1 //===========================================================================
5 // Part of the standard mathematical function library
7 //===========================================================================
8 //####ECOSGPLCOPYRIGHTBEGIN####
9 // -------------------------------------------
10 // This file is part of eCos, the Embedded Configurable Operating System.
11 // Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
13 // eCos is free software; you can redistribute it and/or modify it under
14 // the terms of the GNU General Public License as published by the Free
15 // Software Foundation; either version 2 or (at your option) any later version.
17 // eCos is distributed in the hope that it will be useful, but WITHOUT ANY
18 // WARRANTY; without even the implied warranty of MERCHANTABILITY or
19 // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
22 // You should have received a copy of the GNU General Public License along
23 // with eCos; if not, write to the Free Software Foundation, Inc.,
24 // 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
26 // As a special exception, if other files instantiate templates or use macros
27 // or inline functions from this file, or you compile this file and link it
28 // with other works to produce a work based on this file, this file does not
29 // by itself cause the resulting work to be covered by the GNU General Public
30 // License. However the source code for this file must still be made available
31 // in accordance with section (3) of the GNU General Public License.
33 // This exception does not invalidate any other reasons why a work based on
34 // this file might be covered by the GNU General Public License.
36 // Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
37 // at http://sources.redhat.com/ecos/ecos-license/
38 // -------------------------------------------
39 //####ECOSGPLCOPYRIGHTEND####
40 //===========================================================================
41 //#####DESCRIPTIONBEGIN####
43 // Author(s): jlarmour
44 // Contributors: jlarmour
50 //####DESCRIPTIONEND####
52 //===========================================================================
56 #include <pkgconf/libm.h> // Configuration header
58 // Include the Math library?
61 // Derived from code with the following copyright
64 /* @(#)s_tan.c 1.3 95/01/18 */
66 * ====================================================
67 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
69 * Developed at SunSoft, a Sun Microsystems, Inc. business.
70 * Permission to use, copy, modify, and distribute this
71 * software is freely granted, provided that this notice
73 * ====================================================
77 * Return tangent function of x.
80 * __kernel_tan ... tangent function on [-pi/4,pi/4]
81 * __ieee754_rem_pio2 ... argument reduction routine
84 * Let S,C and T denote the sin, cos and tan respectively on
85 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
86 * in [-pi/4 , +pi/4], and let n = k mod 4.
89 * n sin(x) cos(x) tan(x)
90 * ----------------------------------------------------------
95 * ----------------------------------------------------------
98 * Let trig be any of sin, cos, or tan.
99 * trig(+-INF) is NaN, with signals;
100 * trig(NaN) is that NaN;
103 * TRIG(x) returns trig(x) nearly rounded
106 #include "mathincl/fdlibm.h"
113 /* High word of x. */
118 if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);
120 /* tan(Inf or NaN) is NaN */
121 else if (ix>=0x7ff00000) return x-x; /* NaN */
123 /* argument reduction needed */
125 n = __ieee754_rem_pio2(x,y);
126 return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even
131 #endif // ifdef CYGPKG_LIBM