///////////////////////////////////////////////////////////////////////////////
// For information as to what this class does, see the Javadoc, below.       //
// Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,       //
// 2007, 2008, 2009, 2010, 2014, 2015 by Peter Spirtes, Richard Scheines, Joseph   //
// Ramsey, and Clark Glymour.                                                //
//                                                                           //
// This program is free software; you can redistribute it and/or modify      //
// it under the terms of the GNU General Public License as published by      //
// the Free Software Foundation; either version 2 of the License, or         //
// (at your option) any later version.                                       //
//                                                                           //
// This program 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 General Public License for more details.                              //
//                                                                           //
// You should have received a copy of the GNU General Public License         //
// along with this program; if not, write to the Free Software               //
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA //
///////////////////////////////////////////////////////////////////////////////

package edu.cmu.tetrad.data;

import edu.cmu.tetrad.graph.Node;
import edu.cmu.tetrad.util.TetradSerializable;

/**
 * Interface implemented by classes, instantiations of which are capable of
 * serving as variables for columns in a DataSet. Such a class provides needed
 * details as to how the data in its column are to be interpreted. In
 * particular, a variable has a name and specifies a value in the column that is
 * to be interpreted as a missing datum. The variable also specifies how
 * external data (in String form, say) is to be converted into raw data of the
 * type used in the column in question.
 *
 * @author Joseph Ramsey
 */
public interface Variable extends Node, TetradSerializable {

    /**
     * Required serial version UID for serialization. Must be 23L.
     */
    long serialVersionUID = 23L;

    /**
     * @return the missing value marker as an object--i.e. a double if
     * continuous, an Integer if discrete, etc.
     */
    Object getMissingValueMarker();

    /**
     * Tests whether the given value is the missing data marker.
     *
     * @param value The object value one wants to check as a missing value.
     * @return true iff the given object is equals to <code>getMissingValueMarker()</code>.
     */
    boolean isMissingValue(Object value);

    /**
     * Checks to see whether the passed value can be converted into a
     * value for this variable.
     *
     * @param value The object value to be checked. For instance, for a
     *              continuous variable, this would be a Double, for a discrete
     *              variable, and Integer, etc.
     * @return true iff the object is a valid value for this variable.
     */
    boolean checkValue(Object value);
}