tree-mapの謎

hash-table-mapとhash-table-for-eachはあるのに，tree-map-mapとtree-map-for-eachは何故無いんだろう．語呂が悪いから？
hash-table(手続き)はあるのに，tree-mapはない．
tree-map-minはペアを返すのに，tree-map-successorは多値を返す．

gosh> (define foo (make-tree-map = <))
foo
gosh> (tree-map-put! foo 3 "hoge")
#<undef>
gosh> (tree-map-min foo)
(3 . "hoge")
gosh> (tree-map-successor foo 0)
3
"hoge"

＞＜
ついでに，多分この関係で，tree-map-successor-valueとかはあるけどtree-map-min-valueはない．