/*
 * Copyright 2009-2010 Yuichiro Moriguchi
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.morilib.lisp.nano.subr;

import net.morilib.lisp.nano.Datum;
import net.morilib.lisp.nano.Environment;
import net.morilib.lisp.nano.LispMessage;
import net.morilib.lisp.nano.Subr;

/**
 *
 *
 * @author MORIGUCHI, Yuichiro 2011/03/27
 */
public abstract class NoArgs extends Subr {

	/**
	 * 
	 */
	protected NoArgs() { }

	/**
	 * 
	 * @param s
	 */
	protected NoArgs(String s) {
		super(s);
	}

	/**
	 * 
	 * @param env
	 * @param mesg
	 * @return
	 */
	protected abstract Datum execute(
			Environment env, LispMessage mesg);

	/* (non-Javadoc)
	 * @see net.morilib.lisp.Subr#eval(net.morilib.lisp.Datum, net.morilib.lisp.Environment, net.morilib.lisp.LispMessage)
	 */
	@Override
	public Datum eval(Datum body, Environment env, LispMessage mesg) {
		if(body.isNil()) {
			return execute(env, mesg);
		} else {
			throw mesg.getError("err.argument", body);
		}
	}

}
