/* $NetBSD: cephes_subrf.c,v 1.1 2007/08/20 16:01:34 drochner Exp $ */

/*-
* Copyright (c) 2007 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software written by Stephen L. Moshier.
* It is redistributed by the NetBSD Foundation by permission of the author.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

#include "../src/namespace.h"
#include <complex.h>
#include <math.h>
#include "cephes_subrf.h"

/* calculate cosh and sinh */

void
_cchshf(float x, float *c, float *s)
{
       float e, ei;

       if (fabsf(x) <= 0.5f) {
               *c = coshf(x);
               *s = sinhf(x);
       } else {
               e = expf(x);
               ei = 0.5f / e;
               e = 0.5f * e;
               *s = e - ei;
               *c = e + ei;
       }
}

/* Program to subtract nearest integer multiple of PI */

/* extended precision value of PI: */
static const double DP1 =  3.140625;
static const double DP2 =  9.67502593994140625E-4;
static const double DP3 =  1.509957990978376432E-7;
#define MACHEPF 3.0e-8

float
_redupif(float x)
{
       float t;
       long i;

       t = x / (float)M_PI;
       if (t >= 0.0f)
               t += 0.5f;
       else
               t -= 0.5f;

       i = t;  /* the multiple */
       t = i;
       t = ((x - t * DP1) - t * DP2) - t * DP3;
       return t;
}

/* Taylor series expansion for cosh(2y) - cos(2x) */

float
_ctansf(float complex z)
{
       float f, x, x2, y, y2, rn, t, d;

       x = fabsf(2.0f * crealf(z));
       y = fabsf(2.0f * cimagf(z));

       x = _redupif(x);

       x = x * x;
       y = y * y;
       x2 = 1.0f;
       y2 = 1.0f;
       f = 1.0f;
       rn = 0.0f;
       d = 0.0f;
       do {
               rn += 1.0f;
               f *= rn;
               rn += 1.0f;
               f *= rn;
               x2 *= x;
               y2 *= y;
               t = y2 + x2;
               t /= f;
               d += t;

               rn += 1.0f;
               f *= rn;
               rn += 1.0f;
               f *= rn;
               x2 *= x;
               y2 *= y;
               t = y2 - x2;
               t /= f;
               d += t;
       } while (fabsf(t/d) > MACHEPF);
       return d;
}