public Option <IImmutableEnumeratorElement <U> > MoveNext()
{
if (this.last.EXPLICITLY_DISPOSED)
{
throw new ObjectDisposedException("Cannot use an ImmutableEnumerator after it was explicitly disposed.");
}
return(next.NEXT.Match(
AlreadyUnfoldedEnd: () =>
Option.None <IImmutableEnumeratorElement <U> >(),
AlreadyUnfolded: element =>
element.Some(),
NotUnfoldedYet: (e, last) => {
if (e.MoveNext())
{
var lst = new LazyList {
NEXT = new State.NotUnfoldedYet(e, last)
};
last.LAST = lst;
var elem = new ImmutableEnumeratorElement(
current: e.Current,
next: lst,
last: last);
next.NEXT = new State.AlreadyUnfolded(elem);
return elem.Some();
}
else
{
next.NEXT = new State.AlreadyUnfoldedEnd();
// Call .Dispose() on the underlying enumerator
// because we have read all its elements.
e.Dispose();
return Option.None <IImmutableEnumeratorElement <U> >();
}
}
));
}
public AlreadyUnfolded(ImmutableEnumeratorElement value)
{
this.value = value;
}