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Eric Seidel on Diagnosing Type Errors
Static type systems are a powerful tool for reasoning about our programs. Unfortunately, the global inference found in languages like Haskell and OCaml can lead to confusing error messages, especially for newcomers who have yet to internalize the type system. In this talk, we will present two complementary techniques to help diagnose type errors. First, we will take inspiration from the success of property-based testing techniques, and search for a witness to the type error, i.e. a set of inputs that would lead to a type error at runtime. Armed with a witness, we present an interactive trace of the ill-typed program, demonstrating concretely why it is wrong. Second, we will apply machine learning to the problem of type error localization, i.e. which of the many sub-expressions is the source of the error? Using past student mistakes, we will construct a model of where errors are most likely to be found, and will use this model to produce a ranked-list of likely error locations in new programs.

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    The NY Haskell Users Group is for all programmers either interested in or experienced with the Haskell programming language. We want to build a community of Haskell developers in the New York area that can share knowledge, projects, and experience, and to generally foster and encourage strongly typed functional programming, in all languages, all settings, and all industries. Our events center around talks, but we have also hosted social hours, code workshops, and a hackathon. Regular meetings are on the fourth wednesday of each month.

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