There is ongoing research for purely functional data structures and many implementations to be written for many functional languages, to make use of PFDS. Whene

There is ongoing research for purely functional data structures and many implementations to be written for many functional languages, to make use of PFDS. Whenever one sees a traditional data structure, one can ask oneself, what a persistent functional one might look like, or whether a different solution would be pursued in FP languages. Traditional data structures are often a question of transcribing from an example language into a target language, with variuos language specific changes for optimization. Finding a good way to implement things without mutation or side-effects, is a challenge.