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Diffstat (limited to 'sysdeps/libm-ieee754/s_tanl.c')
| -rw-r--r-- | sysdeps/libm-ieee754/s_tanl.c | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/sysdeps/libm-ieee754/s_tanl.c b/sysdeps/libm-ieee754/s_tanl.c new file mode 100644 index 0000000000..bce6d07f3d --- /dev/null +++ b/sysdeps/libm-ieee754/s_tanl.c @@ -0,0 +1,81 @@ +/* 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(ix <= 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) |