explain xkcd - User contributions [en]

2242: Ground vs Air

2019-12-17T08:43:23Z

162.158.114.82: /* Putting it both in the same order */

{{comic
| number = 2242
| date = December 16, 2019
| title = Ground vs Air
| image = ground vs air.png
| titletext = Water is thinner than both, and fire is *definitely* thicker.
}}

==Explanation==
{{incomplete|Created by a THICK FIRE. Needs a title text explanation and more about the actual data portrayed}}

This is a map comparing the thickness of the ground, apparently referring to the {{w|lithosphere}}, and the thickness of the atmosphere.

Apparently, Randall uses {{w|Kármán line}} (the altitude of 100 km ≈ 62 mi) as the boundary between Earth's atmosphere and space. An alternative definition of the atmosphere boundary (at 80 km ≈ 50 mi) used by US Air Force and NASA would result in a significantly different picture where the ''air'' is thicker than the ''ground'' only inside small areas around mid-ocean ridges.

The title text possibly a joke referring to the four elements. The lithosphere, or ground, is earth, with fire being the various magma layers underneath the crust.

==Transcript==
{{incomplete transcript}}

: [Caption above the comic]:
: Which is thicker—the ground or the air?

: [A Winkel tripel projection of the Earth. The map is mostly unlabeled, with only the outlines of the landmasses present. Various parts of the map are labelled with "Air" or "Ground." Areas marked as "Ground" are differentiated with gray shading.]

: [A small diagram is present in the Pacific Ocean left of South America. The diagram depicts several labelled layers of Earth and its atmosphere, listed below. Cueball, a body of water, and several mountains are shown on the surface part of the diagram. Two arrows representing the thickness of the atmosphere and lithosphere are marked with a question mark.]
: Space
: Atmosphere
: Lithosphere
: Asthenosphere

: [Gray text in the bottom right corner of the comic]:
: Based mostly on Conrad and Lithgow-Bertelloni (2006) DOI.1029/2005GL025621

{{comic discussion}}

[[Category:Maps]]

2202: Earth-Like Exoplanet

2019-09-14T11:13:57Z

162.158.114.82: what is an "ejection of energy"

{{comic
| number = 2202
| date = September 13, 2019
| title = Earth-Like Exoplanet
| image = earth_like_exoplanet.png
| titletext = Fire is actually a potential biosignature, since it means something is filling the atmosphere with an unstable gas like oxygen. If we find a planet covered in flames, it might be an indicator that it supports life—or used to, anyway, before the fire.
}}

==Explanation==
{{incomplete|Created by an EXOPLANET SURVIVOR. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

This comic is a reference to the recent discovery of water vapor in the atmosphere of exoplanet {{w|K2-18b}}, which was discovered orbiting K2-18 by the {{w|Kepler (spacecraft)|Kepler Space Observatory}} in 2015. {{w|Extraterrestrial liquid water|Water}} is considered a biosignature, meaning it's an indicator that there could be life there. However, as Megan reveals the planet's other characteristics, it becomes clear that it is unlikely to actually support life, and in fact is actually a horrible hellscape. The question of habitability by higher forms of life is profoundly different than the way {{w|astrobiology|astrobiologists}} use the term for microbes. Even a smaller "survivable zone" doesn't help mitigate just how inhospitable this new wet planet would be to life as we know it, save for as-yet undiscovered {{w|extremophile}} organisms.

The planet being {{w|Tidal locking|tidally locked}} indicates that the same side would face the planet's star year-round, meaning half of the planet would be in constant day and the other half would be in constant night. Based on our (admittedly limited) understanding of life, {{w|abiogenesis}} can only occur in environments with liquid water; however, the day hemisphere would likely be so hot that all water found there would be in a gaseous state, and all water found in the night hemisphere would likely be frozen due to the sheer cold. If life were to be found on this exoplanet, it would be in the twilight strip, a thin ring around the edge separating the two hemispheres where sunlight can reach but is refracted by the atmosphere. The environment in the twilight strip would thus experience something akin to an eternal sunset, and temperatures there would be moderate enough to allow life to come about.

Unfortunately, the other characteristics of the exoplanet severely undermine our chances of finding life even in its twilight strip:
* [https://www.space.com/massive-stellar-flare-detected-from-distant-star.html Stellar flares] are ejections of radiation and plasma from a star, and it's probable that a planet being blasted with these searing hot flares wouldn't readily support life.
* Meteors are chunks of material that enter a planet's atmosphere, and if the planet is "blasted" by them it is likely that many of them are impacting the surface, thus becoming meteorites. As we know from [https://www.tulane.edu/~sanelson/Natural_Disasters/impacts.htm the extinction of the dinosaurs], meteorites can have a negative effect on a planet's habitability.
* Strong acids are present in some planetary atmospheres, [https://imaginecosmos.com/tag/sulfuric-acid/ including sulfuric acid in Venus's], and their hypothetical presence in the exoplanet's atmosphere would make life there even less likely. While life that evolves in a highly acidic environment might be able to withstand it, most life on Earth reacts poorly to strong acids.

