Relating Functional and Imperative Session Types

Saffrich, Hannes; Thiemann, Peter

doi:10.1007/978-3-030-78142-2_4

Cited by 2 publications

(2 citation statements)

References 25 publications

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“…In this paper we omit choice and recursion from session types because these features are straightforward to add and our results extend seamlessly. Compared to the conference version of this paper [ST21b], we added more explanations, we incorporated full rule sets and proofs, and we made the Agda proof script for Proposition 4.1 (translation preserves typing) available as a supplement [ST21a].…”

Section: Contributionsmentioning

confidence: 99%

Relating Functional and Imperative Session Types

Saffrich¹,

Thiemann²

2022

Logical Methods in Computer Science

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Imperative session types provide an imperative interface to session-typed communication. In such an interface, channel references are first-class objects with operations that change the typestate of the channel. Compared to functional session type APIs, the program structure is simpler at the surface, but typestate is required to model the current state of communication throughout. Following an early work that explored the imperative approach, a significant body of work on session types has neglected the imperative approach and opts for a functional approach that uses linear types to manage channel references soundly. We demonstrate that the functional approach subsumes the early work on imperative session types by exhibiting a typing and semantics preserving translation into a system of linear functional session types. We further show that the untyped backwards translation from the functional to the imperative calculus is semantics preserving. We restrict the type system of the functional calculus such that the backwards translation becomes type preserving. Thus, we precisely capture the difference in expressiveness of the two calculi and conclude that the lack of expressiveness in the imperative calculus is largely due to restrictions imposed by its type system.

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Section: Contributionsmentioning

confidence: 99%

Relating Functional and Imperative Session Types

Saffrich¹,

Thiemann²

2022

Logical Methods in Computer Science

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“…Another tangential study of type-preserving ANF appears in the work of Saffrich & Thiemann (2020), which use ANF as part of a proof to show that imperative session types are subsumed by a functional session types API. The correctness and type-preservation of ANF translation is similarly considered trivial in the text since ANF does not affect typing, although they provide a detailed proof of type preservation in the appendix.…”

Section: Non-dependently Typed Anf Translationmentioning

confidence: 99%

ANF preserves dependent types up to extensional equality

Koronkevich¹,

RAKOW²,

Ahmed³

et al. 2022

J. Funct. Prog.

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Many programmers use dependently typed languages such as Coq to machine-verify high-assurance software. However, existing compilers for these languages provide no guarantees after compiling, nor when linking after compilation. Type-preserving compilers preserve guarantees encoded in types and then use type checking to verify compiled code and ensure safe linking with external code. Unfortunately, standard compiler passes do not preserve the dependent typing of commonly used (intensional) type theories. This is because assumptions valid in simpler type systems no longer hold, and intensional dependent type systems are highly sensitive to syntactic changes, including compilation. We develop an A-normal form (ANF) translation with join-point optimization—a standard translation for making control flow explicit in functional languages—from the Extended Calculus of Constructions (ECC) with dependent elimination of booleans and natural numbers (a representative subset of Coq). Our dependently typed target language has equality reflection, allowing the type system to encode semantic equality of terms. This is key to proving type preservation and correctness of separate compilation for this translation. This is the first ANF translation for dependent types. Unlike related translations, it supports the universe hierarchy, and does not rely on parametricity or impredicativity.

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Relating Functional and Imperative Session Types

Cited by 2 publications

References 25 publications

Relating Functional and Imperative Session Types

Relating Functional and Imperative Session Types

ANF preserves dependent types up to extensional equality

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