private VersionedList <T> _removeWhere(Func <T, int, bool> predicate)
{
var pairs = Items
.Select((T item, int i) => new { Index = i, Item = item })
.ToArray();
var pairsToRemove = pairs
.Where(pair => predicate(pair.Item, pair.Index))
.OrderByDescending(pair => pair.Index)
.ToArray();
var remaining = pairs
.Where(pair => !predicate(pair.Item, pair.Index))
.Select(pair => pair.Item);
var changes = Enumerable.Range(0, pairsToRemove.Length)
.Select(i => ListChange.Removed(Version + i, pairsToRemove[i].Index, pairsToRemove[i].Item));
return(new VersionedList <T>(
ImmutableList.CreateRange(remaining),
Version + pairsToRemove.Length,
Changes.AddRange(changes)
));
}
