úÎw Safe-Inferred  The distance function "d" must be a metric on "s"  ( 5https://en.wikipedia.org/wiki/Metric_space#Definition):  d x y >= 0  d x y == 0 iff x == y  d x y == d y x  d x z <= d x y + d y z  $The maximum distance to search for. ,All the words with a distance less than the % one specified, and their respective  distances.        bk-tree-0.1 Data.BKTreeBKTreeDistanceemptyinsertqueryBKEmptyBKnarrowinsert'query'