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BkTree.OverIndel

Builds an empty tree over Indel.Distance.

public static BkTree OverIndel(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 substitution costs two here, so a radius of 1 excludes it.

using Lodestar.Text.Indexing;

BkTree tree = BkTree.OverIndel();
tree.AddRange(["book", "cook", "boo"]);
int found = tree.WithinDistance("book", 1).Count;   // => 2

Remarks — Indel is len(a) + len(b) - 2 x Lcs.SubsequenceLength(a, b), the LCS edit distance, and it is a metric. It is also the measure behind rapidfuzz's fuzz.ratio, so a radius on this tree and a Fuzz.Ratio cutoff move together whenever the two are used against the same pair of strings.

Lcs itself is not a candidate for a tree — Lcs.SubsequenceLength returns a length, not a distance.

Applies to — net10.0, netstandard2.0.

See also — BkTree, Indel.Distance.