Koka

Established: April 13, 2012

Publications

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- Principal Type Inference under a Prefix
  
  Daan Leijen, Wenjia Ye
  
  PLDI'25 | June 2025
  
  A Fresh Look at Static Overloading. See also the accompanying technical report.
  
  Publication
- Principal Type Inference under a Prefix (TR)
  
  Daan Leijen, Wenjia Ye
  
  MSR-TR-2024-34 | September 2024
  
  Published by Microsoft
  
  A Fresh Look at Static Overloading. Updated 2025-05-19, v7. Extended version of the PLDI'25 paper.
  
  Publication
- The Functional Essence of Imperative Binary Search Trees
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra, Sam Lindley
  
  PLDI'24 | June 2024
  
  Publication
- Tail Recursion Modulo Context: An Equational Approach (extended version)
  
  Daan Leijen, Anton Lorenzen
  
  under submission to JFP. | May 2024
  
  This is an extended version of the POPL'23 publication under submission to a special issue of the Journal of Functional Programming (JFP). Extended topics include an improved TRMC algorithm, composing contexts, _field_ contexts, and first-class constructor contexts.
  
  Publication
- Qualified Effect Types — Taming Control-Flow through Linear Effect Handlers
  
  Jonathan Immanuel Brachthäuser, Daan Leijen
  
  MSR-TR-2023-42 | November 2023
  
  Published by Microsoft
  
  This technical report is the result of an internship of Jonathan Brachthäuser at Microsoft Research, Redmond in 2018. While the report is published in 2023, the paper reflects the work at the time of writing.
  
  Publication
- Continuing WebAssembly with Effect Handlers
  
  LUNA PHIPPS-COSTIN, ANDREAS ROSSBERG, ARJUN GUHA, Daan Leijen, DANIEL HILLERSTRÖM, KC SIVARAMAKRISHNAN, MATIJA PRETNAR, SAM LINDLEY
  
  OOPSLA'23 | October 2023
  
  Publication
- FP$^2$: Fully in-Place Functional Programming
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra
  
  ICFP 2023 | September 2023
  
  preprint
  
  Publication
- Exploring Perceus for OCaml
  
  Elton Pinto, Daan Leijen
  
  September 2023
  
  Presented at the "Higher order, Typed, Strict: ML Family Workshop 2023" co-located with ICFP'23.
  
  Publication
- The Functional Essence of Imperative Binary Search Trees
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra, Sam Lindley
  
  MSR-TR-2023-28 | July 2023
  
  Published by Microsoft
  
  v4, Dec 27, 2023 (previously titled "A Functional Correspondence between Top-down and Bottom-up Tree Algorithms") This is an extended version of the PLDI'24 publication.
  
  Publication
- FP^2: Fully in-Place Functional Programming (TR)
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra
  
  MSR-TR-2023-19 | May 2023
  
  Published by Microsoft
  
  Extended version of the ICFP'23 publication
  
  Publication
- Tail Recursion Modulo Context: An Equational Approach
  
  Daan Leijen, Anton Lorenzen
  
  POPL'23 | January 2023
  
  Publication
- Reference counting with frame limited reuse
  
  Anton Lorenzen, Daan Leijen
  
  ICFP'22 | August 2022
  
  Publication
- What About the Integer Numbers? Fast Arithmetic with Tagged Integers — A Plea for Hardware Support
  
  Daan Leijen
  
  MSR-TR-2022-17 | July 2022
  
  Published by Microsoft
  
  Presented at ML language workshop 2022 (co-located with ICFP'22).
  
  Publication
- Tail Recursion Modulo Context — An Equational Approach
  
  Daan Leijen, Anton Lorenzen
  
  MSR-TR-2022-18 | July 2022
  
  Published by Microsoft
  
  Publication
- Reference Counting with Frame Limited Reuse (extended version, v2)
  
  Anton Lorenzen, Daan Leijen
  
  MSR-TR-2021-30 | November 2021
  
  Published by Microsoft
  
  Mar 15, 2022, v2
  
  Publication
- Generalized Evidence Passing for Effect Handlers (or, Efficient Compilation of Effect Handlers to C)
  
  Ningning Xie, Daan Leijen
  
  Proc. ACM Prog. Lang. (ICFP'21) | August 2021, Vol 5(ICFP): pp. 71
  
  doi: 10.1145/3473576
  
  Publication
- Perceus: Garbage Free Reference Counting with Reuse
  
  Alex Reinking*, Ningning Xie*, Leonardo de Moura, Daan Leijen
  
  The 42nd ACM SIGPLAN International Conference on Programming Language Design and Implementation (PLDI ’21) | June 2021
  
  (*) The first two authors contributed equally to this work. Distinguished paper at PLDI'21.
  
