projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| 6e953631 | 1 | /* s_tanl.c -- long double version of s_tan.c. |
| 6e953631 | 2 | */ |
| 9c84384c | 3 | |
| abfbdde1 | 4 | /* @(#)s_tan.c 5.1 93/09/24 */ |
| 6e953631 UD |
5 | /* |
| 6 | * ==================================================== | |
| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
| 8 | * | |
| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. | |
| 10 | * Permission to use, copy, modify, and distribute this | |
| 11 | * software is freely granted, provided that this notice | |
| 12 | * is preserved. | |
| 13 | * ==================================================== | |
| 14 | */ | |
| 15 | ||
| 6e953631 UD |
16 | /* tanl(x) |
| 17 | * Return tangent function of x. | |
| 18 | * | |
| 19 | * kernel function: | |
| 20 | * __kernel_tanl ... tangent function on [-pi/4,pi/4] | |
| 21 | * __ieee754_rem_pio2l ... argument reduction routine | |
| 22 | * | |
| 23 | * Method. | |
| 24 | * Let S,C and T denote the sin, cos and tan respectively on | |
| 25 | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 | |
| 26 | * in [-pi/4 , +pi/4], and let n = k mod 4. | |
| 27 | * We have | |
| 28 | * | |
| 29 | * n sin(x) cos(x) tan(x) | |
| 30 | * ---------------------------------------------------------- | |
| 31 | * 0 S C T | |
| 32 | * 1 C -S -1/T | |
| 33 | * 2 -S -C T | |
| 34 | * 3 -C S -1/T | |
| 35 | * ---------------------------------------------------------- | |
| 36 | * | |
| 37 | * Special cases: | |
| 38 | * Let trig be any of sin, cos, or tan. | |
| 39 | * trig(+-INF) is NaN, with signals; | |
| 40 | * trig(NaN) is that NaN; | |
| 41 | * | |
| 42 | * Accuracy: | |
| 43 | * TRIG(x) returns trig(x) nearly rounded | |
| 44 | */ | |
| 45 | ||
| 7f3394bd | 46 | #include <errno.h> |
| 1ed0291c RH |
47 | #include <math.h> |
| 48 | #include <math_private.h> | |
| fd3b4e7c | 49 | #include <libm-alias-ldouble.h> |
| 6e953631 | 50 | |
| 15089e04 | 51 | _Float128 __tanl(_Float128 x) |
| 6e953631 | 52 | { |
| 02bbfb41 | 53 | _Float128 y[2],z=0; |
| abfbdde1 | 54 | int64_t n, ix; |
| 6e953631 UD |
55 | |
| 56 | /* High word of x. */ | |
| abfbdde1 | 57 | GET_LDOUBLE_MSW64(ix,x); |
| 6e953631 UD |
58 | |
| 59 | /* |x| ~< pi/4 */ | |
| abfbdde1 UD |
60 | ix &= 0x7fffffffffffffffLL; |
| 61 | if(ix <= 0x3ffe921fb54442d1LL) return __kernel_tanl(x,z,1); | |
| 6e953631 | 62 | |
| abfbdde1 | 63 | /* tanl(Inf or NaN) is NaN */ |
| 7f3394bd UD |
64 | else if (ix>=0x7fff000000000000LL) { |
| 65 | if (ix == 0x7fff000000000000LL) { | |
| 66 | GET_LDOUBLE_LSW64(n,x); | |
| 67 | if (n == 0) | |
| 68 | __set_errno (EDOM); | |
| 69 | } | |
| 70 | return x-x; /* NaN */ | |
| 71 | } | |
| 6e953631 UD |
72 | |
| 73 | /* argument reduction needed */ | |
| 74 | else { | |
| 75 | n = __ieee754_rem_pio2l(x,y); | |
| 76 | return __kernel_tanl(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even | |
| 77 | -1 -- n odd */ | |
| 78 | } | |
| 79 | } | |
| fd3b4e7c | 80 | libm_alias_ldouble (__tan, tan) |