Programming Languages

Dr. Philipp Schuster

Researcher

Photo of Philipp Schuster

Philipp Schuster
Software Engineering
FB Informatik
Universität Tübingen
Sand 13
72076 Tübingen
Germany

E-Mail
philipp.schuster(at)uni-tuebingen.de
Office
B213
Office hours
by appointment

Publications on Google Scholar Publications on DBLP

Publications

Other Publications

  • Effects, Capabilities, and Boxes: From Scope-based Reasoning to Type-based Reasoning and Back

    by Jonathan Immanuel Brachthäuser, Philipp Schuster, Edward Lee, and Aleksander Boruch-Gruszecki

    In Proceedings of the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA), 2022.

  • Region-based Resource Management and Lexical Exception Handlers in Continuation-Passing Style

    by Philipp Schuster, Jonathan Immanuel Brachthäuser, and Klaus Ostermann

    In European Symposium on Programming (ESOP 2022), 2022.

  • A Typed Continuation-Passing Translation for Lexical Effect Handlers

    by Philipp Schuster, Jonathan Immanuel Brachthäuser, Marius Müller, and Klaus Ostermann

    In Proceedings of the International Conference on Programming Language Design and Implementation (PLDI), 2022.

Other Publications

  • The Simple Essence of Monomorphization

    by Matthew Lutze, Philipp Schuster, and Jonathan Immanuel Brachthäuser

    In Proceedings of the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA), 2025.

  • Compiling Classical Sequent Calculus to Stock Hardware: The Duality of Compilation

    by Philipp Schuster, Marius Müller, Klaus Ostermann, and Jonathan Immanuel Brachthäuser

    In Proceedings of the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA), 2025.

Other Publications

  • Back to Direct Style: Typed and Tight

    by Marius Müller, Philipp Schuster, Jonathan Immanuel Brachthäuser, and Klaus Ostermann

    In Proceedings of the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA), 2023.

  • From Capabilities to Regions: Enabling Efficient Compilation of Lexical Effect Handlers

    by Marius Müller, Philipp Schuster, Jonathan Lindegaard Starup, Klaus Ostermann, and Jonathan Immanuel Brachthäuser

    In Proceedings of the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA), 2023.

  • With or Without You: Programming with Effect Exclusion

    by Matthew Lutze, Magnus Madsen, Jonathan Immanuel Brachthäuser, and Philipp Schuster

    In Proceedings of the International Conference on Functional Programming (ICFP). ACM Press, 2023.

Other Publications

  • All About That Stack: A Unified Treatment of Regions and Control Effects

    by Philipp Schuster, Jonathan Immanuel Brachthäuser, and Klaus Ostermann

    Technical report. University of Tübingen, Germany, 2021.

Other Publications

  • Effekt: Capability-Passing Style for Type- and Effect-Safe, Extensible Effect Handlers in Scala

    by Jonathan Immanuel Brachthäuser, Philipp Schuster, and Klaus Ostermann

    In Journal of Functional Programming 30: , 2020.

  • Compiling Effect Handlers in Capability-Passing Style

    by Philipp Schuster, Jonathan Immanuel Brachthäuser, and Klaus Ostermann

    In Proceedings of the International Conference on Functional Programming (ICFP). ACM Press, 2020.

  • Effect Handlers, Evidently

    by Ningning Xie, Jonathan Immanuel Brachthäuser, Daniel Hillerström, Philipp Schuster, and Daan Leijen

    In Proceedings of the International Conference on Functional Programming (ICFP). ACM Press, 2020.

  • Effekt: Lightweight Effect Polymorphism for Handlers (Technical Report)

    by Jonathan Immanuel Brachthäuser, Philipp Schuster, and Klaus Ostermann

    Technical report. University of Tübingen, Germany, 2020.

  • Effects as Capabilities: Effect Handlers and Lightweight Effect Polymorphism

    by Jonathan Immanuel Brachthäuser, Philipp Schuster, and Klaus Ostermann

    In Proceedings of the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA). ACM Press, 2020.

Other Publications

  • Zero-cost Effect Handlers by Staging (Technical Report)

    by Philipp Schuster, Jonathan Immanuel Brachthäuser, and Klaus Ostermann

    Technical report. University of Tübingen, Germany, 2019.

