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

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• Hash : b72938c8
  Author :
  Date : 2015-04-20T12:22:44
  

  Windows: Always set the system timer resolution to 1ms by default.
  
  An existing hint lets apps that don't need the timer resolution changed avoid
  this, to save battery, etc, but this fixes several problems in timing, audio
  callbacks not firing fast enough, etc.
  
  Fixes Bugzilla #2944.
  

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• src/libm/s_tan.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.
   * ====================================================
   */
  
  /* tan(x)
   * Return tangent function of x.
   *
   * kernel function:
   *	__kernel_tan		... tangent 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 tan(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_tan(x,z,1);
  
      /* tan(Inf or NaN) is NaN */
  	else if (ix>=0x7ff00000) return x-x;		/* NaN */
  
      /* argument reduction needed */
  	else {
  	    n = __ieee754_rem_pio2(x,y);
  	    return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
  							-1 -- n odd */
  	}
  }
  libm_hidden_def(tan)
  

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