using System;

using System.Collections.Generic;

using System.Text;

using Wintellect.PowerCollections;



namespace CBucks.Common {



	public delegate bool DoublePred<T1, T2>(T1 a, T2 b);



	public delegate T3 Transform<T1, T2, T3>(T1 a, T2 b);



	/// <summary>

	/// Contains common array operations

	/// </summary>

	public static class ArrOps {



		/// <summary>

		/// Checks whether the specified arrays are equal, i.e., contain equal 

		/// components and are of same length.

		/// </summary>

		/// <typeparam name="T"> The first array </typeparam>

		/// <param name="a"> The first array </param>

		/// <param name="b"> The second array </param>

		/// <returns> True if they are equal and false if not </returns>

		public static bool equal<T>(T[] a, T[] b) {

			if(null == a || null == b)

				return null == a && null == b;

			if(a.Length != b.Length)

				return false;

			int n = a.Length;

			for(int i = 0; i < n; i++)

				if(!object.Equals(a[i], b[i]))

					return false;

			return true;

		}  // end of equal<T>



		/// <summary>

		/// Checks whether the specified arrays contain all their references

		/// equal

		/// </summary>

		/// <typeparam name="T"> The array type </typeparam>

		/// <param name="a"> The first array </param>

		/// <param name="b"> The second array </param>

		/// <returns> True if they do and false if not </returns>

		public static bool equalRef<T>(T[] a, T[] b) where T : class {

			if(null == a || null == b)

				return null == a && null == b;

			if(a.Length != b.Length)

				return false;

			int n = a.Length;

			for(int i = 0; i < n; i++)

				if(a[i] != b[i])

					return false;

			return true;

		}  // end of equalRef<T>



		/// <summary>

		/// Gets whether all elements of the specified array are equal to 

		/// the specified value 

		/// </summary>

		/// <typeparam name="T"> The element type </typeparam>

		/// <param name="a"> The array </param>

		/// <param name="b"> The value </param>

		/// <returns> True if it is and false if not </returns>

		public static bool allEqual<T>(T[] a, T b) {

			if(null == a || a.Length == 0)

				return true;

			for(int i = 0; i < a.Length; i++)

				if(!object.Equals(a[i], b))

					return false;

			return true;

		}  // end of allEqual<T>()



		/// <summary>

		/// Gets whether all elements of the specified array are reference equal to 

		/// the specified value 

		/// </summary>

		/// <typeparam name="T"> The element type </typeparam>

		/// <param name="a"> The array </param>

		/// <param name="b"> The value </param>

		/// <returns> True if it is and false if not </returns>

		public static bool allEqualRef<T>(T[] a, T b) where T: class {

			if(null == a || a.Length == 0)

				return true;

			for(int i = 0; i < a.Length; i++)

				if(b != a[i])

					return false;

			return true;

		}  // end of allEqual<T>()



		/// <summary>

		/// Gets whether all elements of the array are the same

		/// </summary>

		/// <typeparam name="T"> The array element type </typeparam>

		/// <param name="a"> The array </param>

		/// <returns> True if it is and false if not </returns>

		public static bool allSame<T>(T[] a) {

			if(null == a || a.Length <= 1)

				return true;

			return allEqual<T>(a, a[0]);

		}  // end of allSame<T>()



		/// <summary>

		/// Gets whether all array elemetns are the same references

		/// </summary>

		/// <typeparam name="T"> The array element type </typeparam>

		/// <param name="a"> The array to check </param>

		/// <returns> True if it is and false if not </returns>

		public static bool allSameRef<T>(T[] a) where T : class {

			if(null == a || a.Length <= 1)

				return true;

			return allEqualRef<T>(a, a[0]);

		}  // end of allSameRef<T>()



		/// <summary>

		/// Creates an alternative iterator of two arrays of the same length.

		/// If n is the length of both arrays, returns an iterator over a 

		/// sequence of 2^n values. 

