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BkTree.OverDamerauLevenshtein

Builds an empty tree over DamerauLevenshtein.Distance.

public static BkTree OverDamerauLevenshtein(TextElement element = TextElement.Utf16Unit)

Parameters — element says what counts as one character: TextElement.Utf16Unit by default, or TextElement.CodePoint outside the Basic Multilingual Plane.

Returns — an empty BkTree.

Example — a transposition costs one edit here, so the pair is a neighbour.

using Lodestar.Text.Indexing;

BkTree tree = BkTree.OverDamerauLevenshtein();
tree.AddRange(["form", "from"]);
int found = tree.WithinDistance("form", 1).Count;   // => 2

Remarks — the unrestricted variant, which is a true metric. Its restricted cousin Osa is not, and must not be used with this tree: d("ab","bca") = 3 exceeds d("ab","ba") + d("ba","bca") = 2, so the pruning would drop real hits without saying so.

Reach for this over OverLevenshtein when transposed keystrokes are the error you are correcting.

Applies to — net10.0, netstandard2.0.

See also — BkTree, DamerauLevenshtein.Distance.