text: /* s_tanl.c -- long double version of s_tan.c.
   * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   */
  
  /* @(#)s_tan.c 5.1 93/09/24 */
  /*
   * ====================================================
   * 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.
   * ====================================================
   */
  
  /* tanl(x)
   * Return tangent function of x.
   *
   * kernel function:
   *	__kernel_tanl		... tangent function on [-pi/4,pi/4]
   *	__ieee754_rem_pio2l	... 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 <errno.h>
  #include <math.h>
  #include <math_private.h>
  #include <math_ldbl_opt.h>
  
  long double __tanl(long double x)
  {
  	long double y[2],z=0.0L;
  	int64_t n, ix;
  	double xhi;
  
      /* High word of x. */
  	xhi = ldbl_high (x);
  	EXTRACT_WORDS64 (ix, xhi);
  
      /* |x| ~< pi/4 */
  	ix &= 0x7fffffffffffffffLL;
  	if(ix <= 0x3fe921fb54442d10LL) return __kernel_tanl(x,z,1);
  
      /* tanl(Inf or NaN) is NaN */
  	else if (ix>=0x7ff0000000000000LL) {
  	    if (ix == 0x7ff0000000000000LL)
  		__set_errno (EDOM);
  	    return x-x;		/* NaN */
  	}
      /* argument reduction needed */
  	else {
  	    n = __ieee754_rem_pio2l(x,y);
  	    return __kernel_tanl(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
  							-1 -- n odd */
  	}
  }
  long_double_symbol (libm, __tanl, tanl);
  