/*
 * Copyright 2009 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.math;

import net.morilib.lisp.Cons;
import net.morilib.lisp.Datum;
import net.morilib.lisp.Environment;
import net.morilib.lisp.LispMessage;
import net.morilib.lisp.Nil;
import net.morilib.lisp.Subr;

public abstract class PolynomialOperator1 extends Subr {
	
	/**
	 * 
	 * @return
	 */
	protected abstract LispPolynomial initValue();
	
	/**
	 * 
	 * @param o1
	 * @param o2
	 * @return
	 */
	protected abstract LispPolynomial calculate(
			LispPolynomial o1, LispPolynomial o2);
	
	/*
	 * (non-Javadoc)
	 * @see net.morilib.lisp.Subr#eval(net.morilib.lisp.Datum, net.morilib.lisp.Environment, net.morilib.lisp.LispMessage)
	 */
	public Datum eval(
			Datum body,
			Environment env,
			LispMessage mesg) {
		LispPolynomial res = initValue();
		
		Datum li = body;
		while(true) {
			if(li instanceof Nil) {
				return res;
			} else if(li instanceof Cons) {
				Cons c2 = (Cons)li;
				Datum c2a = c2.getCar();
				
				if(c2a instanceof LispPolynomial) {
					res = calculate(res, (LispPolynomial)c2a);
					li = c2.getCdr();
				} else {
					throw mesg.getError("err.require.poly", c2a);
					//throw new LispException("number required");
				}
			} else {
				throw mesg.getError("err.list");
				//throw new LispException("proper list required");
			}
		}
	}

}
