explain xkcd - User contributions [en]

Talk:1960: Code Golf

2022-09-14T18:39:32Z

172.70.211.82:

What's the programming language? It seems to me like a special reverse golf variant of Python, where <code>def</code> is replaced by <code>define</code>, just to make it longer. Or is there a real language with that syntax? --[[Special:Contributions/172.68.110.106|172.68.110.106]] 08:40, 26 February 2018 (UTC)
: Lisp/some derivatives (I'm most familiar with scheme) use <code>define<define></code> as does Slate, however both have a different syntax. Most likely, this is just pseudo-code. [[User:Baldrickk|Baldrickk]] ([[User talk:Baldrickk|talk]]) 09:59, 26 February 2018 (UTC)

Definitely going to have to include a link to the actual longest language: Unary, which is literally just a certain length of 1s. No one actually writes in it: you write in another language and then it gets converted. [[User:Trlkly|Trlkly]] ([[User talk:Trlkly|talk]]) 10:48, 26 February 2018 (UTC)
: You could make a longer programming language by representing "1" with some longer string; perhaps the entire text of Moby Dick. And now the file size can be arbitrarily big. [[Special:Contributions/198.41.230.100|198.41.230.100]] 16:45, 26 February 2018 (UTC)
:: Though this idea is still quite compressible. It might be better (?) to make a language where the file size cannot be easily significantly compressed.[[Special:Contributions/172.68.25.106|172.68.25.106]] 16:48, 26 February 2018 (UTC)

This might be directed at a code golfing challenge currently taking place: https://codegolf.stackexchange.com/questions/152856/write-moby-dick-approximately. The goal is to write a program that outputs a text, that is as closly as possible to moby dick, while no containing it, and of course beeing as small as possible.[[Special:Contributions/141.101.105.150|141.101.105.150]] 13:04, 26 February 2018 (UTC)

Not sure why JSFuck is included in the explanation. Not sure how it really has any relevance here as it is not mentioned in the text and is not the programming language being used by Randall in the comic. [[Special:Contributions/108.162.216.94|108.162.216.94]] 13:18, 26 February 2018 (UTC)

: agreed, JSFuck is not relevant in the explanation. moved it to the discussion (see below) [[User:Thawn|Thawn]] ([[User talk:Thawn|talk]]) 13:56, 26 February 2018 (UTC)

:: Instead of {{w|Python (programming language)|Python}}, one could use {{w|JSFuck}} though, which is valid {{w|JavaScript}} code - but written with only six different characters. Even mundane variable names like `LowestDenominator` will take up hundreds, if not thousands, of bytes in JSFuck. {{unsigned|Comment Police}}
: I added it because JSFuck allows you to write you simple and useful tasks with zillions of bytes, each of which is needed for the programm to run correctly. It's the ultimate Reverse Coding Golf.--[[Special:Contributions/172.68.50.178|172.68.50.178]] 13:53, 27 February 2018 (UTC)
Off Topic: I just realized that statistical thermodynamics is nothing else than reverse molecule golf: The entropy of a given system is equal to the maximum score you can achieve in reverse molecule golf. [[User:Thawn|Thawn]] ([[User talk:Thawn|talk]]) 13:56, 26 February 2018 (UTC)

Seems like Java programmers play this game all the time.[[Special:Contributions/162.158.234.100|162.158.234.100]] 20:13, 26 February 2018 (UTC)

Someone made everyone's comments monospaced. Please fix this. [[Special:Contributions/198.41.230.100|198.41.230.100]] 14:24, 26 February 2018 (UTC)
:Fixed [[Special:Contributions/162.158.155.26|162.158.155.26]] 15:52, 26 February 2018 (UTC)
:They just wanted to play reverse comments golf with the comments section by making the comments take as much space as possible. [[Special:Contributions/162.158.126.76|162.158.126.76]] 15:56, 26 February 2018 (UTC)

This is called Code Bowling.

