text: /* Copyright 2016 Samsung Electronics Co., Ltd.
   * Copyright 2016 University of Szeged
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   * This file is based on work under the following copyright and permission
   * notice:
   *
   *     Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   *
   *     Developed at SunSoft, a Sun Microsystems, Inc. business.
   *     Permission to use, copy, modify, and distribute this
   *     software is freely granted, provided that this notice
   *     is preserved.
   *
   *     @(#)e_acos.c 1.3 95/01/18
   */
  
  #include "jerry-libm-internal.h"
  
  /* acos(x)
   *
   * Method:
   *      acos(x)  = pi/2 - asin(x)
   *      acos(-x) = pi/2 + asin(x)
   * For |x|<=0.5
   *      acos(x) = pi/2 - (x + x*x^2*R(x^2))     (see asin.c)
   * For x>0.5
   *      acos(x) = pi/2 - (pi/2 - 2asin(sqrt((1-x)/2)))
   *              = 2asin(sqrt((1-x)/2))
   *              = 2s + 2s*z*R(z)        ...z=(1-x)/2, s=sqrt(z)
   *              = 2f + (2c + 2s*z*R(z))
   *     where f=hi part of s, and c = (z-f*f)/(s+f) is the correction term
   *     for f so that f+c ~ sqrt(z).
   * For x<-0.5
   *      acos(x) = pi - 2asin(sqrt((1-|x|)/2))
   *              = pi - 0.5*(s+s*z*R(z)), where z=(1-|x|)/2,s=sqrt(z)
   *
   * Special cases:
   *      if x is NaN, return x itself;
   *      if |x|>1, return NaN with invalid signal.
   *
   * Function needed: sqrt
   */
  
  #define one      1.00000000000000000000e+00 /* 0x3FF00000, 0x00000000 */
  #define pi       3.14159265358979311600e+00 /* 0x400921FB, 0x54442D18 */
  #define pio2_hi  1.57079632679489655800e+00 /* 0x3FF921FB, 0x54442D18 */
  #define pio2_lo  6.12323399573676603587e-17 /* 0x3C91A626, 0x33145C07 */
  #define pS0      1.66666666666666657415e-01 /* 0x3FC55555, 0x55555555 */
  #define pS1     -3.25565818622400915405e-01 /* 0xBFD4D612, 0x03EB6F7D */
  #define pS2      2.01212532134862925881e-01 /* 0x3FC9C155, 0x0E884455 */
  #define pS3     -4.00555345006794114027e-02 /* 0xBFA48228, 0xB5688F3B */
  #define pS4      7.91534994289814532176e-04 /* 0x3F49EFE0, 0x7501B288 */
  #define pS5      3.47933107596021167570e-05 /* 0x3F023DE1, 0x0DFDF709 */
  #define qS1     -2.40339491173441421878e+00 /* 0xC0033A27, 0x1C8A2D4B */
  #define qS2      2.02094576023350569471e+00 /* 0x40002AE5, 0x9C598AC8 */
  #define qS3     -6.88283971605453293030e-01 /* 0xBFE6066C, 0x1B8D0159 */
  #define qS4      7.70381505559019352791e-02 /* 0x3FB3B8C5, 0xB12E9282 */
  
  double
  acos (double x)
  {
    double z, p, q, r, w, s, c, df;
    int hx, ix;
  
    hx = __HI (x);
    ix = hx & 0x7fffffff;
    if (ix >= 0x3ff00000) /* |x| >= 1 */
    {
      if (((ix - 0x3ff00000) | __LO (x)) == 0) /* |x| == 1 */
      {
        if (hx > 0) /* acos(1) = 0  */
        {
          return 0.0;
        }
        else /* acos(-1) = pi */
        {
          return pi + 2.0 * pio2_lo;
        }
      }
      return (x - x) / (x - x); /* acos(|x|>1) is NaN */
    }
    if (ix < 0x3fe00000) /* |x| < 0.5 */
    {
      if (ix <= 0x3c600000) /* if |x| < 2**-57 */
      {
        return pio2_hi + pio2_lo;
      }
      z = x * x;
      p = z * (pS0 + z * (pS1 + z * (pS2 + z * (pS3 + z * (pS4 + z * pS5)))));
      q = one + z * (qS1 + z * (qS2 + z * (qS3 + z * qS4)));
      r = p / q;
      return pio2_hi - (x - (pio2_lo - x * r));
    }
    else if (hx < 0) /* x < -0.5 */
    {
      z = (one + x) * 0.5;
      p = z * (pS0 + z * (pS1 + z * (pS2 + z * (pS3 + z * (pS4 + z * pS5)))));
      q = one + z * (qS1 + z * (qS2 + z * (qS3 + z * qS4)));
      s = sqrt (z);
      r = p / q;
      w = r * s - pio2_lo;
      return pi - 2.0 * (s + w);
    }
    else /* x > 0.5 */
    {
      z = (one - x) * 0.5;
      s = sqrt (z);
      df = s;
      __LO (df) = 0;
      c = (z - df * df) / (s + df);
      p = z * (pS0 + z * (pS1 + z * (pS2 + z * (pS3 + z * (pS4 + z * pS5)))));
      q = one + z * (qS1 + z * (qS2 + z * (qS3 + z * qS4)));
      r = p / q;
      w = r * s + c;
      return 2.0 * (df + w);
    }
  } /* acos */
  