  Publication Github
- First-class Named Effect Handlers
  
  Ningning Xie, Youyou Cong, Daan Leijen
  
  MSR-TR-2021-10 | May 2021
  
  Published by Microsoft
  
  Presented at the 8th ACM SIGPLAN Workshop on Higher-Order Programming with Effects (HOPE'21).
  
  Publication
- Generalized Evidence Passing for Effect Handlers (or, Efficient Compilation of Effect Handlers to C) (Extended Version)
  
  Ningning Xie, Daan Leijen
  
  MSR-TR-2021-5 | March 2021
  
  Published by Microsoft
  
  v4, 2021-06-07. Extended version of the ICFP'21 paper.
  
  Publication
- Perceus: Garbage Free Reference Counting with Reuse (Extended version)
  
  Alex Reinking*, Ningning Xie*, Leonardo de Moura, Daan Leijen
  
  MSR-TR-2020-42 | November 2020
  
  Published by Microsoft
  
  (*) The first two authors contributed equally to this work. v4, 2021-06-07. Extended version of the PLDI'21 paper.
  
  Publication Github
- Effect Handlers in Haskell, Evidently
  
  Ningning Xie, Daan Leijen
  
  The 13th ACM SIGPLAN International Haskell Symposium | August 2020
  
  Publication
- Effect Handlers, Evidently
  
  Ningning Xie, Jonathan Brachthauser, Daniel Hillerstrom, Philipp Schuster, Daan Leijen
  
  The 25th ACM SIGPLAN International Conference on Functional Programming (ICFP) | August 2020
  
  Publication
- Effect Handlers, Evidently (Extended Version)
  
  Ningning Xie, Jonathan Brachthauser, Daniel Hillerstrom, Philipp Schuster, Daan Leijen
  
  MSR-TR-2020-23 | July 2020
  
  Published by Microsoft
  
  Extended version of the ICFP'20 article.
  
  Publication
- Structured Asynchrony with Algebraic Effects
  
  Daan Leijen
  
  MSR-TR-2017-21 | May 2017
  
  Publication
- Type Directed Compilation of Row-Typed Algebraic Effects
  
  Daan Leijen
  
  Proceedings of Principles of Programming Languages (POPL'17), Paris, France | January 2017
  
  Publication
- Algebraic Effects for Functional Programming
  
  Daan Leijen
  
  MSR-TR-2016-29 | August 2016
  
  Publication
- Koka: Programming with Row Polymorphic Effect Types
  
  Daan Leijen
  
  Mathematically Structured Functional Programming 2014 | March 2014
  
  Publication Github
- Koka: Programming with Row-Polymorphic Effect Types
  
  Daan Leijen
  
  MSR-TR-2013-79 | August 2013
  
  Published by Microsoft
  
  Publication Github

- Principal Type Inference under a Prefix
  
  Daan Leijen, Wenjia Ye
  
  PLDI'25 | June 2025
  
  A Fresh Look at Static Overloading. See also the accompanying technical report.
  
  Publication
- Principal Type Inference under a Prefix (TR)
  
  Daan Leijen, Wenjia Ye
  
  MSR-TR-2024-34 | September 2024
  
  Published by Microsoft
  
  A Fresh Look at Static Overloading. Updated 2025-05-19, v7. Extended version of the PLDI'25 paper.
  
  Publication
- The Functional Essence of Imperative Binary Search Trees
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra, Sam Lindley
  
  PLDI'24 | June 2024
  
  Publication
- Tail Recursion Modulo Context: An Equational Approach (extended version)
  
  Daan Leijen, Anton Lorenzen
  
  under submission to JFP. | May 2024
  
  This is an extended version of the POPL'23 publication under submission to a special issue of the Journal of Functional Programming (JFP). Extended topics include an improved TRMC algorithm, composing contexts, _field_ contexts, and first-class constructor contexts.
  
  Publication
- Qualified Effect Types — Taming Control-Flow through Linear Effect Handlers
  
  Jonathan Immanuel Brachthäuser, Daan Leijen
  
  MSR-TR-2023-42 | November 2023
  
  Published by Microsoft
  
  This technical report is the result of an internship of Jonathan Brachthäuser at Microsoft Research, Redmond in 2018. While the report is published in 2023, the paper reflects the work at the time of writing.
  
