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Delimited Dynamic Binding
, 2006
"... Dynamic binding and delimited control are useful together in many settings, including Web applications, database cursors, and mobile code. We examine this pair of language features to show that the semantics of their interaction is ill-defined yet not expressive enough for these uses. We solve this ..."
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Cited by 34 (14 self)
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Dynamic binding and delimited control are useful together in many settings, including Web applications, database cursors, and mobile code. We examine this pair of language features to show that the semantics of their interaction is ill-defined yet not expressive enough for these uses. We solve this open and subtle problem. We formalise a typed language DB+DC that combines a calculus DB of dynamic binding and a calculus DC of delimited control. We argue from theoretical and practical points of view that its semantics should be based on delimited dynamic binding: capturing a delimited continuation closes over part of the dynamic environment, rather than all or none of it; reinstating the captured continuation supplements the dynamic environment, rather than replacing or inheriting it. We introduce a type- and reduction-preserving translation from DB + DC to DC, which proves that delimited control macro-expresses dynamic binding. We use this translation to implement DB + DC in Scheme, OCaml, and Haskell. We extend DB + DC with mutable dynamic variables and a facility to obtain not only the latest binding of a dynamic variable but also older bindings. This facility provides for stack inspection and (more generally) folding over the execution context as an inductive data structure.
Shift to control
- In ACM SIGPLAN Scheme Workshop, Snowbird
, 2004
"... Delimited control operators abound, but their relationships are ill-understood, and it remains unclear which (if any) to consider canon-ical. Although all delimited control operators ever proposed can be implemented using undelimited continuations and mutable state, Gasbichler and Sperber [28] showe ..."
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Cited by 25 (3 self)
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Delimited control operators abound, but their relationships are ill-understood, and it remains unclear which (if any) to consider canon-ical. Although all delimited control operators ever proposed can be implemented using undelimited continuations and mutable state, Gasbichler and Sperber [28] showed that an implementation that does not rely on undelimited continuations can be much more ef-ficient. Unfortunately, they only implemented Felleisen’s control
Delimited Control in OCaml, Abstractly and Concretely System Description
"... Abstract. We describe the first implementation of multi-prompt delimited control operators in OCaml that is direct in that it captures only the needed part of the control stack. The implementation is a library that requires no changes to the OCaml compiler or run-time, so it is perfectly compatible ..."
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Cited by 9 (1 self)
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Abstract. We describe the first implementation of multi-prompt delimited control operators in OCaml that is direct in that it captures only the needed part of the control stack. The implementation is a library that requires no changes to the OCaml compiler or run-time, so it is perfectly compatible with existing OCaml source code and byte-code. The library has been in fruitful practical use for four years. We present the library as an implementation of an abstract machine derived by elaborating the definitional machine. The abstract view lets us distill a minimalistic API, scAPI, sufficient for implementing multiprompt delimited control. We argue that a language system that supports exception and stack-overflow handling supports scAPI. Our library illustrates how to use scAPI to implement multi-prompt delimited control in a typed language. The approach is general and can be used to add multi-prompt delimited control to other existing language systems. 1
A static simulation of dynamic delimited control
- HIGHER-ORDER AND SYMBOLIC COMPUTATION
"... We present a continuation-passing-style (CPS) transformation for some dynamic delimited-control operators, including Felleisen’s control and prompt, that extends a standard call-by-value CPS transformation. Based on this new transformation, we show how Danvy and Filinski’s static delimited-control ..."
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Cited by 7 (0 self)
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We present a continuation-passing-style (CPS) transformation for some dynamic delimited-control operators, including Felleisen’s control and prompt, that extends a standard call-by-value CPS transformation. Based on this new transformation, we show how Danvy and Filinski’s static delimited-control operators shift and reset simulate dynamic operators, allaying in passing some skepticism in the literature about the existence of such a simulation. The new CPS transformation and simulation use recursive delimited continuations to avoid undelimited control and the overhead it incurs in implementation and reasoning.
