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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
namespace System.Linq
{
public static partial class EnumerableEx
{
/// <summary>
/// Hides the enumerable sequence object identity.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <returns>Enumerable sequence with the same behavior as the original, but hiding the source object identity.</returns>
/// <remarks>AsEnumerable doesn't hide the object identity, and simply acts as a cast to the IEnumerable&lt;TSource&gt; interface.</remarks>
public static IEnumerable<TSource> Hide<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw new ArgumentNullException("source");
return source.Hide_();
}
private static IEnumerable<TSource> Hide_<TSource>(this IEnumerable<TSource> source)
{
foreach (var item in source)
yield return item;
}
/// <summary>
/// Enumerates the sequence and invokes the given action for each value in the sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="onNext">Action to invoke for each element.</param>
public static void ForEach<TSource>(this IEnumerable<TSource> source, Action<TSource> onNext)
{
if (source == null)
throw new ArgumentNullException("source");
if (onNext == null)
throw new ArgumentNullException("onNext");
foreach (var item in source)
onNext(item);
}
/// <summary>
/// Enumerates the sequence and invokes the given action for each value in the sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="onNext">Action to invoke for each element.</param>
public static void ForEach<TSource>(this IEnumerable<TSource> source, Action<TSource, int> onNext)
{
if (source == null)
throw new ArgumentNullException("source");
if (onNext == null)
throw new ArgumentNullException("onNext");
var i = 0;
foreach (var item in source)
onNext(item, i++);
}
/// <summary>
/// Lazily invokes an action for each value in the sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="onNext">Action to invoke for each element.</param>
/// <returns>Sequence exhibiting the specified side-effects upon enumeration.</returns>
public static IEnumerable<TSource> Do<TSource>(this IEnumerable<TSource> source, Action<TSource> onNext)
{
if (source == null)
throw new ArgumentNullException("source");
if (onNext == null)
throw new ArgumentNullException("onNext");
return DoHelper(source, onNext, _ => { }, () => { });
}
/// <summary>
/// Lazily invokes an action for each value in the sequence, and executes an action for successful termination.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="onNext">Action to invoke for each element.</param>
/// <param name="onCompleted">Action to invoke on successful termination of the sequence.</param>
/// <returns>Sequence exhibiting the specified side-effects upon enumeration.</returns>
public static IEnumerable<TSource> Do<TSource>(this IEnumerable<TSource> source, Action<TSource> onNext, Action onCompleted)
{
if (source == null)
throw new ArgumentNullException("source");
if (onNext == null)
throw new ArgumentNullException("onNext");
if (onCompleted == null)
throw new ArgumentNullException("onCompleted");
return DoHelper(source, onNext, _ => { }, onCompleted);
}
/// <summary>
/// Lazily invokes an action for each value in the sequence, and executes an action upon exceptional termination.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="onNext">Action to invoke for each element.</param>
/// <param name="onError">Action to invoke on exceptional termination of the sequence.</param>
/// <returns>Sequence exhibiting the specified side-effects upon enumeration.</returns>
public static IEnumerable<TSource> Do<TSource>(this IEnumerable<TSource> source, Action<TSource> onNext, Action<Exception> onError)
{
if (source == null)
throw new ArgumentNullException("source");
if (onNext == null)
throw new ArgumentNullException("onNext");
if (onError == null)
throw new ArgumentNullException("onError");
return DoHelper(source, onNext, onError, () => { });
}
/// <summary>
/// Lazily invokes an action for each value in the sequence, and executes an action upon successful or exceptional termination.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="onNext">Action to invoke for each element.</param>
/// <param name="onError">Action to invoke on exceptional termination of the sequence.</param>
/// <param name="onCompleted">Action to invoke on successful termination of the sequence.</param>
/// <returns>Sequence exhibiting the specified side-effects upon enumeration.</returns>
public static IEnumerable<TSource> Do<TSource>(this IEnumerable<TSource> source, Action<TSource> onNext, Action<Exception> onError, Action onCompleted)
{
if (source == null)
throw new ArgumentNullException("source");
if (onNext == null)
throw new ArgumentNullException("onNext");
if (onError == null)
throw new ArgumentNullException("onError");
if (onCompleted == null)
throw new ArgumentNullException("onCompleted");
return DoHelper(source, onNext, onError, onCompleted);
}
#if !NO_RXINTERFACES
/// <summary>
/// Lazily invokes observer methods for each value in the sequence, and upon successful or exceptional termination.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="observer">Observer to invoke notification calls on.</param>
