package org.apidesign.math;

 import org.apidesign.math.Arithmetica;

 import org.apidesign.runtime.check.RuntimeCheck;

 /** Class to simplify arithmetical operations, improved version to compute

  * the sum for ranges, but only if the virtual machine is configured to

  * run in incompatible mode.

  *

  * @author Jaroslav Tulach <jtulach@netbeans.org>

  * @version 2.0

  */

 public class Arithmetica {

     public int sumTwo(int one, int second) {

         return one + second;

     }

     public int sumAll(int... numbers) {

         if (numbers.length == 0) {

             return 0;

         }

         int sum = numbers[0];

         for (int i = 1; i < numbers.length; i++) {

             sum = sumTwo(sum, numbers[i]);

         }

         return sum;

     }

     public int sumRange(int from, int to) {

         if (calledByV2AwareLoader()) {

             return sumRange2(from, to);

         } else {

             return sumRange1(from, to);

         }

     }

     private int sumRange1(int from, int to) {

         int len = to - from;

         if (len < 0) {

             len = -len;

             from = to;

         }

         int[] array = new int[len + 1];

         for (int i = 0; i <= len; i++) {

             array[i] = from + i;

         }

         return sumAll(array);

     }

     private int sumRange2(int from, int to) {

         return (from + to) * (Math.abs(to - from) + 1) / 2;

     }

     private static boolean calledByV2AwareLoader() {

         // BEGIN: design.composition.arith2.6.runtime

         StackTraceElement[] arr = Thread.currentThread().getStackTrace();

         ClassLoader myLoader = Arithmetica.class.getClassLoader();

         for (int i = 0; i < arr.length; i++) {

             ClassLoader caller = arr[i].getClass().getClassLoader();

             if (myLoader == caller) {

                 continue;

             }

             if (RuntimeCheck.requiresAtLeast("2.6", "api.Arithmetica", caller)) {

                 return true;

             }

             return false;

         }

         return true;

         // END: design.composition.arith2.6.runtime

     }

 }