"Biosignatures in the form of screaming" suggests that any life that had developed on the planet would be in continuous pain or fear from the environmental conditions. In addition, this suggests that the screaming of these organisms would be loud enough to be heard light-years away through the vacuum of space, and that it would be more noticeable than other signs of life (such as the spectra from the ash produced by burning organic material.)

The title text mentions that fire could indicate the presence of oxygen, which is required for life on Earth. Here the joke is continued, since it's unlikely anything could survive on a flaming planet.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Side view of Megan standing behind a lectern, speaking to an audience:]
:Megan: We've discovered the most earth-like exoplanet yet!
:Off-screen (at least two audience members): Yay!!

:[Frontal view of Megan behind lectern:]
:Megan: Well, it's in the habitable zone. Habitable-ish. "Habitable."
:Megan: The survivable zone.

:[Frameless panel showing frontal view of Megan behind lectern with her left hand held out palm-side up:]
:Megan: It's tidally locked. And blasted with stellar flares. And probably meteors. And bathed in acid.

:[Closeup view of Megan, now holding up a finger on her left hand:]
:Megan: But we've detected water vapor! In between all the swinging blades.
:Off-screen: I see.
:Megan: We're hoping to find biosignatures in the form of screaming.

{{comic discussion}}

[[Category:Comics featuring Megan]][[Category:Exoplanets]]

2201: Foucault Pendulum

2019-09-12T19:20:24Z

162.158.114.82: /* Explanation */

{{comic
| number = 2201
| date = September 11, 2019
| title = Foucault Pendulum
| image = foucault_pendulum.png
| titletext = Trust me, you don't want to get on the wrong side of the paramilitary enforcement arm of the International Earth Rotation and Reference Systems Service.
}}

==Explanation==
{{incomplete|Created by the International Earth Rotation and Reference Systems Service. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
[[Black Hat]] is attending what appears to be a physics lecture. The professor, [[Megan]], is talking about the {{w|Foucault pendulum}}, a device which demonstrates the rotation of the Earth. Black Hat, being himself, sees an opportunity to cause chaos and seizes it with both hands, quite literally - that is, he grabs the pendulum. The professor objects strongly to this, seemingly for fear of ruining the delicate demonstration. However, the news anchor in the final panel reveals to us that by arresting the motion of the pendulum, Black Hat has somehow stopped the rotation of the Earth. This of course is blatantly impossible since the Foucault pendulum's motion is tied to the earth's rotation, not the other way around.

A Foucault pendulum swings from a bearing that allows rotation in any direction, like your shoulder joint instead of your elbow. If the Earth were stationary, it would continue to swing in the same plane as when it was released. However, because the Earth moves beneath it, over the course of the day the pendulum's motion gradually changes direction relative to the room. The low-resistance bearing doesn't allow the rotation of the Earth to affect the motion of the pendulum, so it stays aligned to its original inertial reference frame rather than the rotating one of the Earth.

The fact that the Earth's rotation does not influence the motion of the pendulum does NOT mean that other things can't affect it - for example, by running up and manually repositioning the pendulum. Of course, the apparent rotation of the pendulum's plane relative to the Earth is an effect of the planet's motion, rather than the cause of it. Thus, stopping a Foucault pendulum manually does not entail pausing the rotation of the Earth.

If it were somehow possible for a Foucault pendulum to control Earth's rotation, Black Hat would probably not want to alter the momentum of the pendulum, unlike most cases where he causes chaos (assuming he was told that it was related to Earth's rotation and assuming that he would prefer to preserve his own life over making chaos). The reason why is because if the rotation of Earth were to be stopped for even very short amounts of time (a few seconds), it would cause everything on Earth that wasn't bolted/fastened to the ground to be sent flying eastward (assuming they are near the Equator) at a speed of 300-360 meters per second, likely causing the death of most lifeforms on Earth within an hour or less, and causing massive windstorms, tsunamis, volcanic and tectonic events on a scale not previously observed on Earth. This would likely cause a mass extinction event and wipe out 99% of humanity in the initial events (which would eventually lead to our extinction). It is possible that Black Hat's grabbing the pendulum would cause a gradual slowing prior to stopping, minimizing the issue (though this doesn't seem to be the case), but the results would still be catastrophic, as the aforementioned events are still likely to occur (specifically the tsunamis and volcanic events). If the earth were to become tidally locked with the sun, it would begin to heat up the side that is facing the sun, and cool down the side that is facing away from the sun, which over a period of several years to decades, would cause the solar side to resemble Venus, and the cool side resembling Pluto. However, there could still be a band of habitability near the twilight zone. The gases from the cool side would condense and create a vacuum, pulling hot air from the solar side, which would continue the storms that initially happened in the moments that earth stopped. It is noted that earth's inner core would eventually stop over a few millennia to a few million years, at which point, our magnetic field would stop being generated and decay to a level similar to Mars over a period of a few hundred million years. By the end of the ordeal, earth would barely resemble what it used to look like.

Randall covered this scenario in detail in his [https://io9.gizmodo.com/xkcds-creator-explains-what-would-happen-if-earth-stopp-1625068208 What If] book.

