Code for a full-featured calculator in dropincc.java

Calculator.java

import com.github.pfmiles.dropincc.Action;
import com.github.pfmiles.dropincc.CC;
import com.github.pfmiles.dropincc.Exe;
import com.github.pfmiles.dropincc.Grule;
import com.github.pfmiles.dropincc.Lang;
import com.github.pfmiles.dropincc.TokenDef;

public class Calculator {
    private static Exe exe = null;
    /**
     * <pre>
     * calc ::= expr $
     * expr ::= addend (('+'|'-') addend)*
     * addend ::= factor (('\*'|'/') factor)*
     * factor ::= '\d+(\.\d+)?'
     *          | '(' expr ')'
     * </pre>
     */
    static {
        // some elements' pre-definitions in order to call the methods
        Lang calc = new Lang("Calc");
        TokenDef a = calc.newToken("\\+");
        TokenDef m = calc.newToken("\\*");
        Grule expr = calc.newGrule();
        Grule addend = calc.newGrule();
        Grule factor = calc.newGrule();

        // grammar definition starts here
        calc.defineGrule(expr, CC.EOF).action(new Action<Object[]>() {
            public Double act(Object[] ms) {
                return (Double) ms[0];
            }
        });
        expr.define(addend, CC.ks(a.or("\\-"), addend)).action(new Action<Object[]>() {
            public Double act(Object[] ms) {
                Double a0 = (Double) ms[0];
                Object[] others = (Object[]) ms[1];
                for (Object other : others) {
                    Object[] opAndFactor = (Object[]) other;
                    if ("+".equals(opAndFactor[0])) {
                        a0 += (Double) opAndFactor[1];
                    } else {
                        a0 -= (Double) opAndFactor[1];
                    }
                }
                return a0;
            }
        });
        addend.define(factor, CC.ks(m.or("/"), factor)).action(new Action<Object[]>() {
            public Double act(Object[] ms) {
                Double f0 = (Double) ms[0];
                Object[] others = (Object[]) ms[1];
                for (Object other : others) {
                    Object[] opAndFactor = (Object[]) other;
                    if ("*".equals(opAndFactor[0])) {
                        f0 *= (Double) opAndFactor[1];
                    } else {
                        f0 /= (Double) opAndFactor[1];
                    }
                }
                return f0;
            }
        });
        factor.define("\\d+(\\.\\d+)?").action(new Action<String>() {
            public Double act(String matched) {
                return Double.parseDouble(matched);
            }
        }).alt("\\(", expr, "\\)").action(new Action<Object[]>() {
            public Double act(Object[] ms) {
                return (Double) ms[1];
            }
        });
        // grammar definition end

        exe = calc.compile();
    }

    public static void main(String... args) {
        System.out.println(exe.eval("1 +2+3+(4 +5*6*7*(64/8/2/(2/1 )/1)*8  +9  )+   10"));
    }
}