I would like to point out that there may be a ReCaptcha site shutdown? It will occur on the 1st of March (maybe). [[User:QATEKLYXM|QATEKLYXM]]

Is the explanation thinking of miniature golf when it mentions a hedge or border and the need for a ramp? In actual golf you can easily hit the ball through the air with almost every single club...and just as easily hit it off of the golf course.
[[[Special:Contributions/172.69.62.64|172.69.62.64]] 15:11, 27 February 2018 (UTC)]

Curious Georges also likes Reverse Regular Golf! [[Special:Contributions/108.162.237.232|108.162.237.232]] 02:18, 28 February 2018 (UTC)

I found this xkcd confusing because there appears to be no obvious limiting principal. The code in the panel is written verbosely, but it could easily be a word longer, a paragraph longer, a page longer, a chapter longer, an entire book longer. Nor is skill (or chance!) particularly required to do such a thing [I suppose in "blinded reverse code golf" the question might be to guess how much length your opponents would bother to express and then to top that]. The result is I feel confused. Maybe my standards for humor are too high, but maybe, also, I'm just missing something here? [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 12:02, 28 February 2018 (UTC)
: +1 [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 12:07, 28 February 2018 (UTC)
: I think that is the joke: what a stupidly bad game reverse code golf is. ditto for reverse regular golf. Or a dumb excuse for writing unreasonably long code/playing with a golfball in random settings [[ User:00N8 ]]

No mention of The International Obfuscated C Code Contest? It's about as close to reverse code golf as there is. [[Special:Contributions/172.68.255.158|172.68.255.158]] 14:20, 28 February 2018 (UTC)

If Randall plays Reverse Golf while playing out-of-bounds, and that means he's getting at least one penalty stroke for every regular, out-of-bounds stroke, it seems to me he perfectly well understood the rules of both golf and reverse golf. He's gaining strokes at twice the regular speed. [[Special:Contributions/141.101.104.17|141.101.104.17]] 15:49, 28 February 2018 (UTC)
:this guy gets it [[ 00N8 ]]

I was so confused by this comic it took me a few minutes to figure out "This was the first comic in the My Hobby series for over a year" is supposed to read "''in'' over a year" [[Special:Contributions/108.162.221.95|108.162.221.95]] 05:43, 23 March 2018 (UTC)

Code golf is the attempt to use as few *key-strokes* as possible, that makes the analogy with regular golf strokes clearer. (currently reads "Code golf is the attempt to use as few characters as possible") [[Special:Contributions/162.158.154.103|162.158.154.103]] 15:16, 19 September 2018 (UTC)

To me, "reverse regular golf" is starting with the ball in the hole, and you need to get it out and to the starting position in as little hits as possible. the second part of the title text is explained by how its very difficult to get the club into the whole and hit the ball out of it. maybe add this to explanation? [[Special:Contributions/108.162.221.193|108.162.221.193]] 11:53, 14 September 2021 (UTC)Bumpf
Isn't the code obviously a reference to "Moby Dick"? I think this should be added to the "Trivia" section. [[Special:Contributions/172.70.211.82|172.70.211.82]] 18:39, 14 September 2022 (UTC)

2606: Weird Unicode Math Symbols

2022-05-04T22:24:14Z

172.70.211.82: Undo revision 254925 by Ex Kay Cee Dee (talk)

{{comic
| number = 2606
| date = April 13, 2022
| title = Weird Unicode Math Symbols
| image = weird_unicode_math_symbols.png
| titletext = U+2A0B ⨋ Mathematicians need to calm down
}}

==Explanation==
{{incomplete|Created by A SNAKE AVOIDING A BEE ON A WHITEBOARD - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic proposes joke explanations for various {{w|unicode symbols}} with obscure or no known uses.

