Wadler's Blog

A big welcome to Neil Ghani, Patricia Johann, and Conor McBride, who are establishing a new research group in Mathematically Structured Programming at the University of Strathclyde. And a big congratulations to Strathclyde, on attracting three top-notch researchers. Their arrival will strengthen the already strong programming languages community in Scotland, and they've already volunteered to host a meeting of SPLS.

As a result of a recent Harvard workshop, there is a proposal to add FP to the ACM curriculum, and ACM members are encouraged to comment. Many excellent arguments appear on the comment page, here are two of my favorites.

Greg Morrisett:

I strongly endorse the recommendation to include functional programming in the curriculum. The most important benefit is a change in the mode of thought that can strongly influence design at all levels, from hardware to distributed systems. If they are to be successful, students must be able to pick up and learn new languages. Without deep experience in at least two very different environments, they will be unable to do so.

Robert Harper:

I endorse the proposed change to PL7/FunctionalProgramming to include more hours on the topic of functional programming and to correspondingly reduce commitment to vague or obsolete topics in the proposed curriculum. Functional programming has emerged as the central organizing principle in programming language design, and is increasingly important in industrial as well as academic settings. Once considered an esoteric niche topic, functional programming has emerged as a unifying conceptual framework that encompasses and enriches traditional concepts such as imperative and object-oriented programming. Many of the major innovations in language design over the last decade have emerged from the functional programming perspective, including reliance on managed storage ("garbage collection"); emphasis on static type disciplines in general and specific advances such as generics in particular; and the role of higher-order techniques, including functions and objects, for building reusable software component.

Current trends in the computer industry favor the functional perspective: (a) very large scale distributed computing models, such as Hadoop or map/reduce, depend essentially on the functional (state-free) model of computing; (b) small to medium-scale parallel computing, such as multicore processors or shared memory multiprocessors, strongly favors the functional model, which ensures determinacy of outcomes even in the presence of parallelism; (c) demand for mechanical verification of program properties to ensure software quality favors the functional model, which emphasizes the single most successful integration of formal methods into programming, rich static type systems.

It is entirely appropriate for ACM to place renewed emphasis on functional programming in the undergraduate curriculum. The present proposal, though overly modest, takes a step towards modernizing undergraduate education in programming languages. I urge that this change be adopted.

This is the most definitive history of lambda calculus of which I am aware, a most useful resource. It includes two contradictory stories, both told by Church, of why Church picked the symbol 'lambda' (see p 7), but not the story that Church conceived the predecessor function after exposure to laughing gas at his dentist. (Does anyone know a source for that story?) My thanks to the authors for their efforts.

Ralf Laemmel and Ondrej Rypacek have a paper in MPC 2008 on the duality of functions and objects, which they formalize as folds over algebras and unfolds over coalgebras, as a step toward deeper understanding of The Expression Problem. I like their idea of dual models of functions and objects as algebras and coalgebras, has this appeared elsewhere?