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/*
Copyright (C) 2015 Fredrik Johansson
This file is part of Arb.
Arb is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "acb_hypgeom.h"
static void
phase(acb_t res, const arb_t re, const arb_t im)
{
if (arb_is_nonnegative(re) || arb_is_negative(im))
{
acb_one(res);
}
else if (arb_is_negative(re) && arb_is_nonnegative(im))
{
acb_set_si(res, -3);
}
else
{
arb_zero(acb_imagref(res));
/* -1 +/- 2 */
arf_set_si(arb_midref(acb_realref(res)), -1);
mag_one(arb_radref(acb_realref(res)));
mag_mul_2exp_si(arb_radref(acb_realref(res)), arb_radref(acb_realref(res)), 1);
}
}
void
acb_hypgeom_bessel_jy(acb_t res1, acb_t res2, const acb_t nu, const acb_t z, slong prec)
{
acb_t jnu, t, u, v;
/* both j and y are zero at -inf and +inf when nu is finite */
if (acb_is_finite(nu) && !acb_is_finite(z) &&
acb_is_real(z) && !acb_contains_zero(z))
{
if (res1 != NULL) acb_zero(res1);
acb_zero(res2);
return;
}
acb_init(jnu);
acb_init(t);
acb_init(u);
acb_init(v);
acb_hypgeom_bessel_j(jnu, nu, z, prec);
if (acb_is_int(nu))
{
int is_real = acb_is_real(nu) && acb_is_real(z)
&& arb_is_positive(acb_realref(z));
acb_mul_onei(t, z);
acb_hypgeom_bessel_k(t, nu, t, prec);
acb_onei(u);
acb_pow(u, u, nu, prec);
acb_mul(t, t, u, prec);
acb_const_pi(u, prec);
acb_div(t, t, u, prec);
acb_mul_2exp_si(t, t, 1);
acb_neg(t, t);
phase(v, acb_realref(z), acb_imagref(z));
acb_mul(u, jnu, v, prec);
acb_mul_onei(u, u);
acb_sub(res2, t, u, prec);
if (is_real)
arb_zero(acb_imagref(res2));
}
else
{
acb_sin_cos_pi(t, u, nu, prec);
acb_mul(v, jnu, u, prec);
acb_neg(u, nu);
acb_hypgeom_bessel_j(u, u, z, prec);
acb_sub(v, v, u, prec);
acb_div(res2, v, t, prec);
}
if (res1 != NULL)
acb_set(res1, jnu);
acb_clear(jnu);
acb_clear(t);
acb_clear(u);
acb_clear(v);
}
void
acb_hypgeom_bessel_y(acb_t res, const acb_t nu, const acb_t z, slong prec)
{
acb_hypgeom_bessel_jy(NULL, res, nu, z, prec);
}
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