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using System;
using System.Collections.Generic;
using Mono;
#if !NET_3_5 && !NET_4_0
namespace System.Linq {
static class Enumerable {
public static IEnumerable<TRet> Select<TItem, TRet> (this IEnumerable<TItem> self, Func<TItem, TRet> selector)
{
foreach (var item in self)
yield return selector (item);
}
public static IEnumerable<T> Where<T> (this IEnumerable<T> self, Func<T, bool> predicate)
{
foreach (var item in self)
if (predicate (item))
yield return item;
}
public static List<T> ToList<T> (this IEnumerable<T> self)
{
return new List<T> (self);
}
public static T [] ToArray<T> (this IEnumerable<T> self)
{
return self.ToList ().ToArray ();
}
public static T First<T> (this IEnumerable<T> self)
{
using (var enumerator = self.GetEnumerator ()) {
if (!enumerator.MoveNext ())
throw new InvalidOperationException ();
return enumerator.Current;
}
}
}
}
#endif