/// <returns>Sequence exhibiting the side-effects of observer method invocation upon enumeration.</returns>
public static IEnumerable<TSource> Do<TSource>(this IEnumerable<TSource> source, IObserver<TSource> observer)
{
if (source == null)
throw new ArgumentNullException("source");
if (observer == null)
throw new ArgumentNullException("observer");
return DoHelper(source, observer.OnNext, observer.OnError, observer.OnCompleted);
}
#endif
private static IEnumerable<TSource> DoHelper<TSource>(this IEnumerable<TSource> source, Action<TSource> onNext, Action<Exception> onError, Action onCompleted)
{
using (var e = source.GetEnumerator())
{
while (true)
{
var current = default(TSource);
try
{
if (!e.MoveNext())
break;
current = e.Current;
}
catch (Exception ex)
{
onError(ex);
throw;
}
onNext(current);
yield return current;
}
onCompleted();
}
}
/// <summary>
/// Generates a sequence of non-overlapping adjacent buffers over the source sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="count">Number of elements for allocated buffers.</param>
/// <returns>Sequence of buffers containing source sequence elements.</returns>
public static IEnumerable<IList<TSource>> Buffer<TSource>(this IEnumerable<TSource> source, int count)
{
if (source == null)
throw new ArgumentNullException("source");
if (count <= 0)
throw new ArgumentOutOfRangeException("count");
return source.Buffer_(count, count);
}
/// <summary>
/// Generates a sequence of buffers over the source sequence, with specified length and possible overlap.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="count">Number of elements for allocated buffers.</param>
/// <param name="skip">Number of elements to skip between the start of consecutive buffers.</param>
/// <returns>Sequence of buffers containing source sequence elements.</returns>
public static IEnumerable<IList<TSource>> Buffer<TSource>(this IEnumerable<TSource> source, int count, int skip)
{
if (source == null)
throw new ArgumentNullException("source");
if (count <= 0)
throw new ArgumentOutOfRangeException("count");
if (skip <= 0)
throw new ArgumentOutOfRangeException("skip");
return source.Buffer_(count, skip);
}
private static IEnumerable<IList<TSource>> Buffer_<TSource>(this IEnumerable<TSource> source, int count, int skip)
{
var buffers = new Queue<IList<TSource>>();
var i = 0;
foreach (var item in source)
{
if (i % skip == 0)
buffers.Enqueue(new List<TSource>(count));
foreach (var buffer in buffers)
buffer.Add(item);
if (buffers.Count > 0 && buffers.Peek().Count == count)
yield return buffers.Dequeue();
i++;
}
while (buffers.Count > 0)
yield return buffers.Dequeue();
}
/// <summary>
/// Ignores all elements in the source sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <returns>Source sequence without its elements.</returns>
public static IEnumerable<TSource> IgnoreElements<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw new ArgumentNullException("source");
return source.IgnoreElements_();
}
private static IEnumerable<TSource> IgnoreElements_<TSource>(this IEnumerable<TSource> source)
{
foreach (var item in source)
;
yield break;
}
/// <summary>
/// Returns elements with a distinct key value by using the default equality comparer to compare key values.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TKey">Key type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="keySelector">Key selector.</param>
/// <returns>Sequence that contains the elements from the source sequence with distinct key values.</returns>
public static IEnumerable<TSource> Distinct<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
if (source == null)
throw new ArgumentNullException("source");
if (keySelector == null)
throw new ArgumentNullException("keySelector");
return source.Distinct_(keySelector, EqualityComparer<TKey>.Default);
}
/// <summary>
/// Returns elements with a distinct key value by using the specified equality comparer to compare key values.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TKey">Key type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="keySelector">Key selector.</param>
/// <param name="comparer">Comparer used to compare key values.</param>
/// <returns>Sequence that contains the elements from the source sequence with distinct key values.</returns>
public static IEnumerable<TSource> Distinct<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
{
if (source == null)
throw new ArgumentNullException("source");
if (keySelector == null)
throw new ArgumentNullException("keySelector");
if (comparer == null)
throw new ArgumentNullException("comparer");
return source.Distinct_(keySelector, comparer);
}
private static IEnumerable<TSource> Distinct_<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
{
var set = new HashSet<TKey>(comparer);
foreach (var item in source)
{
var key = keySelector(item);
if (set.Add(key))
yield return item;
}
}
#if NO_HASHSET
class HashSet<T>
{
private Dictionary<T, object> _set;
public HashSet(IEqualityComparer<T> comparer)
{
_set = new Dictionary<T, object>(comparer);
}
