==========================
 Textbooks and other news
==========================

Another fairly usual month passed by here: things move in the same
directions as they used to, whether good or bad.


Routers
=======

This month's new computer issue: the old router (TP-Link TL-WR841N/ND
v8, with LibreCMC) occasionally shuts down its Ethernet and Wi-Fi
interfaces for an unknown reason, so I have to reset it then. It
happened three times so far, always in the early morning. Fortunately
I had a new router stashed already (TP-Link Archer C7 v5), so unboxed
it and installed OpenWRT on it, though did not switch to it yet: just
ensured that it is ready to be used.


Backups
=======

The new router was sitting boxed near an external HDD, which I decided
to also unbox and turn into an additional backup HDD while at
it. Recently I thought that it would be nice to add single-device
redundancy to backups, perhaps some error correction codes, so that
partial damage to them (bit rot, as opposed to a full device failure)
would be repairable using just a single device: like par2, but faster
and aiming updates, or like RAID 1/5/6 on partitions of the same
device. ZFS has the "copies" parameter to set the number of copies for
each block, while Btrfs has the DUP profile (which is used for
metadata by default, but not for data, and which is like ZFS's
"copies=2"). I decided to use Btrfs on top of LUKS this time, since I
already have ZFS (as well as LUKS with ext4) backups, and it is
potentially useful to employ varied technologies for those. Also have
set Btrfs to use sha256 checksums instead of crc32c this time,
decreasing the chances of collisions. Looks like a nice setup for
backups, even though I had issues with Btrfs on work servers in the
past. Additionally, I created checksum list files with sha256sum(1)
and find(1), to verify the backups independently of the underlying
storage and without comparing to other backups (rsync --checksum), and
updated the personal data storage note accordingly.


Textbooks
=========

Speaking of backups, as well as of libre textbooks mentioned in the
previous post, I rediscovered openstax.org, which has good textbooks
licensed under CC BY, and added those to my public data backups. As
well as some books from libretexts.org: some of its subdomains
geo-block requests from me, but commons.libretexts.org is
available. Many links lead to 404 errors, and some of the books are
messy (not poorly written, but apparently the builds are semi-broken),
but there are seemingly fine ones. Skimmed Wikibooks again, too, but
those are rather disappointing.

Noticed that those textbooks, and documents in PDF format found online
in general, tend to use the US letter paper size, which is something I
did not pay attention to in the past, but now that I am considering
printing them, and since A4 (along with the metric system) is much
more widespread here, will have to deal with that. Then found that the
pdfarranger program appears to be suitable to cut margins on
alternating sides, so that they could be prepared nicely for
binding. Though it takes values in percents, rather than millimeters,
and while it would work for cutting the sides to fit width, I did not
check yet if it will work to fit the height precisely. But even if
that will fail, I could still use the libraries it uses, or adjust
it. Would be easier if sources of those textbooks were available: the
licenses allow to manipulate the books, but do not make it
easy. Actually CNXML (with MathML) sources of some OpenStax books are
available from their GitHub repositories at
<https://github.com/openstax>, and versions of some textbooks
converted into Markdown with MathML are at
<https://github.com/philschatz/textbooks>. Those should be more
suitable for different paper sizes than PDFs are, but once I tried to
convert the CNXML sources into HTML with cnx-transforms, found that it
does not label or enumerate figures and equations, which makes it
unsuitable for printing. The cnxml repository contains
cnxml_render.xsl, which tries to label and enumerate those after some
tinkering (removal of remote and unavailable dependencies, resulting
HTML and MathML adjustments), but still unreliably (or maybe I used it
wrong). There are other repositories that seem potentially relevant to
document compilation, but with larger projects, even more
dependencies, and equally little documentation. There is the
cnxml-help repository, which is supposed to specify CNXML, but it only
contains two strange placeholder images: of frogs, according to a
commit message, yet I do not recognize those as frogs. Which reflects
the state of its overall documentation.

For the potential printing of textbooks and other backups, I decided
to check a large local office supplies company's website (komus.ru)
for paper, and possibly for storage shelves. It welcomed me with HTTP
error 503 (service unavailable), while to curl, links2, and eww it
served status 401 (unauthorized), and when I followed a link from
Wikipedia, which probably added HTTP "referer", it did a few redirects
and served a page saying that it blocked me as a robot, suggested to
contact them by email to fix that. I wrote by email, describing the
situation and attaching a HAR archive from Firefox, as well as curl -v
output, and on the next day they asked me for a screenshot of the
error, an IP address, and an organization's taxpayer number. This
seems to match the unhelpfulness of ISP tech support, approaching that
of government services, which seems a little strange for a store, at
least on the stage when you are trying to buy goods from them. Anyway,
somehow it worked later, while I gave up on that conversation, and
later learned that the website is additionally not available from
foreign IP addresses, serving a page suggesting to "turn VPN off".

