3,552 research outputs found
Combining Static and Dynamic Contract Checking for Curry
Static type systems are usually not sufficient to express all requirements on
function calls. Hence, contracts with pre- and postconditions can be used to
express more complex constraints on operations. Contracts can be checked at run
time to ensure that operations are only invoked with reasonable arguments and
return intended results. Although such dynamic contract checking provides more
reliable program execution, it requires execution time and could lead to
program crashes that might be detected with more advanced methods at compile
time. To improve this situation for declarative languages, we present an
approach to combine static and dynamic contract checking for the functional
logic language Curry. Based on a formal model of contract checking for
functional logic programming, we propose an automatic method to verify
contracts at compile time. If a contract is successfully verified, dynamic
checking of it can be omitted. This method decreases execution time without
degrading reliable program execution. In the best case, when all contracts are
statically verified, it provides trust in the software since crashes due to
contract violations cannot occur during program execution.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
Reducing the Number of Annotations in a Verification-oriented Imperative Language
Automated software verification is a very active field of research which has
made enormous progress both in theoretical and practical aspects. Recently, an
important amount of research effort has been put into applying these techniques
on top of mainstream programming languages. These languages typically provide
powerful features such as reflection, aliasing and polymorphism which are handy
for practitioners but, in contrast, make verification a real challenge. In this
work we present Pest, a simple experimental, while-style, multiprocedural,
imperative programming language which was conceived with verifiability as one
of its main goals. This language forces developers to concurrently think about
both the statements needed to implement an algorithm and the assertions
required to prove its correctness. In order to aid programmers, we propose
several techniques to reduce the number and complexity of annotations required
to successfully verify their programs. In particular, we show that high-level
iteration constructs may alleviate the need for providing complex loop
annotations.Comment: 15 pages, 8 figure
Static and dynamic semantics of NoSQL languages
We present a calculus for processing semistructured data that spans
differences of application area among several novel query languages, broadly
categorized as "NoSQL". This calculus lets users define their own operators,
capturing a wider range of data processing capabilities, whilst providing a
typing precision so far typical only of primitive hard-coded operators. The
type inference algorithm is based on semantic type checking, resulting in type
information that is both precise, and flexible enough to handle structured and
semistructured data. We illustrate the use of this calculus by encoding a large
fragment of Jaql, including operations and iterators over JSON, embedded SQL
expressions, and co-grouping, and show how the encoding directly yields a
typing discipline for Jaql as it is, namely without the addition of any type
definition or type annotation in the code
Lucretia - intersection type polymorphism for scripting languages
Scripting code may present maintenance problems in the long run. There is,
then, the call for methodologies that make it possible to control the
properties of programs written in dynamic languages in an automatic fashion. We
introduce Lucretia, a core language with an introspection primitive. Lucretia
is equipped with a (retrofitted) static type system based on local updates of
types that describe the structure of objects being used. In this way, we deal
with one of the most dynamic features of scripting languages, that is, the
runtime modification of object interfaces. Judgements in our systems have a
Hoare-like shape, as they have a precondition and a postcondition part.
Preconditions describe static approximations of the interfaces of visible
objects before a certain expression has been executed and postconditions
describe them after its execution. The field update operation complicates the
issue of aliasing in the system. We cope with it by introducing intersection
types in method signatures.Comment: In Proceedings ITRS 2014, arXiv:1503.0437
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