[munificent]

> I was inspired by the size of Lua's VM, but deterred by its obscurity (and lack of inline documentation), so my original goal was to create a very clean and minimal VM.

Me too, so I created Wren:

https://github.com/munificent/wren

It's about the same size as Lua, significantly faster, and much more thoroughly documented. I also like the language itself more — it's object model is more familiar to someone coming from Java/C++/C#/etc. — but that's personal preference.

... heh and then I scroll down and see two people have already mentioned Wren. I guess I'm doing a good job of branding it as the "better documented Lua". :)

[tjholowaychuk]

Nice! Looks cool, I thought at first that it was this Wren: https://github.com/darius/wren, it's super compact, but not so easy to read haha.

[munificent]

Oh, dang. When I first picked the name, I hunted around and didn't see if being used for anything, but I guess I missed this one. :(

[naasking]

Interesting language, and looks fairly concise to write. I imagine shoehorning all numbers into doubles makes for slower integer code. Also a shame you included pervasive null.

Wren looks straightforward enough that you could have a static type system without losing any expressiveness. Have you considered that?

[munificent]

> I imagine shoehorning all numbers into doubles makes for slower integer code.

Maybe, though in a bytecode-compiled, dynamically typed language, my hunch is that using doubles for everything is actually faster. If I had separate integer and float types, all of the arithmetic operators would have do runtime type tests to handle the different combinations and conversions.

I could be wrong, though. Either way, only having doubles definitely simplifies the VM.

> Also a shame you included pervasive null.

Yeah, it doesn't come up too often in practice. Unlike, say, JS, Wren considers it a runtime error to call a function without enough arguments. I'm not a big fan of null, but in a dynamically typed language it's sort of inevitable. It's the result type of a function with no explicit return.

> Wren looks straightforward enough that you could have a static type system without losing any expressiveness. Have you considered that?

Yes! I'm interested in trying to layer an optional type system on top of it, and I tried to design most of the language and core library such that it's amenable to that.

However, designing a type system is really hard, so I don't know how well it'll pan out. Now that the language itself is pretty far along and you can write useful programs in it, I'm hoping to start tinkering with this and see what I can come up with.

You can see the first baby steps here:

https://github.com/munificent/wrenalyzer

[naasking]

> Maybe, though in a bytecode-compiled, dynamically typed language, my hunch is that using doubles for everything is actually faster. If I had separate integer and float types, all of the arithmetic operators would have do runtime type tests to handle the different combinations and conversions.

Perhaps. I suppose this dovetails with my preference for static types with optional dynamic behaviour, and not the contrary default which seems to be your position.

> I'm interested in trying to layer an optional type system on top of it, and I tried to design most of the language and core library such that it's amenable to that.

Cool. I think Wren is simple enough that basic type inference should be straightforward and complete, and anything more difficult just infers a top/'dynamic' type. A trivially correct type inference algorithm then just infers type 'dynamic' everywhere, which recovers Wren's current semantics. Then you incrementally add more specific rules where you can, ie. simple data flow from constants will generate more efficient string, floating point and integer code.

That would be enough for a decent speedup on most programs. If you want to type check arbitrary objects (or at least avoid method-not-understood), you can use something like "Type Inference for First-Class Messages with Match-Functions" [1] or the even more general first-class labels [2]. I believe first-class labels are more general than Wren's semantics.

[1] http://lambda-the-ultimate.org/node/4808 [2] http://lambda-the-ultimate.org/node/174

[munificent]

> I suppose this dovetails with my preference for static types with optional dynamic behaviour, and not the contrary default which seems to be your position.

I do like that in general. If I could wave a magic wand and create a language to fit my personal desires, it would be statically typed.

But when I sat down to create Wren, I had to modulate that by what I was capable of. I figured I had the time and skill to pull off a small bytecode-interpreted, embeddable dynamically typed language, I and thought there might be room in the world of languages for it to find a niche as that.

> That would be enough for a decent speedup on most programs.

I'm not currently planning to use static analysis to affect the runtime behavior since I think that would add a bunch of complexity to the VM. I was thinking more about it in terms of finding bugs and code navigation.