Strange Loop

September 26-28 2018


Stifel Theatre


St. Louis, MO

Register for 2018!

The J Programming Language

"A language that doesn't affect the way you think about programming is not worth knowing." – Alan Perlis

J has been an "emerging language" for 23 years. It's strange in appearance, and requires a style of thinking that feels awkward for a while. Learning is worth the effort, though, because with J, the way you look at a problem is often radically different.

Like APL, its predecessor, J sees everything as an array. Computations are expressed as pipelines among functions that apply on the appropriate axis of each array. With some practice, a J programmer learns to fold, flip and manipulate arrays in her mind. The experience is mind-blowing, and the resulting solutions become sleek and simple.

Diverging from its APL roots, J introduces "tacit form" (where arguments are implied.) This concept is fundamental to the definition of J programs. For example, inherent in J's syntax is the "verb train", a kind of branching composition. This lets you naturally express programs as relations among functions.

J embodies a peculiar mixture of mathematical purity and industrial practicality. If you're excited by combinatorial, concatenative, point-free, or functional programming techniques in general, J will inspire you and give you new ways of seeing problems. If you're looking for a mature scripting language with a stable implementation, you'll find J to be a pleasantly functional workhorse.

In this talk, I will introduce you to patterns of thinking that make J coding possible, and provide a rich introduction to the language. You will come away with a clearer understanding of the concepts that are crucial to confident reading and writing of J notation. While no previous knowledge of J will be assumed, people with some previous exposure will get the most benefit.

Tracy Harms

Applied Performance Technologies

Tracy Harms has worked in software development on and off since 1978. He presently helps create test automation for a major scientific document search service.