The title text refers to a (probably) fictional paramilitary enforcement arm of the [https://www.iers.org/IERS/EN/Home/home_node.html International Earth Rotation and Reference Systems Service] and the foolishness of tangling with such a force. If Foucault pendulums were somehow able to influence the rotation of the Earth in any measurable way, the IERS enforcers would probably strictly control their installation and monitor their use (and misuse). Black Hat is likely in for a rough day.

==Trivia==
The Foucault Pendulum in this comic strongly resembles that in the Museum of Science in Boston (both in shape and the way it is knocking over the pegs)

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[Cueball, Black Hat, Ponytail, and Megan are standing next to a large swinging sphere on a pendulum with markers under it; Megan is pointing at it.]

:Megan: This Foucault pendulum demonstrates Earth's rotation. It stays in a fixed plane while the Earth rotates under it.

:[Close-up on Black Hat]

:Black Hat: Hmm, really. So that means...

:[Close-up on Black Hat and pendulum; Black Hat grabs pendulum, and a line points from the pendulum saying "GRAB!"]

:Character out of panel: Hey!

:Character out of panel: Stop him!

:[Blondie is standing next to Black Hat's picture in an inset frame, captioned with "BREAKING NEWS."]

:News Anchor: The Earth's rotation was briefly halted today until geophysicists wrestled the intruder to the ground...

{{comic discussion}}

[[Category:Physics]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Blondie]]

1105: License Plate

2019-09-08T14:07:04Z

162.158.114.82: /* Explanation */ his or her → their

{{comic
| number = 1105
| date = September 7, 2012
| title = License Plate
| image = license_plate.png
| titletext = The next day: 'What? Six bank robberies!? But I just vandalized the library!' 'Nice try. They saw your plate with all the 1's and I's.' 'That's impossible! I've been with my car the whole ti-- ... wait. Ok, wow, that was clever of her.'
}}

==Explanation==
[[Cueball]] has obtained a new {{w|Vehicle registration plate|license plate}}. The license plate number one receives is often the next in sequence, available at the time and place of registration. However, in many localities, for an additional fee one can select their own "personalized" license plate number (called a {{w|vanity plate}}), subject to certain criteria, and availability.

In this comic, Cueball has elected to purchase the personalized license plate number "1I1-III1" or "one, letter I, one, dash, letter I, letter I, letter I and one". He believes the ambiguity between the letter I and the digit 1 on the plate will make it very difficult for anyone to correctly identify his vehicle if he commits a crime. Some localities have more distinct "1" and "I" characters in their license plate font than others, but often when a crime is committed witnesses only has a short time to look at the plate, and will then be confused.

In principle his idea did work, because when the police end up interviewing a witness of a crime scene in the end of the comic, he can only say that "The thief's license plate was all "1"s or something". What Cueball does not count on is that there are no other license plates made up entirely of the letter I and the digit 1. Thus, when witnesses report a vehicle with a license plate of either/or I's and 1's, the police know exactly who the perpetrator is.

Given the fact that the police still haven't caught him even though they have his address written on a {{w|Post-it note}} in their car, it seems like they had already thought of the same idea, and when Cueball registered such a license plate they put up the address in the police cars, as they expected him to begin committing crimes. He may already have committed more than one, but they would soon stop him before it turned into a crime spree. (An alternative interpretation is that his crime spree has so far consisted of minor offenses, so they haven't arrested him, just issued him warnings or citations -- although one would expect him to stop once it became obvious they were onto him.)

[http://imgur.com/jaiblHk Someone in New Hampshire appears to have done this in real life.]

The title text appears to be a conversation between Cueball and the police the next day when they show up at his address. It turns out that the police suspect Cueball of six bank robberies. Cueball responds that "all" he did was vandalize the library. But the police disregards this as a ''nice try'' to avoid being arrested because witnesses saw a license plate with all 1's and I's was used. Cueball does not understand this because he was with his car the entire time since he got the license plate. And just as he says this, he has an epiphany and states ''wait. OK, wow that was clever of her''. It is thus clear that he suspects that [[Megan]] have made a false license plate also with only a combination of I's and 1's. And then she has robbed six banks knowing that the police would be sure to suspect Cueball, who was so foolish to show his criminal intent by registering such a plate in the first place.

Knowing that the police will assume the car is his, she has thus {{w|frameup|framed}} him. Hopefully for Cueball he can prove he was not involved in the robberies, but if the police assumed that he was the one that committed the crimes, they may not have taken so much care in collecting evidence the first day of the crimes. This will have given Megan time to run away with all the money, as no one was looking for her. So she may well have left the country with no one looking for a woman. This will make it more difficult for Cueball to avoid the blame.

It is clear that Megan would not be so stupid as to register another plate, because then they would know that there could be more than one criminal. Also she would not have had time to get it, if the crime spree began soon after Cueball showed the plate to her. But if the fake plate makes people tell about the 1s and Is then the police would not ask further and discover that the plate might have looked fake.

Note the yellow police line seems to say ''Police strip do not cross'', where ''Police line do not cross'' seems to be the only sentence used normally (unless it is ''crime scene do not cross'', but that also does not fit). (Of course, this could be a pun about the fact that this occurrence is a comic ''strip''.)

