MetalScript Progress – July 2018
For those following along, here’s an update on my progress on MetalScript in the last month.
It’s been a bit of a slow month for MetalScript, just because I have a lot going on and MetalScript takes a bit of a backseat to other important things. I expect things to stay like this for a while longer.
The website is not meant to attract customers, because of course there is no product yet. It’s meant to be a representation of the grand vision of MetalScript. It paints the picture of what I’m trying to get to, and so helps me stay focused on the goal. It’s also a place where I can start collecting user documentation so that when I launch the MVP there will already be documentation in place, and the documentation doubles as a spec of what it needs to do.
I didn’t spend much time on it, and it leaves lots to be desired. The markdown at the bottom of the home page is particularly jarring, and the whole thing is not very mobile friendly. But I’ll improve it over time.
I also couldn’t make up my mind on the color scheme, and landed up changing it a number of times. Originally I was thinking pink/orange (excuse my primitive “engineer’s vocabulary” for colors) because I think it has really awesome energy to it, and paints the picture of something new and exciting and different…
But quite frankly, yellow is ugly. Sorry to those who like it. It’s such a stark, flat color, and doesn’t say anything I want it to for MetalScript.
I went through a number of greenish shades which I dismissed. And while it’s probably not final, the website is currently based around an aqua blue.
Not everything matches, because I kept changing my mind about exactly where on the spectrum between blue and green I wanted to be.
Blue is nice because it’s calming but professional. This is very much what I intend MetalScript to be — a tool for professionals, but one without the discomfort and complexity associated with C and C++.
Just because it’s unrealistic and stylized doesn’t mean it’s not a challenge for a Blender amateur like me. There are lots of details I tried to get right that a professional may have achieved better results in a lot less time. Take for example this comparison between an earlier draft (left) and a later one (right)…
(Other differences to note are the corners, the color, and the reflectivity of the surface).
By no means is anything final. I will likely change my mind several more times before MVP, and anyway, as soon as there is money I will probably get this all looked at by someone with better skills than mine.
But to the technical stuff I’ve been doing in the last month…
I’ve added the necessary features to my IL compiler (compiles JS to IL) to support the following traditional example:
// blinky.js MCU.start(); setInterval(() => gpio.pin('B4').toggle(), 500);
This is the hello-world of microcontrollers, to create a blinking LED. Of course, nothing yet blinks since there is a lot of work left to do on the compiler before I have actual machine code running on the device. But nevertheless it demonstrates a number of key features that the IL compiler needs, such as the ability to instantiate closures, call functions, access properties, etc.
Probably the biggest piece of work done in the last month is getting the virtual machine up and running.
Perhaps more interestingly, I have the above blinky example running on the virtual machine. I say “more interesting” because the blinky example demonstrates another key feature: suspending the virtual machine before the next stage of compilation. So what I have currently working is taking a program (blinky) that runs in the VM until the suspension point, and then the suspended machine is serialized as IL, including registers, stack, and heap allocations (the virtual heap includes functions). That’s a pretty cool point to be at!
[Edit] Re-reading this, I think I should clarify what I mean by “virtual machine”. I’ve previously made it clear that MetalScript programs don’t run on a virtual machine, so why is there a virtual machine? The reason is simply because in the two-phase execution model of MetalScript, where a program is executed at both compile time and runtime — it is the compile-time execution that is done on a virtual machine. The runtime execution is bare-metal.
MCU.start was called. This post-processing step is somewhat like a continuation passing style transformation. All the functions that were suspended in the call stack will be turned “inside out” so that their entry point is where they left off when the virtual machine was suspended.
Believe it or not, the VM stack is 5 levels deep at the point where the blinky example is suspended, even though the call is done from the root scope of the script. This is yet another illustration of the fact that “it’s more complicated than it looks”.
The result of this step will be a body of IL that does not need to contain any definition for the current register states or call stack, which will be much easier for the next phase of the compiler to deal with.
I’m also finalizing the design of what I call the “symbolic interpreter” which essentially will step through the IL to figure out what it does (and thus how to implement it in machine code). This is the most complicated and critical piece of the whole project. As I’ve said in previous posts, through the side experiment I called “MiniLanguage” I’ve gone far enough with this idea to feel confident of the direction I’m going, but MetalScript is an order of magnitude more complicated than MiniLanguage so it’s going to take some time to iron out the details.
I’ve also spent some time thinking about how
Looking further into the future, my plan is to keep pushing the blinky example through each phase of the compiler until I eventually get it out the other end and have an actual blinking LED. This would be a point of massive celebration.
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