Other Publications

Other Publications

  • Effekt: Extensible Algebraic Effects in Scala (Short Paper)

    by Jonathan Immanuel Brachthäuser and Philipp Schuster

    In Proceedings of the International Symposium on Scala. ACM Press, 2017.

Assigned Thesis Topics

Marvin Borner (BSc)

Optimal Effects

When evaluating functional programs, there are various strategies for reducing expressions. A strategy is Lévy-optimal if it never does unnecessary work such as duplicating terms that are later erased. To implement this efficiently, graphical representations like Interaction Nets can be used to encode the sharing of duplicated terms. Beyond optimality, Interaction Nets provide elegant solutions for parallelization and distributed computing, making them an attractive backend for programming languages. Side effects such as file I/O are rarely discussed in the context of optimal reduction, despite their necessity for real-world applications. In this thesis, we will therefore analyze and formalize existing implementations, and design and implement an optimal runtime with side effects.

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Dennis Hieber (MSc)

Multiple Return Values in Effekt

Multiple return values in functions have long been regarded as a powerful feature in programming languages, enabling concise and expressive code. However, not all programming languages support this feature natively. Instead, most languages emulate multiple return values only via tuples. In the case of dynamically typed languages like Common Lisp multiple return values are supported but the dynamic handling may cause headaches: (type-of (values x y z)) is the same as (type-of x). This master thesis delves into designing and implementing multiple return values in the Effekt language. The thesis introduces native support for multiple return values in Effekt, exploring their significance and potential impact on software development.

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Finished Thesis Topics

Elisabeth Fritze (MSc)

A Modern Implementation of Cut Elimination for Classical Sequent Calculus

The symmetrical properties of the sequent calculus make it an interesting base for functional programming languages. In contrast to the prevalent base lambda calculus, it allows for an equivalent treatment of terms producing information and evaluation contexts. In this thesis, we have constructed and implemented a term language for the sequent calculus, along with its cut-free fragment. We further present a normalization function that evaluates statements to their cut-free form, utilizing cut elimination and hereditary substitution. Thereby, it lends itself as a compiler intermediate language, shifting computation from runtime to compile-time, and optimizing program execution.

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Lars Seif (BSc)

Kompilierung von Effekthandlern mit Interaktionskombinatoren

In dieser Bachelorarbeit wird beschrieben wie Bend, eine Programmiersprache, die auf Interaktionskombinatoren basiert und noch in Entwicklung ist, als Backend des Effekt Kompilierers hinzugefügt wird. Bend kompiliert zu HVM, was für Higher-order Virtual Mashine steht. HVM implementiert die von Lafont [5] entworfenen Interaktionskombinatoren. Bend kann einige Lambda-Terme in von Levy [7] definierter optimaler Zeit berechnen und sehr leicht mehrere Berechnungen parallel durchführen. Deshalb hoffen wir mit Bend als Backend die Laufzeit von Effekt in einigen Programmen stark zu reduzieren.

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Mattis Böckle (BSc)

Compiling classical sequent calculus to LLVM

This thesis aims to provide a way to translate classical sequent calculus to the LLVM intermediate representation to utilize the LLVM toolchain and achieve greater performance than compiling directly to machine code. We provide examples of how this translation works, what the resulting optimized version looks like and how and why we implemented a custom memory allocater to suit our needs. We show how to evaluate the resulting programs and how we test the validity of the translation. Finally we benchmark our approach against other programming languages and compare the resulting performance.

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Sina Schäfer (BSc)

Probabilistic Effekt

Inference programming - the adaptation of inference algorithms to a particular model or problem - is difficult in languages that do not deal with side effects or do not handle side effects properly due to their nature of relying on effectful computation. In functional programming, monad transformers are the most common approach to control side effects. However, this makes it difficult to customise such algorithms. Effects and effect handlers on the other hand introduce another possibility to deal with programmable inference. This thesis will demonstrates this idea by developing three inference patterns (Metropolis-Hastings, slice sampling and rejection sampling) using the language Effekt. The result is a more user-friendly way to adapt and combine parts of these algorithms

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Maximilian Marschall (BSc)

