/*
 *  acm : an aerial combat simulator for X
 *  Copyright (C) 1991,1992  Riley Rainey
 *
 *  This program 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; version 2 dated June, 1991.
 *
 *  This program 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 this program;  if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave., Cambridge, MA 02139, USA.
 */

#include "interpolate.h"
#include <stdio.h>
#ifdef DUMP
#include <signal.h>
#endif

/*
 *  interpolate :  determine the value of a function of one variable
 *		   by interpolation.  Interpolation tables are built by
 *		   the ibuild utility.
 */

static char *ierrmsg = "interpolate: x value is out of bounds\n";

float_t
interpolate (table, x)
ITable	*table;
double	x;
{

	register int i, count = table->count;

	if (x < table->minX) {
		fprintf (stderr, ierrmsg);
		fprintf (stderr, "minimum x = %g; x = %g\n", table->minX, x);
#ifdef DUMP
		kill (getpid(), SIGBUS);
#endif
		return (float_t) I_NaN;
	}

	for (i=0; i<count; ++i) {
	    if (x <= table->entry[i].x)
		return (float_t)(table->entry[i].m * x + table->entry[i].b);
	}

	fprintf (stderr, ierrmsg);
	fprintf (stderr, "maximum x = %g; x = %g\n", table->entry[i-1].x, x);

#ifdef DUMP
	kill (getpid(), SIGBUS);
#endif

	return (float_t) I_NaN;
}
