Add note about appending trees.

Also remove unused code and clearify append/1.

1 files changed, 10 insertions, 6 deletions

diff --git a/src/ht.erl b/src/ht.erl
index ff7b52a..c10ae33 100644
--- a/src/ht.erl
+++ b/src/ht.erl
@@ -44,10 +44,10 @@ size(Head) ->
 %%
 %% Walk down the tree in Head, stop at The Right Place and make Leaf
 %% the right sibling of that place. To find the right place, let d be
-%% the depth of the tree, then go down the tree on the right side to
-%% level l, where l is the position of the first set bit in d, looking
-%% at d "from the right". l=0 is where the leafs are and l=d-1 is the
-%% root.
+%% the depth of the tree, then go down the tree on the right hand side
+%% to level l, where l is the position of the first set bit in d,
+%% looking at d from the least significant bit. l=0 is where the leafs
+%% are and l=d-1 is the root.
 %%
 %% The depth of the tree is found by walking down the right path. It
 %% would be better if we inserted the leaf and calculated the nodes on
@@ -58,15 +58,19 @@ size(Head) ->
 %% Example: N=4 (100) => l=2, the root (soon not to be root).
 %% Example: N=5 (101) => l=0, the rightmost leaf.
 %% Example: N=6 (110) => l=1, the last and rightmost inner node.
+%%
+%% NOTE: Adding a tree requires some more work. One thing is that if
+%% the tree to append doesn't fit in right-hand subtree, it has to be
+%% added in smaller pieces.
+%%
 -spec append(head(), leaf() | iolist() | binary()) -> head().
 append(#head{version = 0}, Leaf) when is_record(Leaf, leaf) ->
     mkhead(1, Leaf);
 append(Head, Leaf) when is_record(Leaf, leaf) ->
     N = Head#head.version,
-    %Depth = depth(Head),
     Level = fls(N),
     RBD = rightbranchdepth(Head#head.tree),
-    %io:format("N=~p, Depth=~p, Level=~p, RBD=~p~n", [N, Depth, Level, RBD]),
+    %io:format("N=~p, Level=~p, RBD=~p~n", [N, Level, RBD]),
     #head{version = N + 1, tree = append(Head#head.tree, Leaf, RBD-Level-1)};
 append(Head, Data) ->
     append(Head, mkleaf(Data)).