Extending Dylan's type system for better type inference and error detection

Hannes Mehnert

    Research output: Conference Article in Proceeding or Book/Report chapterArticle in proceedingsResearchpeer-review


    Whereas dynamic typing enables rapid prototyping and easy experimentation, static typing provides early error detection and better compile time optimization. Gradual typing [26] provides the best of both worlds. This paper shows how to define and implement gradual typing in Dylan, traditionally a dynamically typed language. Dylan poses several special challenges for gradual typing, such as multiple return values, variable-arity methods and generic functions (multiple dispatch).

    In this paper Dylan is extended with function types and parametric polymorphism. We implemented the type system and aunification-based type inference algorithm in the mainstream Dylan compiler. As case study we use the Dylan standard library (roughly 32000 lines of code), which witnesses that the implementation generates faster code with fewer errors. Some previously undiscovered errors in the Dylan library were revealed.
    Original languageEnglish
    Title of host publicationILC '10 Proceedings of the 2010 international conference on Lisp
    Number of pages10
    Place of PublicationReno/Tahoe, Nevada, USA
    PublisherAssociation for Computing Machinery
    Publication date2010
    ISBN (Print)978-1-4503-0470-2
    Publication statusPublished - 2010


    • dynamic typing
    • static typing
    • gradual typing
    • Dylan programming language
    • parametric polymorphism
    • type inference
    • type system
    • multiple dispatch
    • unification-based algorithm
    • compiler optimization


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