Undergraduate computer science programs have increasingly adopted introductory sequences with multiple entry points in order to accommodate students arriving with varying degrees of prior experience. This paper examines student experiences at the critical stage when multiple introductory tracks merge: the convergence course. We find that students from all tracks arrive with similar levels of enthusiasm and positive attitudes towards collaborative learning. By the end of the convergence course, group differences in self-efficacy and a sense of belonging in the CS community have begun to ease. Importantly, students with the least pre-college CS experience enjoy the most significant gains in self-efficacy. However, curricular techniques intended to integrate these student populations appear insufficient alone to close the achievement gap between these groups, suggesting that alternate approaches may be necessary to supplement.

Assignments determine much of what students actually take away from a course. Sadly, creating successful assignments is difficult and error prone. With that in mind, the Nifty Assignments session is about promoting and sharing successful assignment ideas, and more importantly, making the assignment materials available for others to adopt.

Realizability theory is not just a fundamental tool in logic and computability. It also has direct application to the design and implementation of programs, since it can produce code interfaces for the data structure corresponding to a mathematical theory. Our tool, called RZ, serves as a bridge between the worlds of constructive mathematics and programming. By using the realizability interpretation of constructive mathematics, RZ translates specifications in constructive logic into annotated interface code in Objective Caml. The system supports a rich input language allowing descriptions of complex mathematical structures. RZ does not extract code from proofs, but allows any implementation method, from handwritten code to code extracted from proofs by other tools.

We study the λ ΠΣ S ≤ calculus, which contains singleton types S ( M ) classifying terms of base type provably equivalent to the term M . The system includes dependent types for pairs and functions (Σ and Π) and a subtyping relation induced by regarding singletons as subtypes of the base type. The decidability of type checking for this language is non-obvious, since to type check we must be able to determine equivalence of well-formed terms. But in the presence of singleton types, the provability of an equivalence judgment Γ ⊢ M 1 ≡ M 2 : A can depend both on the typing context Γ and on the particular type A at which M 1 and M 2 are compared.We show how to prove decidability of term equivalence, hence of type checking, in λ ΠΣ S ≤ by exhibiting a type-directed algorithm for directly computing normal forms. The correctness of normalization is shown using an unusual variant of Kripke logical relations organized around sets; rather than defining a logical equivalence relation, we work directly with (subsets of) the corresponding equivalence classes.We then provide a more efficient algorithm for checking type equivalence without constructing normal forms. We also show that type checking, subtyping, and all other judgments of the system are decidable.The λ ΠΣ S ≤ calculus models type constructors and kinds in the intermediate language used by the TILT compiler for Standard ML to implement the SML module system. The decidability of λ ΠΣ S ≤ term equivalence allows us to show decidability of type checking for TILT's intermediate language. We also obtain a consistency result that allows us to prove type safety for the intermediate language. The algorithms derived here form the core of the type checker used for internal type checking in TILT.

Typed object calculi that permit adding new methods to existing objects must address the problem of name clashes: what happens if a new method is added to an object already having one with the same name but a different type? Most systems statically forbid such clashes by restricting the allowable subtypings. In contrast, by reconsidering the runtime meaning of object extension, the object calculus studied in the author's previous work with Jon Riecke allowed any object to be soundly extended with any method of any name, with unrestricted width subtyping. That language permitted a simple encoding of classes as object-generators. Because of width subtyping, subclasses could be typechecked and compiled with little knowledge of the class hierarchy and without any information about superclasses' private components; this made derived classes more robust to changes in the implementations of base classes. However, the system was not well suited for encoding mixins or by-name subtyping of objects.This article addresses those deficiencies by presenting the Calculus of Objects and Indices (COI), a lower-level typed object calculus in which extensible objects are more analogous to tuples than to records. An object is simply a finite sequence of unnamed components referenced by their index in the sequence. Names are then reintroduced by allowing these indices to be first-class values (analogous to pointers to members in C++) that can be bound to variables. Since variables---unlike record labels---freely alpha-vary, difficulties caused by statically undetectable name clashes disappear.By combining COI objects with standard type-theoretic mechanisms, one can encode mixins and classes having the by-name subtyping of languages like C++ or Java but with the robustness of the object-generator encodings. Using records, more standard extensible objects with named components can also be encoded.

Work on the TILT compiler for Standard ML led us to study a language with singleton kinds: S(A) is the kind of all types provably equivalent to the type A. Singletons are interesting because they provide a very general form of definitions for type variables, allow fine-grained control of type computations, and allow many equational constraints to be expressed within the type system.

article Free Access Share on TIL: a type-directed optimizing compiler for ML Authors: D. Tarditi School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PAView Profile , G. Morrisett School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PAView Profile , P. Cheng School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PAView Profile , C. Stone School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PAView Profile , R. Harper School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PAView Profile , P. Lee School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA School of Computer Science, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PAView Profile Authors Info & Claims ACM SIGPLAN NoticesVolume 31Issue 5May 1996 pp 181–192https://doi.org/10.1145/249069.231414Online:01 May 1996Publication History 212citation719DownloadsMetricsTotal Citations212Total Downloads719Last 12 Months39Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF