PersistentJS

Currently in development -- persistent data structures for JavaScript.

Implementation Strategy

All data structures store their data in a closure, which as far as I know is the only way to create truly inaccessible variables in JavaScript. Each data structure is presented as a basic object with functions that can access the data. All "mutator" functions return a new object that shares as much state with the old object as it can.

Tuples

Tuples are implemented with a basic array. They should be used only for small lengths, as any mutation will create a new copy of the whole array (c.f. Erlang).

Tuples are probably not very useful for user code.

Vectors/Arrays

This could be done with the hash-map (integer keys), but that makes slicing operations difficult. It might be better to just have it as a separate tree implementation. Maybe create a base tree that both extend.

Lists

Linked lists are easy to implement as 2-element Tuples -- the head and the tail. You should be familiar with which operations can be expected to perform in linear time vs. constant time.

Hash-Maps