Is Effekt Fast Yet

Alle Programmiersprachen besitzen eine gemeinsame Schnittmenge der grundlegenden Abstraktionen. Durch einen Kompiler oder Interpreter werden die Abstraktionen in Maschinencode umgesetzt und dann ausgeführt. Je besser diese Umsetzung optimiert ist, desto performanter ist die Ausführung des Programmes. Im Paper Are-We-Fast-Yet [ 5 ] werden 9 Microbenchmarks entwickelt, welche in moderat komplexen Programmen jeweils bestimmte Bereiche dieser Core Language testen. Die Benchmarks werden in verschiedene Programmiersprachen implementiert und die Ausführung auf Zeit gemessen. Anhand der Ergebnisse lässt sich eine generelle Aussage über die Performanz einer Programmiersprache, beziehungsweise Kompilers/Interpreters machen.

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Matthias Dunkel (BSc)

Reactive: Design and Implementation of a synchronous reactive programming library in Effekt

Reactive systems are an important part of everyday programming. Still, the implementations of such reactive systems differ hugely, which has a major impact on the style and reliability of reactive programs. The main approach to implementing reactivity and parallelism in the industry is to use multi-threading. This approach often leads to non-deterministic behavior. Additionally, programming languages often need extra implementations for reactivity and parallelism to support multi-threading. Languages such as Effekt eradicate the need for additional reactive system language support, by implementing algebraic effects. With algebraic effects, it is possible to implement a vast amount of programs, including reactive systems. In this work, we present Reactive, a library for the programming language Effekt. Reactive uses algebraic effects to implement reactivity and parallelism in direct style. The ability to write programs in direct style leads to more readable code, as it appears to be sequential, while the control flow is handled with algebraic effects. Reactive defines a synchronous execution model, by interleaving waiting parts of the program. The synchronous approach of the library makes decisions over the execution flow of the program deterministic. Parallelism and reactivity are decoupled by using different effects and handlers. With schedulers, Reactive creates the ability to run parts of a program in parallel. Reactive implements different schedulers, which handle the control flow of the program by enforcing rules. Such rules can be the termination of parts of the program when another has already stopped. The awaiting of an event is done by polling an environment in a busy wait loop, which can be interleaved with other parts of the program. Additional to the Effekt implementation, this thesis implements the ability to wait for JavaScript events inside the Effekt language.

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Serkan Muhcu (MSc)

Mutable State in a Language with Effect Handlers

Effekt is a functional programming language developed for research on algebraic effects and handlers. Aside from algebraic handlers, Effekt also features side effects in form of mutable state using region-based memory management. The Effekt compiler has multiple backends, one of which targets the LLVM Intermediate Representation. The LLVM-IR can be compiled to an executable file with many optimization passes on the way. The LLVM backend of Effekt covers only a subset of Effekt’s features. As part of this thesis, we extend the LLVM backend by support for mutable state.

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Franciszek Piszcz (MSc)

Abstract-Interpretation-Based Language Server for Python

Most IDEs for Python development follow traditional code analysis approaches that are known to work well for statically-typed languages such as Java or C++. A lot of modern Python code is untyped, and these conservative tools tend to assign the “Any” type for variables that do not have explicit type annotations. However, programmers are usually able to deduce types (and often concrete values) by looking at surrounding code and jumping through function definitions and call sites.

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News

Two Papers at OOPSLA 2025 R1

Together with our collaborators the SE group presents two (very) different papers at round 1 of this year’s International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA 2025 R1).

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Three Papers at OOPSLA 2023

Together with our collaborators the SE group presents three different papers at this year’s International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA 2023).

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Paper accepted for publication at OOPSLA 2023

Our paper “From Capabilities to Regions: Enabling Efficient Compilation of Lexical Effect Handlers” (Marius Müller, Philipp Schuster
ResearcherPhilipp Schuster, Jonathan Lindegaard Starup, and Klaus Ostermann, Jonathan Brachthäuser
Head of the SE research groupJonathan Immanuel Brachthäuser) has been accepted for publication at the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA 2023).

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Paper accepted for publication at OOPSLA 2023

Our paper “Continuation-Passing to Direct Style: Typed and Tight” (Marius Müller, Philipp Schuster
ResearcherPhilipp Schuster, Jonathan Brachthäuser
Head of the SE research groupJonathan Immanuel Brachthäuser, and Klaus Ostermann) has been accepted for publication at the International Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA 2023).

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