==Transcript==
:[Cueball is walking in from the right holding a license plate up with both hands for an off-panel Megan to see. It is possible to see the plate, but here it looks like all I's (or 1's).]
:Cueball: Check out my personalized license plate!
:Megan (off-panel): <nowiki>"1I1-III1"?</nowiki>
:Cueball: It's perfect!
:Plate: III-IIII

:[In this frame-less panel Megan is sitting in an office chair holding and looking at the plate while Cueball stand next to her rubbing his hands together in front of him.]
:Cueball: No one will be able to correctly record my plate number!
:Cueball: I can commit any crime I want!
:Megan: Sounds foolproof.

:[A man with hair only around his neg and glasses holds out a hand towards a bald male police officer with a black peaked cap with white emblem on the front. The police man interviews their witness holding a notepad and a pen. Another likewise caped female officer is Ponytail who walks to the left arm pointing left. There is a line of yellow police tape behind them with text partially obscured by the characters. At the top left of the panel there is a small frame with a caption:]
:Soon:
:Witness: The thief's license plate was all "1"s or something.
:Police officer: Oh. ''That'' guy.
:Ponytail: His address is on a post-it in the squad car.
:Yellow strip (text not visible in brackets): Poli[ce strip] do not cross [poli]ce stri[p do not] cross.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]

2198: Throw

2019-09-05T19:59:37Z

162.158.114.82: /* Throwers and throw items */ For heaven's sake, keep explain xkcd clean of these grammar errors. This is not the youtube comment section!

{{comic
| number = 2198
| date = September 3, 2019
| title = Throw
| image = throw.png
| titletext = The keys to successfully throwing a party are location, planning, and one of those aircraft carrier steam catapults.
}}
<div class="toclimit-3">{{TOC}}</div>
*To experience the interactivity of this game, visit the {{xkcd|2198|original comic}}.
==Explanation==
{{incomplete|Created by THOR, GOD OF THUNDER. Add the equation for throwing? Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
This is an interactive comic made to celebrate the release of [[Randall|Randall's]] new book, ''[[How To]]''. The comic is based on a chapter in the book.

As the comic celebrates the book, which was released on Tuesday, September 3rd, 2019, the comic was thus also released on a [[:Category:Tuesday comics|Tuesday]] to coincide with the release day, replacing that week's normal Wednesday release. This was the same timing used for another of Randall's book releases, when [[1608: Hoverboard]] came out on the Tuesday when [[Thing Explainer]] came out. Although the Hoverboard comic is much more complex than this one, they are both [[:Category:Dynamic comics|dynamic]] and [[:Category:Interactive comics|interactive]], with [[:Category:Comics with animation|animations]] a part of them.

In this comic the viewer can select a person/{{w|Pikachu}}/god/squirrel as the thrower and an object (including a person, Pikachu, or squirrel) to be thrown, and get an animation of how the selected throw would work out, along with an estimated distance of the throw (both in SI units and in other very arbitrary units; see [[#Table of distance units|table]] below) if the throw was possible. Impossible throws include ones in which the thrower is smaller than the thrown object. The formula/guideline is apparently based on a chapter from the book. One special case to the calculations is Thor's hammer, which is enchanted such that only those deemed "worthy" are able to lift it. As such, despite its mass being liftable by many of the characters, only Thor, God of Thunder (who is canonically worthy), and self-created characters who are well over the human records for height ({{w|List of tallest people|272 cm}}) and/or weight ({{w|List of heaviest people|635 kg}}) are shown to actually be able to throw it. Also Thor is the only one who uses {{w|furlongs}} to measure his distances.

Interestingly, Thor can throw a squirrel 257 meters. If a Custom Thrower is created, and they are 200 meters tall and 150 KG, they can throw the squirrel 256 meters (1 meter less than Thor). Thor can throw an acorn 136 meters, and the Custom Thrower will throw it 133 meters. Now, Thor can throw Thor's Hammer 19 meters. The Custom Thrower can throw it 44 meters! Apparently there is more to the enchantment of Thor's Hammer than meets the eye, as it would have been expected that if Thor can throw a squirrel and an acorn farther than an extraordinary human, then certainly he could throw his own enchanted Hammer a longer distance.

There are 7 throwers + 1 open option and 15 + 1 things to throw, giving a total of 105 different combinations for the static elements; see the [[#Table of throw distances|table]] below plus those for the open option. The open option can be defined by height, weight and a 1-4 scale of athleticism. But only Thor (or an unrealistically tall and heavy custom character) can throw all 15, with three of the objects (George Washington, hammer, and car) unthrowable by any of the other premade characters. The smaller critters can throw only a few things, so the total number of throws is much less than 100. Still, there is an animation for all 105 combinations, but with no throw distance for some. An object with negative weight (you, probably) flies backward.

The athleticism scale does not define the character used for the animation.

