Reusable Components for Lightweight Mechanisation of Programming Languages

Two of the fundamental uses of generalization in object-oriented software development are the reusability of code and better structuring of the description of objects. Multiple inheritance is one of the important features of object-oriented methodologies which enables developers to combine concepts and increase the reusability of the resulting software. However, multiple inheritance is implemented differently in commonly used programming languages. In this paper, we use Chidamber and Kemerer (CK) metrics to study the complexity and reusability of multiple inheritance as implemented in Python, Java, and C++. The analysis of results suggests that out of the three languages investigated Python and C++ offer better reusability of software when using multiple inheritance, whereas Java has major deficiencies when implementing multiple inheritance resulting in poor structure of objects.

Type-preserving compilation can improve software reliability by generating code that can be verified independently of the compiler. Practical type preserving compilation does not exist for languages with multiple inheritance. This paper presents Emi, the first typed intermediate language to support practical compilation of a programming language with fully general multiple inheritance. The paper demonstrates the practicality of Emi by showing that Emi can be used to faithfully model standard implementation strategies of multiple inheritance for C++, the most widely-used programming language with general multiple inheritance.

We present Fril++ an object-oriented extension to Fril. This new programming language supports the modelling of fuzzy applications by integrating a fuzzy logic programming language with the object-oriented paradigm. Fril++ includes the concept of fuzzy objects as an explicit construction in the language. Fuzzy objects are naturally related with multiple inheritance, and so we allow both of these in the language. The multiple inheritance gives us more flexibility, and in any case, the associated ambiguities are not so much of a problem in logic programming as they are in other paradigms. We also exploit the fact that information is expressed by the hierarchy itself. A Fril++ program can explicitly use the hierarchy by means of special constructions integrated into the language. Fril++ provides support for user decisions when there are several answers for a message by having a library of defuzzification methods.

Developing programming languages is a difficult task that requires a lot of time, effort, and expertise. Reusable programming language components make this task easier, by allowing language designers to grab off-the-shelf components for common language features. Modern functional programming languages, however, lack support for reuse of definitions, and thus language components defined using algebraic data types and pattern matching functions cannot be reused without modifying or copying existing code. To improve the situation, we introduce CS, a functional meta-language for developing reusable programming language components, that features built-in support for extensible data types and functions, as well as effects and handlers. In CS, we can define language components using algebraic data types and pattern matching functions, such that we can compose language components into larger languages and define new interpretations for existing components without modifying existing definitions.

Over 90 percent of all microprocessors are now used for real-time and embedded applications, and the behavior of many of these applications is constrained by the physical world. Higher-level programming languages and middleware are needed to robustly and productively design, implement, compose, integrate, validate, and enforce real-time constraints along with conventional functional requirements and reusable components. Designing real-time and embedded systems that implement their required capabilities, are dependable and predictable, and are parsimonious in their use of limited computing resources is hard; building them on time and within budget is even harder. Moreover, due to global competition for market share and engineering talent, companies are now also faced with the problem of developing and delivering new products in short time frames. Therefore it is essential that the production of real-time embedded systems can take advantage of languages, tools, and methods that enable higher software productivity. Ideally, developers should use a programming language that shields them from many accidental complexities, such as type errors, memory management, and steep learning curves. The Java programming language has become an attractive choice because of its safety, productivity,its relatively low maintenance costs, and the availability of well trained developers. Although it has good software engineering characteristics, Java is unsuitable for developing real-time embedded systems, mainly due to under-specification of thread scheduling and the presence of garbage collection. Recently, to address these problems, a number of extensions to Java have been proposed by the Java Community Process Expert Group for the Real-Time Specification for Java (RTSJ) among others. The intent of these specifications is the development of real-time applications by providing several additions such as extending the Java memory model, providing stronger semantics in thread scheduling, and so on. Interest in real-time Java in both the research community and industry, because of its challenges and its potential impact on the development of embedded and real-time applications, has recently increased, significantly. This interest in the industry comes not only from traditional applications, such as industrial control, but also for business and financial applications. The goal of the proposed workshop is to gather researchers working on real-time and embedded Java to identify the challenging problems that still need to be properly resolved in order to assure the success of the of real-time Java as a technology, and to report results and experience gained by researchers.

The programming language concepts which ought to be presented in the comparative programming languages course (either graduate or undergraduate) are all covered by choosing C++, Java, Perl, and Python as the languages to be compared. These include dynamic typing, object orientation, multiple inheritance, interpreters and compilers, keyword and default parameters, generics, operator overloading, complex numbers, universal hierarchies, exceptions, and garbage collection. We describe such a course, which we have given.

Currently available programming and database systems are insufficient for engineering applications. The authors contend that a logical progression from a formal conceptual model of the engineering domain to a computational model will lead to new programming paradigms capable of directly supporting engineering applications in a rigorous, concise manner. A formal domain model devised by the authors, theHybrid Model (HM) of design information, is briefly introduced. It is an extension of axiomatic set theory and is discussed in detail elsewhere. HM forms the basis ofDesigner, a prototype-based object-oriented programming language supporting a signature-based canonical message-passing mechanism and multiple inheritance. Designer is implemented using the Scheme programming language. Because Designer satisfies a formal conceptual model, and because it is based on a formally specified language, its robustness and logical validity are superior to those of other languages not founded on formal principles. Designer combines concepts of functional and object-oriented programming to provide the formal rigor and flexibility to capture the complex and strongly interrelated information that designers use. Examples demonstrate how Designer represents design information. The results of the authors' research indicate that Designer can capture design information (including aspects of functional requirements and design intent) effectively and efficiently.