  Publication
- Continuing WebAssembly with Effect Handlers
  
  LUNA PHIPPS-COSTIN, ANDREAS ROSSBERG, ARJUN GUHA, Daan Leijen, DANIEL HILLERSTRÖM, KC SIVARAMAKRISHNAN, MATIJA PRETNAR, SAM LINDLEY
  
  OOPSLA'23 | October 2023
  
  Publication
- FP$^2$: Fully in-Place Functional Programming
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra
  
  ICFP 2023 | September 2023
  
  preprint
  
  Publication
- Exploring Perceus for OCaml
  
  Elton Pinto, Daan Leijen
  
  September 2023
  
  Presented at the "Higher order, Typed, Strict: ML Family Workshop 2023" co-located with ICFP'23.
  
  Publication
- The Functional Essence of Imperative Binary Search Trees
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra, Sam Lindley
  
  MSR-TR-2023-28 | July 2023
  
  Published by Microsoft
  
  v4, Dec 27, 2023 (previously titled "A Functional Correspondence between Top-down and Bottom-up Tree Algorithms") This is an extended version of the PLDI'24 publication.
  
  Publication
- FP^2: Fully in-Place Functional Programming (TR)
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra
  
  MSR-TR-2023-19 | May 2023
  
  Published by Microsoft
  
  Extended version of the ICFP'23 publication
  
  Publication
- Tail Recursion Modulo Context: An Equational Approach
  
  Daan Leijen, Anton Lorenzen
  
  POPL'23 | January 2023
  
  Publication
- Reference counting with frame limited reuse
  
  Anton Lorenzen, Daan Leijen
  
  ICFP'22 | August 2022
  
  Publication
- What About the Integer Numbers? Fast Arithmetic with Tagged Integers — A Plea for Hardware Support
  
  Daan Leijen
  
  MSR-TR-2022-17 | July 2022
  
  Published by Microsoft
  
  Presented at ML language workshop 2022 (co-located with ICFP'22).
  
  Publication
- Tail Recursion Modulo Context — An Equational Approach
  
  Daan Leijen, Anton Lorenzen
  
  MSR-TR-2022-18 | July 2022
  
  Published by Microsoft
  
  Publication
- Reference Counting with Frame Limited Reuse (extended version, v2)
  
  Anton Lorenzen, Daan Leijen
  
  MSR-TR-2021-30 | November 2021
  
  Published by Microsoft
  
  Mar 15, 2022, v2
  
  Publication
- Generalized Evidence Passing for Effect Handlers (or, Efficient Compilation of Effect Handlers to C)
  
  Ningning Xie, Daan Leijen
  
  Proc. ACM Prog. Lang. (ICFP'21) | August 2021, Vol 5(ICFP): pp. 71
  
  doi: 10.1145/3473576
  
  Publication
- Perceus: Garbage Free Reference Counting with Reuse
  
  Alex Reinking*, Ningning Xie*, Leonardo de Moura, Daan Leijen
  
  The 42nd ACM SIGPLAN International Conference on Programming Language Design and Implementation (PLDI ’21) | June 2021
  
  (*) The first two authors contributed equally to this work. Distinguished paper at PLDI'21.
  
  Publication Github
- First-class Named Effect Handlers
  
  Ningning Xie, Youyou Cong, Daan Leijen
  
  MSR-TR-2021-10 | May 2021
  
  Published by Microsoft
  
  Presented at the 8th ACM SIGPLAN Workshop on Higher-Order Programming with Effects (HOPE'21).
  
  Publication
- Generalized Evidence Passing for Effect Handlers (or, Efficient Compilation of Effect Handlers to C) (Extended Version)
  
  Ningning Xie, Daan Leijen
  
  MSR-TR-2021-5 | March 2021
  
  Published by Microsoft
  
  v4, 2021-06-07. Extended version of the ICFP'21 paper.
  
  Publication
- Perceus: Garbage Free Reference Counting with Reuse (Extended version)
  
  Alex Reinking*, Ningning Xie*, Leonardo de Moura, Daan Leijen
  
  MSR-TR-2020-42 | November 2020
  
  Published by Microsoft
  
  (*) The first two authors contributed equally to this work. v4, 2021-06-07. Extended version of the PLDI'21 paper.
  
