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Annotation of OpenXM_contrib/gmp/mpfr/tan.c, Revision 1.1

1.1     ! ohara       1: /* mpfr_tan -- tangent of a floating-point number
        !             2:
        !             3: Copyright 2001, 2002 Free Software Foundation, Inc.
        !             4:
        !             5: This file is part of the MPFR Library.
        !             6:
        !             7: The MPFR Library is free software; you can redistribute it and/or modify
        !             8: it under the terms of the GNU Lesser General Public License as published by
        !             9: the Free Software Foundation; either version 2.1 of the License, or (at your
        !            10: option) any later version.
        !            11:
        !            12: The MPFR Library is distributed in the hope that it will be useful, but
        !            13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Lesser General Public License
        !            18: along with the MPFR Library; see the file COPYING.LIB.  If not, write to
        !            19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            20: MA 02111-1307, USA. */
        !            21:
        !            22: #include "gmp.h"
        !            23: #include "gmp-impl.h"
        !            24: #include "mpfr.h"
        !            25: #include "mpfr-impl.h"
        !            26:
        !            27: /* computes tan(x) = sign(x)*sqrt(1/cos(x)^2-1) */
        !            28: int
        !            29: mpfr_tan (mpfr_ptr y, mpfr_srcptr x, mp_rnd_t rnd_mode)
        !            30: {
        !            31:   int precy, m, ok, inexact;
        !            32:   mpfr_t s, c;
        !            33:
        !            34:   if (MPFR_IS_NAN(x) || MPFR_IS_INF(x))
        !            35:     {
        !            36:       MPFR_SET_NAN(y);
        !            37:       MPFR_RET_NAN;
        !            38:     }
        !            39:
        !            40:   if (MPFR_IS_ZERO(x))
        !            41:     {
        !            42:       MPFR_CLEAR_FLAGS(y);
        !            43:       MPFR_SET_ZERO(y);
        !            44:       MPFR_SET_SAME_SIGN(y, x);
        !            45:       MPFR_RET(0);
        !            46:     }
        !            47:
        !            48:   precy = MPFR_PREC(y);
        !            49:   m = precy + _mpfr_ceil_log2 ((double) precy) + ABS(MPFR_EXP(x)) + 13;
        !            50:
        !            51:   mpfr_init2 (s, m);
        !            52:   mpfr_init2 (c, m);
        !            53:
        !            54:   do
        !            55:     {
        !            56:       mpfr_sin_cos (s, c, x, GMP_RNDN); /* err <= 1/2 ulp on s and c */
        !            57:       mpfr_div (c, s, c, GMP_RNDN);     /* err <= 2 ulps */
        !            58:       ok = mpfr_can_round (c, m - 1, GMP_RNDN, rnd_mode, precy);
        !            59:
        !            60:       if (ok == 0)
        !            61:        {
        !            62:          m += BITS_PER_MP_LIMB;
        !            63:          mpfr_set_prec (s, m);
        !            64:          mpfr_set_prec (c, m);
        !            65:        }
        !            66:     }
        !            67:   while (!ok);
        !            68:
        !            69:   inexact = mpfr_set (y, c, rnd_mode);
        !            70:
        !            71:   mpfr_clear (s);
        !            72:   mpfr_clear (c);
        !            73:
        !            74:   return inexact;
        !            75: }