/*
  Copyright 2012 by Sean Luke
  Licensed under the Academic Free License version 3.0
  See the file "LICENSE" for more information
*/


package ec.app.regression.func;
import ec.*;
import ec.app.regression.*;
import ec.gp.*;
import ec.util.*;

/* 
 * Sqrt.java
 * 
 * Created: Mon Apr 23 17:15:35 EDT 2012
 * By: Sean Luke

 
This function appears in the Korns and Keijzer function sets, and is sqrt(x)
 
M. F. Korns. Accuracy in Symbolic Regression. In Proc. GPTP. 2011.
 
M. Keijzer. Improving Symbolic Regression with Interval Arithmetic and Linear Scaling. In Proc. EuroGP. 2003.

*/

/**
 * @author Sean Luke
 * @version 1.0 
 */

public class Sqrt extends GPNode
    {
    public String toString() { return "sqrt"; }

    public int expectedChildren() { return 1; }

    public void eval(final EvolutionState state,
        final int thread,
        final GPData input,
        final ADFStack stack,
        final GPIndividual individual,
        final Problem problem)
        {
        RegressionData rd = ((RegressionData)(input));

        children[0].eval(state,thread,input,stack,individual,problem);
        rd.x = Math.sqrt(rd.x);
        }
    }