arithmeticcalculator.java

Grammatica is a C# and Java parser generator (compiler compiler). It improves upon simlar tools (lik

/*
 * ArithmeticCalculator.java
 *
 * This work 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 work 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
 *
 * As a special exception, the copyright holders of this library give
 * you permission to link this library with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also meet,
 * for each linked independent module, the terms and conditions of the
 * license of that module. An independent module is a module which is
 * not derived from or based on this library. If you modify this
 * library, you may extend this exception to your version of the
 * library, but you are not obligated to do so. If you do not wish to
 * do so, delete this exception statement from your version.
 *
 * Copyright (c) 2003 Per Cederberg. All rights reserved.
 */

package net.percederberg.grammatica.test;

import java.io.StringReader;
import java.util.ArrayList;
import java.util.HashMap;

import net.percederberg.grammatica.parser.Node;
import net.percederberg.grammatica.parser.ParseException;
import net.percederberg.grammatica.parser.Production;
import net.percederberg.grammatica.parser.Token;

/**
 * A simple arithmetic calculator.
 *
 * @author   Per Cederberg, <per at percederberg dot net>
 * @version  1.0
 */
class ArithmeticCalculator extends ArithmeticAnalyzer {

    /**
     * The map with all variable names and values.
     */
    private HashMap variables;

    /**
     * Creates a new arithmetic calculator.
     */
    public ArithmeticCalculator() {
        this(new HashMap());
    }

    /**
     * Creates a new arithmetic calculator.
     * 
     * @param variables      the variable bindings to use
     */
    public ArithmeticCalculator(HashMap variables) {
        this.variables = variables;
    }

    /**
     * Calculates the numeric value of an expression.
     * 
     * @param expression     the expression to calculate
     * 
     * @return the numeric value of the expression
     * 
     * @throws Exception if the expression contained an error
     */
    public int calculate(String expression) throws Exception {
        ArithmeticParser  parser;
        Node              node;
 
        parser = new ArithmeticParser(new StringReader(expression), this);
        parser.prepare();
        node = parser.parse();
        return ((Integer) node.getValue(0)).intValue();
    }

    /**
     * Adds the addition operator as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitAdd(Token node) {
        node.addValue("+");
        return node;
    }

    /**
     * Adds the subtraction operator as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitSub(Token node) {
        node.addValue("-");
        return node;
    }

    /**
     * Adds the multiplication operator as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitMul(Token node) {
        node.addValue("*");
        return node;
    }

    /**
     * Adds the division operator as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitDiv(Token node) {
        node.addValue("/");
        return node;
    }

    /**
     * Adds the number as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitNumber(Token node) {
        node.addValue(new Integer(node.getImage()));
        return node;
    }

    /**
     * Adds the identifier value as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitIdentifier(Token node) {
        node.addValue(variables.get(node.getImage()));
        return node;
    }

    /**
     * Adds the expression result as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitExpression(Production node) {
        ArrayList  values = getChildValues(node);
        Integer    value1;
        Integer    value2;
        String     op;
        int        result;
        
        if (values.size() == 1) {
            result = ((Integer) values.get(0)).intValue();
        } else {
            value1 = (Integer) values.get(0);
            value2 = (Integer) values.get(2);
            op = (String) values.get(1);
            result = operate(op, value1, value2);
        }
        node.addValue(new Integer(result));
        return node;
    }

    /**
     * Adds the child values as node values.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitExpressionRest(Production node) {
        node.addValues(getChildValues(node));
        return node;
    }

    /**
     * Adds the term result as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitTerm(Production node) {
        ArrayList  values = getChildValues(node);
        Integer    value1;
        Integer    value2;
        String     op;
        int        result;
        
        if (values.size() == 1) {
            result = ((Integer) values.get(0)).intValue();
        } else {
            value1 = (Integer) values.get(0);
            value2 = (Integer) values.get(2);
            op = (String) values.get(1);
            result = operate(op, value1, value2);
        }
        node.addValue(new Integer(result));
        return node;
    }

    /**
     * Adds the child values as node values.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitTermRest(Production node) {
        node.addValues(getChildValues(node));
        return node;
    }

    /**
     * Adds the factor value as a node value.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     * 
     * @throws ParseException if the node analysis discovered errors
     */
    protected Node exitFactor(Production node) throws ParseException {
        int  result;
        
        if (node.getChildCount() == 1) {
            result = getIntValue(getChildAt(node, 0), 0);
        } else {
            result = getIntValue(getChildAt(node, 1), 0);
        }
        node.addValue(new Integer(result));
        return node;
    }

    /**
     * Adds the child values as node values.
     * 
     * @param node           the node being exited
     * 
     * @return the node to add to the parse tree
     */
    protected Node exitAtom(Production node) {
        node.addValues(getChildValues(node));
        return node;
    }

    /**
     * Performs a numerical operation. 
     * 
     * @param op             the operator to use
     * @param value1         the first value
     * @param value2         the second value
     * 
     * @return the result of performing the operation
     */
    private int operate(String op, Integer value1, Integer value2) {
        int  i = value1.intValue();
        int  j = value2.intValue();
        
        switch (op.charAt(0)) {
        case '+':
            return i + j;
        case '-':
            return i - j;
        case '*':
            return i * j;
        case '/':
            return i / j;
        default:
            throw new RuntimeException("unknown operator: " + op);
        }
    }
}