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/*
 * This software and all files contained in it are distrubted under the MIT license.
 *
 * Copyright (c) 2013 Cogito Learning Ltd
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package uk.co.cogitolearning.cogpar;

/**
 * An ExpressionNode that stores a named variable
 */
public class VariableExpressionNode implements ExpressionNode {

    /**
     * The name of the variable
     */
    private final String name;
    /**
     * The value of the variable
     */
    private double value;
    /**
     * indicates if the value has been set
     */
    private boolean valueSet;

    /**
     * Construct with the name of the variable.
     *
     * @param name the name of the variable
     */
    public VariableExpressionNode(String name) {
        this.name = name;
        valueSet = false;
    }

    /**
     * @return the name of the variable
     */
    public String getName() {
        return name;
    }

    /**
     * Returns the type of the node, in this case ExpressionNode.VARIABLE_NODE
     */
    public int getType() {
        return VARIABLE_NODE;
    }

    /**
     * Returns the value of the variable but throws an exception if the value has
     * not been set
     */
    public double getValue() {
        if (valueSet)
            return value;
        else
            throw new EvaluationException("Variable '" + name + "' was not initialized.");
    }

    /**
     * Sets the value of the variable
     *
     * @param value the value of the variable
     */
    public void setValue(double value) {
        this.value = value;
        valueSet = true;
    }

    /**
     * Implementation of the visitor design pattern.
     * Calls visit on the visitor.
     *
     * @param visitor the visitor
     */
    public void accept(ExpressionNodeVisitor visitor) {
        visitor.visit(this);
    }

}