Benchmarking a Baseline Fully-in-Place Functional Language Compiler

Jaromír Procházka, Vít Šefl and Tomas Petricek

In Proceedings of TFP 2026

Functional programming makes code easier to reason about, inherently thread-safe, and more testable. However, immutable data struc tures introduce efficiency costs, as many operations require copying rather than performing in-place modifications. To address this, the Koka lan guage introduced a novel mechanism called fully-in-place functional pro gramming (FIP). The mechanism enables safe in-place updates while minimizing unnecessary memory allocations. Nevertheless, Koka’s garbage collection and extensive feature set complicate the task of isolating FIP’s specific memory efficiency advantages. We design a minimal functional language that supports fully in-place updates based on the FIP calculus while omitting garbage collection. This lets us compare the performance of the FIP approach with that of a conventional implementation. Using finger trees, red-black trees, and quicksort as case studies, we show that a language employing the FIP calculus in a garbage-collection-free envi ronment can achieve a significant increase in performance and memory efficiency. Our work confirms the results of the original authors, but it also uncovers potential limitations of the FIP approach

Paper and more information

• Download the paper (PDF)
• StaFip compiler source code on GitHub

Bibtex

If you want to cite the paper, you can use the following BibTeX information.

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@inproceedings{prochazka-2026-stafip,
  author    = {Jaromír Procházka, Vít Šefl and Tomas Petricek},
  title     = {Benchmarking a Baseline Fully-in-Place 
               Functional Language Compiler},
  booktitle = {Trends in Functional Programming},
  year      = {2026},
  publisher = {Springer Nature Switzerland},
  address   = {Cham},
  pages     = {1--19},
  note      = {To appear}
}

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