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Beginning a collection of Futhark examples

Posted on August 31, 2019 by Troels Henriksen

Websites like Go by Example and Rust by Example seem to be pretty popular. They are collections of typically small self-contained programs, with commentary about how they work and what they do. I can see the appeal: for the author, it takes very little effort to add content to such a document, because there is no cohesive narrative to maintain. For the reader, it requires very little time investment to read a single example. Also, for the curious visitor, who is not (yet?) trying to actively learn the language, it provides a good way for getting the feel of the language.

By the standards of obscure academic programming languages, I think that Futhark is decently documented. The reference manual is terse but fairly comprehensive, and the unfinished book contains a good conventional language introduction, as well as some information about tooling. However, while I never had much trouble updating the reference manual, I always felt the book was harder to improve in small increments. Every paragraph in a book must fit in some context, and sometimes I just want to show off some small programming trick, or elaborate on some detail. That’s exactly what a catalogue of examples can do. So, for the past week or so, I have been assembling Futhark by Example, a yet-small collection of Futhark code for doing various things.

As of this writing, most of the examples are still about basic language constructs (which is not too dissimilar to Go by Example). However, while these are necessary, that’s not really where I think the potential lies: the radix sort and gaussian blur examples are much better examples of what I want. I write new examples whenever I think of something interesting, but if there’s something you would like to see, don’t hesitate to get in touch.

In order to make it as low-friction as possible for me to write examples, they are just ordinary Futhark programs processed by the website generator to turn them into Markdown files, which are then translated to HTML. For example, this is what gaussian-blur.fut looks like. It’s a crude technique, and for examples like this one I’d prefer some automated way of showing the values produces by intermediate bindings. Maybe some examples should be programs, and others should be futhark repl sessions? I’m sure I will find some way to over-engineer the infrastructure eventually, but for now I am satisfied just writing content.