gonzui

    1: /* e_acosf.c -- float version of e_acos.c.
    2:  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
    3:  */
    4: 
    5: /*
    6:  * ====================================================
    7:  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
    8:  *
    9:  * Developed at SunPro, 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 "math.h"
   17: #include "math_private.h"
   18: 
   19: static const float 
   20: one =  1.0000000000e+00, /* 0x3F800000 */
   21: pi =  3.1415925026e+00, /* 0x40490fda */
   22: pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
   23: pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
   24: pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
   25: pS1 = -3.2556581497e-01, /* 0xbea6b090 */
   26: pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
   27: pS3 = -4.0055535734e-02, /* 0xbd241146 */
   28: pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
   29: pS5 =  3.4793309169e-05, /* 0x3811ef08 */
   30: qS1 = -2.4033949375e+00, /* 0xc019d139 */
   31: qS2 =  2.0209457874e+00, /* 0x4001572d */
   32: qS3 = -6.8828397989e-01, /* 0xbf303361 */
   33: qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
   34: 
   35: float
   36: acosf(float x)
   37: {
   38:         float z,p,q,r,w,s,c,df;
   39:         int32_t hx,ix;
   40:         GET_FLOAT_WORD(hx,x);
   41:         ix = hx&0x7fffffff;
   42:         if(ix==0x3f800000) {           /* |x|==1 */
   43:             if(hx>0) return 0.0;       /* acos(1) = 0  */
   44:             else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
   45:         } else if(ix>0x3f800000) {     /* |x| >= 1 */
   46:             return (x-x)/(x-x);                /* acos(|x|>1) is NaN */
   47:         }
   48:         if(ix<0x3f000000) {    /* |x| < 0.5 */
   49:             if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
   50:             z = x*x;
   51:             p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
   52:             q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
   53:             r = p/q;
   54:             return pio2_hi - (x - (pio2_lo-x*r));
   55:         } else  if (hx<0) {            /* x < -0.5 */
   56:             z = (one+x)*(float)0.5;
   57:             p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
   58:             q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
   59:             s = sqrtf(z);
   60:             r = p/q;
   61:             w = r*s-pio2_lo;
   62:             return pi - (float)2.0*(s+w);
   63:         } else {                       /* x > 0.5 */
   64:             int32_t idf;
   65:             z = (one-x)*(float)0.5;
   66:             s = sqrtf(z);
   67:             df = s;
   68:             GET_FLOAT_WORD(idf,df);
   69:             SET_FLOAT_WORD(df,idf&0xfffff000);
   70:             c  = (z-df*df)/(s+df);
   71:             p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
   72:             q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
   73:             r = p/q;
   74:             w = r*s+c;
   75:             return (float)2.0*(df+w);
   76:         }
   77: }