public bool Add(T value)
{
if (_set.ContainsKey(value))
return false;
_set[value] = null;
return true;
}
}
#endif
/// <summary>
/// Returns consecutive distinct elements by using the default equality comparer to compare values.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <returns>Sequence without adjacent non-distinct elements.</returns>
public static IEnumerable<TSource> DistinctUntilChanged<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw new ArgumentNullException("source");
return source.DistinctUntilChanged_(x => x, EqualityComparer<TSource>.Default);
}
/// <summary>
/// Returns consecutive distinct elements by using the specified equality comparer to compare values.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="comparer">Comparer used to compare values.</param>
/// <returns>Sequence without adjacent non-distinct elements.</returns>
public static IEnumerable<TSource> DistinctUntilChanged<TSource>(this IEnumerable<TSource> source, IEqualityComparer<TSource> comparer)
{
if (source == null)
throw new ArgumentNullException("source");
if (comparer == null)
throw new ArgumentNullException("comparer");
return source.DistinctUntilChanged_(x => x, comparer);
}
/// <summary>
/// Returns consecutive distinct elements based on a key value by using the specified equality comparer to compare key values.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TKey">Key type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="keySelector">Key selector.</param>
/// <returns>Sequence without adjacent non-distinct elements.</returns>
public static IEnumerable<TSource> DistinctUntilChanged<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
if (source == null)
throw new ArgumentNullException("source");
if (keySelector == null)
throw new ArgumentNullException("keySelector");
return source.DistinctUntilChanged_(keySelector, EqualityComparer<TKey>.Default);
}
/// <summary>
/// Returns consecutive distinct elements based on a key value by using the specified equality comparer to compare key values.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TKey">Key type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="keySelector">Key selector.</param>
/// <param name="comparer">Comparer used to compare key values.</param>
/// <returns>Sequence without adjacent non-distinct elements.</returns>
public static IEnumerable<TSource> DistinctUntilChanged<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
{
if (source == null)
throw new ArgumentNullException("source");
if (keySelector == null)
throw new ArgumentNullException("keySelector");
if (comparer == null)
throw new ArgumentNullException("comparer");
return source.DistinctUntilChanged_(keySelector, comparer);
}
private static IEnumerable<TSource> DistinctUntilChanged_<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
{
var currentKey = default(TKey);
var hasCurrentKey = false;
foreach (var item in source)
{
var key = keySelector(item);
var comparerEquals = false;
if (hasCurrentKey)
{
comparerEquals = comparer.Equals(currentKey, key);
}
if (!hasCurrentKey || !comparerEquals)
{
hasCurrentKey = true;
currentKey = key;
yield return item;
}
}
}
/// <summary>
/// Expands the sequence by recursively applying a selector function.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="selector">Selector function to retrieve the next sequence to expand.</param>
/// <returns>Sequence with results from the recursive expansion of the source sequence.</returns>
public static IEnumerable<TSource> Expand<TSource>(this IEnumerable<TSource> source, Func<TSource, IEnumerable<TSource>> selector)
{
if (source == null)
throw new ArgumentNullException("source");
if (selector == null)
throw new ArgumentNullException("selector");
return source.Expand_(selector);
}
private static IEnumerable<TSource> Expand_<TSource>(this IEnumerable<TSource> source, Func<TSource, IEnumerable<TSource>> selector)
{
var queue = new Queue<IEnumerable<TSource>>();
queue.Enqueue(source);
while (queue.Count > 0)
{
var src = queue.Dequeue();
foreach (var item in src)
{
queue.Enqueue(selector(item));
yield return item;
}
}
}
/// <summary>
/// Returns the source sequence prefixed with the specified value.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="values">Values to prefix the sequence with.</param>
/// <returns>Sequence starting with the specified prefix value, followed by the source sequence.</returns>
public static IEnumerable<TSource> StartWith<TSource>(this IEnumerable<TSource> source, params TSource[] values)
{
if (source == null)
throw new ArgumentNullException("source");
return source.StartWith_(values);
}
private static IEnumerable<TSource> StartWith_<TSource>(this IEnumerable<TSource> source, params TSource[] values)
{
foreach (var x in values)
yield return x;
foreach (var item in source)
yield return item;
}
/// <summary>
/// Generates a sequence of accumulated values by scanning the source sequence and applying an accumulator function.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <typeparam name="TAccumulate">Accumulation type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="seed">Accumulator seed value.</param>
