/*
 *  M_APM  -  mapmgues.c
 *
 *  Copyright (C) 1999 - 2007   Michael C. Ring
 *
 *  Permission to use, copy, and distribute this software and its
 *  documentation for any purpose with or without fee is hereby granted,
 *  provided that the above copyright notice appear in all copies and
 *  that both that copyright notice and this permission notice appear
 *  in supporting documentation.
 *
 *  Permission to modify the software is granted. Permission to distribute
 *  the modified code is granted. Modifications are to be distributed by
 *  using the file 'license.txt' as a template to modify the file header.
 *  'license.txt' is available in the official MAPM distribution.
 *
 *  This software is provided "as is" without express or implied warranty.
 */

/*
 *
 *      This file contains the functions that generate the initial
 *	'guesses' for the sqrt, cbrt, log, arcsin, and arccos functions.
 */

#include "pgAdmin3.h"
#include "pgscript/utilities/mapm-lib/m_apm_lc.h"

/****************************************************************************/
void	M_get_sqrt_guess(M_APM r, M_APM a)
{
	char	buf[48];
	double  dd;

	m_apm_to_string(buf, 15, a);
	dd = atof(buf);                     /* sqrt algorithm actually finds 1/sqrt */
	m_apm_set_double(r, (1.0 / sqrt(dd)));
}
/****************************************************************************/
/*
 *	for cbrt, log, asin, and acos we induce an error of 10 ^ -5.
 *	this enables the iterative routine to be more efficient
 *	by knowing exactly how accurate the initial guess is.
 *
 *	this also prevents some corner conditions where the iterative
 *	functions may terminate too soon.
 */
/****************************************************************************/
void	M_get_cbrt_guess(M_APM r, M_APM a)
{
	char	buf[48];
	double  dd;

	m_apm_to_string(buf, 15, a);
	dd = atof(buf);
	dd = log(dd) / 3.0;                 /* cbrt algorithm actually finds 1/cbrt */
	m_apm_set_double(r, (1.00001 / exp(dd)));
}
/****************************************************************************/
void	M_get_log_guess(M_APM r, M_APM a)
{
	char	buf[48];
	double  dd;

	m_apm_to_string(buf, 15, a);
	dd = atof(buf);
	m_apm_set_double(r, (1.00001 * log(dd)));        /* induce error of 10 ^ -5 */
}
/****************************************************************************/
/*
 *	the implementation of the asin & acos functions
 *	guarantee that 'a' is always < 0.85, so it is
 *	safe to multiply by a number > 1
 */
void	M_get_asin_guess(M_APM r, M_APM a)
{
	char	buf[48];
	double  dd;

	m_apm_to_string(buf, 15, a);
	dd = atof(buf);
	m_apm_set_double(r, (1.00001 * asin(dd)));       /* induce error of 10 ^ -5 */
}
/****************************************************************************/
void	M_get_acos_guess(M_APM r, M_APM a)
{
	char	buf[48];
	double  dd;

	m_apm_to_string(buf, 15, a);
	dd = atof(buf);
	m_apm_set_double(r, (1.00001 * acos(dd)));       /* induce error of 10 ^ -5 */
}
/****************************************************************************/
/*
	convert a C 'double' into an M_APM value.
*/
void	m_apm_set_double(M_APM atmp, double dd)
{
	char	*cp, *p, *ps, buf[64];

	if (dd == 0.0)                     /* special case for 0 exactly */
		M_set_to_zero(atmp);
	else
	{
		sprintf(buf, "%.14E", dd);

		if ((cp = strstr(buf, "E")) == NULL)
		{
			M_apm_log_error_msg(M_APM_RETURN,
			                    "\'m_apm_set_double\', Invalid double input (likely a NAN or +/- INF)");

			M_set_to_zero(atmp);
			return;
		}

		if (atoi(cp + sizeof(char)) == 0)
			*cp = '\0';

		p = cp;

		while (TRUE)
		{
			p--;
			if (*p == '0' || *p == '.')
				*p = ' ';
			else
				break;
		}

		ps = buf;
		p  = buf;

		while (TRUE)
		{
			if ((*p = *ps) == '\0')
				break;

			if (*ps++ != ' ')
				p++;
		}

		m_apm_set_string(atmp, buf);
	}
}
/****************************************************************************/