS3,
  97             SPMul(z, SPAdd(pS4,
  98             SPMul(z, pS5)))))))))));
  99         q = SPAdd(one,
 100             SPMul(z, SPAdd(qS1,
 101             SPMul(z, SPAdd(qS2,
 102             SPMul(z, SPAdd(qS3,
 103             SPMul(z, qS4))))))));
 104         s = SPSqrt(z);
 105         r = SPDiv(q,p); /* r = p/q; */
 106         w = SPMul(r,s);
 107         return SPSub(SPMul(two, SPAdd(s, w)) ,pi);
 108     }
 109
 110     /* error: 8 ulp (this is bad !!!!) */
 111     /* fnum1 > 0.5 */
 112     z = SPMul(onehalf, SPSub(fnum1, one));
 113     s = SPSqrt(z);
 114     df = s;
 115     df = df & 0xfff000ff;
 116     c = SPDiv(SPAdd(df,s),  SPSub( SPMul(df,df), z));
 117     p = SPMul(z, SPAdd(pS0,
 118         SPMul(z, SPAdd(pS1,
 119         SPMul(z, SPAdd(pS2,
 120         SPMul(z, SPAdd(pS3,
 121         SPMul(z, SPAdd(pS4,
 122         SPMul(z, pS5)))))))))));
 123     q = SPAdd(one,
 124         SPMul(z, SPAdd(qS1,
 125         SPMul(z, SPAdd(qS2,
 126         SPMul(z, SPAdd(qS3,
 127         SPMul(z, qS4))))))));
 128     r = SPDiv(q, p);
 129     w = SPAdd(c, SPMul(r,s));
 130
 131     return SPAdd(SPMul(two, SPAdd(df,w)),0x800000a9);
 132
 133     AROS_LIBFUNC_EXIT
 134 }