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Uday S. Reddy

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3 papers

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I&C Journal 2002 Journal Article

Objects and Classes in Algol-Like Languages

Uday S. Reddy

Many object-oriented languages used in practice descend from Algol. With this motivation, we study the theoretical issues underlying such languages via the theory of Algol-like languages. It is shown that the basic framework of this theory extends cleanly and elegantly to the concepts of objects and classes. Moreover, a clear correspondence emerges between classes and abstract data types, whose theory corresponds to that of existential types. Equational and Hoare-like reasoning methods and relational parametricity provide powerful formal tools for reasoning about Algol-like object-oriented programs.

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TCS Journal 1999 Journal Article

Objects, interference, and the Yoneda embedding

Peter W. O'Hearn
Uday S. Reddy

We present a new semantics for Algol-like languages that combines methods from two prior lines of development: 1. the object-based approach of Reddy, where the meaning of an imperative program is described in terms of sequences of observable actions, and 2. the functor-category approach initiated by Reynolds, where the varying nature of the run-time stack is explained using functors from a category of store shapes to a category of cpos. The semantics gives an account of both the phemomena of local state and irreversibility of state change. As an indication of the accuracy obtained, we present a full abstraction result for closed terms of second-order type in a language containing active expressions, i. e. value-returning commands.

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IJCAI Conference 1983 Conference Paper

Theory of Linear Equations Applied to Program Transformation

Uday S. Reddy
Barat Jayaraman

In this paper is presented a technique for transforming a class of recursive equations called linear equations into iterative equations. Linear equations are characterized by involving at the most one recursive call for any invocation. In contrast to the conventional techniques, the scheme of program transformation presented here involves finding the solution of the given linear equation and transforming this solution. The solutions of linear equations can always be expressed using a construct called abstract sequence. Two classes of abstract sequence programs are identified: right-associative and left-associative sequence programs. The former are obtained by solving linear equations and the latter correspond to iterative programs. The task of transforming linear recursive programs into iterative programs is thus reduced to the task of transforming right-associative sequence programs into left associative ones. Various transformation rules are developed based on an algebra of functional programs.

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