Full Persistence

Full persistence allows updates to any version, creating branches:

Version 0 (root)
    |
Version 1 (update from 0)
   / \
v2   v3 (both branch from 1)

Implementation is more complex:

• Fat node method works naturally
• Path copying requires careful version tracking

function update(version, index, value)
    oldRoot := roots[version]
    newRoot := pathCopyUpdate(oldRoot, index, value)
    newVersion := len(roots)
    roots.append(newRoot)
    return newVersion

Same implementation as partial persistence! The only difference is which version you pass to update.