Erik Meijer: Duality and the End of Reactive [video]

In the future, there will be a website dedicated to SolScript itself. This website will be the "technical" website. We already have a domain [2], but there's no website there.

Right now, we are working on getting SolScript into production. This thesis was really the first time anyone ever wrote anything about SolScript. Part of my job, in the future, will be to write blog posts and create tutorials. I'll definitely keep HN posted!

[1] http://www.unmanned.aero/

[2] http://solscri.pt/

Reactive programming is ill-defined and over-hyped, so let's talk about types and math instead (plus some not-very-subtle in-jokes about Microsoft).

An enumerator is basically a getter with the ability to fail and / or terminate. It might also return a promise rather than a value. An enumerable is a getter that returns an enumerator. We can express all this very cleanly in generic types. And if we take the category-theoretic dual of these types we get the observer and observable types.

So who needs reactive? ;-)

I say SolScript is "duck typed" and "scripted", because that's how it feels to program SolScript. However, under the hood, SolScript is a statically typed, compiled language.

About the "spreadsheet" idea, that is exactly what the SolScript IDE (Solide) is going to be. There will be a spreadsheet mode, which displays the source code as a spreadsheet. The last chapter talks about Solide, if you want to know more. (The creation of Solide is going to be my job, and I've been watching Bret Victor videos, all day yesterday, for inspiration.)

We have no "deep copy" of the data. The data is simply mutated in place, for performance. The compiler knows in what order it has to update the datacells, so SolScript users don't notice any of this. If I say `b = a`, then `a` will be calculated before `b` uses it. (If you want the value of `a` before `a` is updated, you say `b = previous a`.)

The whole "plain text" argument is about the fact that companies can die. So can (UN)MANNED, of course. The difference is that plain text files will always be readable, in contrast to Word files. You don't need our software to read plain text documentation.

Releasing the source is not something we plan to do (for now). We are not against the idea, but right now we have other priorities. There will probably be a gratis version, even for commercial use. Only that version won't be certified.

Yes, SolScript is written in an "unsafe" language: C. This makes it extremely cross-platform. We can run on Linux, OS X, Windows, iOS, VxWorks... The coding standards of our C code are extremely strict. Avionics style.

And about Markdown, yes that could be applied to other programming languages. BUT SolScript integrates with Markdown on a whole new level. For example, sections in Markdown are the scopes or namespaces of a SolScript program. Markdown is built into SolScript, not tacked on.

Edit: Circular dependencies really make no sense, in a declarative programming language. Defining `a = b` and `b = a` has no clear meaning, so the compiler will throw an error. However, you can define things recursively using `previous`. For example: `a = b + 1 initially 0` and `b = previous a`. In this case, `b` is 0, 1, 2, 3... and `a` is 1, 2, 3, 4...