Type classes, first proposed during the design of the Haskell programming language, extend standard type systems to support overloaded functions. Since their introduction, type classes have been used to address a range of problems, from typing ordering and arithmetic operators to describing heterogeneous lists and limited subtyping. However, while type class programming is useful for a variety of practical problems, its wider use is limited by the inexpressiveness and hidden complexity of current mechanisms. We propose two improvements to existing class systems. First, we introduce several novel language features, instance chains and explicit failure, that increase the expressiveness of type classes while providing more direct expression of current idioms. To validate these features, we have built an implementation of these features, demonstrating their use in a practical setting and their integration with type reconstruction for a Hindley-Milner type system. Second, we define a set-based semantics for type classes that provides a sound basis for reasoning about type class systems, their implementations, and the meanings of programs that use them.

We often want a compiler to generate executable code that runs as fast as possible. One consideration toward this goal is to keep values in fast registers to limit the number of slower memory accesses that occur. When there are not enough physical registers available for use, values are ``spilled'' to the runtime stack. The need for spills is discovered during register allocation wherein values in use are mapped to physical registers. One factor in the efficacy of register allocation is the number of values in use at one time (register collisions). Register collision is affected by compiler optimizations that take place before register allocation. Though the main purpose of compiler optimizations is to make the overall code better and faster, some optimizations can actually increase register collisions. This may force the register allocation process to spill. This thesis studies the effects of different compiler optimizations on register collisions.

This thesis presents a tool for SPEcification based teSTing (SPEST). SPEST is designed to use well known practices for automated black-box testing to reduce the burden of testing on developers. The tool uses a simple formal specification language to generate highly-readable unit tests that embody best practices for thorough software testing. Because the specification language used to generate the assertions about the code can be compiled, it can also be used to ensure that documentation describing the code is maintained during development and refactoring. The utility and effectiveness of SPEST were validated through several exper- iments conducted with students in undergraduate software engineering classes. The first experiment compared the understandability and efficiency of SPEST generated tests against student written tests based on the Java Modeling Lan- guage (JML)[25] specifications. JML is a widely used language for behavior program specification. A second experiment evaluated readability through a sur- vey comparing SPEST generated tests against tests written by well established software developers. The results from the experiments showed that SPEST’s specification language is at least understandable as JML, SPEST’s specification language is more readable than JML, and strongly suggest that SPEST is capable of reducing the effort required to produce effective tests.

Rust is a relatively new programming language with a unique memory model designed to provide the ease of use of a high-level language as well as the power and control of a low-level language while preserving memory safety. In order to prove the safety and correctness of Rust and to provide analysis tools for its use cases, it is necessary to construct a formal semantics of the language. Existing efforts to construct such a semantic model are limited in their scope and none to date have successfully captured the complete functionality of the language. This thesis focuses on the K-Rust implementation, which is implemented in a rewrite-based semantic framework called K, and expands it to include a larger subset of the Rust language. The K framework allows Rust programs to be executed by the defined semantic model, and the implementation is tested with several Rust programs by comparing the results of execution to the Rust compiler itself.

WebAssembly is an instruction set designed for a stack based virtual machine, with an emphasis on speed, portability and security. As the use cases for WebAssembly grow, so does the desire to target WebAssembly in compilation. In this thesis we present Rasm, a Racket to WebAssembly compiler that compiles a select subset of the top forms of the Racket programming language to WebAssembly. We also present our early findings in our work towards adding a WebAssembly backend to the Chez Scheme compiler that is the backend of Racket. We address initial concerns and roadblocks in adopting a WebAssembly backend and propose potential solutions and patterns to address these concerns. Our work is the first serious effort to compile Racket to WebAssembly, and we believe it will serve as a good aid in future efforts of compiling high-level languages to WebAssembly.

The study of programming languages is a rich field within computer science, incorporating both the abstract theoretical portions of computer science and the platform specific details. Topics studied in programming languages, chiefly compilers or interpreters, are permanent fixtures in programming that students will interact with throughout their career. These systems are, however, considerably complicated, as they must cover a wide range of functionality in order to enable languages to be created and run. The process of educating students thus requires that the demanding workload of creating one of the systems be balanced against the time and resources present in a university classroom setting. Systems building upon these fundamental systems can become out of reach when the number of preceding concepts and thus classes are taken into account. Among these is the study of just-in-time (JIT) compilers, which marry the processes of interpreters and compilers for the purposes of a flexible and fast runtime. The purpose of this thesis is to present JITed, a framework within which JIT compilers can be developed with a time commitment and workload befitting of a classroom setting, specifically one as short as ten weeks. A JIT compiler requires the development of both an interpreter and a compiler. This poses a problem, as classes teaching compilers and interpreters typically feature the construction of one of those systems as their term project. This makes the construction of both within the same time span as is usually allotted for a single system infeasible. To remedy this, JITed features a prebuilt interpreter, that provides the runtime environment necessary for the compiler portion of a JIT compiler to be built. JITed includes an interface for students to provide both their own compiler and the functionality to determine which portions of code should be compiled. The framework allows for important concepts of both compilers in general and JIT compilers to be taught in a reasonable timeframe.

