Delimited Control in OCaml, Abstractly and Concretely: System Description

Kiselyov, Oleg

doi:10.1007/978-3-642-12251-4_22

Cited by 16 publications

(11 citation statements)

References 24 publications

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“…Typing power of exceptions vs. continuations. Lillibridge 22 shows that exceptions introduce a typing loophole that can be used to implement unbounded loops in otherwise strongly-normalizing languages, while continuations cannot do this, giving the slogan "Exceptions are strictly more 17 Filinski (1994) 18 Kiselyov (2010) 19 Pettyjohn, Clements, Marshall, Krishnamurthi, and Felleisen (2005) 20 Thiemann (2006) 21 Corona (2014) 22 Lillibridge (1999) powerful than call/cc." As noted by other authors, 23 this argument only concerns the typing of exceptions rather than their execution semantics, and is inapplicable in languages that already have recursion.…”

Section: Related Workmentioning

confidence: 99%

Capturing the future by replaying the past (functional pearl)

Koppel

Scherer

Solar-Lezama

2018

Proc. ACM Program. Lang.

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Delimited continuations are the mother of all monads! So goes the slogan inspired by Filinski's 1994 paper, which showed that delimited continuations can implement any monadic e ect, letting the programmer use an e ect as easily as if it was built into the language. It's a shame that not many languages have delimited continuations.Luckily, exceptions and state are also the mother of all monads! In this Pearl, we show how to implement delimited continuations in terms of exceptions and state, a construction we call thermometer continuations. While traditional implementations of delimited continuations require some way of "capturing" an intermediate state of the computation, the insight of thermometer continuations is to reach this intermediate state by replaying the entire computation from the start, guiding it using a recording so that the same thing happens until the captured point.Along the way, we explain delimited continuations and monadic re ection, show how the Filinski construction lets thermometer continuations express any monadic e ect, share an elegant special-case for nondeterminism, and discuss why our construction is not prevented by theoretical results that exceptions and state cannot macro-express continuations.

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Section: Related Workmentioning

confidence: 99%

Capturing the future by replaying the past (functional pearl)

Koppel

Scherer

Solar-Lezama

2018

Proc. ACM Program. Lang.

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“…They provide an operational semantics and a monadic translation into a pure λ -calculus extended with stacks, as well as an implementation of the monadic effect in Haskell. A direct implementation of delimited control with multiple prompts in OCaml is given by Kiselyov (2010). In addition, Kiselyov et al (2006) give a language that combines both delimited control and dynamic variables, showing that the two effects interact in subtle ways.…”

Section: Examplementioning

confidence: 99%

Delimited control and computational effects

Downen¹,

Ariola²

2014

J. Funct. Prog.

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We give a framework for delimited control with multiple prompts, in the style of Parigot's λ μ-calculus, through a series of incremental extensions by starting with the pure λ -calculus. Each language inherits the semantics and reduction theory of its parent, giving a systematic way to describe each level of control. For each language of interest, we fully characterize its semantics in terms of a reduction semantics, operational semantics, continuation-passing style transform, and abstract machine. Furthermore, the control operations are expressed in terms of fine-grained primitives that can be used to build well-known, higher-level control operators. In order to illustrate the expressive power provided by various languages, we show how other computational effects can be encoded in terms of these control operators.

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“…Lawall & Danvy (1994) show how to use Danvy and Filinski's delimited control operators shift and reset (Danvy & Filinski, 1989, 1990 to perform letand if-insertion in the familiar direct style by effectively hiding trivial uses of continuations as in sgib_c above. Since delimited control operators are available in MetaOCaml (Kiselyov, 2010), we can build a memoizing staged fixpoint combinator y_ms with this technique so that evaluating…”

Section: Delimited Control and Its Risk Of Scope Extrusionmentioning

confidence: 99%

Shifting the stage

Kameyama¹,

Kiselyov²,

Shan³

2011

J. Funct. Prog.

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It is often hard to write programs that are efficient yet reusable. For example, an efficient implementation of Gaussian elimination should be specialized to the structure and known static properties of the input matrix. The most profitable optimizations, such as choosing the best pivoting or memoization, cannot be expected of even an advanced compiler because they are specific to the domain, but expressing these optimizations directly makes for ungainly source code. Instead, a promising and popular way to reconcile efficiency with reusability is for a domain expert to write code generators.Two pillars of this approach are types and effects. Typed multilevel languages such as MetaOCaml ensure safety and early error reporting: a well-typed code generator neither goes wrong nor generates code that goes wrong. Side effects such as state and control ease correctness and expressivity: An effectful generator can resemble the textbook presentation of an algorithm, as is familiar to domain experts, yet insert let for memoization and if for bounds checking, as is necessary for efficiency. Together, types and effects enable structuring code generators as compositions of modules with well-defined interfaces, and hence scaling to large programs. However, blindly adding effects renders multilevel types unsound.We introduce the first multilevel calculus with control effects and a sound type system. We give small-step operational semantics as well as a one-pass continuation-passing-style translation. For soundness, our calculus restricts the code generator's effects to the scope of generated binders. Even with this restriction, we can finally write efficient code generators for dynamic programming and numerical methods in direct style, like in algorithm textbooks, rather than in continuation-passing or monadic style.

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Delimited Control in OCaml, Abstractly and Concretely: System Description

Cited by 16 publications

References 24 publications

Capturing the future by replaying the past (functional pearl)

Capturing the future by replaying the past (functional pearl)

Delimited control and computational effects

Shifting the stage

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