Visualizing programs with side-effects in a postfix shell with a live-updating text-mode environment. Built all the way up from machine code without any dependencies (except an x86 processor and Linux kernel).


Project page: github.com/akkartik/mu

More context: mastodon.social/@akkartik/1048

*Editing functions in the Mu shell*


Long delay since my last video. Printing floating-point numbers is *really* hard. I'm still half-assing it.

As a follow-up to merveilles.town/@akkartik/1053, I'm tightening focus to two threads:

a) These Mu shell experiments, and
b) An extremely skeletal OS to drop the Linux kernel dependency.

Deprioritized for now:
a) Other processors: RISCV, ARM, RPi, etc.
b) Graphics, mouse, etc. Device priorities for the OS are disk then ethernet.

*Towards running Mu without Linux*

All Mu really needs so far is to print to screen and read from the keyboard. Here's a 2-minute video about achieving that:


It seems such a small thing. But I needed lots of help, as you can see from the additions to my credits: github.com/akkartik/mu/compare

Merry Christmas to all! What a beautiful world.

Project page: github.com/akkartik/mu

More context: mastodon.social/@akkartik/1048

*Switching gears to pure graphics*

Until now Mu has followed classic Unix: stdin, stdout, pure text mode.

But giving up an OS kernel requires controlling the screen myself. Which requires various complicated probing for hardware. Then programs handling various screen sizes.

Easier: just always assume some common graphics mode. Say 1024x768 with 256 colors.

Interestingly, the default palette has far fewer than 256 colors. (Pic: 1024 cols each contain color `col%256`.)


*2020: Flood-filling the Mu computer*

A year ago I had a prototype of a C-level programming language mapping 1:1 to Assembly that I _thought_ could be type-safe.

Since then, I:

* wrote an academic paper on it
* made it type-safe
* began a high-level language atop it
* got into video, with 15 2-minute screencasts
* and ran programs written in it on bare metal, without an OS, like, 5 years before I expected to.

❤️ to everyone who inspired, taught, debated, encouraged.


*Rendering text atop baremetal*

Mu can now render text atop baremetal x86.

Try clicking around from akkartik.github.io/mu/html/bar

The boot-up machine code reads a few sectors from disk, configures a keyboard handler, and loads a bitmap font (2KB for ASCII, with the option for more).

I use GNU Unifont. I believe that means Mu is now GPL v2. So stated. IANAL and I try not to think about software IP. But a font? Copyright seems reasonable there.

Next up: a text editor!


*A more international interface for rendering text*

New 2-minute video: archive.org/details/akkartik-2

You get just one fixed screen resolution: 1024x768, 256 colors. Widely available on modern machines, no drivers needed.

You get just one fixed-width bitmap font. No bold/italics, no anti-aliasing.

BUT it won't make assumptions about English and left-to-right order. I eventually want anybody to be able to customize it to their language.

Main project page: github.com/akkartik/mu

I've been trying to visualize the default 256-color palette I get on baremetal.


To my eyes it looks like I can/should just live in the first 128 colors.

I built a game of "snakes", but it came out more like an etch-a-sketch 😄


Play it on any non-windows:

git clone github.com/akkartik/mu
cd mu
./translate_mu_baremetal_emulated baremetal/ex7.mu
qemu-system-i386 disk.img

h/j/k/l to draw

It took a while, but I've finally ported a pre-existing Mu program to baremetal: an RPN calculator.

This was _hard_, purely because of cursor management. I have a greater appreciation for everything that display hardware and terminal emulators provide for text mode. Mu so far puts the onus on the programmer.


In the end it's interesting to visualize the changes I had to make:

vim -d apps/rpn.mu baremetal/rpn.mu

They're entirely in `main`; the rest is unchanged.

I've been reimplementing my from-scratch live-updating postfix shell to _really_ from scratch (no more OS kernel), while at the same time rewriting the prototype with lots of tests and actually giving the language some sort of rigorous basis. No demos yet, but in the meantime here's Conway's Game of Life running on baremetal Mu.


