// Package iavl implements a versioned, snapshottable (immutable) AVL+ tree
// for persisting key-value pairs.
//
// Basic usage of MutableTree.
//
//	import "github.com/tendermint/iavl"
//	import "github.com/tendermint/tendermint/libs/db"
//	...
//
//	tree := iavl.NewMutableTree(db.NewMemDB(), 128)
//
//	tree.IsEmpty() // true
//
//	tree.Set([]byte("alice"), []byte("abc"))
//	tree.SaveVersion(1)
//
//	tree.Set([]byte("alice"), []byte("xyz"))
//	tree.Set([]byte("bob"), []byte("xyz"))
//	tree.SaveVersion(2)
//
//	tree.LatestVersion() // 2
//
//	tree.GetVersioned([]byte("alice"), 1) // "abc"
//	tree.GetVersioned([]byte("alice"), 2) // "xyz"
//
// Proof of existence:
//
//	root := tree.Hash()
//	val, proof, err := tree.GetVersionedWithProof([]byte("bob"), 2) // "xyz", RangeProof, nil
//	proof.Verify([]byte("bob"), val, root) // nil
//
// Proof of absence:
//
//	_, proof, err = tree.GetVersionedWithProof([]byte("tom"), 2) // nil, RangeProof, nil
//	proof.Verify([]byte("tom"), nil, root) // nil
//
// Now we delete an old version:
//
//	tree.DeleteVersion(1)
//	tree.VersionExists(1) // false
//	tree.Get([]byte("alice")) // "xyz"
//	tree.GetVersioned([]byte("alice"), 1) // nil
//
// Can't create a proof of absence for a version we no longer have:
//
//	_, proof, err = tree.GetVersionedWithProof([]byte("tom"), 1) // nil, nil, error
package iavl