package ac.essex.ooechs.ecj.ecj2java.example.functions; 
 
import ec.EvolutionState; 
import ec.Problem; 
import ec.gp.GPData; 
import ec.gp.ADFStack; 
import ec.gp.GPIndividual; 
import ac.essex.ooechs.ecj.ecj2java.example.data.DoubleData; 
import ac.essex.ooechs.ecj.ecj2java.nodes.ParseableGPNode; 
 
/** 
 * <p/> 
 * 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, 
 * provided that any use properly credits the author. 
 * 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 at http://www.gnu.org 
 * </p> 
 * 
 * @author Olly Oechsle, University of Essex, Date: 08-Dec-2006 
 * @version 1.0 
 */ 
public class Sqrt extends ParseableGPNode { 
 
    public Sqrt() { 
        // I have 1 child - this must match the type in the params file. It is ECJ's checking mechanism. 
        super("sqrt", 1); 
    } 
 
    /** 
     * Called as the function is evaluated. 
     */ 
    public void eval(final EvolutionState state, final int thread, final GPData input, final ADFStack stack, final GPIndividual individual, final Problem problem) { 
 
        DoubleData dd = ((DoubleData) (input)); 
 
        // evaluate the left child 
        children[0].eval(state, thread, input, stack, individual, problem); 
 
        // do a square root 
        dd.x = dd.x > 0? Math.sqrt(dd.x) : 1; 
 
    } 
 
    public int getObjectType() { 
        return ParseableGPNode.DOUBLE; 
    } 
 
    /** 
     * Convert this code to pure Java 
     */ 
    public String getJavaCode() { 
        return getChild(0).getVariableName() + " > 0? Math.sqrt(" + getChild(0).getVariableName() + ") : 0"; 
    } 
 
}