Preorder types

[ms609]

RenumberTips.phylo degenerates preorder into cladewise as it's possible that edges, whilst in preorder, are not in the identical order generated by Preorder.

# If the labels of a tree are modified, then it will no longer be in "strict" 
# preorder. Degenerate to "cladewise".
# TODO in a future release, we may wish to distinguish "strict" preorder
# with a relaxed version that is still "preorder" but doesn't guarantee
# identical edge matrices.
.LapsePreorder <- function (tree) {
  if (attr(tree, "order") == "preorder") {
    attr(tree, "order") <- "cladewise"
  }
  tree
}

We may therefore needlessly run reorder operations on renumbered trees.

Objective: create a suborder attributes that distinguishes trees in strict Preorder, i.e. as output by preorder_edges_and_nodes, from loose preorder, i.e. preorder from a graph theoretic perspective. use this order to determine when reordering is necessary.