+//
+// Enumerable.cs
+//
+// Authors:
+// Marek Safar (marek.safar@gmail.com)
+// Antonello Provenzano <antonello@deveel.com>
+// Alejandro Serrano "Serras" (trupill@yahoo.es)
+// Jb Evain (jbevain@novell.com)
+//
+// Copyright (C) 2007 Novell, Inc (http://www.novell.com)
+//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
-//
+//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
-//
+//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
-// Authors:
-// Marek Safar (marek.safar@gmail.com)
-//
+
+// precious: http://www.hookedonlinq.com
using System;
+using System.Collections;
using System.Collections.Generic;
+using System.Collections.ObjectModel;
namespace System.Linq
{
- public static class Enumerable
- {
- #region Empty
-
- public static IEnumerable<TResult> Empty<TResult> ()
- {
- return new List<TResult> ();
- }
-
- #endregion
- }
-}
\ No newline at end of file
+ public static class Enumerable
+ {
+ enum Fallback {
+ Default,
+ Throw
+ }
+
+ class PredicateOf<T> {
+ public static readonly Func<T, bool> Always = (t) => true;
+ }
+
+ class Function<T> {
+ public static readonly Func<T, T> Identity = (t) => t;
+ }
+
+ #region Aggregate
+
+ public static TSource Aggregate<TSource> (this IEnumerable<TSource> source, Func<TSource, TSource, TSource> func)
+ {
+ Check.SourceAndFunc (source, func);
+
+ // custom foreach so that we can efficiently throw an exception
+ // if zero elements and treat the first element differently
+ using (var enumerator = source.GetEnumerator ()) {
+ if (!enumerator.MoveNext ())
+ throw new InvalidOperationException ("No elements in source list");
+
+ TSource folded = enumerator.Current;
+ while (enumerator.MoveNext ())
+ folded = func (folded, enumerator.Current);
+ return folded;
+ }
+ }
+
+ public static TAccumulate Aggregate<TSource, TAccumulate> (this IEnumerable<TSource> source,
+ TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> func)
+ {
+ Check.SourceAndFunc (source, func);
+
+ TAccumulate folded = seed;
+ foreach (TSource element in source)
+ folded = func (folded, element);
+
+ return folded;
+ }
+
+ public static TResult Aggregate<TSource, TAccumulate, TResult> (this IEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> func, Func<TAccumulate, TResult> resultSelector)
+ {
+ Check.SourceAndFunc (source, func);
+ if (resultSelector == null)
+ throw new ArgumentNullException ("resultSelector");
+
+ var result = seed;
+ foreach (var e in source)
+ result = func (result, e);
+
+ return resultSelector (result);
+ }
+
+ #endregion
+
+ #region All
+
+ public static bool All<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ foreach (var element in source)
+ if (!predicate (element))
+ return false;
+
+ return true;
+ }
+
+ #endregion
+
+ #region Any
+
+ public static bool Any<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ var collection = source as ICollection<TSource>;
+ if (collection != null)
+ return collection.Count > 0;
+
+ using (var enumerator = source.GetEnumerator ())
+ return enumerator.MoveNext ();
+ }
+
+ public static bool Any<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ foreach (TSource element in source)
+ if (predicate (element))
+ return true;
+
+ return false;
+ }
+
+ #endregion
+
+ #region AsEnumerable
+
+ public static IEnumerable<TSource> AsEnumerable<TSource> (this IEnumerable<TSource> source)
+ {
+ return source;
+ }
+
+ #endregion
+
+ #region Average
+
+ public static double Average (this IEnumerable<int> source)
+ {
+ return Average<int, long, double> (source, (a, b) => a + b, (a, b) => (double) a / (double) b);
+ }
+
+ public static double Average (this IEnumerable<long> source)
+ {
+ return Average<long, long, double> (source, (a, b) => a + b, (a, b) => (double) a / (double) b);
+ }
+
+ public static double Average (this IEnumerable<double> source)
+ {
+ return Average<double, double, double> (source, (a, b) => a + b, (a, b) => a / b);
+ }
+
+ public static float Average (this IEnumerable<float> source)
+ {
+ return Average<float, double, float> (source, (a, b) => a + b, (a, b) => (float) a / (float) b);
+ }
+
+ public static decimal Average (this IEnumerable<decimal> source)
+ {
+ return Average<decimal, decimal, decimal> (source, (a, b) => a + b, (a, b) => a / b);
+ }
+
+ static TResult Average<TElement, TAggregate, TResult> (this IEnumerable<TElement> source,
+ Func<TAggregate, TElement, TAggregate> func, Func<TAggregate, long, TResult> result)
+ where TElement : struct
+ where TAggregate : struct
+ where TResult : struct
+ {
+ Check.Source (source);
+
+ var total = default (TAggregate);
+ long counter = 0;
+ foreach (var element in source) {
+ total = func (total, element);
+ ++counter;
+ }
+
+ if (counter == 0)
+ throw new InvalidOperationException ();
+
+ return result (total, counter);
+ }
+
+ static TResult? AverageNullable<TElement, TAggregate, TResult> (this IEnumerable<TElement?> source,
+ Func<TAggregate, TElement, TAggregate> func, Func<TAggregate, long, TResult> result)
+ where TElement : struct
+ where TAggregate : struct
+ where TResult : struct
+ {
+ Check.Source (source);
+
+ var total = default (TAggregate);
+ long counter = 0;
+ foreach (var element in source) {
+ if (!element.HasValue)
+ continue;
+
+ total = func (total, element.Value);
+ counter++;
+ }
+
+ if (counter == 0)
+ return null;
+
+ return new TResult? (result (total, counter));
+ }
+
+ public static double? Average (this IEnumerable<int?> source)
+ {
+ Check.Source (source);
+
+ return source.AverageNullable<int, long, double> ((a, b) => a + b, (a, b) => (double) a / (double) b);
+ }
+
+ public static double? Average (this IEnumerable<long?> source)
+ {
+ Check.Source (source);
+
+ return source.AverageNullable<long, long, double> ((a, b) => a + b, (a, b) => (double) a / b);
+ }
+
+ public static double? Average (this IEnumerable<double?> source)
+ {
+ Check.Source (source);
+
+ return source.AverageNullable<double, double, double> ((a, b) => a + b, (a, b) => a / b);
+ }
+
+ public static decimal? Average (this IEnumerable<decimal?> source)
+ {
+ Check.Source (source);
+
+ return source.AverageNullable<decimal, decimal, decimal> ((a, b) => a + b, (a, b) => a / b);
+ }
+
+ public static float? Average (this IEnumerable<float?> source)
+ {
+ Check.Source (source);
+
+ return source.AverageNullable<float, double, float> ((a, b) => a + b, (a, b) => (float) a / (float) b);
+ }
+
+ public static double Average<TSource> (this IEnumerable<TSource> source, Func<TSource, int> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).Average<int, long, double> ((a, b) => a + b, (a, b) => (double) a / (double) b);
+ }
+
+ public static double? Average<TSource> (this IEnumerable<TSource> source, Func<TSource, int?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).AverageNullable<int, long, double> ((a, b) => a + b, (a, b) => (double) a / (double) b);
+ }
+
+ public static double Average<TSource> (this IEnumerable<TSource> source, Func<TSource, long> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).Average<long, long, double> ((a, b) => a + b, (a, b) => (double) a / (double) b);
+ }
+
+ public static double? Average<TSource> (this IEnumerable<TSource> source, Func<TSource, long?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).AverageNullable<long, long, double> ((a, b) => a + b, (a, b) => (double) a / (double) b);
+ }
+
+ public static double Average<TSource> (this IEnumerable<TSource> source, Func<TSource, double> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).Average<double, double, double> ((a, b) => a + b, (a, b) => a / b);