		/// </summary>

		/// <typeparam name="T"> The element type of the array </typeparam>

		/// <param name="a"> The first array </param>

		/// <param name="b"> The second array </param>

		/// <returns> The resulting iterator </returns>

		/// <remarks> The resulting arrays should not be modified </remarks>

		public static IEnumerable<T[]> alterIter<T>(T[] a, T[] b) {

			if(null == a || null == b)

				throw new ArgumentNullException();

			if(a.Length != b.Length)

				throw new ArgumentException();

			int n = a.Length;

			T[] res = new T[n];

			int[] iis = idarr<int>(-1, n); // -1 - no value, 0 - first array,

			// 1 - second array

			int i = 0;

			while(i > -1) {

				if(i < n) {

					switch(iis[i]) {

						case -1: iis[i]++; res[i] = a[i]; i++; break;

						case 0: iis[i]++; res[i] = b[i]; i++; break;

						case 1: iis[i] = -1; i--; break;

					}  // end of switch()

				} else {

					i--;

					yield return res;

				}  // end of while()

			}  // end of while()

		}  // end of alterIter<T>()



		/// <summary>

		/// Gets the product of all array values and 1 if the array is empty

		/// </summary>

		/// <param name="arr"> The array </param>

		/// <returns> The resulting product </returns>

		public static int prod(params int[] arr) {

			int p = 1;

			foreach(int i in arr)

				p *= i;

			return p;

		}  // end of prod()



		/// <summary>

		/// Negates the array component-wise

		/// </summary>

		/// <param name="arr"> The array to negate </param>

		/// <returns> The negated array </returns>

		public static int[] neg(params int[] arr) {

			int n = arr.Length;

			int[] r = new int[n];

			for(int i = 0; i < n; i++)

				r[i] = -arr[i];

			return r;

		}  // end of neg()



		/// <summary>

		/// Transforms an array into a 2D array of the specified size, 

		/// </summary>

		/// <typeparam name="T"> The type of the array to transform </typeparam>

		/// <param name="arr"> The source array </param>

		/// <param name="s"> The size of the resulting 2D array </param>

		/// <returns> The resulting array </returns>

		public static T[,] to2DArray<T>(Array arr, int s) {

			T[,] arr2 = new T[s, s];

			// copy array values

			int i = 0, j = 0;

			foreach(T v in arr) {

				arr2[i, j++] = v;

				if(j == s) {

					i++;

					j = 0;

				}  // end of if()

			}  // end of foreach()

			return arr2;

		}  // end of to2DArray()

		

		/// <summary>

		/// Reads the data from a 2D array into the specified array

		/// </summary>

		/// <typeparam name="T"> The array element type </typeparam>

		/// <param name="arr"> The source 2D array </param>

		/// <param name="s"> The size of the 2D square array </param>

		/// <param name="sizes"> The size of the resulting array </param>

		/// <returns> The resulting array </returns>

		public static Array from2DArray<T>(T[,] arr, int s, int[] sizes) {

			switch(sizes.Length) {

				case 1:

					return from2DArrayTo1D<T>(arr, s, sizes);

				case 2:

					return arr;

				case 3:

					return from2DArrayTo3D<T>(arr, s, sizes);

				case 4:

					return from2DArrayTo4D<T>(arr, s, sizes);

				default:

					return from2DArrayToND<T>(arr, s, sizes);

			}  // end of switch()

		}  // end of from2DArray<T>()



		/// <summary>

		/// Reads the data from the 2D array into a 1D array

		/// </summary>

		/// <typeparam name="T"> The element type </typeparam>

		/// <param name="arr"> The 2D array </param>

		/// <param name="s"> The size of the 2D array </param>

		/// <param name="sizes"> The sizes of the 1D array </param>

		/// <returns> The resulting 1D array </returns>

		public static T[] from2DArrayTo1D<T>(T[,] arr, int s, int[] sizes) {

			int n = sizes[0];

			T[] arr2 = new T[n];

			int i = 0, j = 0;

			for(int p = 0; p < n; p++) {

				arr2[p] = arr[i, j++];

				if(j == s) {

					i++;

					j = 0;

				}  // end of if()

			}  // end of for()

			return arr2;

		}  // end of from2DArrayTo1D()



		/// <summary>

		/// Converts a 2D array representation into a 3D array

		/// </summary>

		/// <typeparam name="T"> The array type </typeparam>

		/// <param name="arr"> The array to convert </param>

		/// <param name="s"> The size of the 2D array along one 

		/// of the dimensions </param>

		/// <param name="sizes"> The sizes of the 3D array </param>

		/// <returns> The 3D array created </returns>

		public static T[, ,] from2DArrayTo3D<T>(T[,] arr, int s, int[] sizes) {

			int n0 = sizes[0], n1 = sizes[1], n2 = sizes[2];

