A type and effect system for implementing functional arrays with destructive updates

It can be argued that some of the benefits of purely functional languages are counteracted by the lack of efficient and natural-to-use data structures for these languages. Imperative programming is based on manipulating data structures destructively, e.g., updating arrays in-place; however, doing so in a purely functional language violates the language's very nature. In this paper, we present a type and effect system for an eager purely functional language that tracks array usage, i.e., read and write operations, and enables the efficient implementation of purely functional arrays with destructive update.