Paper on purely functional data structures (persistence): https://www.cs.cmu.edu/~rwh/theses/okasaki.pdf https://www.cs.cmu.edu/~rwh/theses/okasaki.pdf Clojure

Paper on purely functional data structures (persistence): https://www.cs.cmu.edu/~rwh/theses/okasaki.pdf https://www.cs.cmu.edu/~rwh/theses/okasaki.pdf Clojure's fantastic contribution to mainstream programming is making these types widely available.