Sources: akkartik.github.io/mu/html/bar

Main project page: github.com/akkartik/mu

The Mu shell is now off Linux


Starting point for the sources: akkartik.github.io/mu/html/bar

The architecture is now much cleaner. Functions contain lines, lines contain words, words contain gap buffers. Rendering a thing renders its constituent things. Render takes a top-left coordinate and returns a bottom-right coordinate. Each thing knows which constituent thing has its cursor, shows its cursor when rendering, redirects incoming keystrokes to it.


An experimental way to do control flow in the postfix Mu shell

The screenshot below shows an idea I've been playing with.

The conventional way Forth does control flow is a little confusing with words like `if` and `then` showing up at the end.

Factor uses quotations to put code blocks on the stack. But then you see a potentially complex chunk of code executing "all at once".

Main project page: github.com/akkartik/mu

Drilling into computations on the Mu shell

This was one of the more difficult things I've built, and yet all I've gotten working so far is some rudimentary tokenization. The reason is one little feature.. well, take a look for yourself.

archive.org/details/akkartik-2 (video; 2 mins)

As always, built all the way up from machine code, and designed primarily to be easy to build, easy to run, comprehensible to others. Also this time with lots of tests


Today was documentation day

Primitives available in the Mu computer when running without an OS: github.com/akkartik/mu/blob/ma

Primitives available when running on Linux: github.com/akkartik/mu/blob/ma

For starters I focused just on making things more discoverable. These files are optimized for opening in your text editor, jumping to definitions to see type signatures, etc. See github.com/akkartik/mu/blob/ma for a ctags configuration for Mu and SubX programs.

Main project page: github.com/akkartik/mu

Mu can now read from an ATA (IDE) disk drive on Qemu.


It wouldn't have been possible without the lovely folks over on . And the inspiration of ColorForth (merveilles.town/@akkartik/1059), though I still don't understand how that driver works.

The Mu computer now has drivers for disk and mouse.

Still extremely klunky. IDE disk drives only, and the mouse driver uses polling because configuring IRQ 12 is still beyond me.

Example programs (as usual memory safe and translating 1:1 to x86 machine code)

Disk: akkartik.github.io/mu/html/ex9

Mouse: akkartik.github.io/mu/html/ex1

Here's video of the mouse example. There's no pointer so you have to imagine me moving the mouse around.

Like I said. Klunky.

Main project page: github.com/akkartik/mu

What should the signature of a program look like?

Typed languages have a fixed signature for function `main`. A list of strings, a window context, or an IO monad.

Here's the signature on the Mu computer:

fn main screen: (addr screen), keyboard: (addr keyboard), data-disk: (addr disk)

A rudimentary, hokey capability system. No mouse yet. 'screen' is only used for text; pixel graphics currently go around it. 'data-disk' can't access code, and will eventually include finer-grained restrictions.

Mu's HLL is now Turing-complete, I think.

Things to notice:
* Wordstar-style menu at the bottom.
* List of available primitive functions in bottom left.
* List of globals on the left side that updates as I add definitions.
* Matching parens highlighted as I type.
* Drilling down into the trace to understand how the program was evaluated.


Main project page: github.com/akkartik/mu

Prototyping on the Mu computer

A 3-minute video showing what it's currently like to prototype programs on the Mu computer. There are lots of limitations. It's slow, and it can only handle short runs.

While these limitations will be relaxed over time, the goal is partly to nudge people to throw the prototype away once they know what they want, and rewrite it one level down. Therefore: encourage people to write lots of tests.


Main project page: github.com/akkartik/mu

Managing side-effects on the Mu computer

archive.org/details/akkartik-m (video; 2 minutes)

The Mu computer's prototyping environment uses _traces_ to explain and debug programs. But traces are expensive to compute and made the environment slow and laggy.

I fixed things by collecting only a shallow trace at first, and iteratively deepening on demand by rerunning programs. This only works because it's safe to rerun functions. There are no side-effects in Mu.

Main project page: github.com/akkartik/mu


Some live-coding in my programming environment, running on my computing stack built up from scratch.

archive.org/details/akkartik-m (video; 6 minutes)

Main project page: github.com/akkartik/mu

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Collaborating on a problem from Advent of Code in Mu

If anybody is into long and rambling 100-minute videos that taper off without a certain conclusion:


Mostly by Sumeet Agarwal (github.com/sumeet)

Here's the working solution if anyone wants to try it out it: akkartik.github.io/mu/html/lin

Main project page: github.com/akkartik/mu

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