+ }
+
+ public static double? Average<TSource> (this IEnumerable<TSource> source, Func<TSource, double?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).AverageNullable<double, double, double> ((a, b) => a + b, (a, b) => a / b);
+ }
+
+ public static float Average<TSource> (this IEnumerable<TSource> source, Func<TSource, float> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).Average<float, double, float> ((a, b) => a + b, (a, b) => (float) a / (float) b);
+ }
+
+ public static float? Average<TSource> (this IEnumerable<TSource> source, Func<TSource, float?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).AverageNullable<float, double, float> ((a, b) => a + b, (a, b) => (float) a / (float) b);
+ }
+
+ public static decimal Average<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).Average<decimal, decimal, decimal> ((a, b) => a + b, (a, b) => a / b);
+ }
+
+ public static decimal? Average<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.Select (selector).AverageNullable<decimal, decimal, decimal> ((a, b) => a + b, (a, b) => a / b);
+ }
+
+ #endregion
+
+ #region Cast
+
+ public static IEnumerable<TResult> Cast<TResult> (this IEnumerable source)
+ {
+ Check.Source (source);
+
+ return CreateCastIterator<TResult> (source);
+ }
+
+ static IEnumerable<TResult> CreateCastIterator<TResult> (IEnumerable source)
+ {
+ foreach (TResult element in source)
+ yield return element;
+ }
+
+ #endregion
+
+ #region Concat
+
+ public static IEnumerable<TSource> Concat<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second)
+ {
+ Check.FirstAndSecond (first, second);
+
+ return CreateConcatIterator (first, second);
+ }
+
+ static IEnumerable<TSource> CreateConcatIterator<TSource> (IEnumerable<TSource> first, IEnumerable<TSource> second)
+ {
+ foreach (TSource element in first)
+ yield return element;
+ foreach (TSource element in second)
+ yield return element;
+ }
+
+ #endregion
+
+ #region Contains
+
+ public static bool Contains<TSource> (this IEnumerable<TSource> source, TSource value)
+ {
+ var collection = source as ICollection<TSource>;
+ if (collection != null)
+ return collection.Contains (value);
+
+ return Contains<TSource> (source, value, null);
+ }
+
+ public static bool Contains<TSource> (this IEnumerable<TSource> source, TSource value, IEqualityComparer<TSource> comparer)
+ {
+ Check.Source (source);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TSource>.Default;
+
+ foreach (var element in source)
+ if (comparer.Equals (element, value))
+ return true;
+
+ return false;
+ }
+ #endregion
+
+ #region Count
+
+ public static int Count<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ var collection = source as ICollection<TSource>;
+ if (collection != null)
+ return collection.Count;
+
+ int counter = 0;
+ using (var enumerator = source.GetEnumerator ())
+ while (enumerator.MoveNext ())
+ counter++;
+
+ return counter;
+ }
+
+ public static int Count<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ int counter = 0;
+ foreach (var element in source)
+ if (selector (element))
+ counter++;
+
+ return counter;
+ }
+
+ #endregion
+
+ #region DefaultIfEmpty
+
+ public static IEnumerable<TSource> DefaultIfEmpty<TSource> (this IEnumerable<TSource> source)
+ {
+ return DefaultIfEmpty (source, default (TSource));
+ }
+
+ public static IEnumerable<TSource> DefaultIfEmpty<TSource> (this IEnumerable<TSource> source, TSource defaultValue)
+ {
+ Check.Source (source);
+
+ return CreateDefaultIfEmptyIterator (source, defaultValue);
+ }
+
+ static IEnumerable<TSource> CreateDefaultIfEmptyIterator<TSource> (IEnumerable<TSource> source, TSource defaultValue)
+ {
+ bool empty = true;
+ foreach (TSource item in source) {
+ empty = false;
+ yield return item;
+ }
+
+ if (empty)
+ yield return defaultValue;
+ }
+
+ #endregion
+
+ #region Distinct
+
+ public static IEnumerable<TSource> Distinct<TSource> (this IEnumerable<TSource> source)
+ {
+ return Distinct<TSource> (source, null);
+ }
+
+ public static IEnumerable<TSource> Distinct<TSource> (this IEnumerable<TSource> source, IEqualityComparer<TSource> comparer)
+ {
+ Check.Source (source);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TSource>.Default;
+
+ return CreateDistinctIterator (source, comparer);
+ }
+
+ static IEnumerable<TSource> CreateDistinctIterator<TSource> (IEnumerable<TSource> source, IEqualityComparer<TSource> comparer)
+ {
+ var items = new HashSet<TSource> (comparer);
+ foreach (var element in source) {
+ if (! items.Contains (element)) {
+ items.Add (element);
+ yield return element;
+ }
+ }
+ }
+
+ #endregion
+
+ #region ElementAt
+
+ static TSource ElementAt<TSource> (this IEnumerable<TSource> source, int index, Fallback fallback)
+ {
+ long counter = 0L;
+
+ foreach (var element in source) {
+ if (index == counter++)
+ return element;
+ }
+
+ if (fallback == Fallback.Throw)
+ throw new ArgumentOutOfRangeException ();
+
+ return default (TSource);
+ }
+
+ public static TSource ElementAt<TSource> (this IEnumerable<TSource> source, int index)
+ {
+ Check.Source (source);
+
+ if (index < 0)
+ throw new ArgumentOutOfRangeException ();
+
+ var list = source as IList<TSource>;
+ if (list != null)
+ return list [index];
+
+ return source.ElementAt (index, Fallback.Throw);
+ }
+
+ #endregion
+
+ #region ElementAtOrDefault
+
+ public static TSource ElementAtOrDefault<TSource> (this IEnumerable<TSource> source, int index)
+ {
+ Check.Source (source);
+
+ if (index < 0)
+ return default (TSource);
+
+ var list = source as IList<TSource>;
+ if (list != null)
+ return index < list.Count ? list [index] : default (TSource);
+
+ return source.ElementAt (index, Fallback.Default);
+ }
+
+ #endregion
+
+ #region Empty
+
+ public static IEnumerable<TResult> Empty<TResult> ()
+ {
+ return new TResult [0];
+ }
+
+ #endregion
+
+ #region Except
+
+ public static IEnumerable<TSource> Except<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second)
+ {
+ return Except (first, second, null);
+ }
+
+ public static IEnumerable<TSource> Except<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
+ {
+ Check.FirstAndSecond (first, second);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TSource>.Default;
+
+ return CreateExceptIterator (first, second, comparer);
+ }
+
+ static IEnumerable<TSource> CreateExceptIterator<TSource> (IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
+ {
+ var items = new HashSet<TSource> (second, comparer);
+ foreach (var element in first) {
+ if (!items.Contains (element, comparer))
+ yield return element;
+ }
+ }
+
+ #endregion
+
+ #region First
+
+ static TSource First<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate, Fallback fallback)
+ {
+ foreach (var element in source)
+ if (predicate (element))
+ return element;
+
+ if (fallback == Fallback.Throw)
+ throw new InvalidOperationException ();
+
+ return default (TSource);
+ }
+
+ public static TSource First<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ var list = source as IList<TSource>;
+ if (list != null) {
+ if (list.Count != 0)
+ return list [0];
+
+ throw new InvalidOperationException ();
+ } else {
+ using (var enumerator = source.GetEnumerator ()) {
+ if (enumerator.MoveNext ())
+ return enumerator.Current;
+ }
+ }
+
+ throw new InvalidOperationException ();
+ }
+
+ public static TSource First<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return source.First (predicate, Fallback.Throw);
