TypeUtils.java

/**
 *  Copyright (C) [2010-2012] dennis zhuang (killme2008@gmail.com)
 *
 *  This library 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 2.1 of the License, or
 *  (at your option) any later version.
 *
 *  This library 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, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 **/
package com.googlecode.aviator.utils;

import java.math.BigDecimal;
import java.math.BigInteger;

import com.googlecode.aviator.AviatorEvaluator;


/**
 * Java type to aviator type utilities
 * 
 * @author boyan
 * 
 */
public class TypeUtils {

    public static final boolean isBigInt(Object value) {
        return value instanceof BigInteger;
    }


    public static final boolean isDecimal(Object value) {
        return value instanceof BigDecimal;
    }


    public static final boolean isLong(Object value) {
        return value instanceof Integer || value instanceof Long || value instanceof Byte || value instanceof Short;
    }


    public static final boolean isDouble(Object value) {
        return value instanceof Float || value instanceof Double;

    }


    public static final boolean isString(Object value) {
        return value instanceof String || value instanceof Character;
    }

    public static long NEWTON_METHOD_REPEATS = 10000;


    public static int comapreLong(long x, long y) {
        if (x > y)
            return 1;
        else if (x < y)
            return -1;
        else
            return 0;
    }


    /**
     * newton method to get natural logarithm
     * 
     * @param x
     * @return
     */
    public static BigDecimal ln(BigDecimal x) {
        if (x.equals(BigDecimal.ONE)) {
            return BigDecimal.ZERO;
        }

        x = x.subtract(BigDecimal.ONE);
        BigDecimal ret = new BigDecimal(NEWTON_METHOD_REPEATS + 1);
        for (long i = NEWTON_METHOD_REPEATS; i >= 0; i--) {
            BigDecimal N = new BigDecimal(i / 2 + 1).pow(2);
            N = N.multiply(x, AviatorEvaluator.getMathContext());
            ret = N.divide(ret, AviatorEvaluator.getMathContext());

            N = new BigDecimal(i + 1);
            ret = ret.add(N, AviatorEvaluator.getMathContext());

        }

        ret = x.divide(ret, AviatorEvaluator.getMathContext());
        return ret;
    }

}