The title text refers to throwing a party (a colloquial synonym of hosting a party) and first makes the assumption of actually giving hints for giving a party, and then switching to suggest a mechanism to literally throw a huge object, such as a house with a party going on inside. An {{w|Aircraft_catapult#Steam_catapult|aircraft steam catapult}} is a mechanism to launch aircraft from ships, typically used on aircraft carriers.

==Throwers and throw items==
George Washington, Pikachu, and a squirrel are both throwers and throw items, as are "You".

{| class="wikitable" |
! Image
! Name
! Explanation
|-
|[[File:2198 Throw - quarterback.png]]
|'''An NFL {{w|quarterback}}'''
|A quarterback in the National Football League is a highly athletic individual. Gridiron football is a full-contact sport that requires durability, speed, and precision. One of the primary skills required of quarterbacks is to be able to throw the football far with precision accuracy.
|-
|[[File:2198 Throw - george.png]]
|'''{{w|George Washington}}'''
|He was the first president of the United States of America. There is a myth that a young George Washington threw a silver dollar across the Potomac River, which is more than a mile wide for much of its length; or alternatively that he would throw rocks across the Rappahannock River, which was about 300 feet wide near George's boyhood home. http://kenmore.org/education/kidstuff/legends.html. He is also used as a throwing item to represent the likelihood of a thrower distance with an average human as the projectile. George Washington is shown as a very powerful thrower; the comic makes fun of the flagrant embellishment of Washington's life.
|-
|[[File:2198 Throw - pikachu.png]]
|'''{{w|Pikachu}}'''
|Pikachu is a species of Pokémon and the mascot of the Pokémon franchise as a whole. Although Pikachu are not normally shown to throw things, the ''Super Smash Bros'' series shows they are perfectly capable of picking things up that do not significantly out-size them. That said, Pikachu is capable of throwing a wide variety of objects through the move Fling, which allows the user to deal damage by throwing its held item (and, incidentally, a Fling TM). Its presence as a throwing item appears to reference the most recently released Pokémon games as of the comic's release, ''Pokémon Let's Go Pikachu'' and ''Pokémon Let's Go Eevee'', where the partner Pokémon of the respective title is not kept in a Poké Ball but thrown into battle when deployed. According to Pokédex entries throughout the series, the average Pikachu is 1'04" (0.4m) tall and weighs 13.2 lbs (6kg). Randall appears to have done his research, as a custom thrower with these stats and default athleticism will have near-identical results to Pikachu for both thrower and thrown item.
|-
|[[File:2198 Throw - carly.png]]
|'''{{w|Carly Rae Jepsen}}'''
|A Canadian music artist.
|-
|[[File:2198 Throw - thor.png]]
|'''{{w|Thor}}'''
|Thor is the god of thunder in Norse mythology, wielding a hammer that returns to its wielder when thrown. He is also {{w|Thor (Marvel Comics)|featured in Marvel comics}} and is portrayed by Chris Hemsworth (listed below) in the Marvel Cinematic Universe series of films. Thor was previously referenced in [[2097: Thor Tools]].
|-
|[[File:2198 Throw - chris hemsworth.png]]
|'''{{w|Chris Hemsworth}}'''
|He is an Australian film actor, best known for his role as Thor in the Marvel Cinematic Universe.
|-
|[[File:2198 Throw - squirrel.png]]
|'''A {{w|squirrel}}'''
|It is a small mammal of the family ''Sciuradae'', known for hoarding acorns. Squirrels have been a [[:Category:Squirrels|recurring topic]] on xkcd and have been used in ''What if?'' in lieu of a subject that Randall really doesn't want to draw. Due to their small size, a squirrel is also selectable as a throwing item.
|-
|[[File:2198 Throw - you.png]]
|'''{{w|human|You}}'''
|The viewer may also choose to create a custom thrower, for instance, themself, inputting a name, height, weight, and general level of athleticism, as measured on a scale from "[[Black Hat]]" to "championship athlete" (a swimmer is pictured). The custom thrower is also selectable as a throwing item, presumably to provide more variety compared to the fixed values of George Washington.
|-
|[[File:2198 Throw - microwave.png]]
|'''A {{w|microwave oven}}'''
|A common household appliance in most American homes, used to heat or reheat food for consumption.
|-
|[[File:2198 Throw - basketball.png]]
|'''A {{w|basketball (ball)|basketball}}'''
|An inflated sphere used as a projectile in the sport of the same name.
|-
|[[File:2198 Throw - blender.png]]
|'''A {{w|blender}}'''
|It is a common household appliance in most American homes, used to shred food or ingredients into slush for consumption or baking.
|-
|[[File:2198 Throw - gold_bar.png]]
|'''A {{w|gold bar}}'''
|It is the form in which gold is cast for storage.
|-
|[[File:2198 Throw - cake.png]]
|'''A {{w|wedding cake}}'''
|It is traditionally a layer cake used for wedding receptions with copious amounts of frosting and figurines of the bride and groom standing upon the top layer. The figurines appear to have been removed before the cake is thrown, as they are before the cake is cut and served.
|-
|[[File:2198 Throw - pingpong.png]]
|'''A {{w|ping pong ball}}'''
|A small sphere designed to bounce, used as a projectile in the sport of table tennis or "ping pong".
|-
|[[File:2198 Throw - acorn.png]]
|'''An {{w|acorn}}'''
|A small nut which serves as a squirrel's primary form of nourishment.
|-
|[[File:2198 Throw - hammer.png]]
|'''{{w|Mjolnir (comics)|Thor's hammer}}'''
|This hammer refers to Mjolnir, an enchanted hammer in the {{w|Marvel universe}} which belongs to {{w|Thor (Marvel Comics)|Thor from Marvels comics}} and can only be lifted by those deemed worthy. It is based on {{w|Mjölnir}} the hammer of Norse God {{w|Thor}}, God of Thunder. In this comic, though, it appears that Mjolnir is just incredibly heavy, and Thor is able to throw it because he is very strong. The custom thrower is also able to throw it if their size and strength are set high enough. Setting aside this customization, Thor is the only standard thrower to be able to throw Thor's hammer. In the movies based on the Marvel universe, Thor is played by Chris Hemsworth, who is also one of the throwers, but in real life, he would of course not be able to throw such a weighty hammer.
|-
|[[File:2198 Throw - javelin.png]]
|'''A {{w|javelin}}'''
|An aerodynamic polearm thrown in Olympic sport.
|-
|[[File:2198 Throw - silver_spin.png]]
|'''A {{w|Dollar coin (United States)|silver dollar}} spinning'''
|A silver coin representing one (1) US dollar in value. The coin is given two trajectories to choose from when thrown; Here '''spinning''', as one would properly throw a discus.
|-
|[[File:2198 Throw - silver_tumble.png]]
|'''A {{w|Dollar coin (United States)|silver dollar}} tumbling'''
|The coin's other possible trajectory, '''tumbling''', as might result from flipping a coin to make a decision. The spinning coin always goes farther than the tumbling one, since facing the air edge-on leads to a smaller area facing the wind and therefore less air resistance.
|-
|[[File:2198 Throw - car.png]]
|'''A {{w|car}}'''
|It is the most common form of long-distance transport in several well-developed countries.
|}