+ }
+
+ #endregion
+
+ #region FirstOrDefault
+
+ public static TSource FirstOrDefault<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ return source.First (PredicateOf<TSource>.Always, Fallback.Default);
+ }
+
+ public static TSource FirstOrDefault<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return source.First (predicate, Fallback.Default);
+ }
+
+ #endregion
+
+ #region GroupBy
+
+ private static List<T> ContainsGroup<K, T> (
+ Dictionary<K, List<T>> items, K key, IEqualityComparer<K> comparer)
+ {
+ IEqualityComparer<K> comparerInUse = (comparer ?? EqualityComparer<K>.Default);
+ foreach (KeyValuePair<K, List<T>> value in items) {
+ if (comparerInUse.Equals (value.Key, key))
+ return value.Value;
+ }
+ return null;
+ }
+
+ public static IEnumerable<IGrouping<TKey, TSource>> GroupBy<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector)
+ {
+ return GroupBy<TSource, TKey> (source, keySelector, null);
+ }
+
+ public static IEnumerable<IGrouping<TKey, TSource>> GroupBy<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+ {
+ Check.SourceAndKeySelector (source, keySelector);
+
+ return CreateGroupByIterator (source, keySelector, comparer);
+ }
+
+ static IEnumerable<IGrouping<TKey, TSource>> CreateGroupByIterator<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+ {
+ Dictionary<TKey, List<TSource>> groups = new Dictionary<TKey, List<TSource>> ();
+ List<TSource> nullList = new List<TSource> ();
+ int counter = 0;
+ int nullCounter = -1;
+
+ foreach (TSource element in source) {
+ TKey key = keySelector (element);
+ if (key == null) {
+ nullList.Add (element);
+ if (nullCounter == -1) {
+ nullCounter = counter;
+ counter++;
+ }
+ } else {
+ List<TSource> group = ContainsGroup<TKey, TSource> (groups, key, comparer);
+ if (group == null) {
+ group = new List<TSource> ();
+ groups.Add (key, group);
+ counter++;
+ }
+ group.Add (element);
+ }
+ }
+
+ counter = 0;
+ foreach (KeyValuePair<TKey, List<TSource>> group in groups) {
+ if (counter == nullCounter) {
+ Grouping<TKey, TSource> nullGroup = new Grouping<TKey, TSource> (default (TKey), nullList);
+ yield return nullGroup;
+ counter++;
+ }
+ Grouping<TKey, TSource> grouping = new Grouping<TKey, TSource> (group.Key, group.Value);
+ yield return grouping;
+ counter++;
+ }
+ }
+
+ public static IEnumerable<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector)
+ {
+ return GroupBy<TSource, TKey, TElement> (source, keySelector, elementSelector, null);
+ }
+
+ public static IEnumerable<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
+ {
+ Check.SourceAndKeyElementSelectors (source, keySelector, elementSelector);
+
+ Dictionary<TKey, List<TElement>> groups = new Dictionary<TKey, List<TElement>> ();
+ List<TElement> nullList = new List<TElement> ();
+ int counter = 0;
+ int nullCounter = -1;
+
+ foreach (TSource item in source) {
+ TKey key = keySelector (item);
+ TElement element = elementSelector (item);
+ if (key == null) {
+ nullList.Add (element);
+ if (nullCounter == -1) {
+ nullCounter = counter;
+ counter++;
+ }
+ } else {
+ List<TElement> group = ContainsGroup<TKey, TElement> (groups, key, comparer);
+ if (group == null) {
+ group = new List<TElement> ();
+ groups.Add (key, group);
+ counter++;
+ }
+ group.Add (element);
+ }
+ }
+
+ counter = 0;
+ foreach (KeyValuePair<TKey, List<TElement>> group in groups) {
+ if (counter == nullCounter) {
+ Grouping<TKey, TElement> nullGroup = new Grouping<TKey, TElement> (default (TKey), nullList);
+ yield return nullGroup;
+ counter++;
+ }
+ Grouping<TKey, TElement> grouping = new Grouping<TKey, TElement> (group.Key, group.Value);
+ yield return grouping;
+ counter++;
+ }
+ }
+
+ public static IEnumerable<TResult> GroupBy<TSource, TKey, TElement, TResult> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector,
+ Func<TKey, IEnumerable<TElement>, TResult> resultSelector)
+ {
+ return GroupBy (source, keySelector, elementSelector, resultSelector, null);
+ }
+
+ public static IEnumerable<TResult> GroupBy<TSource, TKey, TElement, TResult> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector,
+ Func<TKey, IEnumerable<TElement>, TResult> resultSelector,
+ IEqualityComparer<TKey> comparer)
+ {
+ IEnumerable<IGrouping<TKey, TElement>> groups = GroupBy<TSource, TKey, TElement> (
+ source, keySelector, elementSelector, comparer);
+
+ foreach (IGrouping<TKey, TElement> group in groups)
+ yield return resultSelector (group.Key, group);
+ }
+
+ public static IEnumerable<TResult> GroupBy<TSource, TKey, TResult> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector,
+ Func<TKey, IEnumerable<TSource>, TResult> resultSelector)
+ {
+ return GroupBy (source, keySelector, resultSelector, null);
+ }
+
+ public static IEnumerable<TResult> GroupBy<TSource, TKey, TResult> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector,
+ Func<TKey, IEnumerable<TSource>, TResult> resultSelector,
+ IEqualityComparer<TKey> comparer)
+ {
+ IEnumerable<IGrouping<TKey,TSource>> groups = GroupBy<TSource, TKey> (source, keySelector, comparer);
+
+ foreach (IGrouping<TKey, TSource> group in groups)
+ yield return resultSelector (group.Key, group);
+ }
+
+ #endregion
+
+ # region GroupJoin
+
+ public static IEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult> (this IEnumerable<TOuter> outer,
+ IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector,
+ Func<TInner, TKey> innerKeySelector, Func<TOuter, IEnumerable<TInner>, TResult> resultSelector)
+ {
+ return GroupJoin (outer, inner, outerKeySelector, innerKeySelector, resultSelector, null);
+ }
+
+ public static IEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult> (this IEnumerable<TOuter> outer,
+ IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector,
+ Func<TInner, TKey> innerKeySelector, Func<TOuter, IEnumerable<TInner>, TResult> resultSelector,
+ IEqualityComparer<TKey> comparer)
+ {
+ Check.JoinSelectors (outer, inner, outerKeySelector, innerKeySelector, resultSelector);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TKey>.Default;
+
+ return CreateGroupJoinIterator (outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer);
+ }
+
+ static IEnumerable<TResult> CreateGroupJoinIterator<TOuter, TInner, TKey, TResult> (this IEnumerable<TOuter> outer,
+ IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector,
+ Func<TInner, TKey> innerKeySelector, Func<TOuter, IEnumerable<TInner>, TResult> resultSelector,
+ IEqualityComparer<TKey> comparer)
+ {
+ ILookup<TKey, TInner> innerKeys = ToLookup<TInner, TKey> (inner, innerKeySelector, comparer);
+ /*Dictionary<K, List<U>> innerKeys = new Dictionary<K, List<U>> ();
+ foreach (U element in inner)
+ {
+ K innerKey = innerKeySelector (element);
+ if (!innerKeys.ContainsKey (innerKey))
+ innerKeys.Add (innerKey, new List<U> ());
+ innerKeys[innerKey].Add (element);
+ }*/
+
+ foreach (TOuter element in outer) {
+ TKey outerKey = outerKeySelector (element);
+ if (innerKeys.Contains (outerKey))
+ yield return resultSelector (element, innerKeys [outerKey]);
+ else
+ yield return resultSelector (element, Empty<TInner> ());
+ }
+ }
+
+ #endregion
+
+ #region Intersect
+
+ public static IEnumerable<TSource> Intersect<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second)
+ {
+ return Intersect (first, second, null);
+ }
+
+ public static IEnumerable<TSource> Intersect<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
+ {
+ Check.FirstAndSecond (first, second);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TSource>.Default;