Somewhat related, I came across a public data hoarding thread on HN,
<https://news.ycombinator.com/item?id=42030832>. including a link to
<https://the-eye.eu/public/Books/>, which is blocked here already, but
serves a lot of books and assorted but amusing text files, including
small and humorous articles.

Now I wonder about more compact and portable textbooks:
printing-friendly and with compact files (for an easier digital
storage), both of which can be achieved by providing source files, and
preferably easily and reliably buildable ones, likely LaTeX, and being
careful with illustrations (simple and monochrome-friendly ones,
probably SVG). Can also consider abridging the contents: take
something like the Wikibooks physics study guide, with only core
formulae and definitions (or, in case of mathematical theories, with
axioms, main definitions and theorems, sketches of trickier proofs),
encouraging the reader to fill in the gaps, draw (some of) the
illustrations (akin to coloring books, "connect the dots"), to compose
(some of) the problems/exercises themselves, which should be a more
creative and potentially fun process than simply following a textbook
and solving the provided problems. Though creation of exercises, even
with a guide and usage of random numbers (similarly to solo RPGs), is
likely to have the downside of the reader already knowing what went
into the problem construction, which formulae to make use of to solve
those. Maybe that practice should be encouraged, but with some
problems still provided, resulting in something between a study
guide's 25 pages and an actual textbook's 1600. Though STEM books are
fairly information-dense as it is, and those on humanities would be
harder to compress without omitting information, so perhaps it is more
useful to focus on having sources with compact illustrations (either
finding or composing such books), rather than on experimental
adjustments of contents. Besides, one could mark portions that can be
omitted, such as additional exercises and explanations, allowing to
compile different (tiered) textbook versions out of a single
source. Or, as commonly done already, provide an additional problem
book.

I searched more for such libre and open source textbooks on GitHub,
and found "Introductory Physics: Building Models to Describe Our
World", <https://github.com/OSTP/PhysicsArtofModelling>, which covers
some of the common topics (though I did not spot optics,
thermodynamics, or quantum mechanics there), in a way similar to other
textbooks. It needed a couple of fixes (one of which was awkward
though: siunitx aims numbers without constants or variables for
quantities, so one has to call pi a digit or disable number parsing
altogether in order to represent a number like 4\pi e-7), but then I
built it fine: with its US letter size first, then tried A4, and
finally A5. There are some warts with A5, mostly on long equations
(which can be split) or multicolumn tables, and some images seem to be
scaled down, though all those are fixable.

TeX sources for textbooks on STEM subjects are easier to find, on
humanities are harder, though maybe in part it is so because the
latter group rarely requires complex typesetting.


Typesetting
===========

Once again I tried to find a TeX specification to properly learn how
it works, and possibly to employ some of that for the VMS markup as
mentioned in the previous post, but apparently there is no freely
available specification (that is neither a command reference nor a
tutorial), in which it is similar to ISO standards. The approximate
process (macro expansion, followed by primitive control sequences,
combined with use of external programs, producing "boxes and glue") is
mentioned here and there, but it is quite far from a comprehensive
specification.

So I decided to look for the specification of a relatively new
typesetting system, typst, and have not found much, either: similarly
to TeX, there are tutorials and a user reference, but no specification
in sight; the closest thing I found is docs/dev/architecture.md in its
repository, which outlines the process, but does not specify the
system. Though its website's domain name is typst.app, which hints at
this not necessarily aiming to center around a specified language, but
rather around a single program. And it sells some services, which may
explain such an organization. As a side note, I failed to install
typst via cargo, which complained about typst-kit not providing
features needed by typst-cli; unsure if it is just a broken package,
or the way Rust infrastructure is, since there are issues each time I
try to use it.

Then I looked into SILE: it ships a grammar (though its official one
is still that from the reference implementation), and actually looks
like a fine system, which has both XML and TeX-style syntaxes. It is
written in Lua, and provides Lua scripting, which is something I
thought would be nice for a typesetting language: to reuse an existing
one, rather than to invent its own awkward language for macros, though
then it has macros as well. As other typesetting systems, it provides
a dedicated syntax for mathematical formulae, but apparently it is
translated into MathML, which can be used directly as well (at the
cost of being very verbose). Chapter 9 of The SILE Book, "The Nitty
Gritty", describes how it works and the models used, which is the kind
of specification I was looking for with the others. While I have not
tried SILE, it looks nice overall after skimming the documentation.