==Safety Considerations==
Many of the items, even if technically possible to throw, may not be able to be thrown safely.

For example:
* Depending on how the microwave oven is damaged when it hits the ground, it may still be able to appear to function, but no longer seal properly, and therefore leak dangerously high amounts of microwave radiation.
* Blenders have blades and glass. Even if no one is struck by the flying blender, the broken pieces would be hazardous later if they are not properly disposed of.
* Cars have gasoline and battery acid which may spill if one is thrown.
* A squirrel might bite the person attempting to throw it, which is dangerous as some squirrels have rabies.
* Pikachu could shock (possibly fatally) someone trying to throw it.
* If a person is thrown, that person may be badly injured.

==Table of throw distances==
{| class="wikitable"
!Item / Thrower
!NFL Quarterback
!George Washington
!Pikachu
!Carly Rae Jepsen
!Thor
!Chris Hemsworth
!Squirrel
|-
|rowspan="2"|'''Microwave oven'''
|10.32 m
|7.76 m
|N/A
|3.67 m
|181.57 m
|6.15 m
|N/A
|-
|33.85 feet
|25.46 feet
|N/A
|82.65 rack units
|1.99 football fields
|138.40 rack units
|N/A
|-
|rowspan="2"|'''Basketball'''
|40.18 m
|33.22 m
|2.34 m
|19.11 m
|113.67 m
|27.99 m
|N/A
|-
|16.74 horses
|19.54 smoots
|75.90 attoparsecs
|11.24 smoots
|1.42 Manhattan blocks
|16.46 smoots
|N/A
|-
|rowspan="2"|'''Blender'''
|16.58 m
|12.45 m
|N/A
|5.89 m
|333.25 m
|9.86 m
|N/A
|-
|9.75 smoots
|40.85 feet
|N/A
|132.51 rack units
|1.66 furlongs
|32.34 feet
|N/A
|-
|rowspan="2"|'''Gold bar'''
|9.73 m
|7.23 m
|N/A
|3.36 m
|549.28 m
|5.69 m
|N/A
|-
|31.93 feet
|23.73 feet
|N/A
|75.65 rack units
|2.73 furlongs
|128.11 rack units
|N/A
|-
|rowspan="2"|'''Wedding cake'''
|8.96 m
|6.75 m
|N/A
|3.2 m
|146.25 m
|5.35 m
|N/A
|-
|29.40 feet
|22.14 feet
|N/A
|72.00 rack units
|1.60 football fields
|120.45 rack units
|N/A
|-
|rowspan="2"|'''Ping-pong ball'''
|11.8 m
|11.63 m
|9.28 m
|11.25 m
|12.53 m
|11.41 m
|4.95 m
|-
|38.72 feet
|38.17 feet
|30.46 feet
|36.92 feet
|41.10 feet
|37.44 feet
|111.37 rack units
|-
|rowspan="2"|'''Acorn'''
|83.00 m
|75.84 m
|28.16 m
|62.85 m
|135.98 m
|67.91 m
|6.53 m
|-
|1.04 Manhattan blocks
|0.95 Manhattan blocks
|16.57 smoots
|26.19 horses
|1.49 football fields
|28.30 horses
|146.85 rack units
|-
|rowspan="2"|'''Thor's Hammer'''
|N/A
|N/A
|N/A
|N/A
|19.32 m
|N/A
|N/A
|-
|N/A
|N/A
|N/A
|N/A
|11.36 smoots
|N/A
|N/A
|-
|rowspan="2"|'''Javelin'''
|56.10 m
|42.04 m
|N/A
|20.12 m
|3028.75 m
|33.09 m
|N/A
|-
|23.37 horses
|17.51 horses
|N/A
|11.84 smoots
|15.06 furlongs
|19.46 smoots
|N/A
|-
|rowspan="2"|'''George Washington'''
|N/A
|N/A
|N/A
|N/A
|136.65 m
|N/A
|N/A
|-
|N/A
|N/A
|N/A
|N/A
|1.49 football fields
|N/A
|N/A
|-
|rowspan="2"|'''Pikachu'''
|15.22 m
|11.41
|N/A
|5.39 m
|332.52 m
|9.03 m
|N/A
|-
|49.94 feet
|37.45 feet
|N/A
|121.18 rack units
|1.65 furlongs
|29.63 feet
|N/A
|-
|rowspan="2"|'''Car'''
|N/A
|N/A
|N/A
|N/A
|27.22 m
|N/A
|N/A
|-
|N/A
|N/A
|N/A
|N/A
|16.01 smoots
|N/A
|N/A
|-
|rowspan="2"|'''Spinning dollar'''
|177.09 m
|143.96 m
|16.91
|92.63 m
|1331.21 m
|115.89 m
|2.20 m
|-
|1.94 football fields
|1.57 football fields
|9.95 smoots
|1.16 Manhattan blocks
|6.53 furlongs
|1.45 Manhattan blocks
|71.41 attoparsecs
|-
|rowspan="2"|'''Tumbling dollar'''
|58.17 m
|53.77 m
|13.92 m
|44.08 m
|84.82 m
|49.03 m
|2.14 m
|-
|24.24 horses
|22.41 horses
|45.67 feet
|18.37 horses
|1.06 Manhattan blocks
|20.43 horses
|69.42 attoparsecs
|-
|rowspan="2"|'''Squirrel'''
|58.64 m
|46.92 m
|2.92 m
|25.44 m
|256.54 m
|38.50 m
|N/A
|-
|24.43 horses
|19.55 horses
|65.71 rack units
|14.97 smoots
|1.28 furlongs
|16.04 horses
|N/A
|}

