Tree: start on BST
BST: sygnatury
Zpf/Nat.hs
typesafe complete bin trees - start
typesafe 2-3 trees - start
unsafe 2-3 trees - start
UTree: more cases
UTree: depth, balanced
TestBST: depth
TestBST.propMinDepth
UTree: fix addEl@Bin
QC tests for BST (Jpp)
UTree.addEl: fix middle case
QC tests for UTree
TreeDict tests