{| class="wikitable"
|+ Symbols
|-
! Codepoint !! Symbol !! Unicode Name !! Actual use !! Randall's meaning || Explanation
|-
| U+29CD || ⧍ || Triangle with Serifs At Bottom || No standard use, but resembles the {{w|National Park Service}} cartographic symbol for a campsite.[https://github.com/nationalparkservice/symbol-library/] || Shark || May look like a shark fin sticking out of the water.
|-
| U+23E7 || ⏧ || Electrical Intersection || Indicates where wires branch off || Traffic circle || Looks like a diagram of a {{w|roundabout}} as might be shown on a minimap beside a routing direction.
|-
| U+2A33 || ⨳ || {{w|Smash product}} || The quotient of the underlying spaces of two {{w|pointed space}}s, where points in the {{w|product spaces}} are identified if they contain either labeled point as an element. || Hashtag || Looks somewhat like the {{w|Number sign|hash}} symbol (#) – commonly used for indicating tags called {{w|hashtag}}s in social media – turned by 45 degrees.
|-
| U+2A7C || ⩼ || Greater-Than with Question Mark Above || Used in proofs to indicate a greater-than relation that should exist but hasn't been proven yet (non-rigorous) || Confused alligator || One metaphor used when teaching inequality signs in primary school is that the sign looks like an alligator mouth "eating" the larger number. Question marks are commonly used in cartoons to indicate confusion on the part of a character.
|-
| U+299E || ⦞ || Angle with S Inside || Plural for the angle symbol (∠) [https://www.quora.com/Unicode-How-is-the-s-in-triangle-glyph-used-in-mathematics][https://www.birdvilleschools.net/cms/lib2/TX01000797/Centricity/Domain/1114/Homework%20Helper%20Unit%203%20ch%209-10.pdf] rarely used || Snack || May look like a mouth eating an S, where the S symbolizes some snack food.
|-
| U+2A04 || ⨄ || {{w|Arity|N-ary}} Union Operator with Plus || Disjoint union[https://books.google.com/books?id=531cAgAAQBAJ&pg=PA165&lpg=PA165&dq=%E2%A8%84&source=bl&ots=oYXkMNXP-T&sig=ACfU3U2QvMRBkD7uVG0OSumKI0JQtjTIKA&hl=en&sa=X&ved=2ahUKEwios862ypL3AhWXVTABHTnQALQQ6AF6BAgKEAM] (joining a family of sets that have no elements in common) || Drink refill || Looks like a cup with a plus to indicate adding drink to the cup.
|-
| U+2B48 || ⭈ || Rightwards Arrow Above Reverse Almost Equal To || Pairs with ⭂ which could conceivably mean {{w|Assignment (computer science)|assignment}} of an {{w|Approximation|approximation}}, but neither seem to be in use. || Snakes over there || Looks like two squiggles to represent snakes and an arrow indicating the direction where they may be found.
|-
| U+225D || ≝ || Equal To By Definition || Indicates an equation where the left side is to be defined as the right side[https://www.reddit.com/r/math/comments/1z1mty/can_someone_please_explain_the_equal_to_by/] usually used in proofs to indicate a definition is being introduced|| Definitely, for sure || "Def" is a contraction of "definitely" used in slang; the equal sign looks like a double underline, indicating heavy emphasis.
|-
| U+237C || ⍼ || Right Angle with Downwards Zigzag Arrow || No purpose is known.[https://ionathan.ch/2022/04/09/angzarr.html] Speculation includes "Y axis continues downward," a diode with a gate, proof by contradiction, a proofreaders' mark to split a word, and indication of polarization direction. || Larry Potter || Looks like the letter "L" and a lightning bolt. {{w|Harry Potter (character)|Harry Potter}} is known for having a lightning bolt-shaped scar on his forehead. The character {{w|Legal_disputes_over_the_Harry_Potter_series#Nancy_Stouffer|Larry Potter}} figured in a fraudulent legal claim against J.K. Rowling.
|-
| U+2A50 || ⩐ || Closed Union with Serifs and Smash Product || Indicates that a collection of topological spaces is {{w|Union-closed sets conjecture|closed}} when taking arbitrary unions and smash products. That is, if you take the union of any collection of topological spaces in the collection (even uncountably many), or the smash product of them, the result will also be in that collection. This is apparently important because the sets can't be isomorphic (one cannot be rearranged to be exactly the other.) [https://mathoverflow.net/questions/196084/counterexample-for-associativity-of-smash-product] || Spider caught with a cup and index card || Spiders or other bugs found within someone's house or workspace may be caught with a glass and something flat, often a card or a magazine, to be released outside. The projecting lines of the smash product symbol resemble the legs of a spider. Confusingly, some fonts display this symbol with different numbers of "legs": eight, as a 45°-rotated hash symbol, or six as an asterisk.
