We introduce FuSes , a Fu nctional programming language that integrates Ses sion-typed concurrent process calculus code. A functional layer sits on top of a session-typed process layer. To generate and reason about open session-typed processes, the functional layer uses the contextual box modality extended with linear channel contexts. Due to the fundamental differences between the operational semantics of the functional layer and the concurrent semantics of processes, we bridge the two layers using a set of primitives to run and observe the behavior of closed processes within the functional layer. In addition, FuSes supports code analysis and manipulation of open session-typed process code. To showcase its benefit to programmers, we implement well-known optimizations, such as batch optimizations, as type-safe metaprograms over concurrent processes. Our technical contributions include a type system for FuSes , an operational semantics, a proof of its type safety, and an implementation.

@article{paperbot3062,
  title = {Fusing Session-Typed Concurrent Programming into Functional Programming},
  author = {Chuta Sano and Deepak Garg and Ryan Kavanagh and Brigitte Pientka and Bernardo Toninho},
  journal = {Proceedings of the ACM on Programming Languages},
  volume = {9},
  number = {ICFP},
  year = {2025},
  doi = {10.1145/3747519}
}