Traits offer a fine-grained mechanism to compose classes from reusable components while avoiding problems of fragility brought by multiple inheritance and mixins. Traits as originally proposed are stateless, that is, they contain only methods, but no instance variables. State can only be accessed within traits by accessors, which become required methods of the trait. Although this approach works reasonably well in practice, it means that many traits, viewed as software components, are artificially incomplete, and classes that use such traits may contain significant amounts of boilerplate glue code. Although these limitations are largely mitigated by proper tool support, we seek a cleaner solution that supports stateful traits. The key difficulty is how to handle conflicts that arise when composed traits contribute instance variables whose names clash. We present a solution that is faithful to the guiding principle of stateless traits: the client retains control of the composition. Stateful traits consist of a minimal extension to stateless traits in which instance variables are purely local to the scope of a trait, unless they are explicitly made accessible by the composing client of a trait. Naming conflicts are avoided, and variables of disjoint traits can be explicitly merged by clients. We discuss and compare two implementation strategies, and briefly present a case study in which stateful traits have been used to refactor the trait-based version of the Smalltalk collection hierarchy.KeywordsInstance VariableStateful TraitTrait CompositionMultiple InheritanceClient ClassThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

A significant percentage of warnings reported by tools to detect coding standard violations are false positives. Thus, there are some works dedicated to provide better rules by mining them from source code history, analyzing bug-fixes or changes between system releases. However, software evolves over time, and during development not only bugs are fixed, but also features are added, and code is refactored. In such cases, changes must be consistently applied in source code to avoid maintenance problems. In this paper, we propose to extract system specific rules by mining systematic changes over source code history, i.e., not just from bug-fixes or system releases, to ensure that changes are consistently applied over source code. We focus on structural changes done to support API modification or evolution with the goal of providing better rules to developers. Also, rules are mined from predefined rule patterns that ensure their quality. In order to assess the precision of such specific rules to detect real violations, we compare them with generic rules provided by tools to detect coding standard violations on four real world systems covering two programming languages. The results show that specific rules are more precise in identifying real violations in source code than generic ones, and thus can complement them.

In object-oriented systems, assessing reusability plays a key role in reducing a cost and improving the quality of the software. Objectoriented programming helps in achieving the concept of reusability through different types of inheritance programs, which further help in developing reusable software modules. And object-oriented metrics identify the effectiveness of each reuse strategy. Software reusability has considerable effect on software quality. Software quality increases as reuse of software components increases. But software quality improvement cannot be understood unless it is measured. This paper focuses on an empirical evaluation of object-oriented metrics in C++ using three different object-oriented features. Three programs have been considered as input for the study -- the first program uses multilevel inheritance, the second program uses multiple inheritance and the third program uses hierarchical inheritance. We have found that multilevel inheritance has more impact on reusability among these three features.

This paper discusses an approach called Draco to the construction of software systems from reusable software parts. In particular we are concerned with the reuse of analysis and design information in addition to programming language code. The goal of the work on Draco has been to increase the productivity of software specialists in the construction of similar systems. The particular approach we have taken is to organize reusable software components by problem area or domain. Statements of programs in these specialized domains are then optimized by source-to-source program transformations and refined into other domains. The problems of maintaining the representational consistency of the developing program and producing efficient practical programs are discussed. Some examples from a prototype system are also given.

Eiffel : A language and environment for software engineering

Inheritance is a powerful concept employed in computer science, especially in artificial intelligence (AI), object-oriented programming (OOP), and object-oriented databases (OODB). In the field of AI, inheritance has been primarily used as a concise and effective means of representing and reasoning with common-sense knowledge (Thirunarayan, 1995). In programming languages and databases, inheritance has been used for the purpose of sharing data and methods, and for enabling modularity of software (re)use and maintenance (Lakshmanan & Thirunarayan, 1998). In this chapter, we present various design choices for incorporating inheritance into programming languages from an application programmer’s perspective. In contrast with the language of mathematics, which is mature and well-understood, the embodiment of object-oriented concepts and constructs in a concrete programming language is neither fixed nor universally accepted. We exhibit programs with similar syntax in different languages that have very different semantics, and different looking programs that are equivalent. We compare and contrast method inheritance, interaction of type system with method binding, constructs for method redefinition, and their implementation in widely used languages such as C++ (Stroustrup, 1997), Java (Arnold, Gosling, & Holmes, 2005), and C# (Hejlsberg, Wiltamuth, & Golde, 2006), to illustrate subtle issues of interest to programmers. Finally, we discuss multiple inheritance briefly.

Much recent work in polymorphic programming languages allows subtyping and multiple inheritance for records. In such systems, we would like to extract a field from a record with the same efficiency as if we were not making use of subtyping and multiple inheritance. Methods currently used make field extraction 3-5 times slower, which can produce a significant overall performance slowdown.

The porting or translation of software applications from one programming language to another is a common requirement of organisations that utilise software, and the increasing number and diversity of programming languages makes this capability as relevant today as in previous decades. Several approaches have been used to address this challenge, including machine learning and the manual definition of direct language-to-language translation rules, however the accuracy of these approaches remains unsatisfactory. In this paper we describe a new approach to program translation using model-driven engineering techniques: reverse-engineering source programs into specifications in the UML and OCL formalisms, and then forward-engineering the specifications to the required target language. This approach can provide assurance of semantic preservation, and additionally has the advantage of extracting precise specifications of software from code. We provide an evaluation based on a comprehensive dataset of examples, including industrial cases, and compare our results to those of other approaches and tools. Our specific contributions are: (1) Reverse-engineering source programs to detailed semantic models of software behaviour, to enable semantically-correct translations and reduce re-testing costs; (2) Program abstraction processes defined by precise and explicit rules, which can be edited and configured by users; (3) A set of reusable OCL library components appropriate for representing program semantics, and which can also be used for OCL specification of new applications; (4) A systematic procedure for building program abstractors based on language grammars and semantics.