			T[,,] arr2 = new T[n0, n1, n2];

			int i = 0, j = 0;

			for(int p0 = 0; p0 < n0; p0++)

				for(int p1 = 0; p1 < n1; p1++)

					for(int p2 = 0; p2 < n2; p2++) {

						arr2[p0, p1, p2] = arr[i, j++];

						if(j == s) {

							i++;

							j = 0;

						}  // end of if()

					}  // end of for()

			return arr2;

		}  // end of from2DArrayTo3D<T>()



		/// <summary>

		/// Converts a 2D array representation into a 4D array

		/// </summary>

		/// <typeparam name="T"> The array type </typeparam>

		/// <param name="arr"> The array to convert </param>

		/// <param name="s"> The size of the 2D array along one 

		/// of the dimensions </param>

		/// <param name="sizes"> The sizes of the 4D array </param>

		/// <returns> The 4D array created </returns>

		public static T[,, ,] from2DArrayTo4D<T>(T[,] arr, int s, int[] sizes) {

			int n0 = sizes[0], n1 = sizes[1], n2 = sizes[2], n3 = sizes[3];

			T[, , ,] arr2 = new T[n0, n1, n2, n3];

			int i = 0, j = 0;

			for(int p0 = 0; p0 < n0; p0++)

				for(int p1 = 0; p1 < n1; p1++)

					for(int p2 = 0; p2 < n2; p2++)

						for(int p3 = 0; p3 < n3; p3++) {

						arr2[p0, p1, p2, p3] = arr[i, j++];

						if(j == s) {

							i++;

							j = 0;

						}  // end of if()

					}  // end of for()

			return arr2;

		}  // end of from2DArrayTo4D<T>()



		/// <summary>

		/// Reads the data from the 2D array into an ND array

		/// </summary>

		/// <typeparam name="T"> The element type </typeparam>

		/// <param name="arr"> The 2D array </param>

		/// <param name="s"> The size of the 2D array </param>

		/// <param name="sizes"> The sizes of the ND array </param>

		/// <returns> The resulting ND array </returns>

		public static Array from2DArrayToND<T>(T[,] arr, int s, int[] sizes) {

			int n = sizes[0];

			Array arr2 = Array.CreateInstance(typeof(T), sizes);

			int i = 0, j = 0;

			foreach(int[] p in pointIter(sizes)) {

				arr2.SetValue(arr[i, j++], p);

				if(j == s) {

					i++;

					j = 0;

				}  // end of if()

			}  // end of for()

			return arr2;

		}  // end of from2DArrayToND()



		/// <summary>

		/// Checks whether the arrays have equal length and whether the predicate

		/// is valid for both of them

		/// </summary>

		/// <typeparam name="T1"> The type of the first array </typeparam>

		/// <typeparam name="T2"> The type of the second array </typeparam>

		/// <param name="arr1"> The first array </param>

		/// <param name="arr2"> The second array </param>

		/// <param name="prd"> The predicate to check </param>

		/// <returns> True iff either both <paramref name="arr1"/>

		/// and <paramref name="arr2"/> are null or both of them have equal length

		/// and for each pair of their respective elements the predicate 

		/// <paramref name="prd"/> holds, i.e., returns true </returns>

		public static bool allTrue<T1, T2>(T1[] arr1, T2[] arr2, DoublePred<T1, T2> prd) {

			// check for null

			if(arr1 == null || arr2 == null) {

				return arr1 == null && arr2 == null;

			}

			if(prd == null)

				throw new ArgumentNullException();

			if(arr1.Length != arr2.Length)

				return false;

			int n = arr1.Length;

			for(int i = 0; i < n; i++)

				if(!prd(arr1[i], arr2[i]))

					return false;

			return true;

		}



		/// <summary>

		/// Concatenates the first array with the second array

		/// </summary>

		/// <typeparam name="T"> The type of the arrays being concatenated </typeparam>

		/// <param name="arr1"> The first array to be concatenated </param>

		/// <param name="arr2"> The second array to be concatenated </param>

		/// <returns> The result of concatenation </returns>

		public static T[] con<T>(T[] arr1, T[] arr2) {

			if(arr1 == null)

				return arr2;

			if(arr2 == null)

				return arr1;

			int l1 = arr1.Length, l2 = arr2.Length;

			int l = l1 + l2;

