/// <summary>
/// Sets the value of the item at the specified index.
/// </summary>
/// <param name="index"> The index of the item to update. </param>
/// <param name="item"> The new value of the item. </param>
/// <returns> </returns>
/// <exception cref="ArgumentOutOfRangeException">Thrown if the index doesn't exist.</exception>
public ImmList <T> Update(int index, T item)
{
index.CheckIsBetween("index", -Root.Measure, Root.Measure - 1);
index = index < 0 ? index + Root.Measure : index;
if (index == 0)
{
return(RemoveFirst().AddFirst(item));
}
if (index == Root.Measure - 1)
{
return(RemoveLast().AddLast(item));
}
var ret = Root.Update(index, item, Lineage.Mutable()).Wrap();
ret[index].AssertEqual(item);
ret.Root.Measure.AssertEqual(Root.Measure);
return(ret);
}