Due to the difficulty of obtaining formal proofs, there is increasing interest in partially or completely automating proof search in interactive theorem provers. Despite being a theorem prover with an active community and plentiful corpus of 170,000+ theorems, no deep learning system currently exists to help automate theorem proving in ACL2. We have developed a machine learning system that generates recommendations to automatically complete proofs. We show that our system benefits from the copy mechanism introduced in the context of program repair. We make our system directly accessible from within ACL2 and use this interface to evaluate our system in a realistic theorem proving environment.

Racket is a modern, general-purpose programming language with a language-oriented focus. To date, Racket has found notable uses in research and education, among other applications. To expand the reach of the language, there has been a desire to develop an efficient platform for running Racket in a web-based environment. WebAssembly (Wasm) is a binary executable format for a stack-based virtual machine designed to provide a fast, efficient, and secure execution environment for code on the web. Wasm is primarily intended to be a compiler target for higher-level languages. Providing Wasm support for the Racket project may be a promising way to bring Racket to the browser. To this end, we present an incremental approach to the development of a Racket- to-Wasm compiler. We make use of an existing backend for Racket that targets a portable bytecode known as PB, along with the associated PB interpreter. We per- form an ahead-of-time static translation of sections of PB into native Wasm, linking the chunks back to the interpreter before execution. By replacing portions of PB with native Wasm, we can eliminate some portion of interpretation overhead and move closer to native Wasm support for Chez Scheme (Racket’s Backend). Due to the use of an existing backend and interpreter, our approach already supports nearly all features of the Racket language – including delimited continuations, tail-calling behavior, and garbage collection – and excluding threading and FFI support for the time being. We perform benchmarks against a baseline to validate our approach, to promising results.

Software design continues to evolve from the structured programming paradigm of the 1970s and 1980s and the object-oriented programming (OOP) paradigm of the 1980s and 1990s. The functional decomposition design methodology used in these paradigms reduced the prominence of non-functional requirements, which resulted in scattered and tangled code to address non-functional elements. Aspect-oriented programming (AOP) allowed the removal of crosscutting concerns scattered throughout class code into single modules known as aspects. Aspectization resulted in increased modularity in class code, but introduced new types of problems that did not exist in OOP. One such problem was aspect interference, in which aspects meddled with the data flow or control flow of a program. Research has developed various solutions for detecting and addressing aspect interference using formal design and specification methods, and by programming techniques that specify aspect precedence. Such explicit specifications required practitioners to have a complete understanding of possible aspect interference in an AOP system under development. However, as system size increased, understanding of possible aspect interference could decrease. Therefore, practitioners needed a way to increase their understanding of possible aspect interference within a program. This study used clustering analysis to locate potential aspect interference within an aspect-oriented program under development, using k-means partitional clustering. Vector space models, using two newly defined metrics, interference potential (IP) and interference causality potential (ICP), and an existing metric, coupling on advice execution (CAE), provided input to the clustering algorithms. Resulting clusters were analyzed via an internal strategy using the R-Squared, Dunn, Davies-Bouldin, and SD indexes. The process was evaluated on both a smaller scale AOP system (AspectTetris), and a larger scale AOP system (AJHotDraw). By seeding potential interference problems into these programs and comparing results using visualizations, this study found that clustering analysis provided a viable way for detecting interference problems in aspect-oriented software. The ICP model was best at detecting interference problems, while the IP model produced results that were more sporadic. The CAE clustering models were not effective in pinpointing potential aspect interference problems. This was the first known study to use clustering analysis techniques specifically for locating aspect interference.

Mobile devices connected to cloud based services are becoming a mainstream method of delivery up-to-date and context aware information to users. Connecting mobile applications to cloud service require significant developer effort. Yet this communication code usually follows certain patterns, varying accordingly to the specific type of data sent and received from the server. By analyzing the causes of theses variations, we can create a system that can automate the code creation for communication from a mobile device to a cloud server. To automate code creation, a general pattern must extracted. This general solution can then be applied to any database configuration. Automating this process frees up valuable development time, allowing developers to make other parts of the application and/or backend service a better experience for the end user.