public override FTree <TChild> AddFirst(TChild item, Lineage lineage)
{
FTree <TChild> ret;
#if ASSERTS
var expectedSize = Measure + item.Measure;
#endif
if (LeftDigit.Size < 4)
{
ret = MutateOrCreate(LeftDigit.AddFirst(item, lineage), DeepTree, RightDigit, lineage);
}
else
{
var leftmost = new Digit(item, LeftDigit.First, lineage);
var rightmost = LeftDigit.RemoveFirst(lineage);
var newDeep = DeepTree.AddFirst(rightmost, lineage);
ret = MutateOrCreate(leftmost, newDeep, RightDigit, lineage);
}
#if ASSERTS
ret.Measure.AssertEqual(expectedSize);
ret.Left.AssertEqual(item);
#endif
return(ret);
}
/// <summary>
/// Splits the finger tree right before the specified index.
/// </summary>
/// <param name="index">The index.</param>
/// <param name="left">The left.</param>
/// <param name="right">The right.</param>
/// <param name="lineage">The lineage.</param>
public void Split(int index, out FTree<TChild> left, out FTree<TChild> right, Lineage lineage) {
if (index == Measure) {
left = this;
right = Empty;
return;
}
#if ASSERTS
var oldValue = this[index];
var oldFirst = Left;
var oldLast = Right;
#endif
TChild center;
Split(index, out left, out center, out right, lineage);
right = right.AddFirst(center, lineage);
#if ASSERTS
center[0].AssertEqual(oldValue);
if (left.Measure != 0) {
left.Left.AssertEqual(oldFirst);
}
if (right.Measure != 0) {
right.Right.AssertEqual(oldLast);
}
#endif
}