//-----------------------------------------------------------------------------
// Copyright © 2003 - Philip Howard - All rights reserved
//
// 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; either version 2
// of the License, or (at your option) any later version.
//
// 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//-----------------------------------------------------------------------------
// package	libh/arith
// homepage	http://libh.slashusr.org/
//-----------------------------------------------------------------------------
// author	Philip Howard
// email	libh at ipal dot org
// homepage	http://phil.ipal.org/
//-----------------------------------------------------------------------------
// This file is best viewed using a fixed spaced font such as Courier
// and in a display at least 120 columns wide.
//-----------------------------------------------------------------------------

#include <stdarg.h>
#include "arith_lib.h"

__FMACRO_BEGIN__
//-----------------------------------------------------------------------------
// macro	rescale_dm
//
// purpose	Given a new linear number range and an old linear number range,
//		rescale multiple numbers from the old range to the new range,
//		storing back the results in the pointed to arguments given.
//
// arguments	1 (double) 1st value of new number range
//		2 (double) 2nd value of new number range
//		3 (double) 1st value of old number range
//		4 (double) 2nd value of old number range
//		5..N (double *) pointer to one or more values
//
// returns	(int) 0
//-----------------------------------------------------------------------------
#define rescale_dm(na,nz,oa,oz,a...) ((rescale_dm)((na),(nz),(oa),(oz),a,((double*)(NULL))))

__FMACRO_END__

__PROTO_BEGIN__
//-----------------------------------------------------------------------------
// function	(rescale_dm)
//
// purpose	Given a new linear number range and an old linear number range,
//		rescale multiple numbers from the old range to the new range,
//		storing back the results in the pointed to arguments given.
//
// arguments	1 (double) 1st value of new number range
//		2 (double) 2nd value of new number range
//		3 (double) 1st value of old number range
//		4 (double) 2nd value of old number range
//		5..N (double *) pointer to one or more values
//		N+1 (double *) NULL to indicate end of list
//
// returns	(int) 0
//-----------------------------------------------------------------------------
int
(rescale_dm) (
    double		arg_new_a
    ,
    double		arg_new_z
    ,
    double		arg_old_a
    ,
    double		arg_old_z
    ,
    double *		arg_value_p
    ,
    ...
    )
__PROTO_END__
{
    va_list		var_args	;
    double *		value_p		;
    double		new_diff	;
    double		old_diff	;
    double		factor		;
    
    new_diff = arg_new_z - arg_new_a;
    old_diff = arg_old_z - arg_old_a;
    factor = arg_new_a * old_diff;

    value_p = arg_value_p;
    va_start( var_args, arg_value_p );

    do {
	* value_p = ( ( new_diff * ( * value_p - arg_old_a ) ) + factor ) / old_diff;
    } while ( ( value_p = va_arg( var_args, double * ) ) );

    return 0;
}