Exp0 - Java

package com.jswrenn.exp0;

import static com.jswrenn.grammar.PatternBuilder.first;
import static com.jswrenn.grammar.PatternBuilder.just;

import com.jswrenn.grammar.Rule;

public class Exp0 {

    private static final Rule
            Statement = new Statement(),
            Expression = new Expression(),
            LHSVar = new LHSVar(),
            RHSVar = new RHSVar(),
            Num = new Num();

    public static class Statement extends Rule {{
        matches(first('s').then(Expression).last(Expression),
        /*or*/  first('p').last(Expression));}}

    public static class Expression extends Rule {{
        matches(first('+').then(Expression).last(Expression),
        /*or*/  first('-').then(Expression).last(Expression),
        /*or*/  first('(').then(Expression).last(')'),
        /*or*/  just(LHSVar),
        /*or*/  just(Num));}}

    public static class LHSVar extends Rule {{
        matches(just('x'),
        /*or*/  just('y'),
        /*or*/  just('z'));}}

    public static class RHSVar extends Rule {{
        matches(just('x'),
        /*or*/  just('y'),
        /*or*/  just('z'));}}

    public static class Num extends Rule {{
        matches(just('0'),
        /*or*/  just('1'),
        /*or*/  just('2'),
        /*or*/  just('3'),
        /*or*/  just('4'),
        /*or*/  just('5'),
        /*or*/  just('6'),
        /*or*/  just('7'),
        /*or*/  just('8'),
        /*or*/  just('9'));}}
}