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TOVAL comprises a set of java classes for common programming issues. It includes utils for arrays, lists, sets and collections for convenient handling and modification, but also support for mathematic definitions concerning logic (clauses + resolution) together with some algorithms for permutations, powersets and resolution. Additionally it contains a number of types for multisets, matrices with object keys and much more.

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package de.invation.code.toval.math;

import java.math.BigInteger;

public class MathUtils {

        /**
         * Calculates the factorial of number.
         *
         * @param number Basic number for operation
         * @return The factorial of number
         */
        public static BigInteger getFactorial(int number) {
                BigInteger factorial = BigInteger.ONE;
                for (int i = number; i > 1; i--) {
                        factorial = factorial.multiply(new BigInteger(Integer.toString(i)));
                }
                return factorial;
        }

        /**
         * Returns the binomial coefficient.

         * For any set containing n elements, this is the number of distinct
         * k-element subsets of it.
         *
         * @param n Set size
         * @param k Subset size
         * @return The binomial coefficient of n and k
         */
        public static long binCoeff(int n, int k) {
                if (k > n) {
                        return 0;
                }
                if (k == 0 || k == n) {
                        return 1;
                }
                long result = 1;
                for (int i = 1; i <= k; i++) {
                        result *= (n - i + 1) / i;
                }
                return result;
        }

        /**
         * Constucts a truth-table for the given column-number. 

         * The number of table rows is 2^columnCount.

         * A truth-table with three columns looks like this:

         * (0=false, 1=true)

         * 

         * 
         * 0 0 0
         * 0 0 1
         * 0 1 0
         * 0 1 1
         * 1 0 0
         * 1 0 1
         * 1 1 0
         * 1 1 1
         * 
         * 

         *
         * @param colCount The number of columns.
         * @return The constructed truth-table
         */
        public static boolean[][] getTruthTable(int colCount) {
                boolean[][] table = new boolean[colCount][(int) Math.pow(2, colCount)];
                for (int i = 1; i <= colCount; i++) {
                        for (int j = 0; j < (int) Math.pow(2, colCount); j++) {
                                //System.out.println(i+" "+j+" "+(int) Math.floor(j/Math.pow(2,i-1)));
                                table[i - 1][j] = (((int) Math.floor(j / Math.pow(2, i - 1))) % 2) == 0;
                        }
                }
                return table;
        }

        /**
         * Returns the number of places after the decimal separator of the given
         * number.
         *
         * @param  Number type
         * @param number Basic number for operation
         * @return The number of places after the decimal separator of
         * number
         */
        public static  int getRHD(N number) {
                String numberAsString = String.valueOf(number);
                return numberAsString.substring(numberAsString.lastIndexOf('.') + 1).length();
        }

        /**
         * Returns the number of zeros after the decimal separator of the given
         * number before another digit appears.
         *
         * @param number Basic number for operation
         * @return The number of zeros after the decimal separator before
         * another digit appears
         */
        public static int getRHD(double number) {
                double n = number % 1;
                int rhd = 0;
                while ((n *= 10) < 1) {
                        rhd++;
                }
                return ++rhd;
        }

}