Barry Jay invented tree calculus. He has been professionally researching calculi for computation for decades. For instance, his programming language bondi (WGP 2013) is a realization of pattern calculus (Springer 2009). Since then he has developed novel combinatory calculi that support program analysis as part of a general account of intensional computation, culminating in his discovery of tree calculus (2021). His latest work Typed Program Analysis without Encodings (PEPM 2025, preprint) demonstrates how tree calculus supports program analysis and introduces a type system that can type a self-interpreter. Check out Barry’s blog! Contact: [email protected]

I (Johannes Bader) maintain this website and explore immediate practical implications of tree calculus for software engineers. My passion is finding ways to improve life for developers, have spent my entire career building developer tools, and did some research on adjacent topics. Barry’s work caught my attention after years of investigating minimal combinatory calculi and we got in touch. I firmly believe that tree calculus has profound implications for both theory and practice of computer science! This website is an attempt to share my excitement with the broader developer population. It conveys flavors of tree calculus’ semantics and features, showing off what it unlocks using interactive demos, like a small stream fusion optimizer. Potential mistakes are mine. Contact: [email protected]

We highly appreciate your feedback and welcome contributions!