C POSIX library Updated 2025-07-16
Quick overview at stackoverflow.com/questions/1780599/what-is-the-meaning-of-posix/31865755#31865755
Exmples under c/posix:
- c/posix/signal_return.c: stackoverflow.com/questions/37063212/where-does-signal-handler-return-back-to
- c/posix/inet/pton.c:
inet_ptondemo. Adapted fromman inet_ptonon Ubuntu 23.04. Usage:Output:./pton.out 192.187.1.42So we see that the strings was converted to an integer, e.g.:0xc0bb012aSee also: stackoverflow.com/questions/1680622/ip-address-to-integer-c/76520978#76520978- 0xc0 = 192
- 0xbb = 187
- 0x01 = 1
- 0x2a = 42
- c/posix/inet/ntop.c:
inet_ntopdemo. Adapted fromman inet_ptonon Ubuntu 23.04. Usage:Output:./ntop.out 0x01021AA0./ntop.out 0x01021AA0
C (programming language) Updated 2025-07-16
It is interesting to note how late C appeared: 1972, compared e.g. to Fortran which is from 1957. This is basically because C was a "systems programming language", i.e. with focus on pointer manipulation, and because early computers were so weak, there was no operating system or many software layers in the early days. Fortran however was a numerical language, and it ran directly on bare metal, an application that existed before systems programming.
Examples under c.
Craig Silverstein Updated 2025-07-16
How Google began by Craig Silverstein part 1 (2006)
Source. Talk given at the University of North Carolina. A possibly official invitation from the time: www.ibiblio.org/pjones/blog/googles-craig-silverstein-at-unc-1026/. Craig Steven Wright is the Billy Mitchell of Bitcoin Updated 2025-07-16
Billy Mitchell comes strongly to mind!They even look similarly fraudulent.
Cray Updated 2025-07-16
Create a test user in PostgreSQL Updated 2025-07-16
In order to create a test user with password instead of peer authentication, let's create test user:
createuser -P user0
createdb user0-P makes it prompt for the users password.Alternatively, to create the password non-interactively stackoverflow.com/questions/42419559/postgres-createuser-with-password-from-terminal:Can't find a way using the
psql -c "create role NewRole with login password 'secret'"createuser helper.We can then login with that password with:which asks for the password we've just set, because the
psql -U user0 -h localhost-h option turns off peer authentication, and turns off password authentication.The password can be given non-interactively as shown at stackoverflow.com/questions/6405127/how-do-i-specify-a-password-to-psql-non-interactively with the
PGPASSWORD environment variable:PGPASSWORD=a psql -U user0 -h localhostNow let's create a test database which
user0 can access with an existing superuser account:createdb user0db0
psql -c 'GRANT ALL PRIVILEGES ON DATABASE user0db0 TO user0'We can check this permission with:which now contains:The permission letters are explained at:
psql -c '\l' List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
user0db0 | ciro | UTF8 | en_GB.UTF-8 | en_GB.UTF-8 | =Tc/ciro +
| | | | | ciro=CTc/ciro +
| | | | | user0=CTc/cirouser0 can now do the usual table operations on that table:PGPASSWORD=a psql -U user0 -h localhost user0db0 -c 'CREATE TABLE table0 (int0 INT, char0 CHAR(16));'
PGPASSWORD=a psql -U user0 -h localhost user0db0 -c "INSERT INTO table0 (int0, char0) VALUES (2, 'two'), (3, 'three'), (5, 'five'), (7, 'seven');"
PGPASSWORD=a psql -U user0 -h localhost user0db0 -c 'SELECT * FROM table0;' Crushbridge Updated 2025-07-16
It is good to see that top-universities is still keeping up with it's main purpose: spontaneous eugenics:
Cryogenic electron microscopy Updated 2025-07-16
This technique has managed to determine protein 3D structures for proteins that people were not able to crystallize for X-ray crystallography.
It is said however that cryoEM is even fiddlier than X-ray crystallography, so it is mostly attempted if crystallization attempts fail.
We just put a gazillion copies of our molecule of interest in a solution, and then image all of them in the frozen water.
Each one of them appears in the image in a random rotated view, so given enough of those point of view images, we can deduce the entire 3D structure of the molecule.
Ciro Santilli once watched a talk by Richard Henderson about cryoEM circa 2020, where he mentioned that he witnessed some students in the 1980's going to Germany, and coming into contact with early cryoEM. And when they came back, they just told their principal investigator: "I'm going to drop my PhD theme and focus exclusively on cryoEM". That's how hot the cryo thing was! So cool.
Cryptocurrency swapper Updated 2025-07-16
It is basically the same as buying and selling from exchanges for fiat, except that you only get fiat.
Swappers are in general able to receive send coins from any address, including self custody addresses.
