ForEach for dictionaries

* Eager evaluation of iterating functions,
  they are already in System.Linq
* Remove index parameters in functions
* Create array or list of anonymous objects
* Dictionary creation
* ToArray and ToList

src/main/AdrianKousz.Util/Enumerables.cs

@@ -10,30 +10,53 @@ namespace AdrianKousz.Util
 	{
 		#region Fillers
 
-		public static T[] Fill<T>(this T[] array) where T : new() { return Fill(array, i => new T()); }
-		public static T[] Fill<T>(this T[] array, T value) { return Fill(array, i => value); }
-		public static T[] Fill<T>(this T[] array, Func<T> f) { return Fill(array, i => f()); }
-		public static T[] Fill<T>(this T[] array, Func<int, T> f)
+		public static T[] Fill<T>(this T[] array) where T : new() { return Fill(array, () => new T()); }
+		public static T[] Fill<T>(this T[] array, T value) { return Fill(array, () => value); }
+		public static T[] Fill<T>(this T[] array, Func<T> f)
 		{
-			var min = array.GetLowerBound(0);
-			var max = array.GetUpperBound(0);
-			for (var i = min; i <= max; i++)
-				array[i] = f(i);
+			var len = array.Length;
+			for (var i = 0; i < len; i++) array[i] = f();
 			return array;
 		}
 
-		public static IList<T> Fill<T>(this IList<T> list, int count) where T : new() { return Fill(list, i => new T(), count); }
-		public static IList<T> Fill<T>(this IList<T> list, T value, int count) { return Fill(list, i => value, count); }
-		public static IList<T> Fill<T>(this IList<T> list, Func<T> f, int count) { return Fill(list, i => f(), count); }
-		public static IList<T> Fill<T>(this IList<T> list, Func<int, T> f, int count)
+		public static ICollection<T> Fill<T>(this ICollection<T> list, int count) where T : new() { return Fill(list, count, () => new T()); }
+		public static ICollection<T> Fill<T>(this ICollection<T> list, int count, T value) { return Fill(list, count, () => value); }
+		public static ICollection<T> Fill<T>(this ICollection<T> list, int count, Func<T> f)
 		{
-			for (var i = 0; i < count; i++)
-				list.Add(f(i));
+			for (var i = 0; i < count; i++) list.Add(f());
 			return list;
 		}
 
 		#endregion
 
+		#region Anonymous Type Helpers
+
+		public static T[] CreateArray<T>(this T example, int count)
+		{
+			return new T[count];
+		}
+
+		public static List<T> CreateList<T>(this T example)
+		{
+			return new List<T>();
+		}
+
+		#endregion
+
+		#region Materializers
+
+		public static List<T> ToList<T>(this IEnumerable<T> source)
+		{
+			return source as List<T> ?? new List<T>(source);
+		}
+
+		public static T[] ToArray<T>(this IEnumerable<T> source)
+		{
+			return source as T[] ?? ToList(source).ToArray();
+		}
+
+		#endregion
+
 		#region Functional Classics
 
 		public static int IndexOf<T>(this IEnumerable<T> source, T value, Func<T, T, bool> comparer)
@@ -46,58 +69,105 @@ namespace AdrianKousz.Util
 			return -1;
 		}
 
-		public static IEnumerable<T> ForEach<T>(this IEnumerable<T> source, Action<T> f) { return ForEach(source, (i, x) => f(x)); }
-		public static IEnumerable<T> ForEach<T>(this IEnumerable<T> source, Action<int, T> f)
+		public static IEnumerable<T> ForEach<T>(this IEnumerable<T> source, Action<T> f)
 		{
-			var i = 0;
-			foreach (var el in source) f(i++, el);
+			foreach (var el in source) f(el);
+			return source;
+		}
+
+		public static IDictionary<K, V> ForEach<K, V>(this IDictionary<K, V> source, Action<K, V> f)
+		{
+			foreach (var el in source) f(el.Key, el.Value);
 			return source;
 		}
 
 		// Linq: Select
 		public static IEnumerable<TResult> Map<T, TResult>(this IEnumerable<T> source, Func<T, TResult> f)
 		{
-			foreach (var el in source) yield return f(el);
+			var result = GetList<T, TResult>(source);
+			foreach (var el in source) result.Add(f(el));
+			return result;
 		}
 
 		// Linq: Where
 		public static IEnumerable<T> Filter<T>(this IEnumerable<T> source, Func<T, bool> f)
 		{
-			foreach (var el in source) if (f(el)) yield return el;
+			var result = GetList<T, T>(source);
+			foreach (var el in source) if (f(el)) result.Add(el);
+			return result;
 		}
 
 		public static TResult FoldL<T, TResult>(this IEnumerable<T> source, TResult initial, Action<TResult, T> f)
 		{ return FoldL(source, initial, (folded, el) => { f(folded, el); return folded; }); }
 		public static TResult FoldL<T, TResult>(this IEnumerable<T> source, TResult initial, Func<TResult, T, TResult> f)
 		{
-			var folded = initial;
-			foreach (var el in source) folded = f(folded, el);
-			return folded;
+			var result = initial;
+			foreach (var el in source) result = f(result, el);
+			return result;
 		}
 
 		// Linq: Aggregate
 		public static T FoldL1<T>(this IEnumerable<T> source, Func<T, T, T> f)
 		{
-			using (var en = source.GetEnumerator()) {
+			using (var en = source.GetEnumerator())
+			{
 				if (!en.MoveNext()) throw new InvalidOperationException("No elements");
-				T folded = en.Current;
-				while (en.MoveNext()) folded = f(folded, en.Current);
-				return folded;
+				T result = en.Current;
+				while (en.MoveNext()) result = f(result, en.Current);
+				return result;
 			}
 		}
 
+		#endregion
+
+		#region Zippers
+
+		public static IDictionary<K, V> ToDictionary<K, V>(this IEnumerable<K> ks, IEnumerable<V> vs)
+		{
+			var result = new Dictionary<K, V>();
+			using (var en1 = ks.GetEnumerator())
+			using (var en2 = vs.GetEnumerator())
+			{
+				while (en1.MoveNext() && en2.MoveNext())
+					result[en1.Current] = en2.Current;
+			}
+			return result;
+		}
+
+		public static IDictionary<T, T> ToDictionary<T>(this IEnumerable<T> source)
+		{
+			var result = new Dictionary<T, T>();
+			var iskey = true;
+			var k = default(T);
+			foreach (var el in source)
+				if (iskey = !iskey) result[k] = el;
+				else k = el;
+			return result;
+		}
+
 		public static IEnumerable<TResult> Zip<T1, T2, TResult>(this IEnumerable<T1> s1, IEnumerable<T2> s2, Func<T1, T2, TResult> f)
 		{
-			using (var en1 = s1.GetEnumerator()) {
-				using (var en2 = s2.GetEnumerator()) {
-					while (en1.MoveNext() && en2.MoveNext()) {
-						yield return f(en1.Current, en2.Current);
-					}
+			var result = GetList<T1, TResult>(s1);
+			using (var en1 = s1.GetEnumerator())
+			using (var en2 = s2.GetEnumerator())
+			{
+				while (en1.MoveNext() && en2.MoveNext())
+					result.Add(f(en1.Current, en2.Current));
 			}
+			return result;
 		}
+
+		#endregion
+
+		#region Implementation Detail
+
+		private static List<TResult> GetList<T, TResult>(IEnumerable<T> source)
+		{
+			var collection = source as ICollection<T>;
+			var length = collection == null ? 4 : collection.Count;
+			return new List<TResult>(length);
 		}
 
 		#endregion
 	}
 }
-