*Update on the Mu computer's memory-safe language*

Progress has been slow over the holiday season because I've been working on a paper about Mu for 2020.programming-conference.or

But functions can now return outputs.

fn foo a: int -> result/eax: int {
result <- copy a
increment result

Project page: github.com/akkartik/mu#readme

Sources for the memory-safe language, now at 5kLoC: akkartik.github.io/mu/html/app

Caveats: no checking yet, only int types supported.

*Update on the Mu computer's memory-safe language*

Still no type-checking or memory-safety, but we can now write any programs with int variables.

There's still no 'var' keyword, so we can't define local variables yet. But that's not insurmountable; just pass in extra arguments for any space you want on the stack 😀

result <- factorial n 0 0 0

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*Update on the Mu computer's memory-safe language*

Basic language is done! Here's factorial. (Compare mastodon.social/@akkartik/1027.)

Still todo:
- user-defined types
- type checking and memory-safety

In other words, I'm about a third of the way there 😂 More detailed todo list: lobste.rs/s/pv8jpr/what_are_yo

(More details on the Mu project: akkartik.name/post/mu-2019-1. Repo: github.com/akkartik/mu)

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A brief timeline of the Mu computing stack

Jul 6, 2014: commit 0, tree-based interpreter for a statement-oriented language (github.com/akkartik/mu)

Jul 19, 2017: commit 3930, start of SubX machine code (akkartik.name/post/mu-2019-1)

Sep 20, 2018: started building SubX in SubX (mastodon.social/@akkartik/1007)

Jul 24, 2019: SubX in SubX done, commit 5461 (mastodon.social/@akkartik/1024)

Oct 2, 2019: started designing the Mu memory-safe language (akkartik.name/post/mu-2019-2)

Oct 29: started akkartik.github.io/mu/html/app

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I'll be in Porto, Portugal on Mar 24 to present a paper on Mu at the Convivial Computing Salon: 2020.programming-conference.or

Hoping for some great conversation and disagreements.

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*Update on the Mu computer's memory-safe language*

Mu just got its first couple of non-integer types: addresses and arrays. As a result, the factorial app can _finally_ run its tests based on command-line args.


Addresses are accessed using a '*' operator. Arrays are accessed using an 'index' instruction that takes an address (addr array T) and returns an address (addr T).

Literal indexes aren't supported yet.

Open q: indexing arrays of non-power-of-2 element sizes.

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*Update on the Mu computer's memory-safe language*

Still no type-checking or memory-safety, but we have partial support for arrays and product types. Still several sharp edges:

- can't index an array with a literal
- can't index an array with non-power-of-2-sized elements
- can allocate but not use arrays/records on the stack

My todo list is growing. But work per item is shrinking. Hopefully there's an asymptote.

(More details: akkartik.name/post/mu-2019-1. Repo: github.com/akkartik/mu)

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*Update on the Mu computer's memory-safe language*

Arrays and product types are now done. Any remaining rough edges are working as intended 😄 Only hex literals, for example.

What's left? Actually making it safe.

Complexity outlay so far: 16k lines of code, but only 6.5k if you exclude tests. Tests get _very_ repetitive in machine code. Hopefully we won't need another 15k LoC.

Example program: akkartik.github.io/mu/html/app

(More details: akkartik.name/post/mu-2019-2. Repo: github.com/akkartik/mu)

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The Mu compiler summarized in one page: akkartik.github.io/mu/html/mu_

More details: akkartik.name/akkartik-convivi

Repo: github.com/akkartik/mu

(Brief update since there isn't much to report: I'm working on safe heap allocations as described in the paper. But it's slow going because of life and the need to unwind some past decisions.)

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I'm back from a death march.

Mu is a safe language built in machine code, translating almost 1:1 to machine code. A key check is for use-after-free errors, using a second address type (akkartik.name/akkartik-convivi, section 4.4)

I spent the last 2 months switching all of Mu's implementation to this scheme. It was a tough time: lobste.rs/s/vcx5vu/what_are_yo. But now I know it works (with 10-15% slowdown), and Mu functions calling low-level libraries should behave unsurprisingly.


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I'm starting to build some simple apps in Mu, my memory-safe language that translates 1:1 to machine code.

Today I built a program to print a file to screen: akkartik.github.io/mu/html/app

Experience report: github.com/akkartik/mu/commit/

- I fixed a bug in the process: github.com/akkartik/mu/commit/
- I wished I already had clobbered-variable warnings.
- I wished I had type checks.

All in all, this language isn't ready for others yet. I'm constantly inspecting the code generated by the translator.

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A new day, a new app

A text-mode paginator for text files. Think `more`, but no ncurses, no termbox, no libc, just Linux syscalls.

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

App sources: akkartik.github.io/mu/html/app

Repo: github.com/akkartik/mu

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It's amazing how much you can do layout-wise with just plain text. Pictured in this toot:

Alice in Wonderland by Lewis Carroll

Poems by e e cummings (en.wikipedia.org/wiki/E._E._Cu)

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My text-mode paginator for text files implemented all the way up from machine code now supports a tiny subset of Markdown syntax. Screenshots below.

The code is terribly ugly, and there are zero tests. But it did help flush out three bugs in Mu. Next steps:

- Build out the compiler checks I missed the most.
- Implement a fake screen and keyboard so I can write tests for this app.
- Throw the app away and redo it right.

(Background: akkartik.name/akkartik-convivi. Repo: github.com/akkartik/mu)

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Why do programming languages require us to specify what modules we use? I think that stuff is easy to deduce. Even in machine code.


cc @s_ol

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@akkartik @s_ol Two modules, A and B, both implement a procedure P. Your program needs to use both implementations of P. How is the language to know which one to call where?


@akkartik @s_ol One thing I absolutely abhore about Scala is that it has *implicit* parameters to some types of methods. You don't need to mention them in the method call, but they're there. I learned about them while trying to use Chisel (hardware description language).

It was a **horrible** experience to me as a programmer. Made debugging nigh impossible.

IMHO, explicit is always better than implicit. Unconditionally.

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@akkartik @s_ol That said, what you're doing in the video reminds me a great deal of some early research into statically compiled, prototype-based object oriented languages (I can't recall specific names at the moment; it's been a while!), where the compiler infers types based on static analysis of prototypes and how they're created and later used.

It's been a few years; I can't recall details at the moment.

@vertigo Agreed! I'm not sure if this was pushing back on something I said, but I was thinking the same in my parting shot on implicitly loaded standard libraries.

@akkartik I was actually thinking about the case of having smaller libraries built by different people, rather than a large library.

For example, a GUI toolkit could have a procedure named DrawLine, while a Postscript printer interface might also have a DrawLine procedure.

You mention namespaces, but how would they work? Are namespaces also implicitly created?

@vertigo I wasn't thinking of a single approach:

1. Some languages support local names for imports.

2. Some languages (C++) have idioms of libraries putting their code in 'unique' namespaces.

Stuff like that.

Scala sucks for many reasons, not least that all the rich type information is lost in the jvm bytecode. A lot of behaviors in Scala are just impossible to debug in a debugger. Lazy initialization had me running in circles for weeks once (because the debugger would initialize the variable to show it's value.)
@akkartik @s_ol

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