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We present a declarative debugger for sequential Erlang programs. The tool is started when a program produces some unexpected result, and proceeds asking questions to the user about the correctness of some subcomputations until an erroneous program function is found. Then, the user can refine the granularity by zooming in the function, checking the values bound to variables and the if/case/try-catch branches taken during the execution. We show by means of an extensive benchmark that the result is a usable, scalable tool that complements already existing debugging tools such as the Erlang tracer and Dialyzer. Since the technique is based on a formal calculus, we are able to prove the soundness and completeness of the approach. [ABSTRACT FROM AUTHOR]

Multi-methods are functions whose calls at runtime are resolved depending on the dynamic types of more than one argument. They are useful for common programming problems. However, while many languages provide different mechanisms to implement them in one way or another, there is still, to the best of our knowledge, no library or language feature that handles them in a general and flexible way. In this paper, we present the EVL (Extended Virtual function Library) framework which provides a set of classes in C++ aiming at solving this problem. The EVL framework provides a generalization of virtual function dispatch through the number of dimensions and the selection of the function to invoke using a so-called Function Comparison Operator . Our library provides both symmetric and asymmetric dispatch algorithms that can be refined by the programmer to include criteria other than class inheritance. For instance, the EVL framework provides multi-methods with predicate dispatch by defining a dedicated FCO based not only on the dynamic types of the arguments but also on their values. This flexibility greatly helps to resolve ambiguities without having to define new functions. Our multi-methods also unify dispatch tables and caching by introducing cache strategies for which the implementation is a balance between memory and speed. To define multi-methods in C++, we implement a non-intrusive reflection library providing fast dynamic casting and supporting dynamic class loading. Our multi-methods are policy-based class templates that support virtual but not repeated inheritance. They check the type compatibility of functions at compile-time, preserve type-safety and resolve function calls at runtime by invoking the cache or updating it by computing the selected function for the requested tuple of types. By default, our multi-methods handle dispatch errors at runtime by throwing exceptions but an error-code strategy can be set up by defining a dedicated policy class. Performance of our multi-methods is comparable with that of standard virtual functions when configured with fast cache. [ABSTRACT FROM AUTHOR]

Abstract: The automation of user routine tasks is one of the most important challenges in the development of Ambient Intelligence systems. However, this automation may be annoying since some tasks may grab users attention in inappropriate situations. Since user attention is a valuable resource, task automation must behave in a considerate manner demanding user attention only when it is required. To address this issue, this work presents a systematic method for supporting the design and automation of unobtrusive routine tasks that can adjust their obtrusiveness level at runtime according to the user attentional resources and context. This method proposes to design the routine tasks that the system must carry out and how they must interact with users in terms of obtrusiveness. The method also provides a software infrastructure that makes the execution of the tasks at the appropriate obtrusiveness degree a reality. Finally, the system has been validated by means of usefulness and performance tests and a practical case study that demonstrates the correctness and applicability of our approach without compromising system performance. [Copyright &y& Elsevier]

Abstract: The detection of similarities in source code has applications not only in software re-engineering (to eliminate redundancies) but also in software plagiarism detection. This later can be a challenging problem since more or less extensive edits may have been performed on the original copy: insertion or removal of useless chunks of code, rewriting of expressions, transposition of code, inlining and outlining of functions, etc. In this paper, we propose a new similarity detection technique not only based on token sequence matching but also on the factorization of the function call graphs. The factorization process merges shared chunks (factors) of codes to cope, in particular, with inlining and outlining. The resulting call graph offers a view of the similarities with their nesting relations. It is useful to infer metrics quantifying similarity at a function level. [Copyright &y& Elsevier]

Abstract: In functional programming it is common to write programs as compositions of other simpler functions. This makes it possible to take advantage of the well-known benefits of modular programming. However, in many cases, the resulting programs have efficiency problems caused by the generation of data structures that are solely used for communication between the functions that take part in the compositions. Many of those intermediate structures can be eliminated by an appropriate combination of the codes of the involved functions using a technique called program fusion. In this work, we propose a program fusion technique for accumulations, which are recursive functions that use additional parameters, called accumulators, for keeping intermediate results. Accumulations are known to be difficult to be fused because of the presence of the accumulators and the fact that results are usually computed in those parameters. Our technique is based on a shortcut fusion approach which turns out to be effective in the case of accumulations. We present benchmarks that illustrate the impact of shortcut fusion on accumulations. [Copyright &y& Elsevier]

Abstract: Coercion can greatly improve the readability of programs, especially in arithmetic expressions. However, coercion interacts with other features of programming languages, particularly subtyping and overloaded functions and operators, in ways that can produce surprising behavior. We study examples of such surprising behavior in existing languages. This study informs the design of the coercion mechanism of Fortress, an object-oriented language with multiple dynamic dispatch, multiple inheritance and user-defined coercion. We describe this design and show how its restrictions on overloaded declarations prevent ambiguous calls due to coercion. [Copyright &y& Elsevier]