We describe an approach to introducing non-science majors to programming and computation in part by teaching them applets, servlets, and groupware applications. The course uses a dialect of didactic Scheme that is implemented in, and tightly integrated with, Java. The declarative nature of our approach allows non-science majors with no programming background to develop surprisingly complex web applications in about half a semester. This level of programming provides a context for a deeper understanding of computation than is usually feasible in a Computer Literacy course.

Haskell today provides good support not only for a functional programming style, but also for an imperative one. Elements of imperative programming are needed in applications such as web servers, or to provide efficient implementations of well-known algorithms, such as many graph algorithms. However, one element of imperative programming, the global variable, is surprisingly hard to emulate in Haskell. We discuss several existing methods, none of which is really satisfactory, and finally propose a new approach based on implicit parameters. This approach is simple, safe, and efficient, although it does reveal weaknesses in Haskell's present type system.

Haskell code is developed for two ways to list the strings of the language defined by a regular expression: directly by set operations and indirectly by converting to and simulating an equivalent automaton. The exercise illustrates techniques for dealing with infinite ordered domains and leads to an effective standard form for nondeterministic finite automata.

In this paper we present a notion of expansion of a term in the lambda-calculus which transforms terms into linear terms. This transformation replaces each occurrence of a variable in the original term by a fresh variable taking into account non-trivial implications in the structure of the term caused by these simple replacements. We prove that the class of terms which can be expanded is the same of terms typable in an Intersection Type System, i.e. the strongly normalizable terms. We then show that expansion is preserved by weak-head reduction, the reduction considered by functional programming languages.

In this paper, we describe two techniques for the efficient, modularized implementation of a large class of algorithms. We illustrate these techniques using several examples, including efficient generic unification algorithms that use reference cells to encode substitutions, and highly modular language implementations. We chose these examples to illustrate the following important techniques that we believe many functional programmers would find useful. First, defining recursive data types by splitting them into two levels: a structure defining level, and a recursive knot-tying level. Second, the use of rank-2 polymorphism inside Haskell's record types to implement a kind of type-parameterized modules. Finally, we explore techniques that allow us to combine already existing recursive Haskell data-types with the highly modular style of programming proposed here.