Toward Semantic Foundations for Program Editors

Omar, Cyrus; Voysey, Ian; Hilton, Michael; Sunshine, Joshua; Goues, Claire Le; Aldrich, Jonathan; Hammer, Matthew A.

doi:10.4230/lipics.snapl.2017.11

Cited by 6 publications

(4 citation statements)

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“…Let us start with an example-driven overview of this paper's approach in Hazel, a live programming environment being developed by Omar et al [2017b]. The Hazel user interface is based roughly on IPython/Jupyter [Pérez and Granger 2007], with a result appearing below each cell that contains an expression, and the Hazel language is tracking toward feature parity with Elm (elm-lang.org) [Czaplicki 2012[Czaplicki , 2018, a popular pure functional programming language similar to "core ML", with which we assume familiarity.…”

Section: Live Programming In Hazelmentioning

confidence: 99%

“…This paper builds directly on the static semantics developed by Omar et al [2017a]. That paper, as well as a subsequent "vision paper" introducing Hazel [Omar et al 2017b], suggested as future work a corresponding dynamic semantics for the purposes of live programming without gaps. Bayne et al [2011] have also extensively argued the value of assigning meaning even to incomplete and erroneous programs.…”

Section: Related and Future Workmentioning

confidence: 99%

“…they internalize the "red underline" that editors commonly display under a type inconsistency). Omar et al [2017b] discuss several ways to determine an incomplete expression from the editor state. When the editor state is a text buffer, error recovery mechanisms might insert holes implicitly [Aho and Peterson 1972;Charles 1991;Graham et al 1979;Kats et al 2009].…”

Section: Introductionmentioning

confidence: 99%

“…has been implemented into the Hazel programming environment being developed by Omar et al [2017b]. In particular, we describe Hazel's novel live context inspector, which combines static type information with hole closure information and interactively presents nested hole closures.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Live functional programming with typed holes

Omar

Voysey

Chugh

et al. 2019

Proc. ACM Program. Lang.

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Live programming environments aim to provide programmers (and sometimes audiences) with continuous feedback about a program's dynamic behavior as it is being edited. The problem is that programming languages typically assign dynamic meaning only to programs that are complete, i.e. syntactically well-formed and free of type errors. Consequently, live feedback presented to the programmer exhibits temporal or perceptive gaps. This paper confronts this "gap problem" from type-theoretic first principles by developing a dynamic semantics for incomplete functional programs, starting from the static semantics for incomplete functional programs developed in recent work on Hazelnut. We model incomplete functional programs as expressions with holes, with empty holes standing for missing expressions or types, and non-empty holes operating as membranes around static and dynamic type inconsistencies. Rather than aborting when evaluation encounters any of these holes as in some existing systems, evaluation proceeds around holes, tracking the closure around each hole instance as it flows through the remainder of the program. Editor services can use the information in these hole closures to help the programmer develop and confirm their mental model of the behavior of the complete portions of the program as they decide how to fill the remaining holes. Hole closures also enable a fill-and-resume operation that avoids the need to restart evaluation after edits that amount to hole filling. Formally, the semantics borrows machinery from both gradual type theory (which supplies the basis for handling unfilled type holes) and contextual modal type theory (which supplies a logical basis for hole closures), combining these and developing additional machinery necessary to continue evaluation past holes while maintaining type safety. We have mechanized the metatheory of the core calculus, called Hazelnut Live, using the Agda proof assistant.We have also implemented these ideas into the Hazel programming environment. The implementation inserts holes automatically, following the Hazelnut edit action calculus, to guarantee that every editor state has some (possibly incomplete) type. Taken together with this paper's type safety property, the result is a proof-of-concept live programming environment where rich dynamic feedback is truly available without gaps, i.e. for every reachable editor state.

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Section: Live Programming In Hazelmentioning

confidence: 99%