///////////////////////////////////////////////////////////////////////////////
// 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, 2022 by Peter Spirtes, Richard        //
// Scheines, Joseph Ramsey, and Clark Glymour.                               //
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package edu.cmu.tetrad.study.gene.tetrad.gene.history;

import edu.cmu.tetrad.util.TetradSerializable;

/**
 * <p>Implements a function from the previous time steps of a history array to
 * the getModel time step. The function is implemented factor by factor; for each
 * factor, the indexed connectivity specifies a specific set of parents
 * (IndexedParents) that the function is permitted to depend on for that factor;
 * the getLabel method returns the value for that set of parents in the
 * history. The update function may optionally be associated with an
 * IndexedLagGraph to provide information about the <i>intended</i> graphical
 * structure of the function (say, from a causal point of view). This
 * IndexedLagGraph gives information about the string names and order of the
 * factors and the number and order of the parents (IndexedParent's) for each
 * factor. This information should be encoded in the function itself, but there
 * is no requirement that the function be checked against the graph explicitly
 * to make sure the graph is actually implemented.
 *
 * @author josephramsey
 */
public interface UpdateFunction extends TetradSerializable {
    long serialVersionUID = 23L;

    /**
     * Returns the indexed lag graph, if one is available.
     */
    IndexedLagGraph getIndexedLagGraph();

    /**
     * Returns the value of the glass function for a given factor.
     *
     * @param factorIndex the index of the factor
     * @param history     the history array.
     * @return the value of the Glass function for this factor.
     */
    double getValue(int factorIndex, double[][] history);

    /**
     * Returns the number of factors in the history. This is used to set up the
     * initial history array.
     */
    int getNumFactors();

    /**
     * Returns the max lag of the gene history. This is used to set up the
     * initial history array.
     */
    int getMaxLag();
}






