arb/fmprb/exp.c
Fredrik Johansson 0847d21f66 exp and log
2012-09-07 12:19:27 +02:00

61 lines
1.9 KiB
C

/*=============================================================================
This file is part of ARB.
ARB is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
ARB is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with ARB; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2012 Fredrik Johansson
******************************************************************************/
#include "fmprb.h"
void
fmprb_exp(fmprb_t z, const fmprb_t x, long prec)
{
long r;
if (fmprb_is_exact(x))
{
r = fmpr_exp(fmprb_midref(z), fmprb_midref(x), prec, FMPR_RND_DOWN);
fmpr_set_error_result(fmprb_radref(z), fmprb_midref(z), r);
}
else
{
/*
exp(a+b) - exp(a) = exp(a) * (exp(b)-1)
*/
fmpr_t t, u;
fmpr_init(t);
fmpr_init(u);
fmpr_exp(t, fmprb_midref(x), FMPRB_RAD_PREC, FMPR_RND_UP);
fmpr_expm1(u, fmprb_radref(x), FMPRB_RAD_PREC, FMPR_RND_UP);
fmpr_mul(t, t, u, FMPRB_RAD_PREC, FMPR_RND_UP);
r = fmpr_exp(fmprb_midref(z), fmprb_midref(x), prec, FMPR_RND_DOWN);
fmpr_add_error_result(fmprb_radref(z), t, fmprb_midref(z), r,
FMPRB_RAD_PREC, FMPR_RND_UP);
fmpr_clear(t);
fmpr_clear(u);
}
fmprb_adjust(z);
}