+
+ return CreateIntersectIterator (first, second, comparer);
+ }
+
+ static IEnumerable<TSource> CreateIntersectIterator<TSource> (IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
+ {
+ var items = new HashSet<TSource> (second, comparer);
+ foreach (TSource element in first) {
+ if (items.Remove (element))
+ yield return element;
+ }
+ }
+
+ #endregion
+
+ # region Join
+
+ public static IEnumerable<TResult> Join<TOuter, TInner, TKey, TResult> (this IEnumerable<TOuter> outer,
+ IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector,
+ Func<TInner, TKey> innerKeySelector, Func<TOuter, TInner, TResult> resultSelector, IEqualityComparer<TKey> comparer)
+ {
+ Check.JoinSelectors (outer, inner, outerKeySelector, innerKeySelector, resultSelector);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TKey>.Default;
+
+ return CreateJoinIterator (outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer);
+ }
+
+ static IEnumerable<TResult> CreateJoinIterator<TOuter, TInner, TKey, TResult> (this IEnumerable<TOuter> outer,
+ IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector,
+ Func<TInner, TKey> innerKeySelector, Func<TOuter, TInner, TResult> resultSelector, IEqualityComparer<TKey> comparer)
+ {
+ ILookup<TKey, TInner> innerKeys = ToLookup<TInner, TKey> (inner, innerKeySelector, comparer);
+ /*Dictionary<K, List<U>> innerKeys = new Dictionary<K, List<U>> ();
+ foreach (U element in inner)
+ {
+ K innerKey = innerKeySelector (element);
+ if (!innerKeys.ContainsKey (innerKey))
+ innerKeys.Add (innerKey, new List<U> ());
+ innerKeys[innerKey].Add (element);
+ }*/
+
+ foreach (TOuter element in outer) {
+ TKey outerKey = outerKeySelector (element);
+ if (innerKeys.Contains (outerKey)) {
+ foreach (TInner innerElement in innerKeys [outerKey])
+ yield return resultSelector (element, innerElement);
+ }
+ }
+ }
+
+ public static IEnumerable<TResult> Join<TOuter, TInner, TKey, TResult> (this IEnumerable<TOuter> outer,
+ IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector,
+ Func<TInner, TKey> innerKeySelector, Func<TOuter, TInner, TResult> resultSelector)
+ {
+ return outer.Join (inner, outerKeySelector, innerKeySelector, resultSelector, null);
+ }
+
+ #endregion
+
+ #region Last
+
+ static TSource Last<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate, Fallback fallback)
+ {
+ var empty = true;
+ var item = default (TSource);
+
+ foreach (var element in source) {
+ if (!predicate (element))
+ continue;
+
+ item = element;
+ empty = false;
+ }
+
+ if (!empty)
+ return item;
+
+ if (fallback == Fallback.Throw)
+ throw new InvalidOperationException ();
+
+ return item;
+ }
+
+ public static TSource Last<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ var collection = source as ICollection<TSource>;
+ if (collection != null && collection.Count == 0)
+ throw new InvalidOperationException ();
+
+ var list = source as IList<TSource>;
+ if (list != null)
+ return list [list.Count - 1];
+
+ return source.Last (PredicateOf<TSource>.Always, Fallback.Throw);
+ }
+
+ public static TSource Last<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return source.Last (predicate, Fallback.Throw);
+ }
+
+ #endregion
+
+ #region LastOrDefault
+
+ public static TSource LastOrDefault<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ var list = source as IList<TSource>;
+ if (list != null)
+ return list.Count > 0 ? list [list.Count - 1] : default (TSource);
+
+ return source.Last (PredicateOf<TSource>.Always, Fallback.Default);
+ }
+
+ public static TSource LastOrDefault<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return source.Last (predicate, Fallback.Default);
+ }
+
+ #endregion
+
+ #region LongCount
+
+ public static long LongCount<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+#if !NET_2_1
+ var array = source as TSource [];
+ if (array != null)
+ return array.LongLength;
+#endif
+
+ long counter = 0;
+ using (var enumerator = source.GetEnumerator ())
+ while (enumerator.MoveNext ())
+ counter++;
+
+ return counter;
+ }
+
+ public static long LongCount<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ long counter = 0;
+ foreach (TSource element in source)
+ if (selector (element))
+ counter++;
+
+ return counter;
+ }
+
+ #endregion
+
+ #region Max
+
+ public static int Max (this IEnumerable<int> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, int.MinValue, (a, b) => Math.Max (a, b));
+ }
+
+ public static long Max (this IEnumerable<long> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, long.MinValue, (a, b) => Math.Max (a, b));
+ }
+
+ public static double Max (this IEnumerable<double> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, double.MinValue, (a, b) => Math.Max (a, b));
+ }
+
+ public static float Max (this IEnumerable<float> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, float.MinValue, (a, b) => Math.Max (a, b));
+ }
+
+ public static decimal Max (this IEnumerable<decimal> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, decimal.MinValue, (a, b) => Math.Max (a, b));
+ }
+
+ public static int? Max (this IEnumerable<int?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Max (a, b));
+ }
+
+ public static long? Max (this IEnumerable<long?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Max (a, b));
+ }
+
+ public static double? Max (this IEnumerable<double?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Max (a, b));
+ }
+
+ public static float? Max (this IEnumerable<float?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Max (a, b));
+ }
+
+ public static decimal? Max (this IEnumerable<decimal?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Max (a, b));
+ }
+
+ static T? IterateNullable<T> (IEnumerable<T?> source, Func<T, T, T> selector) where T : struct
+ {
+ bool empty = true;
+ T? value = null;
+ foreach (var element in source) {
+ if (!element.HasValue)
+ continue;
+
+ if (!value.HasValue)
+ value = element.Value;
+ else
+ value = selector (element.Value, value.Value);
+
+ empty = false;
+ }
+
+ if (empty)
+ return null;
+
+ return value;
+ }
+
+ static TRet? IterateNullable<TSource, TRet> (
+ IEnumerable<TSource> source,
+ Func<TSource, TRet?> source_selector,
+ Func<TRet?, TRet?, bool> selector) where TRet : struct
+ {
+ bool empty = true;
+ TRet? value = null;
+ foreach (var element in source) {
+ TRet? item = source_selector (element);
+
+ if (!value.HasValue)
+ value = item;
+ else if (selector (item, value))
+ value = item;
+
+ empty = false;
+ }
+
+ if (empty)
+ return null;
+
+ return value;
+ }
+
+ public static TSource Max<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ bool notAssigned = true;
+ TSource maximum = default (TSource);
+ int counter = 0;
+ foreach (TSource element in source) {
+ if (notAssigned) {
+ maximum = element;
+ notAssigned = false;
+ } else {
+ int comparison;
+ if (element is IComparable<TSource>)
+ comparison = ((IComparable<TSource>) element).CompareTo (maximum);
+ else if (element is System.IComparable)
+ comparison = ((System.IComparable) element).CompareTo (maximum);
+ else
+ throw new ArgumentNullException ();
+
+ if (comparison > 0)
+ maximum = element;
+ }
+ counter++;
+ }
+
+ if (counter == 0)
+ throw new InvalidOperationException ();
+ else
+ return maximum;
+ }
+
+ public static int Max<TSource> (this IEnumerable<TSource> source, Func<TSource, int> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, int.MinValue, (a, b) => Math.Max (selector (a), b));
+ }
+