|-
| U+2A69 || ⩩ || Triple Horizontal Bar with Triple Vertical Stroke || Emblem of the Romanian {{w|Iron Guard}} fascist political movement; possibly a four-by-four {{w|tic-tac-toe}} board.[https://pages.cs.wisc.edu/~sandlund/NumericalTicTacToe.pdf] || ℍ𝕒𝕤𝕙𝕥𝕒𝕘 || Hash symbol with one extra vertical and horizontal line, or perhaps a hash symbol which has been accidentally double-struck or overprinted.
|-
| U+2368 || ⍨ || APL Functional Symbol Tilde Diaeresis || Used for a two-argument operation to [https://aplwiki.com/wiki/Commute commute] (swap) its arguments or allow it to use a single provided argument in both argument slots, and to convert a value into a [https://aplwiki.com/wiki/Constant constant] function || :/ || Looks like a confused or disappointed face. Randall's use is in fact common among {{w|APL (programming language)|APL}} programmers in the comments, as documented [https://aplwiki.com/wiki/APL_Orchard#Emoticons here] and [https://aplwiki.com/wiki/Humour#Glyph_puns here].
|-
| U+2118 || ℘ || Script Capital [''sic''] P || A stylized {{w|round hand}} 'p' used by Weierstrass for his "{{w|Weierstrass elliptic function|p-function}}," with features of both capital 𝒫  and small 𝓅. Sometimes also used as the {{w|power set}} operator.
|| Snake || This symbol coils around like a long snake, with a tapering-off tail on one end and a small "head" on the other.
|-
| U+2AC1 || ⫁ || Subset with Multiplication Sign Below || Indicates that one set is subset of another by means of the cross product || <div style="writing-mode: vertical-rl; text-align: center;">User experience</div> || Looks like the letters "Ux" sideways; UX is a common abbreviation for {{w|user experience}}.
|-
| U+232D || ⌭ || {{w|Cylindricity}} || A symbol used in geometric dimensioning and tolerancing (GD&T) to represent a parameter called "cylindricity" which describes the statistical deviation of an ensemble of surfaces from a reference cylinder. [https://cimquest-inc.com/metrology-minute-cylindricity/ example use] || Rolling dough between your hands to shape it into a ball || Looks like two flat hands (perhaps like stick-figure arms) rolling a ball between them. Rolling dough between one's hands to make it into a ball is an important step in making many kinds of pastry and bread.
|-
| U+2A13 || ⨓ || Line Integration with Semicircular Path Around Pole || Very rare symbol for half of a closed {{w|Contour integration|contour}} or {{w|Line integral|line}} integral which contains the {{w|Origin (mathematics)|origin}} in its interior. Contour integrals which circle the origin are very important in complex analysis. If such an integral were split into two parts, each could be represented by this symbol (which can be mistaken for ⨔, the integral not including the {{w|Zeros and poles|pole}}, with a wider and more complete arc around an offset dot.) [https://math.stackexchange.com/questions/2299363/where-is-the-%E2%A8%93-integral-symbol-defined]
|| Integral that avoids a bee on the whiteboard || Looks like an {{w|integral}} symbol with a bump that goes around a dot, as if a professor was drawing an integral on a whiteboard but did not want to disturb a bee that had landed right in the path of their marker.
|-
| U+2A0B (title text)|| ⨋ || Summation with Integral || The sum of the sum of the discrete elements (∑) and the integrals (∫) over the connected pieces. This symbol requires context to be meaningful but could occur, for instance, when computing probabilities using mixed distributions.
[https://twitter.com/fermatslibrary/status/1308743505309822977 see also]
|| Mathematicians need to calm down || Each of the two symbols is specifically used to represent a kind of summation that is calculated completely differently from the other. Combining them could produce frustration for people unfamiliar with the usage. The comment given may make fun of mathematicians' tendency to form increasingly complex expressions in their work. It may as well be a pun on the pronounciation of the letter {{w|Esh_(letter)|Esh}} (Shhhh).
|-
|}

