/// <summary>
/// Removes the first item from the list.
/// </summary>
/// <returns> </returns>
/// <exception cref="InvalidOperationException">Thrown if the list is empty.</exception>
public ImmList <T> RemoveFirst()
{
this.CheckNotEmpty();
if (Root.IsEmpty)
{
throw Errors.Is_empty;
}
var ret = Root.RemoveFirst(Lineage.Immutable).Wrap();
#if ASSERTS
if (Root.Measure > 1)
{
ret.First.AssertEqual(this[1]);
}
else
{
ret.Root.Measure.AssertEqual(Root.Measure - 1);
}
#endif
return(ret);
}
