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EnumerableExtension.cs
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using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.Contracts;
using System.Linq;
namespace ReClassNET.Extensions
{
public static class EnumerableExtension
{
[DebuggerStepThrough]
public static bool None<TSource>(this IEnumerable<TSource> source)
{
Contract.Requires(source != null);
return !source.Any();
}
[DebuggerStepThrough]
public static bool None<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
Contract.Requires(source != null);
Contract.Requires(predicate != null);
return !source.Any(predicate);
}
[DebuggerStepThrough]
public static IEnumerable<TSource> WhereNot<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
Contract.Requires(source != null);
Contract.Requires(predicate != null);
return source.Where(item => predicate(item) == false);
}
[DebuggerStepThrough]
public static int FindIndex<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
Contract.Requires(source != null);
Contract.Requires(predicate != null);
Contract.Ensures(Contract.Result<int>() >= -1);
var index = 0;
foreach (var item in source)
{
if (predicate(item))
{
return index;
}
++index;
}
return -1;
}
[DebuggerStepThrough]
public static void ForEach<TSource>(this IEnumerable<TSource> source, Action<TSource> func)
{
Contract.Requires(source != null);
Contract.Requires(func != null);
foreach (var item in source)
{
func(item);
}
}
[DebuggerStepThrough]
public static IEnumerable<TSource> Traverse<TSource>(this IEnumerable<TSource> source, Func<TSource, IEnumerable<TSource>> childSelector)
{
Contract.Requires(source != null);
Contract.Requires(childSelector != null);
Contract.Ensures(Contract.Result<IEnumerable<TSource>>() != null);
var queue = new Queue<TSource>(source);
while (queue.Count > 0)
{
var next = queue.Dequeue();
yield return next;
foreach (var child in childSelector(next))
{
queue.Enqueue(child);
}
}
}
[DebuggerStepThrough]
public static IEnumerable<TSource> TakeWhileInclusive<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
Contract.Requires(source != null);
Contract.Requires(predicate != null);
Contract.Ensures(Contract.Result<IEnumerable<TSource>>() != null);
foreach (var item in source)
{
yield return item;
if (!predicate(item))
{
yield break;
}
}
}
[DebuggerStepThrough]
public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
Contract.Requires(source != null);
Contract.Requires(keySelector != null);
Contract.Ensures(Contract.Result<IEnumerable<TSource>>() != null);
var knownKeys = new HashSet<TKey>();
foreach (var element in source)
{
if (knownKeys.Add(keySelector(element)))
{
yield return element;
}
}
}
[DebuggerStepThrough]
public static bool IsEquivalentTo<T>(this IEnumerable<T> source, IEnumerable<T> other)
{
Contract.Requires(source != null);
Contract.Requires(other != null);
var expected = new List<T>(source);
if (other.Any(item => !expected.Remove(item)))
{
return false;
}
return expected.Count == 0;
}
/// <summary>
/// Scans the source and returns the first element where the predicate matches.
/// If the predicate doesn't match the first element of the source is returned.
/// </summary>
/// <param name="source"></param>
/// <param name="predicate"></param>
/// <returns></returns>
public static TSource PredicateOrFirst<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
Contract.Requires(source != null);
Contract.Requires(predicate != null);
var result = default(TSource);
var first = true;
foreach (var element in source)
{
if (predicate(element))
{
return element;
}
if (first)
{
result = element;
first = false;
}
}
if (first)
{
throw new InvalidOperationException("Sequence contains no elements");
}
return result;
}
public static IEnumerable<IEnumerable<T>> GroupWhile<T>(this IEnumerable<T> source, Func<T, T, bool> condition)
{
Contract.Requires(source != null);
Contract.Requires(condition != null);
using var it = source.GetEnumerator();
if (it.MoveNext())
{
var previous = it.Current;
var list = new List<T> { previous };
while (it.MoveNext())
{
var item = it.Current;
if (condition(previous, item) == false)
{
yield return list;
list = new List<T>();
}
list.Add(item);
previous = item;
}
yield return list;
}
}
}
}