Programming language

In type-theoretic research on object-oriented programming, the issue of “covariance versus contravariance” is a topic of continuing debate. In this short note we argue that covariance and contravariance appropriately characterize two distinct and independent mechanisms. The so-called contravariance rule correctly captures the subtyping relation (that relation which establishes which sets of functions can replace another given set in every context ). A covariant relation, instead, characterizes the specialization of code (i.e., the definition of new code which replaces old definitions in some particular cases ). Therefore, covariance and contravariance are not opposing views, but distinct concepts that each have their place in object-oriented systems. Both can (and should) be integrated in a type-safe manner in object-oriented languages. We also show that the independence of the two mechanisms is not characteristic of a particular model but is valid in general, since covariant specia...

The work reported here is part of the PROGRES (PROgrammed Graph Rewriting Systems) project. PROGRES is a very high level multi paradigm language for the specification of complex structured data types and their operations. The data structures are modelled as directed, attributed, node and edge labelled graphs (diane graphs). The basic programming constructs of PROGRES are graph rewriting rules (productions and tests) and derived relations on nodes (paths and restrictions). These basic operations may be combined to build partly imperative, partly rule based, complex graph transformations by special control structures which regard the nondeterministic nature of graph rewriting rules. PROGRES offers its users a convenient, partly textual, partly graphical concrete syntax and a rich system of consistency checking rules for the underlying calculus of programmed diane-graph rewriting systems. This paper presents the key techniques used for the execution of PROGRES programs. We will discuss...

9.2 Writing and reading values on a channel . . . . . . . . . . . . . . . . . . . . . . . . . ... 10.4 Using open to expose a namespace . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 ... This document is an introduction to ML programming, specifically for the Objective Caml ... (OCaml) programming ...

The specification of all aspects of a programming language requires adequate formal models and tool support. Montages specifications combine graphical and textual elements to yield language descriptions similar in structure, length, and complexity to those in common language manuals, but with a formal semantics. A broad range of people involved in programming language design and use may find it convenient to use Montages in combination with the tool GEM-MEX. It allows the automatic generation of high-quality documents, type-checkers, interpreters and symbolic debuggers.

Source code retrieval is of immense importance in the software engineering field. The complex tasks of retrieving and extracting information from source code documents is vital in the development cycle of the large software systems. The two main subtasks which result from these activities are code duplication prevention and plagiarism detection. In this paper, we propose a Mohamed Amine Ouddan, and Hassane Essafi source code retrieval system based on two-level fingerprint representation, respectively the structural and the semantic information within a source code. A sequence alignment technique is applied on these fingerprints in order to quantify the similarity between source code portions. The specific purpose of the system is to detect plagiarism and duplicated code between programs written in different programming languages belonging to the same class, such as C, Cµ, Java and CSharp. These four languages are supported by the actual version of the system which is designed such t...

The challenge for the metaobject protocol designer is to balance the conflicting demands of efficiency, simplicity, and extensibility. It is impossible to know all desired extensions in advance; some of them will require greater functionality, while others require greater efficiency. In addition, the protocol itself must be sufficiently simple that it can be fully documented and understood by those who need to use it. This paper presents a metaobject protocol for EuLisp which provides expressiveness by a multi-leveled protocol and achieves efficiency by static semantics for predefined metaobjects and modularizing their operations. The EuLisp module system supports global optimizations of metaobject applications. The metaobject system itself is structured into modules, taking into account the consequences for the compiler. It provides introspective operations as well as extension interfaces for various functionalities, including new inheritance, allocation and slot access semantics. ...

Over time the level of abstraction embodied in programming languages has continued to grow. Yet, most programming languages still require programmers to conform to the language's rigid constructs. These constructs have been implemented in the name of efficiency for the computer. The continual increase in computing power allows us to consider techniques that are no longer limited by this constraint. To this end, we have created CABERNET, a Controlled Nature Language (CNL) approach. CABERNET allows programmers to use a simple outline-based syntax. This allows increased programmer efficiency and syntax flexibility. CNLs have successfully been used for writing requirements documents. We propose taking this approach well beyond this to fully functional programs. Our approach uses heuristics and inference to analyze and determine the programmer's intent. The goal is for programs to be aligned with the way that the humans think rather than the way computers process information.

This paper presents a programming language which includes paradigms that are usually associated with declarative languages, such as sets, rules and search, into an imperative (functional) language. Although these paradigms are separately well known and are available under various programming environments, the originality of the CLAIRE language comes from the tight integration, which yields interesting run-time performances, and from the

Developers around the world have used previous editions to quickly gain a deep understanding of the Java programming language, its design goals, and how to use it most effectively in real-world development. Now, Ken Arnold, James Gosling, and David Holmes have ...

Meta-programming languages provide infrastructure to generate and execute object programs at run-time. In a typed setting, they contain a modal type constructor which classifies object code. These code types generally come in two flavors: closed and open. Closed code expressions can be invoked at run-time, but the computations over them are more rigid, and typically produce less efficient residual object programs. Open code provides better inlining and partial evaluation of object programs, but once constructed, expressions of this type cannot in general be evaluated.Recent work in this area has focused on combining the two notions into a sound system. We present a novel way to achieve this. It is based on adding the notion of names from the work on Nominal Logic and FreshML to the λ -calculus of proof terms for the necessity fragment of modal logic S4. The resulting language provides a more fine-grained control over free variables of object programs when compared to the existing la...

The NYU-Ada project is engaged in the design and implementation of a translator-interpreter for the Ada language. The objectives of this project are twofold: a) to provide an executable semantic model for the full Ada language, that can be used for teaching, and serve as a starting point for the design of an efficient Ada compiler; b) to serve as a testing ground for the software methodology that has emerged from our experience with the very-high level language SETL. In accordance with these objectives, the NYU-Ada system is written in a particularly high-level, abstract SETL style that emphasizes clarity of design and user interface over speed and efficiency. A number of unusual design features of the translator and interpreter follow from this emphasis. Some of these features are described below. We also discuss the question of semantic specification of programming languages, and the general methodology of “Software Prototyping” of which the NYU-Ada system is a sizeable example.