+ public static long Max<TSource> (this IEnumerable<TSource> source, Func<TSource, long> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, long.MinValue, (a, b) => Math.Max (selector (a), b));
+ }
+
+ public static double Max<TSource> (this IEnumerable<TSource> source, Func<TSource, double> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, double.MinValue, (a, b) => Math.Max (selector (a), b));
+ }
+
+ public static float Max<TSource> (this IEnumerable<TSource> source, Func<TSource, float> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, float.MinValue, (a, b) => Math.Max (selector (a), b));
+ }
+
+ public static decimal Max<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, decimal.MinValue, (a, b) => Math.Max (selector (a), b));
+ }
+
+ static U Iterate<T, U> (IEnumerable<T> source, U initValue, Func<T, U, U> selector)
+ {
+ bool empty = true;
+ foreach (var element in source) {
+ initValue = selector (element, initValue);
+ empty = false;
+ }
+
+ if (empty)
+ throw new InvalidOperationException ();
+
+ return initValue;
+ }
+
+ public static int? Max<TSource> (this IEnumerable<TSource> source, Func<TSource, int?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a > b);
+ }
+
+ public static long? Max<TSource> (this IEnumerable<TSource> source, Func<TSource, long?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a > b);
+ }
+
+ public static double? Max<TSource> (this IEnumerable<TSource> source, Func<TSource, double?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a > b);
+ }
+
+ public static float? Max<TSource> (this IEnumerable<TSource> source, Func<TSource, float?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a > b);
+ }
+
+ public static decimal? Max<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a > b);
+ }
+
+ public static TResult Max<TSource, TResult> (this IEnumerable<TSource> source, Func<TSource, TResult> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ bool notAssigned = true;
+ TResult maximum = default (TResult);
+ int counter = 0;
+ foreach (TSource item in source) {
+ TResult element = selector (item);
+ if (notAssigned) {
+ maximum = element;
+ notAssigned = false;
+ } else {
+ int comparison;
+ if (element is IComparable<TResult>)
+ comparison = ((IComparable<TResult>) element).CompareTo (maximum);
+ else if (element is System.IComparable)
+ comparison = ((System.IComparable) element).CompareTo (maximum);
+ else
+ throw new ArgumentNullException ();
+
+ if (comparison > 0)
+ maximum = element;
+ }
+ counter++;
+ }
+
+ if (counter == 0)
+ throw new InvalidOperationException ();
+ else
+ return maximum;
+ }
+
+ #endregion
+
+ #region Min
+
+ public static int Min (this IEnumerable<int> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, int.MaxValue, (a, b) => Math.Min (a, b));
+ }
+
+ public static long Min (this IEnumerable<long> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, long.MaxValue, (a, b) => Math.Min (a, b));
+ }
+
+ public static double Min (this IEnumerable<double> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, double.MaxValue, (a, b) => Math.Min (a, b));
+ }
+
+ public static float Min (this IEnumerable<float> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, float.MaxValue, (a, b) => Math.Min (a, b));
+ }
+
+ public static decimal Min (this IEnumerable<decimal> source)
+ {
+ Check.Source (source);
+
+ return Iterate (source, decimal.MaxValue, (a, b) => Math.Min (a, b));
+ }
+
+ public static int? Min (this IEnumerable<int?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Min (a, b));
+ }
+
+ public static long? Min (this IEnumerable<long?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Min (a, b));
+ }
+
+ public static double? Min (this IEnumerable<double?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Min (a, b));
+ }
+
+ public static float? Min (this IEnumerable<float?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Min (a, b));
+ }
+
+ public static decimal? Min (this IEnumerable<decimal?> source)
+ {
+ Check.Source (source);
+
+ return IterateNullable (source, (a, b) => Math.Min (a, b));
+ }
+
+ public static TSource Min<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ bool notAssigned = true;
+ TSource minimum = default (TSource);
+ int counter = 0;
+ foreach (TSource element in source) {
+ if (notAssigned) {
+ minimum = element;
+ notAssigned = false;
+ } else {
+ int comparison;
+ if (element is IComparable<TSource>)
+ comparison = ((IComparable<TSource>) element).CompareTo (minimum);
+ else if (element is System.IComparable)
+ comparison = ((System.IComparable) element).CompareTo (minimum);
+ else
+ throw new ArgumentNullException ();
+
+ if (comparison < 0)
+ minimum = element;
+ }
+ counter++;
+ }
+
+ if (counter == 0)
+ throw new InvalidOperationException ();
+ else
+ return minimum;
+ }
+
+ public static int Min<TSource> (this IEnumerable<TSource> source, Func<TSource, int> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, int.MaxValue, (a, b) => Math.Min (selector (a), b));
+ }
+
+ public static long Min<TSource> (this IEnumerable<TSource> source, Func<TSource, long> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, long.MaxValue, (a, b) => Math.Min (selector (a), b));
+ }
+
+ public static double Min<TSource> (this IEnumerable<TSource> source, Func<TSource, double> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, double.MaxValue, (a, b) => Math.Min (selector (a), b));
+ }
+
+ public static float Min<TSource> (this IEnumerable<TSource> source, Func<TSource, float> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, float.MaxValue, (a, b) => Math.Min (selector (a), b));
+ }
+
+ public static decimal Min<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Iterate (source, decimal.MaxValue, (a, b) => Math.Min (selector (a), b));
+ }
+
+ public static int? Min<TSource> (this IEnumerable<TSource> source, Func<TSource, int?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a < b);
+ }
+
+ public static long? Min<TSource> (this IEnumerable<TSource> source, Func<TSource, long?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a < b);
+ }
+
+ public static float? Min<TSource> (this IEnumerable<TSource> source, Func<TSource, float?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a < b);
+ }
+
+ public static double? Min<TSource> (this IEnumerable<TSource> source, Func<TSource, double?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a < b);
+ }
+
+ public static decimal? Min<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return IterateNullable (source, selector, (a, b) => a < b);
+ }
+
+ public static TResult Min<TSource, TResult> (this IEnumerable<TSource> source, Func<TSource, TResult> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ bool notAssigned = true;
+ TResult minimum = default (TResult);
+ int counter = 0;
+ foreach (TSource item in source) {
+ TResult element = selector (item);
+ if (notAssigned) {
+ minimum = element;
+ notAssigned = false;
+ } else {
+ int comparison;
+ if (element is IComparable<TResult>)
+ comparison = ((IComparable<TResult>) element).CompareTo (minimum);
+ else if (element is System.IComparable)
+ comparison = ((System.IComparable) element).CompareTo (minimum);
+ else
+ throw new ArgumentNullException ();
+
+ if (comparison < 0)
+ minimum = element;
+ }
+ counter++;
+ }
+
+ if (counter == 0)
+ throw new InvalidOperationException ();
+ else
+ return minimum;
+ }
+
+ #endregion
+
+ #region OfType
+
+ public static IEnumerable<TResult> OfType<TResult> (this IEnumerable source)
+ {