			T[] res = new T[l];

			int i = 0;

			for(; i < l1; i++)

				res[i] = arr1[i];

			for(; i < l; i++)

				res[i] = arr2[i - l1];

			return res;

		}



		/// <summary>

		/// Concatenates any number of arrays of the same type specified

		/// </summary>

		/// <typeparam name="T"> The element type of the arrays to concatenate </typeparam>

		/// <param name="arrs"> The arrays to concatenate </param>

		/// <returns> The result of concatenation </returns>

		public static T[] con<T>(params T[][] arrs) {

			if(arrs == null)

				return null;

			if(arrs.Length == 0)

				return new T[] { };

			//if(Array.TrueForAll<T[]>(arrs, delegate(T[] a) { return a == null; }))

			//	return null;

			if(null == arrs[0] && allEqualRef<T[]>(arrs, null))

				return null;

			int n = 0;

			for(int i = 0; i < arrs.Length; i++)

				n += arrs[i].Length;

			T[] res = new T[n];

			int k = 0;

			for(int i = 0; i < arrs.Length; i++)

				for(int j = 0; j < arrs[i].Length; j++)

					res[k++] = arrs[i][j];

			return res;

		}  // end of con<T>()



		/// <summary>

		/// Adds an element to the end of the array

		/// </summary>

		/// <typeparam name="T"> The type of the array element </typeparam>

		/// <param name="arr"> The array to concatenate </param>

		/// <param name="el"> The element to concatenate </param>

		/// <returns> The resulting array </returns>

		public static T[] con<T>(T[] arr, T el) {

			return con<T>(arr, new T[] { el });

		}  // end of con<T>



		/// <summary>

		/// Adds an element to the beginning of the array

		/// </summary>

		/// <typeparam name="T"> The type of the array element </typeparam>

		/// <param name="el"> The element to concatenate </param>

		/// <param name="arr"> The array to concatenate </param>

		/// <returns> The resulting array </returns>

		public static T[] con<T>(T el, T[] arr) {

			return con<T>(new T[] { el }, arr);

		}  // end of con<T>



		/// <summary>

		/// Indexes the array with an array of indices and returns the result of the 

		/// indexing

		/// </summary>

		/// <typeparam name="T"> The type of the array to index </typeparam>

		/// <param name="arr"> The array to index </param>

		/// <param name="inds"> The indices of the elements to retrieve </param>

		/// <returns> The list of indices for indexing </returns>

		public static T[] index<T>(T[] arr, params int[] inds) {

			List<T> l = new List<T>();

			if(inds == null)

				return l.ToArray();

			if(arr == null) {

				if(inds == null || inds.Length == 0)

					return l.ToArray();

				throw new ArgumentNullException();

			}

			foreach(int i in inds)

				l.Add(arr[i]);

			return l.ToArray();

		}  // end of index()



		/// <summary>

		/// Creates a new array which contains original values except

		/// those specified in <paramref name="inds"/>; they are removed

		/// </summary>

		/// <typeparam name="T"> The type of the array element </typeparam>

		/// <param name="arr"> The source array </param>

		/// <param name="inds"> The indices to be except </param>

		/// <returns> The resulting array </returns>

		public static T[] indexExcept<T>(T[] arr, params int[] inds) {

			int rn = arr.Length - inds.Length;

			T[] ra = new T[rn];

			// current index to inds array

			int k = 0;

			// current index to resulting array

			int j = 0;

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

				if(k >= inds.Length || inds[k] != i)

					ra[j++] = arr[i];

				else

					k++;

			}  // end of for()

			return ra;

		}  // end of indexExcept<T>()



		/// <summary>

		/// Gets the indices of the array given the single cumulative index.

