/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.math.optimization.linear;

/**
 * Types of relationships between two cells in a Solver
 * {@link LinearConstraint}.
 * 
 * @version $Revision$ $Date$
 * @since 2.0
 */
public enum Relationship {

	/** Equality relationship. */
	EQ("="),

	/** Lesser than or equal relationship. */
	LEQ("<="),

	/** Greater than or equal relationship. */
	GEQ(">=");

	/** Display string for the relationship. */
	private String stringValue;

	/**
	 * Simple constructor.
	 * 
	 * @param stringValue
	 *            display string for the relationship
	 */
	private Relationship(String stringValue) {
		this.stringValue = stringValue;
	}

	/** {@inheritDoc} */
	@Override
	public String toString() {
		return stringValue;
	}

	/**
	 * Get the relationship obtained when multiplying all coefficients by -1.
	 * 
	 * @return relationship obtained when multiplying all coefficients by -1
	 */
	public Relationship oppositeRelationship() {
		switch (this) {
		case LEQ:
			return GEQ;
		case GEQ:
			return LEQ;
		default:
			return EQ;
		}
	}

}
