The Mu shell has no string literals, only streams. No random access,
only sequential access. But I've been playing fast and loose with its
read pointer until now. Hopefully things are cleaned up now.
Like parenthesize, I'm copying tests over from https://github.com/akkartik/wart
Unlike parenthesize, though, I can't just transliterate the code itself.
Wart was operating on an intermediate AST representation. Here I'm all
the way down to cells. That seemed like a good idea when I embarked, but
now I'm not so sure. Operating with the right AST data structure allowed
me to more easily iterate over the elements of a list. The natural recursion
for cells is not a good fit.
This patch and the next couple is an interesting case study in what makes
Unix so effective. Yes, you have to play computer, and yes it gets verbose
and ugly. But just diff and patch go surprisingly far in helping build a
picture of the state space in my brain.
Then again, there's a steep gradient of skills here. There are people who
can visualize state spaces using diff and patch far better than me, and
people who can't do it as well as me. Nature, nurture, having different
priorities, whatever the reason. Giving some people just the right crutch
excludes others.
We now use traces everywhere for error-checking. Null traces introduce
the possibility of changing a functions error response, and therefore its
semantics.
I just realized Mu has a pretty big weakness: writes to null pointers don't
error out. Perhaps writes to address 0 do, but address 1 and so on don't?
I need a slightly more sophisticated page table.
Baremetal is now the default build target and therefore has its sources
at the top-level. Baremetal programs build using the phase-2 Mu toolchain
that requires a Linux kernel. This phase-2 codebase which used to be at
the top-level is now under the linux/ directory. Finally, the phase-2 toolchain,
while self-hosting, has a way to bootstrap from a C implementation, which
is now stored in linux/bootstrap. The bootstrap C implementation uses some
literate programming tools that are now in linux/bootstrap/tools.
So the whole thing has gotten inverted. Each directory should build one
artifact and include the main sources (along with standard library). Tools
used for building it are relegated to sub-directories, even though those
tools are often useful in their own right, and have had lots of interesting
programs written using them.
A couple of things have gotten dropped in this process:
- I had old ways to run on just a Linux kernel, or with a Soso kernel.
No more.
- I had some old tooling for running a single test at the cursor. I haven't
used that lately. Maybe I'll bring it back one day.
The reorg isn't done yet. Still to do:
- redo documentation everywhere. All the README files, all other markdown,
particularly vocabulary.md.
- clean up how-to-run comments at the start of programs everywhere
- rethink what to do with the html/ directory. Do we even want to keep
supporting it?
In spite of these shortcomings, all the scripts at the top-level, linux/
and linux/bootstrap are working. The names of the scripts also feel reasonable.
This is a good milestone to take stock at.
Kartik K. Agaram
Sumeet Agarwal