This comic may have been inspired by [https://ionathan.ch/2022/04/09/angzarr.html this blog post], which went viral (in a limited sense) the same day the comic was published.

==Transcript==
<big>Weird Unicode Math Symbols</big>
And their meanings

{|
| U+29CD || ⧍ || Shark
|-
| U+23E7 || ⏧ || Traffic circle
|-
| U+2A33 || ⨳ || Hashtag [the text is slanted counterclockwise]
|-
| U+299E || ⦞ || Snack
|-
| U+2A04 || ⨄ || Drink refill
|-
| U+2B48 || ⭈ || Snakes over there
|-
| U+225D || ≝ || Definitely, for sure
|-
| U+237C || ⍼ || Larry Potter
|-
| U+2A50 || ⩐ || Spider caught with a cup and index card
|-
| U+2A69 || ⩩ || [The word "hashtag" but with extra horizontal and vertical lines]
|-
| U+2368 || ⍨ || :/
|-
| U+2118 || ℘ || Snake
|-
| U+2AC1 || ⫁ || [The words "user experience" rotated clockwise 90 degrees]
|-
| U+232D || ⌭ || Rolling dough between your hands to shape it into a ball
|-
| U+2A13 || ⨓ || Integral that avoids a bee on the whiteboard
|}

{{comic discussion}}
[[Category:Unicode]]
[[Category:Math]]
[[Category:Harry Potter]]

2186: Dark Matter

2022-05-03T23:25:47Z

172.70.211.82: Undo revision 234279 by X. K. C. D. (talk)

{{comic
| number = 2186
| date = August 7, 2019
| title = Dark Matter
| image = dark_matter.png
| titletext = To detect dark matter, we just need to build a bird feeder that spins two squirrels around the rim in opposite directions at relativistic speeds and collides them together.
}}

==Explanation==
[[Megan]] and [[Cueball]] are talking about {{w|dark matter}}, the mysterious invisible mass observed indirectly by the rate at which galaxies rotate. Megan states that dark matter's density in the solar system is 0.3 GeV/cm3, as claimed, for example, by [https://arxiv.org/abs/1205.4033 Bovy and Tremaine (2012) "On the local dark matter density" in ''The Astrophysical Journal''.] Cueball does not understand what that means, so Megan explains that it equates to one squirrel's mass of dark matter in the volume of the {{w|Earth}}. In the final two panels, Cueball humorously misinterprets this as implying dark matter is actually one or more squirrels, and thereby provides the mass which causes [https://www.youtube.com/watch?v=PfHu-UJaK0Q squirrels to spin on bird feeders designed to deter them] while birds, with lower mass, do not. This enrages Megan.

