The HtDP and DeinProgramm languages are wonderful tools for teaching—they support the pedagogy of systematic design, give excellent feedback, and DrRacket is an uncluttered environment appropriate for beginners.

Yet, the user experience has fallen somewhat behind: The test-results window is clunky, Check Syntax isn’t concurrent with editing, links to documentation don’t quite work. This is all despite the fact that DrRacket in principle can do these things well.

Remedying these problems means digging deep into historically grown code that is hard to change: I’ll talk about what the issues with the code are, what I’ve done recently both to improve the general infrastructure and to make the teaching languages use it, and what might be in store.

Many Racket templating facilities involve using read/eval on text files loaded at runtime. Beeswax is a Pollen-friendly DSL that turns document templates into normal Racket modules and functions. I’ll talk about why this might be great, how I made it, and things I still haven’t figured out.

One problem the Racket database (db) library has faced is that an FFI call blocks all Racket threads from running, so a long-running query on a sqlite3 or ODBC connection can make an entire Racket application or server unresponsive. The old fix was to run queries in a separate place, but this has high overhead. Racket CS supports an alternative: running (restricted) Racket code in OS threads with shared memory. I’ve recently added support for this alternative to the db library; it requires some changes to the code, but it seems to have much lower overhead.

Come with me on a journey into unfamiliar territory for Lispers, we’re going to interact with a Racket REPL from Neovim! Then we’ll take a peek behind the curtain at the other Lisp that drives the whole experience (no Vim Script here!) and the other Lisps we can talk to. I hope you enjoy this Lisp polyglot buffet!

My brother an I run a small software company in Germany. The main focus of our work is on business software like Enterprise Resource Planning. But, we both love parentheses as well. In this short talk I will show some of the applications we developed for our customers using Racket (and other Lisps). In addition to using it for commercial software, I also use Racket for teaching programming to our apprentices. Therefore I’ll close my talk with with some comments on why this makes sense from my point of view.

Redex is a domain-specific language for writing mechanized language models embedded in Racket. Having a Redex model lets us quickly run our research. In addition, a Redex model is generally very similar to how formal language models are expressed on paper.

In this talk, I will show how we used Redex to model WebAssembly, a low-level language meant to run alongside JavaScript in the browser for performance critical applications, and how the Redex model is useful in our research.

Macros are used to abstract over patterns in the code, from the elimination of repetitive boilerplate to the automatic generation of complex code.

This is exactly the job of functions: packaging a frequently-used idiom into a reusable library function. We use macros to write abstractions that cannot be written as functions:

1. adding/reading bindings to/from the environment (let, define-struct, anaphoric, match, …)
2. changing the order of execution (if, match, for/list, …)
3. syntactic sugar (infix operators, anything written using syntax-parse’s ~datum or ~literal, identifier prefix/postfix annotations, …)
4. optimisations, i.e. semantics-preserving compile-time transformations of the program
5. tracking and propagating annotations on the code (types, source locations, tooltips, …)
6. …

These concepts can only be manipulated by macros because they are second-class citizens that cannot be assigned to variables, passed around by functions, and manipulated at run-time. The following features would allow these concepts to be within the reach of functions:

1. first-class environments (an extra env parameter threaded through all functions)
2. lazy by default, continuations, effects
3. #%app, extensible parser, polysemic bindings (in both as a (let x = v in body) keyword and a (for x in list do body) keyword), first-class sub-expressions
4. markers around values that should be computed at compile-time, and a perfectly hygienic rewriting metalanguage that is closer to Coq’s tactics than to macros.
5. same: markers to track what should be done at compile-time

This talk will give an overview of how making some concepts first-class allows most macros to be rewritten as functions.

We are working on Rosette 4.0! This version has a new technical core, which is faster and supports new features, including a more powerful synthesis library. In this talk, I will give a quick tour of the upcoming version.

rs is a live coding tool that lets you sequence MIDI instruments using Racket. This talk will show you can use it, how it works and what some of the benefits are of using the programming language we all know and love for making music.

I’ve been teaching compilers with a nanopass architecture, and typesetting a lot of eBNF grammars in the process. As a language-oriented programmer, I naturally wrote a language for typesetting them. The language can hyperlink Racket identifiers that appear in grammars, compute and render differences between grammars, render n-way diffs with tabbed interface, and convert the typesetable grammar to a Redex language.

At code clubs for young people (6-16 year olds) people typically start with a block-based programming language such as Scratch. When they are ready they move on to a text-based programming language, usually Python.

But what about Racket? It’s got a great environment, it’s good with graphics, pretty concise (so not too much typing) but I’ve not seen it at any code club.

So can I make a case for learning Racket, and teaching Racket? Will I convince some young people to try it?

A bit of background: I mentor at Brighton Coder Dojo and we’ve written a number of tutorials for young people new to Python. I’ve also created various Racket games examples over the years, with an idea that they may work at our code club. But I’ve never used them. Maybe because I’ve never tried to answer the question: why learn Racket?

url2script is a DrRacket quickscript that makes it faster to install other quickscripts published on Gist and elsewhere, just from their url. Once url2script is installed, no package installation and no copy-paste of code are needed. Scripts can be easily updated as well, if the owner changes the published script.

Xsmith is a Racket library for creating fuzz testers that exercise programming language compilers and interpreters. In other words, Xsmith is a library for creating random program generators. Xsmith aims to help testers generate well-formed, well-behaving programs and thereby search for deep bugs in a programming language implementation: i.e., errors that cause correct programs to produce incorrect results. This talk briefly describes Xsmith and a few of the bugs discovered with the help of Xsmith to date.

We build our own environment for a type system, but reusing macro environment is possible. In this talk, I present how to convert programs to do so, and show possibilities, limitations, and future works.