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Added default predicate value to Any(), new DefaultIfEmpty method and converted Count() method to switch.

pull/10/head
David Hall 2018-01-12 11:39:58 -07:00
parent a0f9ed04d0
commit 67fe9d4632
1 changed files with 38 additions and 8 deletions
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46
Core/BkwdComp/Linq.NET2.cs
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@ -26,12 +26,11 @@ namespace System.Linq
/// <param name="source">An <see cref="IEnumerable{T}"/> whose elements to apply the predicate to.</param>
/// <param name="predicate">A function to test each element for a condition.</param>
/// <returns><c>true</c> if any elements in the source sequence pass the test in the specified predicate; otherwise, <c>false</c>.</returns>
public static bool Any<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
public static bool Any<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate = null)
{
if (source == null) throw new ArgumentNullException(nameof(source));
if (predicate == null) throw new ArgumentNullException(nameof(predicate));
foreach (TSource element in source)
if (predicate(element)) return true;
if (predicate == null || predicate(element)) return true;
return false;
}
@ -62,13 +61,44 @@ namespace System.Linq
/// <param name="source">A sequence that contains elements to be counted.</param>
/// <returns>The number of elements in the input sequence.</returns>
public static int Count<TSource>(this IEnumerable<TSource> source)
{
switch (source)
{
case null:
throw new ArgumentNullException(nameof(source));
case ICollection<TSource> c:
return c.Count;
case ICollection ngc:
return ngc.Count;
default:
var i = 0;
foreach (var e in source) i++;
return i;
}
}
/// <summary>Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.</summary>
/// <typeparam name="TSource">The type of the elements of <paramref name="source"/>.</typeparam>
/// <param name="source">The sequence to return the specified value for if it is empty.</param>
/// <param name="defaultValue">The value to return if the sequence is empty. This value defaults to <see cref="default(TSource)"/>.</param>
/// <returns>An <see cref="IEnumerable{T}"/> that contains <paramref name="defaultValue"/> if source is empty; otherwise, source.</returns>
public static IEnumerable<TSource> DefaultIfEmpty<TSource>(this IEnumerable<TSource> source, TSource defaultValue = default(TSource))
{
if (source == null) throw new ArgumentNullException(nameof(source));
if (source is ICollection<TSource> c) return c.Count;
if (source is ICollection ngc) return ngc.Count;
var i = 0;
foreach (var e in source) i++;
return i;
using (var e = source.GetEnumerator())
{
if (e.MoveNext())
{
do
{
yield return e.Current;
} while (e.MoveNext());
}
else
{
yield return defaultValue;
}
}
}
/// <summary>Returns distinct elements from a sequence by using the default equality comparer to compare values.</summary>