arb/fmpcb_poly/atan_series.c
2013-07-27 18:11:29 +02:00

87 lines
2.4 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) 2013 Fredrik Johansson
******************************************************************************/
#include "fmpcb_poly.h"
void
_fmpcb_poly_atan_series(fmpcb_ptr g, fmpcb_srcptr h, long hlen, long n, long prec)
{
fmpcb_t c;
fmpcb_init(c);
/* TODO: fmpcb_atan(c, h, prec); */
if (!fmpcb_is_zero(h))
abort();
fmpcb_zero(g);
hlen = FLINT_MIN(hlen, n);
if (hlen == 1)
{
_fmpcb_vec_zero(g + 1, n - 1);
}
else
{
fmpcb_ptr t, u;
long ulen;
t = _fmpcb_vec_init(n);
u = _fmpcb_vec_init(n);
/* atan(h(x)) = integral(h'(x)/(1+h(x)^2)) */
ulen = FLINT_MIN(n, 2 * hlen - 1);
_fmpcb_poly_mullow(u, h, hlen, h, hlen, ulen, prec);
fmpcb_add_ui(u, u, 1, prec);
_fmpcb_poly_derivative(t, h, hlen, prec);
_fmpcb_poly_div_series(g, t, hlen - 1, u, ulen, n, prec);
_fmpcb_poly_integral(g, g, n, prec);
_fmpcb_vec_clear(t, n);
_fmpcb_vec_clear(u, n);
}
fmpcb_swap(g, c);
fmpcb_clear(c);
}
void
fmpcb_poly_atan_series(fmpcb_poly_t g, const fmpcb_poly_t h, long n, long prec)
{
long hlen = h->length;
if (hlen == 0 || n == 0)
{
fmpcb_poly_zero(g);
return;
}
fmpcb_poly_fit_length(g, n);
_fmpcb_poly_atan_series(g->coeffs, h->coeffs, hlen, n, prec);
_fmpcb_poly_set_length(g, n);
_fmpcb_poly_normalise(g);
}