+ Check.Source (source);
+
+ return CreateOfTypeIterator<TResult> (source);
+ }
+
+ static IEnumerable<TResult> CreateOfTypeIterator<TResult> (IEnumerable source)
+ {
+ foreach (object element in source)
+ if (element is TResult)
+ yield return (TResult) element;
+ }
+
+ #endregion
+
+ #region OrderBy
+
+ public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector)
+ {
+ return OrderBy<TSource, TKey> (source, keySelector, null);
+ }
+
+ public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector,
+ IComparer<TKey> comparer)
+ {
+ Check.SourceAndKeySelector (source, keySelector);
+
+ return new OrderedSequence<TSource, TKey> (source, keySelector, comparer, SortDirection.Ascending);
+ }
+
+ #endregion
+
+ #region OrderByDescending
+
+ public static IOrderedEnumerable<TSource> OrderByDescending<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector)
+ {
+ return OrderByDescending<TSource, TKey> (source, keySelector, null);
+ }
+
+ public static IOrderedEnumerable<TSource> OrderByDescending<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
+ {
+ Check.SourceAndKeySelector (source, keySelector);
+
+ return new OrderedSequence<TSource, TKey> (source, keySelector, comparer, SortDirection.Descending);
+ }
+
+ #endregion
+
+ #region Range
+
+ public static IEnumerable<int> Range (int start, int count)
+ {
+ if (count < 0)
+ throw new ArgumentOutOfRangeException ("count");
+
+ long upto = ((long) start + count) - 1;
+
+ if (upto > int.MaxValue)
+ throw new ArgumentOutOfRangeException ();
+
+ return CreateRangeIterator (start, (int) upto);
+ }
+
+ static IEnumerable<int> CreateRangeIterator (int start, int upto)
+ {
+ for (int i = start; i <= upto; i++)
+ yield return i;
+ }
+
+ #endregion
+
+ #region Repeat
+
+ public static IEnumerable<TResult> Repeat<TResult> (TResult element, int count)
+ {
+ if (count < 0)
+ throw new ArgumentOutOfRangeException ();
+
+ return CreateRepeatIterator (element, count);
+ }
+
+ static IEnumerable<TResult> CreateRepeatIterator<TResult> (TResult element, int count)
+ {
+ for (int i = 0; i < count; i++)
+ yield return element;
+ }
+
+ #endregion
+
+ #region Reverse
+
+ public static IEnumerable<TSource> Reverse<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ var list = source as IList<TSource>;
+ if (list == null)
+ list = new List<TSource> (source);
+
+ return CreateReverseIterator (list);
+ }
+
+ static IEnumerable<TSource> CreateReverseIterator<TSource> (IList<TSource> source)
+ {
+ for (int i = source.Count; i > 0; --i)
+ yield return source [i - 1];
+ }
+
+ #endregion
+
+ #region Select
+
+ public static IEnumerable<TResult> Select<TSource, TResult> (this IEnumerable<TSource> source, Func<TSource, TResult> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return CreateSelectIterator (source, selector);
+ }
+
+ static IEnumerable<TResult> CreateSelectIterator<TSource, TResult> (IEnumerable<TSource> source, Func<TSource, TResult> selector)
+ {
+ foreach (var element in source)
+ yield return selector (element);
+ }
+
+ public static IEnumerable<TResult> Select<TSource, TResult> (this IEnumerable<TSource> source, Func<TSource, int, TResult> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return CreateSelectIterator (source, selector);
+ }
+
+ static IEnumerable<TResult> CreateSelectIterator<TSource, TResult> (IEnumerable<TSource> source, Func<TSource, int, TResult> selector)
+ {
+ int counter = 0;
+ foreach (TSource element in source) {
+ yield return selector (element, counter);
+ counter++;
+ }
+ }
+
+ #endregion
+
+ #region SelectMany
+
+ public static IEnumerable<TResult> SelectMany<TSource, TResult> (this IEnumerable<TSource> source, Func<TSource, IEnumerable<TResult>> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return CreateSelectManyIterator (source, selector);
+ }
+
+ static IEnumerable<TResult> CreateSelectManyIterator<TSource, TResult> (IEnumerable<TSource> source, Func<TSource, IEnumerable<TResult>> selector)
+ {
+ foreach (TSource element in source)
+ foreach (TResult item in selector (element))
+ yield return item;
+ }
+
+ public static IEnumerable<TResult> SelectMany<TSource, TResult> (this IEnumerable<TSource> source, Func<TSource, int, IEnumerable<TResult>> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return CreateSelectManyIterator (source, selector);
+ }
+
+ static IEnumerable<TResult> CreateSelectManyIterator<TSource, TResult> (IEnumerable<TSource> source, Func<TSource, int, IEnumerable<TResult>> selector)
+ {
+ int counter = 0;
+ foreach (TSource element in source) {
+ foreach (TResult item in selector (element, counter))
+ yield return item;
+ counter++;
+ }
+ }
+
+ public static IEnumerable<TResult> SelectMany<TSource, TCollection, TResult> (this IEnumerable<TSource> source,
+ Func<TSource, IEnumerable<TCollection>> collectionSelector, Func<TSource, TCollection, TResult> selector)
+ {
+ Check.SourceAndCollectionSelectors (source, collectionSelector, selector);
+
+ return CreateSelectManyIterator (source, collectionSelector, selector);
+ }
+
+ static IEnumerable<TResult> CreateSelectManyIterator<TSource, TCollection, TResult> (IEnumerable<TSource> source,
+ Func<TSource, IEnumerable<TCollection>> collectionSelector, Func<TSource, TCollection, TResult> selector)
+ {
+ foreach (TSource element in source)
+ foreach (TCollection collection in collectionSelector (element))
+ yield return selector (element, collection);
+ }
+
+ public static IEnumerable<TResult> SelectMany<TSource, TCollection, TResult> (this IEnumerable<TSource> source,
+ Func<TSource, int, IEnumerable<TCollection>> collectionSelector, Func<TSource, TCollection, TResult> selector)
+ {
+ Check.SourceAndCollectionSelectors (source, collectionSelector, selector);
+
+ return CreateSelectManyIterator (source, collectionSelector, selector);
+ }
+
+ static IEnumerable<TResult> CreateSelectManyIterator<TSource, TCollection, TResult> (IEnumerable<TSource> source,
+ Func<TSource, int, IEnumerable<TCollection>> collectionSelector, Func<TSource, TCollection, TResult> selector)
+ {
+ int counter = 0;
+ foreach (TSource element in source)
+ foreach (TCollection collection in collectionSelector (element, counter++))
+ yield return selector (element, collection);
+ }
+
+ #endregion
+
+ #region Single
+
+ static TSource Single<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate, Fallback fallback)
+ {
+ var found = false;
+ var item = default (TSource);
+
+ foreach (var element in source) {
+ if (!predicate (element))
+ continue;
+
+ if (found)
+ throw new InvalidOperationException ();
+
+ found = true;
+ item = element;
+ }
+
+ if (!found && fallback == Fallback.Throw)
+ throw new InvalidOperationException ();
+
+ return item;
+ }
+
+ public static TSource Single<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ return source.Single (PredicateOf<TSource>.Always, Fallback.Throw);
+ }
+
+ public static TSource Single<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return source.Single (predicate, Fallback.Throw);
+ }
+
+ #endregion
+
+ #region SingleOrDefault
+
+ public static TSource SingleOrDefault<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ return source.Single (PredicateOf<TSource>.Always, Fallback.Default);
+ }
+
+ public static TSource SingleOrDefault<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return source.Single (predicate, Fallback.Default);
+ }
+
+ #endregion
+
+ #region Skip
+
+ public static IEnumerable<TSource> Skip<TSource> (this IEnumerable<TSource> source, int count)
+ {