		/// </summary>

		/// <param name="index"> The cumulative index of the array </param>

		/// <param name="cumSizes"> The cumulative sizes of the array. The 

		/// last of it equals to 1, the next-to-last to cumSizes[cumSizes.Length - 1] * 

		/// sizes[cumSizes.length - 1], etc. </param>

		/// <returns> The resulting set of indices </returns>

		public static int[] indices(int index, int[] cumSizes) {

			int n = cumSizes.Length;

			int[] inds = new int[n];

			int j = index;

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

				inds[i] = j / cumSizes[i];

				j %= cumSizes[i];

			}

			return inds;

		}  // end of indices()



		/// <summary>

		/// Creates the array of cumulative sizes from the array of sizes

		/// </summary>

		/// <param name="sizes"> The array of sizes </param>

		/// <returns> The array of cumulative sizes </returns>

		/// <remarks> When it is created, it is assumed that the first index in 

		/// the array changes the slowest </remarks>

		public static int[] cumSizes(int[] sizes) {

			int n = sizes.Length;

			int[] cs = new int[n];

			cs[n - 1] = 1;

			for(int i = n - 2; i >= 0; i--)

				cs[i] = cs[i + 1] * sizes[i + 1];

			return cs;

		}



		/// <summary>

		/// Creates a tail from an array starting from the specified element

		/// </summary>

		/// <typeparam name="T"> The type of the array element </typeparam>

		/// <param name="arr"> The array from which to create a tail </param>

		/// <param name="start"> The start element of the tail </param>

		/// <returns> The tail created </returns>

		public static T[] tail<T>(T[] arr, int start) {

			if(start <= 0)

				return arr;

			if(start >= arr.Length)

				throw new IndexOutOfRangeException();

			int nl = arr.Length - start;

			T[] res = new T[nl];

			for(int i = 0; i < nl; i++)

				res[i] = arr[start + i];

			return res;

		}



		/// <summary>

		/// Gets the array of sizes of the array.

		/// </summary>

		/// <param name="arr"> The array for which to get the sizes. </param>

		/// <returns> The array of sizes of the array, staring from the one 

		/// along which changes the slowest (i.e., the first). Returns null for 

		/// null arrays. </returns>

		public static int[] sizes(Array arr) {

			if(null == arr)

				return null;

			int n = arr.Rank;

			int[] sz = new int[n];

			for(int i = 0; i < n; i++)

				sz[i] = arr.GetLength(i);

			return sz;

		}



		/// <summary>

		/// Creates a 1D array of the specified type and of specified size with all

		/// elements equal to a specified value

		/// </summary>

		/// <typeparam name="T"> The type of the array to create </typeparam>

		/// <param name="val"> The value of the array element </param>

		/// <param name="size"> The length of the array to create </param>

		/// <returns> The array created </returns>

		public static T[] idarr<T>(T val, int size) {

			if(size < 0)

				throw new ArgumentOutOfRangeException();

			T[] arr = new T[size];

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

				arr[i] = val;

			return arr;

		}



		/// <summary>

		/// Transforms two arrays of values into a single array of values

		/// </summary>

		/// <typeparam name="T1"> The type of the first array of values </typeparam>

		/// <typeparam name="T2"> The type of the second array of values </typeparam>

		/// <typeparam name="T3"> The type of the resulting array of values </typeparam>

		/// <param name="arr1"> The first array of values </param>

		/// <param name="arr2"> The second array of values </param>

		/// <param name="trs"> The transform to apply </param>

		/// <returns> The resulting array of values </returns>

		public static T3[] map2<T1, T2, T3>(T1[] arr1, T2[] arr2, Transform<T1, T2, T3>

			trs) {

			// check for nulls

			if(arr1 == null || arr2 == null) {

				if(arr1 == null && arr2 == null)

					return null;

				else

					throw new ArgumentNullException();

			}

			if(trs == null)

				throw new ArgumentNullException();

			if(arr1.Length != arr2.Length)

				throw new ArgumentException();

			int n = arr1.Length;

			T3[] res = new T3[n];

			for(int i = 0; i < n; i++)

				res[i] = trs(arr1[i], arr2[i]);

			return res;

		}



		/// <summary>

		/// Performs the reduction of the specified array by the specified function

		/// </summary>

		/// <typeparam name="T"> The type of the array to reduce </typeparam>

		/// <param name="arr"> The array being reduced </param>

		/// <param name="red"> The reducing function </param>

		/// <returns> The result of the reduciton </returns>

		public static T reduce<T>(T[] arr, Transform<T, T, T> red) {

			if(null == arr || null == red)

				throw new ArgumentNullException();

			if(arr.Length == 0)

				return default(T);

			if(arr.Length == 1)

				return arr[0];

			T res = arr[0];

			for(int i = 1; i < arr.Length; i++)

				res = red(res, arr[i]);

			return res;

