public static IEnumerable <IEnumerable <T> > Permutation <T>(this IEnumerable <T> source, int len)
{
var source2 = source.Select((n, i) => new { n, i }).ToArray();
var source3 = Enumerable.Range(0, len).Select(j => source2.Skip(j).Take(2).ToArray()) /*.Take(len)*/.ToArray();
var t = new[] { new { n = default(T), i = 0 } };
var comp = MonoidsCore.ToFunc(t, t, (a1, a2) => a1.Select(z => z.n).SequenceEqual(a2.Select(z => z.n)));
return(source3.CartesianProduct()
.Select(x => x.OrderBy(i1 => i1.i).Distinct().ToArray())
.Where(x => x.Count() == len)
.Distinct(LambdaComparer.Factory(comp))
.Select(x => x.Select(z => z.n)));
}
static CharterSnapshotControl() {
_newsEventComparer = new LambdaComparer<Event__News>((l, r) => CompareNewsEvents(l, r));
}