+ Check.Source (source);
+
+ return CreateSkipIterator (source, count);
+ }
+
+ static IEnumerable<TSource> CreateSkipIterator<TSource> (IEnumerable<TSource> source, int count)
+ {
+ int i = 0;
+ foreach (var element in source) {
+ if (i++ < count)
+ continue;
+
+ yield return element;
+ }
+ }
+
+ #endregion
+
+ #region SkipWhile
+
+ public static IEnumerable<TSource> SkipWhile<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return CreateSkipWhileIterator (source, predicate);
+ }
+
+ static IEnumerable<TSource> CreateSkipWhileIterator<TSource> (IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ bool yield = false;
+
+ foreach (TSource element in source) {
+ if (yield)
+ yield return element;
+ else
+ if (!predicate (element)) {
+ yield return element;
+ yield = true;
+ }
+ }
+ }
+
+ public static IEnumerable<TSource> SkipWhile<TSource> (this IEnumerable<TSource> source, Func<TSource, int, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return CreateSkipWhileIterator (source, predicate);
+ }
+
+ static IEnumerable<TSource> CreateSkipWhileIterator<TSource> (IEnumerable<TSource> source, Func<TSource, int, bool> predicate)
+ {
+ int counter = 0;
+ bool yield = false;
+
+ foreach (TSource element in source) {
+ if (yield)
+ yield return element;
+ else
+ if (!predicate (element, counter)) {
+ yield return element;
+ yield = true;
+ }
+ counter++;
+ }
+ }
+
+ #endregion
+
+ #region Sum
+
+ public static int Sum (this IEnumerable<int> source)
+ {
+ Check.Source (source);
+
+ return Sum<int, int> (source, (a, b) => checked (a + b));
+ }
+
+ public static int? Sum (this IEnumerable<int?> source)
+ {
+ Check.Source (source);
+
+ return source.SumNullable<int?, int?> (0, (total, element) => element.HasValue ? checked (total + element) : total);
+ }
+
+ public static int Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, int> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Sum<TSource, int> (source, (a, b) => checked (a + selector (b)));
+ }
+
+ public static int? Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, int?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.SumNullable<TSource, int?> (0, (a, b) => {
+ var value = selector (b);
+ return value.HasValue ? checked (a + value.Value) : a;
+ });
+ }
+
+ public static long Sum (this IEnumerable<long> source)
+ {
+ Check.Source (source);
+
+ return Sum<long, long> (source, (a, b) => checked (a + b));
+ }
+
+ public static long? Sum (this IEnumerable<long?> source)
+ {
+ Check.Source (source);
+
+ return source.SumNullable<long?, long?> (0, (total, element) => element.HasValue ? checked (total + element) : total);
+ }
+
+ public static long Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, long> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Sum<TSource, long> (source, (a, b) => checked (a + selector (b)));
+ }
+
+ public static long? Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, long?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.SumNullable<TSource, long?> (0, (a, b) => {
+ var value = selector (b);
+ return value.HasValue ? checked (a + value.Value) : a;
+ });
+ }
+
+ public static double Sum (this IEnumerable<double> source)
+ {
+ Check.Source (source);
+
+ return Sum<double, double> (source, (a, b) => checked (a + b));
+ }
+
+ public static double? Sum (this IEnumerable<double?> source)
+ {
+ Check.Source (source);
+
+ return source.SumNullable<double?, double?> (0, (total, element) => element.HasValue ? checked (total + element) : total);
+ }
+
+ public static double Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, double> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Sum<TSource, double> (source, (a, b) => checked (a + selector (b)));
+ }
+
+ public static double? Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, double?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.SumNullable<TSource, double?> (0, (a, b) => {
+ var value = selector (b);
+ return value.HasValue ? checked (a + value.Value) : a;
+ });
+ }
+
+ public static float Sum (this IEnumerable<float> source)
+ {
+ Check.Source (source);
+
+ return Sum<float, float> (source, (a, b) => checked (a + b));
+ }
+
+ public static float? Sum (this IEnumerable<float?> source)
+ {
+ Check.Source (source);
+
+ return source.SumNullable<float?, float?> (0, (total, element) => element.HasValue ? checked (total + element) : total);
+ }
+
+ public static float Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, float> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Sum<TSource, float> (source, (a, b) => checked (a + selector (b)));
+ }
+
+ public static float? Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, float?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.SumNullable<TSource, float?> (0, (a, b) => {
+ var value = selector (b);
+ return value.HasValue ? checked (a + value.Value) : a;
+ });
+ }
+
+ public static decimal Sum (this IEnumerable<decimal> source)
+ {
+ Check.Source (source);
+
+ return Sum<decimal, decimal> (source, (a, b) => checked (a + b));
+ }
+
+ public static decimal? Sum (this IEnumerable<decimal?> source)
+ {
+ Check.Source (source);
+
+ return source.SumNullable<decimal?, decimal?> (0, (total, element) => element.HasValue ? checked (total + element) : total);
+ }
+
+ public static decimal Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return Sum<TSource, decimal> (source, (a, b) => checked (a + selector (b)));
+ }
+
+ public static decimal? Sum<TSource> (this IEnumerable<TSource> source, Func<TSource, decimal?> selector)
+ {
+ Check.SourceAndSelector (source, selector);
+
+ return source.SumNullable<TSource, decimal?> (0, (a, b) => {
+ var value = selector (b);
+ return value.HasValue ? checked (a + value.Value) : a;
+ });
+ }
+
+ static TR Sum<TA, TR> (this IEnumerable<TA> source, Func<TR, TA, TR> selector)
+ {
+ TR total = default (TR);
+ long counter = 0;
+ foreach (var element in source) {
+ total = selector (total, element);
+ ++counter;
+ }
+
+ return total;
+ }
+
+ static TR SumNullable<TA, TR> (this IEnumerable<TA> source, TR zero, Func<TR, TA, TR> selector)
+ {
+ TR total = zero;
+ foreach (var element in source) {
+ total = selector (total, element);
+ }
+
+ return total;
+ }
+
+ #endregion
+
+ #region Take
+
+ public static IEnumerable<TSource> Take<TSource> (this IEnumerable<TSource> source, int count)
+ {
+ Check.Source (source);
+
+ return CreateTakeIterator (source, count);
+ }
+
+ static IEnumerable<TSource> CreateTakeIterator<TSource> (IEnumerable<TSource> source, int count)
+ {
+ if (count <= 0)
+ yield break;
+
+ int counter = 0;
+ foreach (TSource element in source) {
+ yield return element;
+
+ if (++counter == count)
+ yield break;
+ }
+ }
+
+ #endregion
+
+ #region TakeWhile
+
+ public static IEnumerable<TSource> TakeWhile<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return CreateTakeWhileIterator (source, predicate);
+ }
+
+ static IEnumerable<TSource> CreateTakeWhileIterator<TSource> (IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ foreach (var element in source) {
+ if (!predicate (element))
+ yield break;
+
+ yield return element;
+ }
+ }
+
+ public static IEnumerable<TSource> TakeWhile<TSource> (this IEnumerable<TSource> source, Func<TSource, int, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return CreateTakeWhileIterator (source, predicate);
+ }
+
+ static IEnumerable<TSource> CreateTakeWhileIterator<TSource> (IEnumerable<TSource> source, Func<TSource, int, bool> predicate)
+ {
+ int counter = 0;
