Section: New Results

Faster Immutable Data Structures for the JVM

Immutable data structures involve copying when updating. Efficient implementations use persistent data-structures, so that most of the unchanged data is shared between the copies. Existing libraries for such data structures in the context of the Java virtual machine (JVM), such as the data structures in Clojure and Scala, are based on Hash Array-Mapped Tries (HAMTs), which provide efficient insertion and concatenation operations for persistent maps and sets. In [37] Steindorfer and Vinju presented additional optimisation which allow such operations to be up to 28 times faster than in the Clojure and Scala libraries. Furthermore, the cost of equality checking of such data structures is lower as well. All this, without incurring additional memory.