  Publication Github
- Effect Handlers in Haskell, Evidently
  
  Ningning Xie, Daan Leijen
  
  The 13th ACM SIGPLAN International Haskell Symposium | August 2020
  
  Publication
- Effect Handlers, Evidently
  
  Ningning Xie, Jonathan Brachthauser, Daniel Hillerstrom, Philipp Schuster, Daan Leijen
  
  The 25th ACM SIGPLAN International Conference on Functional Programming (ICFP) | August 2020
  
  Publication
- Effect Handlers, Evidently (Extended Version)
  
  Ningning Xie, Jonathan Brachthauser, Daniel Hillerstrom, Philipp Schuster, Daan Leijen
  
  MSR-TR-2020-23 | July 2020
  
  Published by Microsoft
  
  Extended version of the ICFP'20 article.
  
  Publication
- Structured Asynchrony with Algebraic Effects
  
  Daan Leijen
  
  MSR-TR-2017-21 | May 2017
  
  Publication
- Type Directed Compilation of Row-Typed Algebraic Effects
  
  Daan Leijen
  
  Proceedings of Principles of Programming Languages (POPL'17), Paris, France | January 2017
  
  Publication
- Algebraic Effects for Functional Programming
  
  Daan Leijen
  
  MSR-TR-2016-29 | August 2016
  
  Publication
- Koka: Programming with Row Polymorphic Effect Types
  
  Daan Leijen
  
  Mathematically Structured Functional Programming 2014 | March 2014
  
  Publication Github
- Koka: Programming with Row-Polymorphic Effect Types
  
  Daan Leijen
  
  MSR-TR-2013-79 | August 2013
  
  Published by Microsoft
  
  Publication Github

- Principal Type Inference under a Prefix
  
  Daan Leijen, Wenjia Ye
  
  PLDI'25 | June 2025
  
  A Fresh Look at Static Overloading. See also the accompanying technical report.
  
  Publication
- The Functional Essence of Imperative Binary Search Trees
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra, Sam Lindley
  
  PLDI'24 | June 2024
  
  Publication
- Continuing WebAssembly with Effect Handlers
  
  LUNA PHIPPS-COSTIN, ANDREAS ROSSBERG, ARJUN GUHA, Daan Leijen, DANIEL HILLERSTRÖM, KC SIVARAMAKRISHNAN, MATIJA PRETNAR, SAM LINDLEY
  
  OOPSLA'23 | October 2023
  
  Publication
- FP$^2$: Fully in-Place Functional Programming
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra
  
  ICFP 2023 | September 2023
  
  preprint
  
  Publication
- Tail Recursion Modulo Context: An Equational Approach
  
  Daan Leijen, Anton Lorenzen
  
  POPL'23 | January 2023
  
  Publication
- Reference counting with frame limited reuse
  
  Anton Lorenzen, Daan Leijen
  
  ICFP'22 | August 2022
  
  Publication
- Perceus: Garbage Free Reference Counting with Reuse
  
  Alex Reinking*, Ningning Xie*, Leonardo de Moura, Daan Leijen
  
  The 42nd ACM SIGPLAN International Conference on Programming Language Design and Implementation (PLDI ’21) | June 2021
  
  (*) The first two authors contributed equally to this work. Distinguished paper at PLDI'21.
  
  Publication Github
- Effect Handlers in Haskell, Evidently
  
  Ningning Xie, Daan Leijen
  
  The 13th ACM SIGPLAN International Haskell Symposium | August 2020
  
  Publication
- Effect Handlers, Evidently
  
  Ningning Xie, Jonathan Brachthauser, Daniel Hillerstrom, Philipp Schuster, Daan Leijen
  
  The 25th ACM SIGPLAN International Conference on Functional Programming (ICFP) | August 2020
  
  Publication
- Type Directed Compilation of Row-Typed Algebraic Effects
  
  Daan Leijen
  
  Proceedings of Principles of Programming Languages (POPL'17), Paris, France | January 2017
  
  Publication
- Koka: Programming with Row Polymorphic Effect Types
  
  Daan Leijen
  
  Mathematically Structured Functional Programming 2014 | March 2014
  
  Publication Github
- Principal Type Inference under a Prefix (TR)
  
  Daan Leijen, Wenjia Ye
  
  MSR-TR-2024-34 | September 2024
  
  Published by Microsoft
  
  A Fresh Look at Static Overloading. Updated 2025-05-19, v7. Extended version of the PLDI'25 paper.
  
  Publication
- Qualified Effect Types — Taming Control-Flow through Linear Effect Handlers
  
  Jonathan Immanuel Brachthäuser, Daan Leijen
  
  MSR-TR-2023-42 | November 2023
  
  Published by Microsoft
  
  This technical report is the result of an internship of Jonathan Brachthäuser at Microsoft Research, Redmond in 2018. While the report is published in 2023, the paper reflects the work at the time of writing.
  
