I know about different data structures but they are all more complicated than mutable data structures. For example, if you "store only changes", it will take mo

I know about different data structures but they are all more complicated than mutable data structures. For example, if you "store only changes", it will take more time to access the data, and you need to flatten your changes once in a while. Also, for nested data structures you need to either do path copying, or use "modification boxes" [1]. [1] https://en.wikipedia.org/wiki/Persistent_data_structure#Techniques_for_preserving_previous_versions https://en.wikipedia.org/wiki/Persistent_data_structure#Tech...