/*
 * 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.r6rs.fixnum;

import net.morilib.lisp.ConsIterator;
import net.morilib.lisp.Datum;
import net.morilib.lisp.Environment;
import net.morilib.lisp.LispInteger;
import net.morilib.lisp.LispMessage;
import net.morilib.lisp.Subr;
import net.morilib.lisp.subr.SubrUtils;
import net.morilib.util.Iterators;

/**
 *
 *
 * @author MORIGUCHI, Yuichiro 2012/08/29
 */
public abstract class AbstractFixnumBinaryOp2 extends Subr {

	/**
	 * 
	 * @param x
	 * @return
	 */
	protected abstract int op1(int x, LispMessage mesg);

	/**
	 * 
	 * @param x
	 * @param y
	 * @return
	 */
	protected abstract int op2(int x, int y, 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 m) {
		ConsIterator itr = new ConsIterator(body);
		int x = SubrUtils.nextSmallInt(itr, m, body);
		Datum yd = Iterators.nextIf(itr);

		SubrUtils.checkTerminated(itr, body, m);
		return LispInteger.valueOf((yd == null) ?
				op1(x, m) : op2(x, SubrUtils.getSmallInt(yd, m), m));
	}

}