MathML itself is thoroughly documented. It is a declarative markup
language, not a typesetting system, but could still be a starting
point, and maybe later I will read on its rendering techniques. Though
rendering may be relatively straightforward once all the elements are
clearly defined: traverse the parsed MathML tree, put together boxes
and glue, then render those (while going through the regular pain of
text rendering).

Then I tried and failed to find a troff specification, beyond
tutorials and user references, but played with its eqn(1) a
little. There are program sources which one may use as documentation,
but those are not suited for a quick skimming and comparison. At least
DVI has an unofficial description, and PostScript's reference looks
fairly comprehensive (it is not just a command reference, but also a
language reference, complete with an introduction and
explanations). For document preparation, perhaps the most practical
way is to keep using LaTeX while treating the lower layers as opaque,
or possibly XML with MathML, akin to CNXML (but with working tools and
documentation other than supposedly-frog pictures), or MathML directly
in HTML (though HTML LS is not exactly a fixed specification now), but
typesetting may still be interesting to play with someday. Maybe I
could update (or rewrite) wwwlite, adding MathML support there, and
switching away from GTK, decoupling rendering from the interactive
interface.

While for study notes (primarily problem solutions), I consider
adjusting my usage of mostly plain text with Emacs Lisp embedded for
basic calculations and some Unicode for compact representations of
basic formulae, and occasional embedded LaTeX for more complex
formulae, to Lisp covering all those cases, convertible into LaTeX
(e.g., as with SymPy, but Python's non-lisp syntax is not as clearly
embeddable into plain text). A Lisp-style syntax could work well for
formulae instead of LaTeX (let alone MathML), likely focusing more on
semantics (which makes more sense for reading as plain text, though
presentation-oriented languages may be simpler and more flexible). I
tend to think of URL references as of tricky parts of markup languages
usable as a plain text, but compared to formulae, they are relatively
straightforward.


Food
====

I tried a new syrniki (small cheesecakes) recipe, which I liked: 280 g
of low-fat tvorog (quark cheese), one egg yolk (though approximating
that with whole eggs is fine), 40 g of flour, up to 40 g of sugar,
some vanilla. Combine those, roll into a cylinder, cut into six
smaller cylinders, round them a little, place on a baking tray lined
with parchment paper, bake for 10 minutes at 180 degrees Celsius (or
fry on a pan a little, and then bake for 5 minutes). Quick, fairly
easy, protein-rich, and tasty.

I also looked into long-term food storage a little: usually I am not
into survivalism or emergency preparedness, but the way things around
here seem to be headed, including the economy, suggests that it may be
useful to convert some of the quickly inflating currency into a food
stockpile. Apparently finding proper Mylar bags is going to be tricky
here, though there are some stores with those (selling them as
accessories for freeze drying), and could try ordering those from
China, if I will figure how to access AliExpress without it freezing
Firefox. Tried to search for articles about local long-term food
storage practices, but only found SEO spam, translated or generated
texts.

Coincidentally, a new Technology Connections video about freeze dryers
came out soon after my little investigation, and as other videos on
that channel, it was nice and interesting.


Email
=====

Occasionally I wonder why there are no lightweight webmail projects
around, and considered writing one. At first I thought to use Maildir
and sendmail, then it seemed like IMAP and SMTP would be better to
use, allowing to not run it as a superuser or per-user processes, but
then noticed that since I usually set IMAP and SMTP to require TLS,
that would be an unnecessary dependency for a lightweight MUA. Now I
am more inclined towards Maildir again.

I tried to initialize a Rust project for that, to poke at it again,
with a dependency on the "imap" crate, but yet again Cargo took a few
minutes to update the package index, then failed because of my "old"
compiler version, suggesting to do a package manager's job and pick
the last dependency version that supports this compiler version. I
tried to do that, but then there were other packages not happy with
that version, and I gave up: it is just too bad. It is particularly
odd for a language that is about performance and safety, to have a
package manager this slow and aiming to ignore the standard
infrastructure, while asking the user to do a good chunk of a package
manager's job manually. Which is a shame, since the language still
looks promising, despite this infrastructure and its awkward
syntax. Noticed that when I see projects written in Rust, I expect
this broken build process with a suggestion to "curl | sh" things, and
probably covered in emojis, rather than something comparable to C, but
safer.

Though I rarely need a webmail, and rather short on time, so ended up
not starting that project at all.

In other email news, I learned about Dovecot's LAYOUT=fs option for
Maildir, as set in mail_location:
<https://doc.dovecot.org/2.3/configuration_manual/mail_location/Maildir/>. It
disables the Maildir++ directory layout, making Maildir compatible
with the way MUAs (including mu4e) tend to handle that, so running
MUAs on the server and on a personal computer does not lead to
directories duplicated with slightly different names. Renamed existing
directories manually to match that setting, though an automated
conversion would be tricky, it seems: Dovecot itself refuses to
convert mailboxes between formats with different folder separators,
and I have not found such converters among other Maildir-related
tools. Looks like it should be an easy task, though the Maildir++
specification is vague enough to make it quite error-prone; possibly
this is why there are no tools for that around.