A Substructural Type System for Delimited Continuations
"... We propose type systems that abstractly interpret small-step rather than big-step operational semantics. We treat an expression or evaluation context as a structure in a linear logic with hypothetical reasoning. Evaluation order is not only regulated by familiar focusing rules in the operational sem ..."
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Cited by 6 (0 self)
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We propose type systems that abstractly interpret small-step rather than big-step operational semantics. We treat an expression or evaluation context as a structure in a linear logic with hypothetical reasoning. Evaluation order is not only regulated by familiar focusing rules in the operational semantics, but also expressed by structural rules in the type system, so the types track control flow more closely. Binding and evaluation contexts are related, but the latter are linear. We use these ideas to build a type system for delimited continuations. It lets control operators change the answer type or act beyond the nearest dynamically-enclosing delimiter, yet needs no extra fields in judgments and arrow types to record answer types. The typing derivation of a directstyle program desugars it into continuation-passing style.
Delimited continuations in operating systems
"... Abstract. Delimited continuations are the meanings of delimited evaluation contexts in programming languages. We show they offer a uniform view of many scenarios that arise in systems programming, such as a request for a system service, an event handler for input/output, a snapshot of a process, a f ..."
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Cited by 3 (0 self)
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Abstract. Delimited continuations are the meanings of delimited evaluation contexts in programming languages. We show they offer a uniform view of many scenarios that arise in systems programming, such as a request for a system service, an event handler for input/output, a snapshot of a process, a file system being read and updated, and a Web page. Explicitly recognizing these uses of delimited continuations helps us design a system of concurrent, isolated transactions where desirable features such as snapshots, undo, copy-on-write, reconciliation, and interposition fall out by default. It also lets us take advantage of efficient implementation techniques from programming-language research. The Zipper File System prototypes these ideas. 1
A Call-by-Name CPS Hierarchy
"... Abstract. The Continuation-Passing-Style (CPS) translation gives semantics to control operators such as exception and first-class continuations. By iterating this translation, Danvy and Filinski obtained a CPS hierarchy, and used it to specify a series of control operators, hierarchical (or layered) ..."
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Abstract. The Continuation-Passing-Style (CPS) translation gives semantics to control operators such as exception and first-class continuations. By iterating this translation, Danvy and Filinski obtained a CPS hierarchy, and used it to specify a series of control operators, hierarchical (or layered) delimited-control operators, We introduce a call-by-name variant of the CPS hierarchy. While most of the work on delimited-control operators is based on call-by-value calculi, call-by-name delimited-control operators are an active target of recent studies. Our strategy for developing such a hierarchy is to use the results for the call-by-value calculi as much as possible. The key tool is Hatcliff and Danvy’s factorization of Plotkin’s call-by-name CPS translation into a thunk translation and a call-by-value CPS translation. We show that a call-by-name CPS hierarchy can be obtained by naturally extending the factorization to the calculi with control operators, and then prove several properties for this hierarchy. 1
Abstract Oleg Kiselyov
"... Dynamic binding and delimited control are useful together in many settings, including Web applications, database cursors, and mobile code. We examine this pair of language features to show that the semantics of their interaction is ill-defined yet not expressive enough for these uses. We solve this ..."
Abstract
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Dynamic binding and delimited control are useful together in many settings, including Web applications, database cursors, and mobile code. We examine this pair of language features to show that the semantics of their interaction is ill-defined yet not expressive enough for these uses. We solve this open and subtle problem. We formalise a typed language DB+DC that combines a calculus DB of dynamic binding and a calculus DC of delimited control. We argue from theoretical and practical points of view that its semantics should be based on delimited dynamic binding: capturing a delimited continuation closes over part of the dynamic environment, rather than all or none of it; reinstating the captured continuation supplements the dynamic environment, rather than replacing or inheriting it. We introduce a type- and reduction-preserving translation from DB + DC to DC, which proves that delimited control macro-expresses dynamic binding. We use this translation to implement DB + DC in Scheme, OCaml, and Haskell. We extend DB + DC with mutable dynamic variables and a facility to obtain not only the latest binding of a dynamic variable but also older bindings. This facility provides for stack inspection and (more generally) folding over the execution context as an inductive data structure.
