arXiv subjects

Paul Tarau

Publications and source records attributed to Paul Tarau.

41 records · Page 3Linked to original sources

arXiv2008

Ranking and Unranking of Hereditarily Finite Functions and Permutations

Prolog's ability to return multiple answers on backtracking provides an elegant mechanism to derive reversible encodings of combinatorial objects as Natural Numbers i.e. {\em ranking} and {\em unranking} functions. Starting from a generalization of Ackerman's encoding of Hereditarily Finite Sets with Urelements and a novel tupling/untupling operation, we derive encodings for Finite Functions and use them as building blocks for an executable theory of {\em Hereditarily Finite Functions}. The more difficult problem of {\em ranking} and {\em unranking} {\em Hereditarily Finite Permutations} is then tackled using Lehmer codes and factoradics. The paper is organized as a self-contained literate Prolog program available at \url{http://logic.csci.unt.edu/tarau/research/2008/pHFF.zip}

cs.LO↗

arXiv2008

Logic Engines as Interactors

We introduce a new programming language construct, Interactors, supporting the agent-oriented view that programming is a dialog between simple, self-contained, autonomous building blocks. We define Interactors as an abstraction of answer generation and refinement in Logic Engines resulting in expressive language extension and metaprogramming patterns, including emulation of Prolog's dynamic database. A mapping between backtracking based answer generation in the callee and "forward" recursion in the caller enables interaction between different branches of the callee's search process and provides simplified design patterns for algorithms involving combinatorial generation and infinite answer streams. Interactors extend language constructs like Ruby, Python and C#'s multiple coroutining block returns through yield statements and they can emulate the action of monadic constructs and catamorphisms in functional languages. Keywords: generalized iterators, logic engines, agent oriented programming language constructs, interoperation with stateful objects, metaprogramming

cs.PL↗

arXiv2008

A Logic Programming Framework for Combinational Circuit Synthesis

Logic Programming languages and combinational circuit synthesis tools share a common "combinatorial search over logic formulae" background. This paper attempts to reconnect the two fields with a fresh look at Prolog encodings for the combinatorial objects involved in circuit synthesis. While benefiting from Prolog's fast unification algorithm and built-in backtracking mechanism, efficiency of our search algorithm is ensured by using parallel bitstring operations together with logic variable equality propagation, as a mapping mechanism from primary inputs to the leaves of candidate Leaf-DAGs implementing a combinational circuit specification. After an exhaustive expressiveness comparison of various minimal libraries, a surprising first-runner, Strict Boolean Inequality "<" together with constant function "1" also turns out to have small transistor-count implementations, competitive to NAND-only or NOR-only libraries. As a practical outcome, a more realistic circuit synthesizer is implemented that combines rewriting-based simplification of (<,1) circuits with exhaustive Leaf-DAG circuit search. Keywords: logic programming and circuit design, combinatorial object generation, exact combinational circuit synthesis, universal boolean logic libraries, symbolic rewriting, minimal transistor-count circuit synthesis

cs.LO↗

arXiv2004

High-Level Networking With Mobile Code And First Order AND-Continuations

We describe a scheme for moving living code between a set of distributed processes coordinated with unification based Linda operations, and its application to building a comprehensive Logic programming based Internet programming framework. Mobile threads are implemented by capturing first order continuations in a compact data structure sent over the network. Code is fetched lazily from its original base turned into a server as the continuation executes at the remote site. Our code migration techniques, in combination with a dynamic recompilation scheme, ensure that heavily used code moves up smoothly on a speed hierarchy while volatile dynamic code is kept in a quickly updatable form. Among the examples, we describe how to build programmable client and server components (Web servers, in particular) and mobile agents.

cs.PL↗

arXiv1995

Treating Coordination with Datalog Grammars

In previous work we studied a new type of DCGs, Datalog grammars, which are inspired on database theory. Their efficiency was shown to be better than that of their DCG counterparts under (terminating) OLDT-resolution. In this article we motivate a variant of Datalog grammars which allows us a meta-grammatical treatment of coordination. This treatment improves in some respects over previous work on coordination in logic grammars, although more research is needed for testing it in other respects.

cmp-lg↗