And I had to migrate one of my mailboxes to a new server. Tried to
simply synchronize it using mbsync, but that led to duplicated
messages (as I noticed when decided to check it with mutt; mu4e did
not show the duplicates). Apparently this happens with mbsync after it
adds differing X-TUID headers, and then one may have to remove those,
and deduplicate the files. Fortunately I had a Maildir backup in a tar
archive, so simply wiped the Maildir, restored from the backup,
uploaded to the server with rsync, downloaded back with mbsync. Then
it was fine.


Work
====

There are still urgent tasks at work. For once implementing an open
protocol, called TLS (not Transport Layer Security, but Technische
Lieferbedingungen für Streckenstationen). The initially provided
documentation in Russian (with some highly bureaucratic notes around
it, chunks of which I saw) and English (TLS 2002) did not describe the
packets that were sent by a test remote device, but I found a TLS 2012
documentation in German (which I had to read with a dictionary or a
translator), which did (but I still had to check what and how is
implemented on the used controllers). The protocol aims to be general,
which comes with drawbacks, but it is sensible overall, compared to
the many proprietary ones used for similar purposes.

It aims always-on connections for both actuation (to keep signs and
messages shown in the manual mode) and data collection (to collect
"spontaneously" sent data messages), which is a little awkward to
implement in Haskell: while for data collection it fits the current
model without adjustments (accepting tasks and spawning independent
per-task threads, connecting to a node, streaming the results from its
multiple traffic detectors, one per lane, indefinitely), the actuation
process has to keep a single connection to a node that may contain
multiple VMS, while new independent tasks for those arrive
occasionally, and actuation status responses should be returned for
those, so the program should read packets from multiple connections
and new tasks simultaneously (in order to respond quickly), which is a
job for either an event loop or multiple threads with
synchronization. Inter-thread synchronization can be quite error-prone
and verbose, yet it is more or less idiomatic for Haskell. For now I
made an event loop with Control.Concurrent.Async's waitAny, to avoid
explicit threads with synchronization between them, but it would have
been more straightforward if the I/O functions were asynchronous in
the first place. I generally like Haskell, but not the blocking I/O,
the exceptions, and a few other things.

Among other tasks was debugging of the project mentioned in the
"useless code" post from 2018 here, which is not actively
developed. Now it turned out that some frontend changes related to
hurriedly introduced new functionality half a year ago broke some of
the old functionality, and nobody noticed until now. The frontend
development is outsourced, so I added a workaround in the backend,
which uncovered further frontend issues, which cannot be worked
around, like a seemingly hardcoded user ID in settings (also a sign of
hurried work and shipment). I would feel bad for its users, but
apparently nobody really uses it, except for occasional inspections or
presentations.


Other news
==========

- Had my sleep schedule disrupted by a combination of urgent work and
  investigation of things like food storage, printing, and typesetting
  systems, as well as some physics problems. Had unplanned naps as a
  consequence.

- Yet another law was passed here, voted for unanimously as usual,
  punishing for expression of more views. I would have violated quite
  a few of those (which are applied retroactively) already if I was
  more chatty on less technical topics, not to mention that those lead
  to more and more Internet resources blocked.

- Checked vacancies abroad yet again, confirmed again that those are
  dominated by Java. Some Python ones are available, mostly for "data
  engineering" and "data science", often additionally requiring
  technologies I am not familiar with, and often at startups, which do
  not seem to provide a good job security. Articles and threads like
  <https://news.ycombinator.com/item?id=42010249> suggest that much of
  commercial programming is like that these days.

- Discovered <https://www.nandgame.com/>, a nice game. Apparently
  based on nand2tetris courses, which are hosted on Coursera, and this
  is how I found that Coursera is now among the many blocked
  resources. Anyway, the game is nice: the subject is interesting, and
  it guides you, but you still basically build a simple relay computer
  there, and then program it in the "software" part. I had it long
  planned to go through some CPU design course, likely using VHDL (or
  maybe Verilog), to learn those at once, but postponing it, since
  there is plenty of other stuff to learn and to try. But at least
  touched this subject with that game, which was enjoyable.

- Working through the physics textbook at about the same rate as
  before, a chapter per month; finished chapter eight recently,
  reached chapter nine problems (on rotation of rigid bodies). Other
  studies and exercises also go slowly, but persistently. Except for
  ear training: not practicing that much, but maybe will resume in the
  future.


----

:Date: 2024-11-14
