kc3-lang/SDL/src/libm/s_cos.c

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• Hash : 6cf06575
  Author :
  Date : 2017-11-04T15:53:19
  

  Updated math code from the uClibc 0.9.33 release

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• src/libm/s_cos.c

• /*
   * ====================================================
   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   *
   * Developed at SunPro, a Sun Microsystems, Inc. business.
   * Permission to use, copy, modify, and distribute this
   * software is freely granted, provided that this notice
   * is preserved.
   * ====================================================
   */
  
  /* cos(x)
   * Return cosine function of x.
   *
   * kernel function:
   *	__kernel_sin		... sine function on [-pi/4,pi/4]
   *	__kernel_cos		... cosine function on [-pi/4,pi/4]
   *	__ieee754_rem_pio2	... argument reduction routine
   *
   * Method.
   *      Let S,C and T denote the sin, cos and tan respectively on
   *	[-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
   *	in [-pi/4 , +pi/4], and let n = k mod 4.
   *	We have
   *
   *          n        sin(x)      cos(x)        tan(x)
   *     ----------------------------------------------------------
   *	    0	       S	   C		 T
   *	    1	       C	  -S		-1/T
   *	    2	      -S	  -C		 T
   *	    3	      -C	   S		-1/T
   *     ----------------------------------------------------------
   *
   * Special cases:
   *      Let trig be any of sin, cos, or tan.
   *      trig(+-INF)  is NaN, with signals;
   *      trig(NaN)    is that NaN;
   *
   * Accuracy:
   *	TRIG(x) returns trig(x) nearly rounded
   */
  
  #include "math_libm.h"
  #include "math_private.h"
  
  double cos(double x)
  {
  	double y[2],z=0.0;
  	int32_t n, ix;
  
      /* High word of x. */
  	GET_HIGH_WORD(ix,x);
  
      /* |x| ~< pi/4 */
  	ix &= 0x7fffffff;
  	if(ix <= 0x3fe921fb) return __kernel_cos(x,z);
  
      /* cos(Inf or NaN) is NaN */
  	else if (ix>=0x7ff00000) return x-x;
  
      /* argument reduction needed */
  	else {
  	    n = __ieee754_rem_pio2(x,y);
  	    switch(n&3) {
  		case 0: return  __kernel_cos(y[0],y[1]);
  		case 1: return -__kernel_sin(y[0],y[1],1);
  		case 2: return -__kernel_cos(y[0],y[1]);
  		default:
  		        return  __kernel_sin(y[0],y[1],1);
  	    }
  	}
  }
  libm_hidden_def(cos)
  

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