		}



		/// <summary>

		/// Gets the head of the specified array 

		/// </summary>

		/// <param name="arr"> The array from which to get the head </param>

		/// <param name="end"> The index of the last element to be included in

		/// the head array </param>

		/// <returns> The head of the array </returns>

		public static T[] head<T>(T[] arr, int end) {

			if(null == arr)

				return null;

			if(end < 0)

				throw new IndexOutOfRangeException();

			if(end >= arr.Length)

				return arr;

			T[] res = new T[end + 1];

			for(int i = 0; i <= end; i++)

				res[i] = arr[i];

			return res;

		}



		/// <summary>

		/// Accepts the list of arrays and returns 

		/// their union

		/// </summary>

		/// <typeparam name="T"> The type of the arrays to unite </typeparam>

		/// <param name="arr"> The arrays to unite </param>

		/// <returns> The union of the arrays </returns>

		/// <remarks> The result does not have any repeating elements; that is, 

		/// even if a single array is passed, it has its repeating elements 

		/// removed </remarks>

		public static T[] union<T>(params T[][] arr) {

			if(null == arr || arr.Length == 0)

				return new T[] { };

			//List<T> l = new List<T>();

			//Set<T> s = new Set<T>();

			//foreach(T[] a in arr) {

			//  if(null == a)

			//    continue;

			//  foreach(T el in a)

			//    if(!s.Contains(el)) {

			//      s.Add(el);

			//      l.Add(el);

			//    }

			//}

			//return l.ToArray();

			List<T> l = new List<T>(arr.Length * arr[0].Length);

			for(int i = 0; i < arr[0].Length; i++)

				l.Add(arr[0][i]);

			for(int i = 1; i < arr.Length; i++) 

				for(int j = 0; j < arr[i].Length; j++) {

					T v = arr[i][j];

					if(l.IndexOf(v) == -1)

						l.Add(v);

				}  // end of for()

			return l.ToArray();

		}  // end of union()



		/// <summary>

		/// Accepts two arrays and returns their difference

		/// </summary>

		/// <typeparam name="T"> The type of the array </typeparam>

		/// <param name="arr1"> The first array </param>

		/// <param name="arr2"> The second array </param>

		/// <returns> The difference of the first and second arrays </returns>

		public static T[] diff<T>(T[] arr1, T[] arr2) {

			//if(null == arr1 || null == arr2)

			//	throw new ArgumentNullException();

			//List<T> l = new List<T>();

			//Set<T> s = new Set<T>(arr1).Difference(new Set<T>(arr2));

			//Set<T> s1 = new Set<T>(); // for there be no identical elements

			//foreach(T el in arr1)

			//  if(s.Contains(el) && !s1.Contains(el)) {

			//    s1.Add(el);

			//    l.Add(el);

			//  }

			//return l.ToArray();

			int n = arr1.Length;

			List<T> l = new List<T>(n);

			for(int i = 0; i < arr1.Length; i++) {

				T val = arr1[i];

				if(Array.IndexOf<T>(arr2, val) == -1)

					l.Add(val);

			}  // end of for()

			return l.ToArray();

		}  // end of diff();



		/// <summary>

		/// Gets the array containing integer span of data between a and b

		/// </summary>

		/// <param name="a"> The start of the span </param>

		/// <param name="b"> The end of the span </param>

		/// <returns> The span created or null if none </returns>

		public static int[] span(int a, int b) {

			if(b < a) return null;

			int n = b - a + 1;

			int[] arr = new int[n];

			for(int i = a; i <= b; i++) arr[i - a] = i;

			return arr;

		}  // end of span()



		/// <summary>

		/// Iterates over a rectangular set of integer points, starting from

		/// (0, ..., 0) and ending with (sizes[0]-1, ..., sizes[n-1]-1), with

		/// first index chaning the slowest. In case null or zero-length array

		/// is passed, returns a single zero-length array

		/// </summary>

		/// <param name="sizes"> The limits of the domain over which to 

		/// iterate </param>

		/// <returns> The iterator over the point domain </returns>

		public static IEnumerable<int[]> pointIter(int[] sizes) {

			if(null == sizes || sizes.Length == 0) {

				yield return new int[0];

				yield break;

			} else {

				int n = sizes.Length;

				int[] vals = idarr<int>(-1, n);

				int ptr = 0;

				while(ptr != -1) {

					if(ptr == n) {

						yield return (int[])vals.Clone();

						ptr--;

