/*
 * register - set or print a custom register value
 *
 * Copyright (C) 2007  Landon Curt Noll
 *
 * Calc is open software; you can redistribute it and/or modify it under
 * the terms of the version 2.1 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * Calc 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 Lesser General
 * Public License for more details.
 *
 * A copy of version 2.1 of the GNU Lesser General Public License is
 * distributed with calc under the filename COPYING-LGPL.  You should have
 * received a copy with calc; if not, write to Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @(#) $Revision: 30.1 $
 * @(#) $Id: register.cal,v 30.1 2007/07/05 19:35:54 chongo Exp $
 * @(#) $Source: /usr/local/src/cmd/calc/custom/RCS/register.cal,v $
 *
 * Under source code control:	2007/07/05 11:11:11
 * File existed as early as:	2007
 *
 * chongo <was here> /\oo/\	http://www.isthe.com/chongo/
 * Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/
 */

/*
 * This file is part of the custom sample calc files.
 *
 * NOTE: You must use a calc that was compiled with ALLOW_CUSTOM= -DCUSTOM
 *	 and run with a -C arg.
 */
if (config("compile_custom") == 0) {
	quit "calc compiled without -DCUSTOM";
} else if (config("allow_custom") == 0) {
	quit "calc was run without the -D command line option";
}


define register(num)
{
	local reg_max;	    /* number of registers */

	/*
	 * firewall
	 */
	if (!isnum(num)) {
		return newerror("register only works on numeric values");
	}

	/*
	 * determine register count
	 */
	reg_max = custom("sysinfo", "REGNUM_MAX");

	/*
	 * determine the HALF length of a numeric value
	 */
	if (num < 0) {
		return newerror("register number must be >= 0");
	} else if (num > reg_max) {
		return newerror("register number must be < REGNUM_MAX");
	} else {
		return custom("register", num);
	}
}