Catálogo de publicaciones - libros

This paper presents a semantics of self-adjusting computation and proves that the semantics is correct and consistent. The semantics integrates change propagation with the classic idea of memoization to enable reuse of computations under mutation to memory. During evaluation, reuse of a computation via memoization triggers a change propagation that adjusts the reused computation to reflect the mutated memory. Since the semantics combines memoization and change-propagation, it involves both non-determinism and mutation. Our consistency theorem states that the non-determinism is not harmful: any two evaluations of the same program starting at the same state yield the same result. Our correctness theorem states that mutation is not harmful: self-adjusting programs are consistent with purely functional programming. We formalized the semantics and its meta-theory in the LF logical framework and machine-checked the proofs in Twelf.

We propose , a novel approach to the problem of migrating code from a legacy language (such as C) to a new language. We maintain two parallel versions of every source file, one in the legacy language, and one in the new language. Both of these files are fully editable, and the two files are kept automatically in sync so that they have the same semantic meaning and, where possible, have the same comments and layout.

We propose as a means to implement multi-language synchronization. If a file is modified in language A, we produce a new version in language B by translating the file into a non-deterministic description of many ways that it could be encoded in language B and then choosing the version that is closest to the old file in language B.

To demonstrate the feasibility of this approach, we have implemented a translator that can synchronize files written in a straw-man language, Jekyll, with files written in C. Jekyll is a high level functional programming language that has many of the features found in modern programming languages.

The goal of our research project is to establish a type-based method for verification of certain critical properties (such as deadlock- and race-freedom) of operating system kernels. As operating system kernels make heavy use of threads and interrupts, it is important that the method can properly deal with both of the two features. As a first step towards the goal, we formalize a concurrent calculus equipped with primitives for threads and interrupts handling. We also propose a type system that guarantees deadlock-freedom in the presence of interrupts. To our knowledge, ours is the first type system for deadlock-freedom that can deal with both thread and interrupt primitives.

allow types to be refined by predicates written in a general-purpose programming language, and can express function pre- and postconditions and data structure invariants. In this setting, with expressive and possibly verbose types, type reconstruction is particularly valuable, yet typeability is undecidable because it subsumes type checking. Using a generalized notion of type reconstruction, we present the first type reconstruction algorithm for a type system with base types refined by abitrary program terms. Our algorithm is a typeability- transformation and defers type checking to a subsequent phase. The algorithm generates and solves a collection of implication constraints over refinement predicates, inferring maximally precise refinement predicates in a largely syntactic manner that is reminiscent of strongest postcondition calculation. Perhaps surprisingly, our notion of type reconstruction is decidable even though type checking is not.

In this paper, we describe the key principles of a dependent type system for low-level imperative languages. The major contributions of this work are (1) a sound type system that combines dependent types and mutation for variables and for heap-allocated structures in a more flexible way than before and (2) a technique for automatically inferring dependent types for local variables. We have applied these general principles to design Deputy, a dependent type system for C that allows the user to describe bounded pointers and tagged unions. Deputy has been used to annotate and check a number of real-world C programs.