3 Search Results for "Liu, Fengyun"


Document
Artifact
Scala with Explicit Nulls (Artifact)

Authors: Abel Nieto, Yaoyu Zhao, Ondřej Lhoták, Angela Chang, and Justin Pu

Published in: DARTS, Volume 6, Issue 2, Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020)


Abstract
This artifact is a companion to the paper "Scala with Explicit Nulls", where we present a modification to the Scala type system that makes nullability explicit in the types. Specifically, we make reference types non-nullable by default, while still allowing for nullable types via union types. The artifact contains an implementation of this new type system design as a fork of the Dotty (Scala 3) compiler. Additionally, the artifact contains the source code of multiple Scala libraries that we used to evaluate our design.

Cite as

Abel Nieto, Yaoyu Zhao, Ondřej Lhoták, Angela Chang, and Justin Pu. Scala with Explicit Nulls (Artifact). In Special Issue of the 34th European Conference on Object-Oriented Programming (ECOOP 2020). Dagstuhl Artifacts Series (DARTS), Volume 6, Issue 2, pp. 14:1-14:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


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@Article{nieto_et_al:DARTS.6.2.14,
  author =	{Nieto, Abel and Zhao, Yaoyu and Lhot\'{a}k, Ond\v{r}ej and Chang, Angela and Pu, Justin},
  title =	{{Scala with Explicit Nulls (Artifact)}},
  pages =	{14:1--14:2},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2020},
  volume =	{6},
  number =	{2},
  editor =	{Nieto, Abel and Zhao, Yaoyu and Lhot\'{a}k, Ond\v{r}ej and Chang, Angela and Pu, Justin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DARTS.6.2.14},
  URN =		{urn:nbn:de:0030-drops-132117},
  doi =		{10.4230/DARTS.6.2.14},
  annote =	{Keywords: Scala, Java, nullability, language interoperability, type systems}
}
Document
Scala with Explicit Nulls

Authors: Abel Nieto, Yaoyu Zhao, Ondřej Lhoták, Angela Chang, and Justin Pu

Published in: LIPIcs, Volume 166, 34th European Conference on Object-Oriented Programming (ECOOP 2020)


Abstract
The Scala programming language makes all reference types implicitly nullable. This is a problem, because null references do not support most operations that do make sense on regular objects, leading to runtime errors. In this paper, we present a modification to the Scala type system that makes nullability explicit in the types. Specifically, we make reference types non-nullable by default, while still allowing for nullable types via union types. We have implemented this design for explicit nulls as a fork of the Dotty (Scala 3) compiler. We evaluate our scheme by migrating a number of Scala libraries to use explicit nulls. Finally, we give a denotational semantics of type nullification, the interoperability layer between Java and Scala with explicit nulls. We show a soundness theorem stating that, for variants of System F_ω that model Java and Scala, nullification preserves values of types.

Cite as

Abel Nieto, Yaoyu Zhao, Ondřej Lhoták, Angela Chang, and Justin Pu. Scala with Explicit Nulls. In 34th European Conference on Object-Oriented Programming (ECOOP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 166, pp. 25:1-25:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


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@InProceedings{nieto_et_al:LIPIcs.ECOOP.2020.25,
  author =	{Nieto, Abel and Zhao, Yaoyu and Lhot\'{a}k, Ond\v{r}ej and Chang, Angela and Pu, Justin},
  title =	{{Scala with Explicit Nulls}},
  booktitle =	{34th European Conference on Object-Oriented Programming (ECOOP 2020)},
  pages =	{25:1--25:26},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-154-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{166},
  editor =	{Hirschfeld, Robert and Pape, Tobias},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2020.25},
  URN =		{urn:nbn:de:0030-drops-131821},
  doi =		{10.4230/LIPIcs.ECOOP.2020.25},
  annote =	{Keywords: Scala, Java, nullability, language interoperability, type systems}
}
Document
Theory and Practice of Coroutines with Snapshots

Authors: Aleksandar Prokopec and Fengyun Liu

Published in: LIPIcs, Volume 109, 32nd European Conference on Object-Oriented Programming (ECOOP 2018)


Abstract
While event-driven programming is a widespread model for asynchronous computing, its inherent control flow fragmentation makes event-driven programs notoriously difficult to understand and maintain. Coroutines are a general control flow construct that can eliminate control flow fragmentation. However, coroutines are still missing in many popular languages. This gap is partly caused by the difficulties of supporting suspendable computations in the language runtime. We introduce first-class, type-safe, stackful coroutines with snapshots, which unify many variants of suspendable computing. Our design relies solely on the static metaprogramming support of the host language, without modifying the language implementation or the runtime. We also develop a formal model for type-safe, stackful and delimited coroutines, and we prove the respective safety properties. We show that the model is sufficiently general to express iterators, single-assignment variables, async-await, actors, event streams, backtracking, symmetric coroutines and continuations. Performance evaluations reveal that the proposed metaprogramming-based approach has a decent performance, with workload-dependent overheads of 1.03-2.11 x compared to equivalent manually written code, and improvements of up to 6 x compared to other approaches.

Cite as

Aleksandar Prokopec and Fengyun Liu. Theory and Practice of Coroutines with Snapshots. In 32nd European Conference on Object-Oriented Programming (ECOOP 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 109, pp. 3:1-3:32, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)


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@InProceedings{prokopec_et_al:LIPIcs.ECOOP.2018.3,
  author =	{Prokopec, Aleksandar and Liu, Fengyun},
  title =	{{Theory and Practice of Coroutines with Snapshots}},
  booktitle =	{32nd European Conference on Object-Oriented Programming (ECOOP 2018)},
  pages =	{3:1--3:32},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-079-8},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{109},
  editor =	{Millstein, Todd},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2018.3},
  URN =		{urn:nbn:de:0030-drops-92087},
  doi =		{10.4230/LIPIcs.ECOOP.2018.3},
  annote =	{Keywords: coroutines, continuations, coroutine snapshots, asynchronous programming, inversion of control, event-driven programming}
}
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