  Publication
- The Functional Essence of Imperative Binary Search Trees
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra, Sam Lindley
  
  MSR-TR-2023-28 | July 2023
  
  Published by Microsoft
  
  v4, Dec 27, 2023 (previously titled "A Functional Correspondence between Top-down and Bottom-up Tree Algorithms") This is an extended version of the PLDI'24 publication.
  
  Publication
- FP^2: Fully in-Place Functional Programming (TR)
  
  Anton Lorenzen, Daan Leijen, Wouter Swierstra
  
  MSR-TR-2023-19 | May 2023
  
  Published by Microsoft
  
  Extended version of the ICFP'23 publication
  
  Publication
- What About the Integer Numbers? Fast Arithmetic with Tagged Integers — A Plea for Hardware Support
  
  Daan Leijen
  
  MSR-TR-2022-17 | July 2022
  
  Published by Microsoft
  
  Presented at ML language workshop 2022 (co-located with ICFP'22).
  
  Publication
- Tail Recursion Modulo Context — An Equational Approach
  
  Daan Leijen, Anton Lorenzen
  
  MSR-TR-2022-18 | July 2022
  
  Published by Microsoft
  
  Publication
- Reference Counting with Frame Limited Reuse (extended version, v2)
  
  Anton Lorenzen, Daan Leijen
  
  MSR-TR-2021-30 | November 2021
  
  Published by Microsoft
  
  Mar 15, 2022, v2
  
  Publication
- First-class Named Effect Handlers
  
  Ningning Xie, Youyou Cong, Daan Leijen
  
  MSR-TR-2021-10 | May 2021
  
  Published by Microsoft
  
  Presented at the 8th ACM SIGPLAN Workshop on Higher-Order Programming with Effects (HOPE'21).
  
  Publication
- Generalized Evidence Passing for Effect Handlers (or, Efficient Compilation of Effect Handlers to C) (Extended Version)
  
  Ningning Xie, Daan Leijen
  
  MSR-TR-2021-5 | March 2021
  
  Published by Microsoft
  
  v4, 2021-06-07. Extended version of the ICFP'21 paper.
  
  Publication
- Perceus: Garbage Free Reference Counting with Reuse (Extended version)
  
  Alex Reinking*, Ningning Xie*, Leonardo de Moura, Daan Leijen
  
  MSR-TR-2020-42 | November 2020
  
  Published by Microsoft
  
  (*) The first two authors contributed equally to this work. v4, 2021-06-07. Extended version of the PLDI'21 paper.
  
  Publication Github
- Effect Handlers, Evidently (Extended Version)
  
  Ningning Xie, Jonathan Brachthauser, Daniel Hillerstrom, Philipp Schuster, Daan Leijen
  
  MSR-TR-2020-23 | July 2020
  
  Published by Microsoft
  
  Extended version of the ICFP'20 article.
  
  Publication
- Structured Asynchrony with Algebraic Effects
  
  Daan Leijen
  
  MSR-TR-2017-21 | May 2017
  
  Publication
- Algebraic Effects for Functional Programming
  
  Daan Leijen
  
  MSR-TR-2016-29 | August 2016
  
  Publication
- Koka: Programming with Row-Polymorphic Effect Types
  
  Daan Leijen
  
  MSR-TR-2013-79 | August 2013
  
  Published by Microsoft
  
  Publication Github
- Tail Recursion Modulo Context: An Equational Approach (extended version)
  
  Daan Leijen, Anton Lorenzen
  
  under submission to JFP. | May 2024
  
  This is an extended version of the POPL'23 publication under submission to a special issue of the Journal of Functional Programming (JFP). Extended topics include an improved TRMC algorithm, composing contexts, _field_ contexts, and first-class constructor contexts.
  
  Publication
- Generalized Evidence Passing for Effect Handlers (or, Efficient Compilation of Effect Handlers to C)
  
  Ningning Xie, Daan Leijen
  
  Proc. ACM Prog. Lang. (ICFP'21) | August 2021, Vol 5(ICFP): pp. 71
  
  doi: 10.1145/3473576
  
  Publication
- Exploring Perceus for OCaml
  
  Elton Pinto, Daan Leijen
  
  September 2023
  
  Presented at the "Higher order, Typed, Strict: ML Family Workshop 2023" co-located with ICFP'23.
  
  Publication

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Daan Leijen

Senior Principal Researcher

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