					} else {

						vals[ptr]++;

						if(vals[ptr] == sizes[ptr]) {

							vals[ptr] = -1;

							ptr--;

						} else {

							ptr++;

						}  // end of if()-else

					}  // end of if()-else

				}  // end of while()

			}  // end of if()-else

		}  // end of pointIter()



		/// <summary>

		/// Creates an array of <paramref name="size"/> elements, all of

		/// which are equal to <paramref name="val"/>, except for element

		/// with index <paramref name="pos"/>, which is equal to 

		/// <paramref name="diffVal"/>

		/// </summary>

		/// <typeparam name="T"> The type of the element & array </typeparam>

		/// <param name="size"> The size of the resulting array </param>

		/// <param name="pos"> The position in the array which shall differ </param>

		/// <param name="val"> The value of the array element </param>

		/// <param name="diffVal"> The different value of the single element </param>

		/// <returns> The array created </returns>

		public static T[] singleDiff<T>(int size, int pos, T val, T diffVal) {

			T[] a = idarr<T>(val, size);

			a[pos] = diffVal;

			return a;

		}  // end of singleDiff<T>()



		/// <summary>

		/// Evaluates the dot product of two integer arrays

		/// </summary>

		/// <param name="a1"> The first array </param>

		/// <param name="a2"> The second array </param>

		/// <returns> The dot product of two arrays </returns>

		public static int dot(int[] a1, int[] a2) {

			int n = a1.Length;

			if(a2.Length != n)

				throw new ArgumentException();

			int r = 0;

			for(int i = 0; i < n; i++)

				r += a1[i] * a2[i];

			return r;

		}  // end of dot()



		/// <summary>

		/// Assigns values of <paramref name="src"/> to <paramref name="tgt"/>,

		/// so that each element of <paramref name="src"/> is assigned to the 

		/// <paramref name="inds"/> position with respective index of 

		/// <paramref name="tgt"/>. If there are several candidates to the

		/// same position, any of them can be assigned. 

		/// </summary>

		/// <typeparam name="T"> The type of the array </typeparam>

		/// <param name="tgt"> The target array </param>

		/// <param name="src"> The source array </param>

		/// <param name="inds"> The indices at which to assign </param>

		public static void arrass<T>(T[] tgt, T[] src, int[] inds) {

			int n = src.Length;

			if(inds.Length != n)

				throw new ArgumentException("Source and indices lengths do not match");

			for(int i = 0; i < n; i++) tgt[inds[i]] = src[i];

		}  // end of arrass<T>



		/// <summary>

		/// Removes duplicates in the array

		/// </summary>

		/// <param name="arr"> The array from which to remove duplicates </param>

		/// <returns> The array with all duplicates removed </returns>

		public static T[] removeDups<T>(T[] arr) {

			List<T> l = new List<T>();

			Set<T> s = new Set<T>();

			foreach(T t in arr)

				if(!s.Contains(t)) {

					s.Add(t);

					l.Add(t);

				}  // end of if()

			return l.ToArray();

		}  // end of removeDups()



		/// <summary>

		/// Gets the indices of objects of <paramref name="arr2"/> with which

		/// they are present in <paramref name="arr1"/>

		/// </summary>

		/// <typeparam name="T"> The array type </typeparam>

		/// <param name="arr1"> The first array </param>

		/// <param name="arr2"> The second array </param>

		/// <returns> The array of indices </returns>

		public static int[] indicesOf<T>(T[] arr1, T[] arr2) {

			int n = arr2.Length;

			int[] inds = new int[n];

			for(int i = 0; i < n; i++)

				inds[i] = Array.IndexOf<T>(arr1, arr2[i]);

			return inds;

		}  // end of indicesOf<T>



		/// <summary>

		/// Reverses the given array

		/// </summary>

		/// <typeparam name="T"> The type of the array to reverse </typeparam>

		/// <param name="arr"> The array to reverse </param>

		/// <returns> The reversed array </returns>

		/// <remarks> Reversing a null array returns null. </remarks>

		public static T[] reverse<T>(T[] arr) {

			if(null == arr)

				return null;

			int n = arr.Length;

			T[] arr2 = new T[n];

			for(int i = 0; i < n; i++)

				arr2[i] = arr[n - i - 1];

			return arr2;

		}  // end of reverse<T>()



	}  // end of class ArrOps

}