Centralized swappers were a good way to workaround the endless Monero bans from exchanges circa 2024, e.g. x.com/cirosantilli/status/1771900725649371240 as they effectively serve as proxies for exchanges that are still legal in other countries.
They will eventually have to ban Monero of course, and then the only way left will be decentralized exchanges.
This leads to a scenario where the only effective way to ban Monero is to also ban all other cryptocurrencies. The question is if countries will go that far or not.
Csound FLOSS manual Updated 2025-07-16
Includes introduction to the basic sound synthesis and their implementation in Csound.
Examples run on browser via Emscripten and just worked on Ubuntu 20.04!
Examples can also be downloaded all at once from: www.csound-tutorial.net/floss_manual/ Shame not in Git as standalone files.
CSS flex Updated 2025-07-16
Other examples include:
- css/flex-fill-vertical.html: minimal setup for a editor: docs.ourbigbook.com/editor
That example calculates and displays the final widths via JavaScript, making it easier to understand the calculations being done.
csvgrep and select column in csvkit Updated 2025-07-16
There seems to be no way without a pipe, you seem to need to reparse the columns, e.g. the tutorial at: csvkit.readthedocs.io/en/latest/tutorial/2_examining_the_data.html#csvgrep-find-the-data-you-need does:
csvcut -c county,item_name,total_cost data.csv | csvgrep -c county -m LANCASTER Cuju Updated 2025-07-16
Lit. "to kick (leather) ball".
Figures notbaly in Water Margin, where it is played by Gao Qiu. The novel also suggests that it was considered a lesser art, e.g. as opposed to the scholarly four arts and the "proper" martial arts.
Cycle graph (algebra) Updated 2025-07-16
How to build it: math.stackexchange.com/questions/3137319/how-in-general-does-one-construct-a-cycle-graph-for-a-group/3162746#3162746 good answer with ASCII art. You basically just pick each element, and repeatedly apply it, and remove any path that has a longer version.
Immediately gives the generating set of a group by looking at elements adjacent to the origin, and more generally the order of each element.
TODO uniqueness: can two different groups have the same cycle graph? It does not seem to tell us how every element interact with every other element, only with itself. This is in contrast with the Cayley graph, which more accurately describes group structure (but does not give the order of elements as directly), so feels like it won't be unique.
Cycle notation Updated 2025-07-16
A permutation group can then be described in terms of the generating set of a group of specific elements given in cycle notation.
E.g. en.wikipedia.org/w/index.php?title=Mathieu_group&oldid=1034060469#Permutation_groups mentions that the Mathieu group is generated by three elements:which feels quite compact for a simple group with 95040 elements, doesn't it!
- (0123456789a)
- (0b)(1a)(25)(37)(48)(69)
- (26a7)(3945)
Cycle of an element of a group Updated 2025-07-16
Take the element and apply it to itself. Then again. And so on.
In the case of a finite group, you have to eventually reach the identity element again sooner or later, giving you the order of an element of a group.
The continuous analogue for the cycle of a group are the one parameter subgroups. In the continuous case, you sometimes reach identity again and to around infinitely many times (which always happens in the finite case), but sometimes you don't.
Cycler Turing machine Updated 2025-07-16
Bibliography: discuss.bbchallenge.org/t/decider-cyclers/33
Example: bbchallenge.org/279081.
These are very simple, they just check for exact state repetitions, which obviously imply that they will run forever.
Unfortunately, cyclers may need to run through an initial setup phase before reaching the initial cycle point, which is not very elegant.
Cycling in the United Kingdom Updated 2025-07-16
The United Kingdom is a great place to cycle in general as there's plenty of small country roads and interesting new small towns to discover, perhaps much like the rest of Europe, as opposed to the United States, which likely has some huge infinitely long straight roads with a lot of nothing in between.
Of particular interest is the large amount of airfields and small air raid shelters in the fields, an ominous reminder of world war 2. The airfields are in various states, from functional military fields, many converted to civilian usage, some have barely any tarmac left but still see usage. And some were just completely abandoned and decayed and became recreation grounds and farms. The UK is therefore also a great place to be if you want to learn to fly as a hobby!
Good starting point:
Next, you want to decide about nice destinations to reach/go through, and these are good ideas to look into:
- Area of Outstanding Natural Beauty
- National Trust
- Royal Society for the Protection of Birds (RSPB)
Czochralski method Updated 2025-07-16
Dance of the Yi People Updated 2025-07-16
Composed by Wang Huiran in 1960.
The Yi people are one of the 55 Chinese ethnic minorities officially recognized by the Chinese government.
Dance of the Yi People performed by Liu Dehai
. Source. From the album Chinese Plucked Instruments: Vol. 2 - Fishermen’s Song At South Sea: www.amazon.co.uk/Chinese-Plucked-Instruments-Fishermens-South/dp/B001HUECZQ (2004) There are unlisted articles, also show them or only show them.