The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''2. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of {{w|Dark matter#Composition of dark matter: baryonic vs. nonbaryonic|several contending possibilities}} for the still-open question of the composition of dark matter, and one which Megan's uniform density figure implies constitutes most of it. For example, the mass of a proton is 0.938 GeV/''c''2. However, it is common to omit the ''c''2 denominator, representing masses as GeV or MeV. A mass represented as 0.3 GeV is equal to 5.35 × 10−25 grams [https://www.wolframalpha.com/input/?i=0.3+(GeV%2Fc%5E2)+in+grams]. Since the {{w|Figure_of_the_Earth#Volume|Earth's volume}} is 1.083 × 1027 cm3 Megan's figures imply that a {{w|squirrel}} has a mass of about 1.3 lb (1.083 x 5.35 × 1027−25 g = 580 g [https://www.wolframalpha.com/input/?i=(0.3+(GeV%2Fc%5E2)%2Fcm%5E3)+*+(volume+of+earth)+in+grams]), a typical weight for several species of common squirrels.

[[:Category:Squirrels|Squirrels]] are a recurring topic on xkcd, but are not a serious alternative to WIMPs as a scientific explanation for [[2035: Dark Matter Candidates|the composition of dark matter]]. Since the September 2015 detection by the {{w|LIGO|Laser Interferometer Gravitational-Wave Observatory}} (LIGO) and subsequent confirmation by the {{w|Virgo interferometer}} of gravitational waves from unexpectedly many merging {{w|black hole|black holes}} substantially more massive than those produced by stellar collapse, {{w|primordial black hole| primordial black holes}} (PBHs) have become a popular alternative explanation to WIMPs (or squirrels), attracting [https://arxiv.org/abs/1605.04023 proponents at NASA,] and [http://www.buchaltercosmologyprize.org/#announcements other cosmologists] for [https://arxiv.org/abs/1711.10458 several reasons.] But PBHs remain controversial, because if they constituted more than a very small portion of dark matter, [https://iopscience.iop.org/article/10.1088/2041-8205/720/1/L67 alternative explanations would be almost entirely excluded.]

Other alternative hypotheses for the observations suggesting dark matter, such as theories involving the {{w|Modified Newtonian dynamics|gravitational force varying over different distances}}, often upset cosmologists as much as Megan is shown to be, because they violate the {{w|cosmological principle}} among other issues. Part of this frustration may be due to the fact that even after many decades of careful, tremendously expensive, and often [http://www.allesfoen.de/artinscience/wordpress/?p=236 stunningly beautiful] experiments, none of the many explanations for dark matter or the observations suggesting it have as yet any support from direct empirical observations.

To help resolve this mystery, the title text imagines using a spinning bird feeder like a {{w|particle accelerator}}, colliding squirrels at relativistic speeds as if they were subatomic particles, to detect dark matter particles like the CERN accelerator discovered the {{w|Higgs boson}}. (Note, however, that accelerating even [https://what-if.xkcd.com/1/ one squirrel] to relativistic velocities would destroy the feeder along with any nearby birds, not to mention the squirrels, and the surrounding city.)

==Transcript==
:[Megan walks with Cueball. She is holding a hand out while telling Cueball something.]
:Megan: Dark matter density in the solar system is around 0.3 GeV/cm3
:Cueball: Is... that a lot?

:[As they continue to walk and talk she spreads her arms out.]
:Megan: In terms of mass, it means the Earth contains one squirrel worth of dark matter at any given time.
:Cueball: Wow.

:[In a frame-less panel Cueball stops while Megan walks past him. Megan is face-palming herself while looking down.]
:Cueball: Is there any way to find out which squirrel it is?
:Megan: No, it's not literally-

:[Cueball holds his hand with one finger up in front of Megan, while she has turned towards him and is holding both arms up, possible with balled fist, as she shouts back at him, shown both with large fat letters and with small lines emanating above her head.]
:Cueball: Oh, that explains why they weigh enough to set off those spinning bird feeders!
:Megan: '''''Dark matter isn't squirrels!

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Squirrels]]
[[Category:Astronomy]]
[[Category:Physics]]