40,163 research outputs found
A Swiss Pocket Knife for Computability
This research is about operational- and complexity-oriented aspects of
classical foundations of computability theory. The approach is to re-examine
some classical theorems and constructions, but with new criteria for success
that are natural from a programming language perspective.
Three cornerstones of computability theory are the S-m-ntheorem; Turing's
"universal machine"; and Kleene's second recursion theorem. In today's
programming language parlance these are respectively partial evaluation,
self-interpretation, and reflection. In retrospect it is fascinating that
Kleene's 1938 proof is constructive; and in essence builds a self-reproducing
program.
Computability theory originated in the 1930s, long before the invention of
computers and programs. Its emphasis was on delimiting the boundaries of
computability. Some milestones include 1936 (Turing), 1938 (Kleene), 1967
(isomorphism of programming languages), 1985 (partial evaluation), 1989 (theory
implementation), 1993 (efficient self-interpretation) and 2006 (term register
machines).
The "Swiss pocket knife" of the title is a programming language that allows
efficient computer implementation of all three computability cornerstones,
emphasising the third: Kleene's second recursion theorem. We describe
experiments with a tree-based computational model aiming for both fast program
generation and fast execution of the generated programs.Comment: In Proceedings Festschrift for Dave Schmidt, arXiv:1309.455
Rewriting Constraint Models with Metamodels
An important challenge in constraint programming is to rewrite constraint
models into executable programs calculat- ing the solutions. This phase of
constraint processing may require translations between constraint programming
lan- guages, transformations of constraint representations, model
optimizations, and tuning of solving strategies. In this paper, we introduce a
pivot metamodel describing the common fea- tures of constraint models including
different kinds of con- straints, statements like conditionals and loops, and
other first-class elements like object classes and predicates. This metamodel
is general enough to cope with the constructions of many languages, from
object-oriented modeling languages to logic languages, but it is independent
from them. The rewriting operations manipulate metamodel instances apart from
languages. As a consequence, the rewriting operations apply whatever languages
are selected and they are able to manage model semantic information. A bridge
is created between the metamodel space and languages using parsing techniques.
Tools from the software engineering world can be useful to implement this
framework
The essence of component-based design and coordination
Is there a characteristic of coordination languages that makes them
qualitatively different from general programming languages and deserves special
academic attention? This report proposes a nuanced answer in three parts. The
first part highlights that coordination languages are the means by which
composite software applications can be specified using components that are only
available separately, or later in time, via standard interfacing mechanisms.
The second part highlights that most currently used languages provide
mechanisms to use externally provided components, and thus exhibit some
elements of coordination. However not all do, and the availability of an
external interface thus forms an objective and qualitative criterion that
distinguishes coordination. The third part argues that despite the qualitative
difference, the segregation of academic attention away from general language
design and implementation has non-obvious cost trade-offs.Comment: 8 pages, 2 figures, 3 table
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