Finding The Lazy Programmer's Bugs

Traditionally developers and testers created huge numbers of explicit tests, enumerating interesting cases, perhaps biased by what they believe to be the current boundary conditions of the function being tested. Or at least, they were supposed to. A major step forward was the development of property testing. Property testing requires the user to write a few functional properties that are used to generate tests, and requires an external library or tool to create test data for the tests. As such many thousands of tests can be created for a single property. For the purely functional programming language Haskell there are several such libraries; for example QuickCheck [CH00], SmallCheck and Lazy SmallCheck [RNL08]. Unfortunately, property testing still requires the user to write explicit tests. Fortunately, we note there are already many implicit tests present in programs. Developers may throw assertion errors, or the compiler may silently insert runtime exceptions for incomplete pattern matches. We attempt to automate the testing process using these implicit tests. Our contributions are in four main areas: (1) We have developed algorithms to automatically infer appropriate constructors and functions needed to generate test data without requiring additional programmer work or annotations. (2) To combine the constructors and functions into test expressions we take advantage of Haskell's lazy evaluation semantics by applying the techniques of needed narrowing and lazy instantiation to guide generation. (3) We keep the type of test data at its most general, in order to prevent committing too early to monomorphic types that cause needless wasted tests. (4) We have developed novel ways of creating Haskell case expressions to inspect elements inside returned data structures, in order to discover exceptions that may be hidden by laziness, and to make our test data generation algorithm more expressive. In order to validate our claims, we have implemented these techniques in Irulan, a fully automatic tool for generating systematic black-box unit tests for Haskell library code. We have designed Irulan to generate high coverage test suites and detect common programming errors in the process

Multiple analytical perspectives of the Eleme Anterior-Perfective

There is increasing recognition in typology that linguistic categories are language-specific and not universal, increasing the need for explicitness in language descriptions. In light of this development, I argue in this paper that preexisting labels and descriptions for a set of subject-marking TAM prefixes in Eleme do not adequately characterise the distribution and use of these forms, which is conditioned by the complex interaction of person and number features, Aktionsart, epistemic modality and information structure. In response to the challenges raised by these data, I argue that when multiple analytical perspectives are required to understand the function of a grammatical form, fine-grained quantitative analyses with description give a complex but useful basis on which to compare languages

Associated W+/- H-/+ production at e+ e- and hadron colliders

We show some results in the minimal supersymmetric Standard Model (MSSM) and the two Higgs doublet model (THDM) for W+/- H-/+ production cross sections at e+ e- and hadron colliders. We demonstrate that the predictions for the cross sections in the two models can be vastly different. Observing these processes, once the existence of a charged Higgs is established, might shed some light on the underlying model for an extended Higgs sector.Comment: 8 pages, 5 figures, Contribution to SUSY 02, Hamburg, Germany, June 200

Job Promotion Tournaments and Imperfect Recall

In this paper, a promotion tournament is considered, where, at the beginning of the tournament, it is unknown how long the tournament lasts. Further, the promotion decision is based on the assessments of a supervisor with imperfect recall. In line with psychological research, the supervisor is assumed to either value early or recent impressions more strongly. It is shown that effort may increase or decrease, as the probability of promotion in a certain period gets higher. The single effects determining the sign of the effort change oftentimes depend on how the supervisor processes information