Gradual Program Analysis

Dataflow analysis and gradual typing are both well-studied methods to gain information about computer programs in a finite amount of time. The gradual program analysis project seeks to combine those two techniques in order to gain the benefits of both. This thesis explores the background information necessary to understand gradual program analysis, and then briefly discusses the research itself, with reference to publication of work done so far. The background topics include essential aspects of programming language theory, such as syntax, semantics, and static typing; dataflow analysis concepts, such as abstract interpretation, semilattices, and fixpoint computations; and gradual typing theory, such as the concept of an unknown type, liftings of predicates, and liftings of functions

Static Typing of Complex Presence Constraints in Interfaces

Many functions in libraries and APIs have the notion of optional parameters, which can be mapped onto optional properties of an object representing those parameters. The fact that properties are optional opens up the possibility for APIs and libraries to design a complex "dependency logic" between properties: for example, some properties may be mutually exclusive, some properties may depend on others, etc. Existing type systems are not strong enough to express such dependency logic, which can lead to the creation of invalid objects and accidental usage of absent properties. In this paper we propose TypeScriptIPC: a variant of TypeScript with a novel type system that enables programmers to express complex presence constraints on properties. We prove that it is sound with respect to enforcing complex dependency logic defined by the programmer when an object is created, modified or accessed

Static Typing of Complex Presence Constraints in Interfaces (Artifact)

This artifact is based on TypeScriptIPC, a statically typed programming language with interfaces in which complex presence constraints can be defined. This enables developers to express inter-property constraints on interface properties. The need for these inter-property constraints stems from web APIs, which often impose a complex "dependency logic" between properties. For example, some properties may be mutually exclusive, or the presence of a property may depend on the presence of others, etc. TypeScriptIPC is a variant of TypeScript, in which interfaces are extended to express constraints over multiple properties, using propositional logic. This artifact contains documentation on how to build and run TypeScriptIPC, such that the code snippets from the paper can be run

Dynamically typed languages

Dynamically typed languages such as Python and Ruby have experienced a rapid grown in popularity in recent times. However, there is much confusion as to what makes these languages interesting relative to statically typed languages, and little knowledge of their rich history. In this chapter I explore the general topic of dynamically typed languages, how they differ from statically typed languages, their history, and their defining features

An Algorithm for Inferring Quasi-Static Types

This report presents an algorithm, and its implementation, for doing type inference in the context of Quasi-Static Typing (QST) ["Quasy-static Typing." Satish Thatte Proc. ACM Symp. on Principles of Programming Languages, 1988]. The package infers types a la "QST" for the simply typed λ-calculus.CONACyT (54716

Gradual Certified Programming in Coq

Expressive static typing disciplines are a powerful way to achieve high-quality software. However, the adoption cost of such techniques should not be under-estimated. Just like gradual typing allows for a smooth transition from dynamically-typed to statically-typed programs, it seems desirable to support a gradual path to certified programming. We explore gradual certified programming in Coq, providing the possibility to postpone the proofs of selected properties, and to check "at runtime" whether the properties actually hold. Casts can be integrated with the implicit coercion mechanism of Coq to support implicit cast insertion a la gradual typing. Additionally, when extracting Coq functions to mainstream languages, our encoding of casts supports lifting assumed properties into runtime checks. Much to our surprise, it is not necessary to extend Coq in any way to support gradual certified programming. A simple mix of type classes and axioms makes it possible to bring gradual certified programming to Coq in a straightforward manner.Comment: DLS'15 final version, Proceedings of the ACM Dynamic Languages Symposium (DLS 2015