/// <param name="accumulator">Accumulation function to apply to the current accumulation value and each element of the sequence.</param>
/// <returns>Sequence with all intermediate accumulation values resulting from scanning the sequence.</returns>
public static IEnumerable<TAccumulate> Scan<TSource, TAccumulate>(this IEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> accumulator)
{
if (source == null)
throw new ArgumentNullException("source");
if (accumulator == null)
throw new ArgumentNullException("accumulator");
return source.Scan_(seed, accumulator);
}
private static IEnumerable<TAccumulate> Scan_<TSource, TAccumulate>(this IEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> accumulator)
{
var acc = seed;
foreach (var item in source)
{
acc = accumulator(acc, item);
yield return acc;
}
}
/// <summary>
/// Generates a sequence of accumulated values by scanning the source sequence and applying an accumulator function.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="accumulator">Accumulation function to apply to the current accumulation value and each element of the sequence.</param>
/// <returns>Sequence with all intermediate accumulation values resulting from scanning the sequence.</returns>
public static IEnumerable<TSource> Scan<TSource>(this IEnumerable<TSource> source, Func<TSource, TSource, TSource> accumulator)
{
if (source == null)
throw new ArgumentNullException("source");
if (accumulator == null)
throw new ArgumentNullException("accumulator");
return source.Scan_(accumulator);
}
private static IEnumerable<TSource> Scan_<TSource>(this IEnumerable<TSource> source, Func<TSource, TSource, TSource> accumulator)
{
var hasSeed = false;
var acc = default(TSource);
foreach (var item in source)
{
if (!hasSeed)
{
hasSeed = true;
acc = item;
continue;
}
acc = accumulator(acc, item);
yield return acc;
}
}
/// <summary>
/// Returns a specified number of contiguous elements from the end of the sequence.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="count">The number of elements to take from the end of the sequence.</param>
/// <returns>Sequence with the specified number of elements counting from the end of the source sequence.</returns>
public static IEnumerable<TSource> TakeLast<TSource>(this IEnumerable<TSource> source, int count)
{
if (source == null)
throw new ArgumentNullException("source");
if (count < 0)
throw new ArgumentOutOfRangeException("count");
return source.TakeLast_(count);
}
private static IEnumerable<TSource> TakeLast_<TSource>(this IEnumerable<TSource> source, int count)
{
var q = new Queue<TSource>(count);
foreach (var item in source)
{
if (q.Count >= count)
q.Dequeue();
q.Enqueue(item);
}
while (q.Count > 0)
yield return q.Dequeue();
}
/// <summary>
/// Bypasses a specified number of contiguous elements from the end of the sequence and returns the remaining elements.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="count">The number of elements to skip from the end of the sequence before returning the remaining elements.</param>
/// <returns>Sequence bypassing the specified number of elements counting from the end of the source sequence.</returns>
public static IEnumerable<TSource> SkipLast<TSource>(this IEnumerable<TSource> source, int count)
{
if (source == null)
throw new ArgumentNullException("source");
if (count < 0)
throw new ArgumentOutOfRangeException("count");
return source.SkipLast_(count);
}
private static IEnumerable<TSource> SkipLast_<TSource>(this IEnumerable<TSource> source, int count)
{
var q = new Queue<TSource>();
foreach (var x in source)
{
q.Enqueue(x);
if (q.Count > count)
yield return q.Dequeue();
}
}
/// <summary>
/// Repeats and concatenates the source sequence infinitely.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <returns>Sequence obtained by concatenating the source sequence to itself infinitely.</returns>
public static IEnumerable<TSource> Repeat<TSource>(this IEnumerable<TSource> source)
{
if (source == null)
throw new ArgumentNullException("source");
return Repeat_(source);
}
private static IEnumerable<TSource> Repeat_<TSource>(IEnumerable<TSource> source)
{
while (true)
foreach (var item in source)
yield return item;
}
/// <summary>
/// Repeats and concatenates the source sequence the given number of times.
/// </summary>
/// <typeparam name="TSource">Source sequence element type.</typeparam>
/// <param name="source">Source sequence.</param>
/// <param name="count">Number of times to repeat the source sequence.</param>
/// <returns>Sequence obtained by concatenating the source sequence to itself the specified number of times.</returns>
public static IEnumerable<TSource> Repeat<TSource>(this IEnumerable<TSource> source, int count)
{
if (source == null)
throw new ArgumentNullException("source");
if (count < 0)
throw new ArgumentOutOfRangeException("count");
return Repeat_(source, count);
}
private static IEnumerable<TSource> Repeat_<TSource>(IEnumerable<TSource> source, int count)
{
for (var i = 0; i < count; i++)
foreach (var item in source)
yield return item;
}
}
}
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