4,210 research outputs found
Conjoined Events
Many existing synchronous message-passing systems support
choice: engaging in one event XOR another. This paper introduces the AND operator that allows a process to engage in multiple
events together (one AND one more AND another; all conjoined),
engaging in each event only if it can atomically engage in all the
conjoined events. We demonstrate using several examples that this
operator supports new, more ?exible models of programming. We
show that the AND operator allows the behaviour of processes to
be expressed in local rules rather than system-wide constructs. We
give an optimised implementation of the AND operator and explore
the performance effect on standard communications of supporting
this new operator
Left Recursion in Parsing Expression Grammars
Parsing Expression Grammars (PEGs) are a formalism that can describe all
deterministic context-free languages through a set of rules that specify a
top-down parser for some language. PEGs are easy to use, and there are
efficient implementations of PEG libraries in several programming languages.
A frequently missed feature of PEGs is left recursion, which is commonly used
in Context-Free Grammars (CFGs) to encode left-associative operations. We
present a simple conservative extension to the semantics of PEGs that gives
useful meaning to direct and indirect left-recursive rules, and show that our
extensions make it easy to express left-recursive idioms from CFGs in PEGs,
with similar results. We prove the conservativeness of these extensions, and
also prove that they work with any left-recursive PEG.
PEGs can also be compiled to programs in a low-level parsing machine. We
present an extension to the semantics of the operations of this parsing machine
that let it interpret left-recursive PEGs, and prove that this extension is
correct with regards to our semantics for left-recursive PEGs.Comment: Extended version of the paper "Left Recursion in Parsing Expression
Grammars", that was published on 2012 Brazilian Symposium on Programming
Language
A Linear Logic Programming Language for Concurrent Programming over Graph Structures
We have designed a new logic programming language called LM (Linear Meld) for
programming graph-based algorithms in a declarative fashion. Our language is
based on linear logic, an expressive logical system where logical facts can be
consumed. Because LM integrates both classical and linear logic, LM tends to be
more expressive than other logic programming languages. LM programs are
naturally concurrent because facts are partitioned by nodes of a graph data
structure. Computation is performed at the node level while communication
happens between connected nodes. In this paper, we present the syntax and
operational semantics of our language and illustrate its use through a number
of examples.Comment: ICLP 2014, TPLP 201
Finite domain constraint programming systems
Tutorial at CP'2002, Principles and Practice of Constraint Programming. Powerpoint slides.</p
TOR: modular search with hookable disjunction
Horn Clause Programs have a natural exhaustive depth-first procedural
semantics. However, for many programs this semantics is
ineffective. In order to compute useful solutions, one needs the
ability to modify the search method that explores the alternative
execution branches.
Tor, a well-defined hook into Prolog disjunction, provides this ability.
It is light-weight thanks to its library approach and efficient
because it is based on program transformation.
Tor is general enough to mimic search-modifying
predicates like ECLiPSe's search/6. Moreover, Tor supports
modular composition of search methods and other hooks.
The Tor library is already
provided and used as an add-on to SWI-Prolog.publisher: Elsevier
articletitle: Tor: Modular search with hookable disjunction
journaltitle: Science of Computer Programming
articlelink: http://dx.doi.org/10.1016/j.scico.2013.05.008
content_type: article
copyright: Copyright © 2013 Elsevier B.V. All rights reserved.status: publishe
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