+ foreach (var element in source) {
+ if (!predicate (element, counter))
+ yield break;
+
+ yield return element;
+ counter++;
+ }
+ }
+
+ #endregion
+
+ #region ThenBy
+
+ public static IOrderedEnumerable<TSource> ThenBy<TSource, TKey> (this IOrderedEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+ {
+ return ThenBy<TSource, TKey> (source, keySelector, null);
+ }
+
+ public static IOrderedEnumerable<TSource> ThenBy<TSource, TKey> (this IOrderedEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
+ {
+ Check.SourceAndKeySelector (source, keySelector);
+
+ return source.CreateOrderedEnumerable (keySelector, comparer, false);
+ }
+
+ #endregion
+
+ #region ThenByDescending
+
+ public static IOrderedEnumerable<TSource> ThenByDescending<TSource, TKey> (this IOrderedEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector)
+ {
+ return ThenByDescending<TSource, TKey> (source, keySelector, null);
+ }
+
+ public static IOrderedEnumerable<TSource> ThenByDescending<TSource, TKey> (this IOrderedEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
+ {
+ Check.SourceAndKeySelector (source, keySelector);
+
+ return source.CreateOrderedEnumerable (keySelector, comparer, true);
+ }
+
+ #endregion
+
+ #region ToArray
+
+ public static TSource [] ToArray<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ var collection = source as ICollection<TSource>;
+ if (collection != null) {
+ var array = new TSource [collection.Count];
+ collection.CopyTo (array, 0);
+ return array;
+ }
+
+ return new List<TSource> (source).ToArray ();
+ }
+
+ #endregion
+
+ #region ToDictionary
+ public static Dictionary<TKey, TElement> ToDictionary<TSource, TKey, TElement> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector)
+ {
+ return ToDictionary<TSource, TKey, TElement> (source, keySelector, elementSelector, null);
+ }
+
+ public static Dictionary<TKey, TElement> ToDictionary<TSource, TKey, TElement> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
+ {
+ Check.SourceAndKeyElementSelectors (source, keySelector, elementSelector);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TKey>.Default;
+
+ var dict = new Dictionary<TKey, TElement> (comparer);
+ foreach (var e in source)
+ dict.Add (keySelector (e), elementSelector (e));
+
+ return dict;
+ }
+
+ public static Dictionary<TKey, TSource> ToDictionary<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector)
+ {
+ return ToDictionary (source, keySelector, null);
+ }
+
+ public static Dictionary<TKey, TSource> ToDictionary<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+ {
+ return ToDictionary<TSource, TKey, TSource> (source, keySelector, Function<TSource>.Identity, comparer);
+ }
+
+ #endregion
+
+ #region ToList
+ public static List<TSource> ToList<TSource> (this IEnumerable<TSource> source)
+ {
+ Check.Source (source);
+
+ return new List<TSource> (source);
+ }
+ #endregion
+
+ #region ToLookup
+
+ public static ILookup<TKey, TSource> ToLookup<TSource, TKey> (this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+ {
+ return ToLookup<TSource, TKey, TSource> (source, keySelector, Function<TSource>.Identity, null);
+ }
+
+ public static ILookup<TKey, TSource> ToLookup<TSource, TKey> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+ {
+ return ToLookup<TSource, TKey, TSource> (source, keySelector, element => element, comparer);
+ }
+
+ public static ILookup<TKey, TElement> ToLookup<TSource, TKey, TElement> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector)
+ {
+ return ToLookup<TSource, TKey, TElement> (source, keySelector, elementSelector, null);
+ }
+
+ public static ILookup<TKey, TElement> ToLookup<TSource, TKey, TElement> (this IEnumerable<TSource> source,
+ Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
+ {
+ Check.SourceAndKeyElementSelectors (source, keySelector, elementSelector);
+
+ var dictionary = new Dictionary<TKey, List<TElement>> (comparer ?? EqualityComparer<TKey>.Default);
+ foreach (var element in source) {
+ var key = keySelector (element);
+ if (key == null)
+ throw new ArgumentNullException ("key");
+
+ List<TElement> list;
+ if (!dictionary.TryGetValue (key, out list)) {
+ list = new List<TElement> ();
+ dictionary.Add (key, list);
+ }
+
+ list.Add (elementSelector (element));
+ }
+
+ return new Lookup<TKey, TElement> (dictionary);
+ }
+
+ #endregion
+
+ #region SequenceEqual
+
+ public static bool SequenceEqual<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second)
+ {
+ return first.SequenceEqual (second, null);
+ }
+
+ public static bool SequenceEqual<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
+ {
+ Check.FirstAndSecond (first, second);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TSource>.Default;
+
+ using (IEnumerator<TSource> first_enumerator = first.GetEnumerator (),
+ second_enumerator = second.GetEnumerator ()) {
+
+ while (first_enumerator.MoveNext ()) {
+ if (!second_enumerator.MoveNext ())
+ return false;
+
+ if (!comparer.Equals (first_enumerator.Current, second_enumerator.Current))
+ return false;
+ }
+
+ return !second_enumerator.MoveNext ();
+ }
+ }
+
+ #endregion
+
+ #region Union
+
+ public static IEnumerable<TSource> Union<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second)
+ {
+ Check.FirstAndSecond (first, second);
+
+ return first.Union (second, null);
+ }
+
+ public static IEnumerable<TSource> Union<TSource> (this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
+ {
+ Check.FirstAndSecond (first, second);
+
+ if (comparer == null)
+ comparer = EqualityComparer<TSource>.Default;
+
+ return CreateUnionIterator (first, second, comparer);
+ }
+
+ static IEnumerable<TSource> CreateUnionIterator<TSource> (IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
+ {
+ var items = new HashSet<TSource> (comparer);
+ foreach (var element in first) {
+ if (! items.Contains (element)) {
+ items.Add (element);
+ yield return element;
+ }
+ }
+
+ foreach (var element in second) {
+ if (! items.Contains (element, comparer)) {
+ items.Add (element);
+ yield return element;
+ }
+ }
+ }
+
+ #endregion
+
+ #region Where
+
+ public static IEnumerable<TSource> Where<TSource> (this IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return CreateWhereIterator (source, predicate);
+ }
+
+ static IEnumerable<TSource> CreateWhereIterator<TSource> (IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ foreach (TSource element in source)
+ if (predicate (element))
+ yield return element;
+ }
+
+ public static IEnumerable<TSource> Where<TSource> (this IEnumerable<TSource> source, Func<TSource, int, bool> predicate)
+ {
+ Check.SourceAndPredicate (source, predicate);
+
+ return CreateWhereIterator (source, predicate);
+ }
+
+ static IEnumerable<TSource> CreateWhereIterator<TSource> (this IEnumerable<TSource> source, Func<TSource, int, bool> predicate)
+ {
+ int counter = 0;
+ foreach (TSource element in source) {
+ if (predicate (element, counter))
+ yield return element;
+ counter++;
+ }
+ }
+
+ #endregion
+
+ class ReadOnlyCollectionOf<T> {
+ public static readonly ReadOnlyCollection<T> Empty = new ReadOnlyCollection<T> (new T [0]);
+ }
+
+ internal static ReadOnlyCollection<TSource> ToReadOnlyCollection<TSource> (this IEnumerable<TSource> source)
+ {
+ if (source == null)
+ return ReadOnlyCollectionOf<TSource>.Empty;
+
+ var ro = source as ReadOnlyCollection<TSource>;
+ if (ro != null)
+ return ro;
+
+ return new ReadOnlyCollection<TSource> (source.ToArray<TSource> ());
+ }
+ }
+}
projects / mono.git / blobdiff