==Table of distance units==
*This is a table of the alternative distance units shown and their lengths in meters.
**Three of the units shown here are listed in the Wikipedia articles {{w|List of humorous units of measurement}}
**Five the units shown here are listed in the Wikipedia article {{w|List of unusual units of measurement}}.
***Only Furlong and Feet are not in any of the lists (although a different type of feet is in the last list).
**There are ten alternative units in the source code for the comic. However, the wiffle unit cannot be used, and the light-nanosecond unit is inaccessible except by customization.
**Two of the units are off by an order of magnitude.
{| class="wikitable"
!Unit name
!Length in comic in meters
!Explanation
|-
|{{w|List_of_humorous_units_of_measurement#Wiffle|Wiffles}}
|0.0089
|A Wiffle, also referred to as a WAM for Wiffle (ball) Assisted Measurement, is equal to a sphere 0.089 m (3.5 inches) in diameter – the size of a {{w|Wiffle ball}}, a perforated, light-weight plastic ball frequently used by marine biologists as a size reference in photos to measure corals and other objects. Randall is thus a factor 10 off. While wiffles should be the next unit after rack-units and before feet, the unit conversion typo seems to prevent it from being accessible by any thrower-object combination, as it is now even smaller than the wrong measure for light-nanoseconds. Wiffles have thus only been discovered in the data of the comic, as it seems to be impossible to get it displayed in the comic itself.
|-
|{{w|List of unusual units of measurement#Light-nanosecond|Light-nanoseconds}}
|0.0299
|The light-nanosecond was popularized by Grace Hopper, referring to the length light could travel in a nanosecond. The actual length of a light-nanosecond is 0.299 m, about a foot long, but it seems that [[Randall]] was off by an order of magnitude. This measurement is used for lengths from 1 to 1.06 m, but none of the standard throwers or objects can be thrown for this short a distance, so it is not included in the table above. But with the custom user it is possible to get down to 1 m where it will then be used, but of course, since it says 33 light-nanoseconds instead of 3 it is wrong.
|-
|{{w|List_of_humorous_units_of_measurement#Attoparsec|Attoparsecs}}
|0.03086
|The parsec is a unit of length used to measure large distances to astronomical objects outside the Solar System. A parsec is defined as the distance at which one {{w|astronomical unit}} subtends an angle of one {{w|arcsecond}}. One parsec is equal to about 3.26 light-years or 31 trillion kilometers (31×1012 km) or 19 trillion miles (19×1012 mi). Atto- is a unit prefix in the metric system denoting a factor of 10−18 or 0.000000000000000001. Together the two-unit exponents will almost cancel out, as 31 trillion kilometers can be written as 3.1×1018cm, meaning that an attoparsec is 3.1 cm. The unit is only used three times in non-customized settings: once for Pikachu and twice for the squirrel. It is used for lengths from 1.06 to 2.69 meters.
|-
|{{w|List_of_unusual_units_of_measurement#Rack_unit|Rack units}}
|0.0445
|A {{w|Rack unit}} (abbreviated U or RU) is a unit of measure defined as 1 3⁄4 inches (44.45 mm). Mainly used to measure the overall height of the likes of {{w|19-inch rack}} frames or the equipment put in there. It is used for lengths from 2.69 to 6.67 meters.
|-
|{{w|Foot (unit)|Feet}}
|0.3048
|One foot is defined as 0.3048 meters. In customary and imperial units, the foot comprises 12 inches and three feet compose a yard. It is used for lengths from 6.67 to 16 meters.
|-
|{{w|List_of_humorous_units_of_measurement#Smoot|Smoots}}
|1.7000
