article published yes Fabian Mühlböck author 6395C5F6-89DF-11E9-9C97-6BDFE56974250000-0003-1548-0177 Ross Tate author ToHe department OOPSLA: Object-Oriented Programming, Systems, Languages, and Applications Formal methods for the design and analysis of complex systems project Gradual typing is a principled means for mixing typed and untyped code. But typed and untyped code often exhibit different programming patterns. There is already substantial research investigating gradually giving types to code exhibiting typical untyped patterns, and some research investigating gradually removing types from code exhibiting typical typed patterns. This paper investigates how to extend these established gradual-typing concepts to give formal guarantees not only about how to change types as code evolves but also about how to change such programming patterns as well. In particular, we explore mixing untyped "structural" code with typed "nominal" code in an object-oriented language. But whereas previous work only allowed "nominal" objects to be treated as "structural" objects, we also allow "structural" objects to dynamically acquire certain nominal types, namely interfaces. We present a calculus that supports such "cross-paradigm" code migration and interoperation in a manner satisfying both the static and dynamic gradual guarantees, and demonstrate that the calculus can be implemented efficiently. https://research-explorer.ista.ac.at/download/10153/10154/monnom-oopsla21.pdf application/pdfno https://creativecommons.org/licenses/by-nd/4.0/ Association for Computing Machinery2021Chicago, IL, United States eng gradual typinggradual guaranteenominalstructuralcall tags 2475-142110.1145/3485504 5 F. Mühlböck, R. Tate, Proceedings of the ACM on Programming Languages 5 (2021). Mühlböck, Fabian, and Ross Tate. “Transitioning from Structural to Nominal Code with Efficient Gradual Typing.” <i>Proceedings of the ACM on Programming Languages</i>, vol. 5, 127, Association for Computing Machinery, 2021, doi:<a href="https://doi.org/10.1145/3485504">10.1145/3485504</a>. Mühlböck F, Tate R. 2021. Transitioning from structural to nominal code with efficient gradual typing. Proceedings of the ACM on Programming Languages. 5, 127. Mühlböck, F., &#38; Tate, R. (2021). Transitioning from structural to nominal code with efficient gradual typing. <i>Proceedings of the ACM on Programming Languages</i>. Chicago, IL, United States: Association for Computing Machinery. <a href="https://doi.org/10.1145/3485504">https://doi.org/10.1145/3485504</a> Mühlböck, Fabian, and Ross Tate. “Transitioning from Structural to Nominal Code with Efficient Gradual Typing.” <i>Proceedings of the ACM on Programming Languages</i>. Association for Computing Machinery, 2021. <a href="https://doi.org/10.1145/3485504">https://doi.org/10.1145/3485504</a>. Mühlböck F, Tate R. Transitioning from structural to nominal code with efficient gradual typing. <i>Proceedings of the ACM on Programming Languages</i>. 2021;5. doi:<a href="https://doi.org/10.1145/3485504">10.1145/3485504</a> F. Mühlböck and R. Tate, “Transitioning from structural to nominal code with efficient gradual typing,” <i>Proceedings of the ACM on Programming Languages</i>, vol. 5. Association for Computing Machinery, 2021. 101532021-10-19T12:48:44Z2025-04-15T06:25:55Z