ArithmeticBuilderPop.java

/*
    BeepBeep, an event stream processor
    Copyright (C) 2008-2018 Sylvain Hallé

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published
    by the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package dsl;

import ca.uqac.lif.bullwinkle.BnfParser.InvalidGrammarException;
import ca.uqac.lif.bullwinkle.Builds;
import ca.uqac.lif.cep.dsl.GrammarObjectBuilder;
import ca.uqac.lif.cep.functions.Constant;
import ca.uqac.lif.cep.functions.Function;
import ca.uqac.lif.cep.functions.FunctionTree;
import ca.uqac.lif.cep.util.Numbers;

/**
 * Use a {@link ca.uqac.lif.cep.dsl.GrammarObjectBuilder GrammarObjectBuilder}
 * to parse and evaluate a string in Polish notation.
 * @author Sylvain Hallé
 * @difficulty Medium
 */
public class ArithmeticBuilderPop extends GrammarObjectBuilder<Function>
{
    public static void main(String[] args) throws BuildException
    {
        //&
        ArithmeticBuilderPop builder = new ArithmeticBuilderPop();
        Function f = builder.build("+ 3 - 4 5");
        Object[] value = new Object[1];
        f.evaluate(new Object[]{}, value);
        System.out.println(value[0]);
        //&
    }
    
    ///
    public ArithmeticBuilderPop()
    {
        super();
        try
        {
            setGrammar("<exp> := <add> | <sbt> | <num>;\n"
                    + "<add> := + <exp> <exp>;\n"
                    + "<sbt> := - <exp> <exp>;\n"
                    + "<num> := ^[0-9]+;");
        }
        catch (InvalidGrammarException e)
        {
            // Do nothing
        }
    }
    ///

    //*
    @Builds(rule="<num>", pop=true)
    public Constant handleNum(Object ... parts)
    {
        return new Constant(Float.parseFloat((String) parts[0]));
    }
    //*

    //%
    @Builds(rule="<add>", pop=true)
    public FunctionTree handleAdd(Object ... parts)
    {
        return new FunctionTree(Numbers.addition,
                (Function) parts[1], (Function) parts[2]);
    }
    //%

    //!
    @Builds(rule="<sbt>", pop=true)
    public FunctionTree handleSbt(Object ... parts)
    {
        return new FunctionTree(Numbers.subtraction,
                (Function) parts[1], (Function) parts[2]);
    }
    //!

}