Merge pull request #13 from tendermint/develop

Develop

README.md

@@ -1,12 +1,12 @@
 ## IAVL+ Tree
 
-A snapshottable (immutable) AVL+ tree for persistent data
+**Note: Requires Go 1.8+**
 
-**Note** Please make sure you read the [caveat](https://github.com/tendermint/merkleeyes/blob/develop/iavl/iavl_tree.go#L34-L40) on `Copy`. If you have a backing DB and call `Save` to persist the state, all existing copies become potentially invalid and may panic if used. For safe coding, you must throw away all references upon save, and `Copy` again from the new, committed state.
+A versioned, snapshottable (immutable) AVL+ tree for persistent data.
 
 The purpose of this data structure is to provide persistent storage for key-value pairs (say to store account balances) such that a deterministic merkle root hash can be computed.  The tree is balanced using a variant of the [AVL algortihm](http://en.wikipedia.org/wiki/AVL_tree) so all operations are O(log(n)).
 
-Nodes of this tree are immutable and indexed by its hash.  Thus any node serves as an immutable snapshot which lets us stage uncommitted transactions from the mempool cheaply, and we can instantly roll back to the last committed state to process transactions of a newly committed block (which may not be the same set of transactions as those from the mempool).
+Nodes of this tree are immutable and indexed by their hash.  Thus any node serves as an immutable snapshot which lets us stage uncommitted transactions from the mempool cheaply, and we can instantly roll back to the last committed state to process transactions of a newly committed block (which may not be the same set of transactions as those from the mempool).
 
 In an AVL tree, the heights of the two child subtrees of any node differ by at most one.  Whenever this condition is violated upon an update, the tree is rebalanced by creating O(log(n)) new nodes that point to unmodified nodes of the old tree.  In the original AVL algorithm, inner nodes can also hold key-value pairs.  The AVL+ algorithm (note the plus) modifies the AVL algorithm to keep all values on leaf nodes, while only using branch-nodes to store keys.  This simplifies the algorithm while keeping the merkle hash trail short.