JEff: objects for effect

Inostroza, Pablo; Storm, Tijs van der

doi:10.1145/3276954.3276955

Cited by 7 publications

(6 citation statements)

References 22 publications

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“…Recent work (Inostroza & van der Storm 2018, Brachthäuser et al 2019, unpublished draft, 7 Zhang & Myers 2019) explores alternative formulations of effect handlers with close connections to object-oriented programming models. We would like to apply our methodology to study the relative expressiveness of these alternative formulations.…”

Section: Conclusion and Further Workmentioning

confidence: 99%

On the expressive power of user-defined effects: Effect handlers, monadic reflection, delimited control

Forster

Kammar²,

Lindley

et al. 2019

J. Funct. Prog.

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We compare the expressive power of three programming abstractions for user-defined computational effects: Plotkin and Pretnar’s effect handlers, Filinski’s monadic reflection, and delimited control. This comparison allows a precise discussion about the relative expressiveness of each programming abstraction. It also demonstrates the sensitivity of the relative expressiveness of user-defined effects to seemingly orthogonal language features. We present three calculi, one per abstraction, extending Levy’s call-by-push-value. For each calculus, we present syntax, operational semantics, a natural type-and-effect system, and, for effect handlers and monadic reflection, a set-theoretic denotational semantics. We establish their basic metatheoretic properties: safety, termination, and, where applicable, soundness and adequacy. Using Felleisen’s notion of a macro translation, we show that these abstractions can macro express each other, and show which translations preserve typeability. We use the adequate finitary set-theoretic denotational semantics for the monadic calculus to show that effect handlers cannot be macro expressed while preserving typeability either by monadic reflection or by delimited control. Our argument fails with simple changes to the type system such as polymorphism and inductive types. We supplement our development with a mechanised Abella formalisation.

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Section: Conclusion and Further Workmentioning

confidence: 99%

On the expressive power of user-defined effects: Effect handlers, monadic reflection, delimited control

Forster

Kammar²,

Lindley

et al. 2019

J. Funct. Prog.

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show abstract

“…More than that, Fig. 2 shows that we can directly map concepts from programming with effect handlers to object-oriented programming-an observation that we made in prior work [6,7,9] and that has been made independently by other researchers in the field [28,60].…”

Section: Effect Handlers and Object-oriented Programmingmentioning

confidence: 85%

What You See Is What You Get: Practical Effect Handlers in Capability-Passing Style

Brachthäuser

2022

Ernst Denert Award for Software Engineering 2020

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Structuring control flow is an essential task almost every programmer faces on a daily basis. At the same time, the control flow of software applications is becoming increasingly complicated, motivating languages to include more and more features like asynchronous programming and generators. Effect handlers are a promising alternative since they can express many of these features as libraries. To bring effect handlers closer to the software engineering practice, we present capability passing as an implementation technique for effect handlers. Capability passing provides the basis for the integration of effect handlers into mainstream object-oriented programming languages and thereby unlocks novel modularization strategies. It also enables programmers to apply lexical reasoning about effects and gives rise to a new form of effect polymorphism. Finally, it paves the path for efficient compilation strategies of control effects.

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“…They are encapsulated and do not appear in the signature. Existing implementations of languages with effect handlers either completely lack a static effect system-this includes Multicore OCaml (Dolan et al, 2014), Eff (Bauer & Pretnar, 2015), embeddings of Eff in OCaml (Kiselyov & Sivaramakrishnan, 2016), and previous versions of Effekt (Brachthäuser & Schuster, 2017;Brachthäuser et al, 2018)-or they do not have sufficient support for effect polymorphism (Kammar et al, 2013;Inostroza & van der Storm, 2018). Languages and libraries with effect systems like Extensible Effects (Kiselyov et al, 2013), Koka (Leijen, 2017c), Links (Hillerström et al, 2017), Frank (Lindley et al, 2017), and Helium (Biernacki et al, 2019) require explicit lifting annotations to encapsulate effects in effectful higher-order functions, like the function mapM above.…”

Section: Effekt -Effect Handlers and Capability Passingmentioning

confidence: 99%

Effekt: Capability-passing style for type- and effect-safe, extensible effect handlers in Scala

Brachthäuser¹,

Schuster²,

Ostermann³

2020

J. Funct. Prog.

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Effect handlers are a promising way to structure effectful programs in a modular way. We present the Scala library Effekt, which is centered around capability passing and implemented in terms of a monad for multi-prompt delimited continuations. Effekt is the first library implementation of effect handlers that supports effect safety and effect polymorphism without resorting to type-level programming. We describe a novel way of achieving effect safety using intersection types and path-dependent types. The effect system of our library design fits well into the programming paradigm of capability passing and is inspired by the effect system of Zhang & Myers (2019, Proc. ACM Program. Lang.3(POPL), 5:1-5:29). Capabilities carry an abstract type member, which represents an individual effect type and reflects the use of the capability on the type level. We represent effect rows as the contravariant intersection of effect types. Handlers introduce capabilities and remove components of the intersection type. Reusing the existing type system of Scala, we get effect subtyping and effect polymorphism for free.

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JEff: objects for effect

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Cited by 7 publications

References 22 publications

On the expressive power of user-defined effects: Effect handlers, monadic reflection, delimited control

On the expressive power of user-defined effects: Effect handlers, monadic reflection, delimited control

What You See Is What You Get: Practical Effect Handlers in Capability-Passing Style

Effekt: Capability-passing style for type- and effect-safe, extensible effect handlers in Scala

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