| /* s_tanl.c -- long double version of s_tan.c. |
| * Conversion to long double by Ulrich Drepper, |
| * Cygnus Support, drepper@cygnus.com. |
| */ |
| |
| /* |
| * ==================================================== |
| * 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. |
| * ==================================================== |
| */ |
| |
| #if defined(LIBM_SCCS) && !defined(lint) |
| static char rcsid[] = "$NetBSD: $"; |
| #endif |
| |
| /* 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 "math.h" |
| #include "math_private.h" |
| |
| #ifdef __STDC__ |
| long double __tanl(long double x) |
| #else |
| long double __tanl(x) |
| long double x; |
| #endif |
| { |
| long double y[2],z=0.0; |
| int32_t n, se; |
| |
| /* High word of x. */ |
| GET_LDOUBLE_EXP(se,x); |
| |
| /* |x| ~< pi/4 */ |
| se &= 0x7fff; |
| if(se <= 0x3ffe) return __kernel_tanl(x,z,1); |
| |
| /* tan(Inf or NaN) is NaN */ |
| else if (se==0x7fff) 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 */ |
| } |
| } |
| weak_alias (__tanl, tanl) |
