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Visión panorámica de Haskell.

This course offers a perspective on algorithm specification, in terms of purely functional programming. An algorithm is an effective method expressed as a list of instructions describing a computation for calculating a result. Algorithms have to be written in human readable form, either using pseudocode (natural language looking like executable code), a high level specification language like Dijkstra's Guarded Command Language, or an executable formal specification formalism such as Z. The course will develop a purely functional perspective on algorithm specification, and demonstrate how this can be used for specifying (executable) algorithms, and for automated testing of Hoare correctness statements about these algorithms. The small extension of Haskell that we will present and discuss can be viewed as a domain specific language for algorithm specification and testing. Inspiration for this was the talk by Leslie Lamport at CWI on the executable algorithm specification language PlusCal plus Edsger W. Dijkstra, "EWD472: Guarded commands, non-determinacy and formal derivation of programs." Instead of formal program derivation, we demonstrate test automation of Hoare style assertions.

"We argue that teaching purely functional programming as such in freshman courses is detrimental to both the curriculum as well as to promoting the paradigm. Instead, we need to focus on the more general aims of teaching elementary techniques of programming and essential concepts of computing. We support this viewpoint with experience gained during several semesters of teaching large first-year classes (up to 600 students) in Haskell. These classes consisted of computer science students as well as students from other disciplines. We have systematically gathered student feedback by conducting surveys after each semester. This article contributes an approach to the use of modern functional languages in first year courses and, based on this, advocates the use of functional languages in this setting. "

Traversal strategies `a la Stratego (also `a la Strafunski and 'Scrap Your Boilerplate') provide an exceptionally versatile and uniform means of querying and transforming deeply nested and heterogeneously structured data including terms in functional programming and rewriting, objects in OO programming, and XML documents in XML programming. However, the resulting traversal programs are prone to programming errors. We are specifically concerned with errors that go beyond conservative type errors; examples we examine include divergent traversals, prematurely terminated traversals, and traversals with dead code. Based on an inventory of possible programming errors we explore options of static typing and static analysis so that some categories of errors can be avoided. This exploration generates suggestions for improvements to strategy libraries as well as their underlyingq programming languages. Haskell is used for illustrations and specifications with sufficient explanations to make the presentation comprehensible to the non-specialist. The overall ideas are language-agnostic and they are summarized accordingly.

Introducción a las mónadas en Haskell.