|The {{w|Smoot}} is a nonstandard, humorous unit of length created as part of an MIT fraternity prank. One smoot is equal to Oliver Smoot's height at the time of the prank, 5 feet 7 inches (1.70 m). Mr. Smoot was used to measure the length of the Harvard Bridge (connecting Boston and Cambridge) by being repeatedly laid down along the length of the bridge; the markings indicating distances in smoots along the bridge have been maintained by the fraternity. The smoot is used for lengths from 16 to 36 meters. While the smoot is a nonstandard unit of length, Oliver Smoot has been chairman of the American National Standards Institute (ANSI) and President of the International Organization for Standardization (ISO). ANSI and ISO are among the world's main standardizing bodies, so Randall may indirectly be making the pun that while Smoot's body isn't a standard measure, Smoot has been in charge of bodies that standardize measurements.
|-
|{{w|List_of_unusual_units_of_measurement#Horse|Horses}}
|2.4
|The length of a {{w|horse}} varies a lot with the horse type, breed, age, and genes. In the Wikipedia article on horses, the length of a horse is not even mentioned, only the height and weight. But Randall has used horses for measurements before. A {{w|horse length}} is approximately 8 feet (2.4 m). It is used for lengths from 36 to 75 meters.
|-
|{{w|List_of_unusual_units_of_measurement#Block|Manhattan blocks}}
|80.0
|The numbered streets in {{w|Manhattan}} run east-west and are generally 60 feet (18 m) wide, with about 200 feet (61 m) between each pair of streets. With each combined street and {{w|City block|block}} adding up to about 260 feet (79 m), there are almost exactly 20 blocks per mile. The typical block in Manhattan is 250 by 600 feet (76 by 183 m). When driving in a grid-like city, the {{w|Manhattan distance}} between two points is a concept, although it is also called {{w|Taxicab geometry}}. It seems like it is indeed the combined street and block distance. This measurement is used for lengths from 75 to 131 meters.
|-
|{{w|List_of_unusual_units_of_measurement#Football_field_(length)|Football fields}}
|91.44
|An {{w|American football field}} is 100 yards or 91.44 m long. It is used for lengths from 131 to 201 meters.
|-
|{{w|Furlongs}}
|201.168
|A furlong is a measure of distance in imperial units and U.S. customary units equal to one-eighth of a mile. It is part of the {{w|List_of_humorous_units_of_measurement#FFF_units|FFF_units}} of the {{w|FFF system}} for furlong/firkin/fortnight, length, mass and time. One furlong should therefore be 201.168 meters, though the United States does not uniformly use this conversion ratio. Older ratios are in use for surveying purposes in some states. Only Thor's distances are given in furlongs. The unit is used for distances of 201 meters (1 furlong) up. For the standard throwers and items only Thor can throw over 200 m, thus only he uses Furlongs to measure his throws. Given that this is an old unit, and Thor is based on ancient Nordic Mythology, this may seem appropriate.
|}

==Transcript==
:[As this is an interactive comic, not all possible text should be given in this transcript. Also, it is not possible to see all the different throwers or objects in one image. This transcript here includes the text that can be found when loading the page, without changing the thrower or object (the default), but also includes the text that can be found by scrolling in the two select "windows" as that would be similar to a long comic where you need to scroll as well as customization options. For further differences that occur by changing the objects refer to a table of all combinations.]

:[A heading with a subheading is above a line, beneath which are a sentence, that is generated by the selections in the two windows beneath this sentence:]
:<big>'''Throw Calculator'''</big>
:This calculator implements the approximate throwing distance estimation model from ''How To'' Chapter 10: ''How to throw things''.

:How far could George Washington throw a Microwave oven?

:[Beneath this sentence are two "windows" with a frame around them, one to the left and one to the right, each with a heading breaking the top frame. Each also has a scroll bar to the right, which allows one to scroll down through 8 different possible selections in the left window and 16 in the right window. There are, depending on the browser zoom level, one or two selections on each line. Each window's content is given here under their respective headings. Each possible selection is a drawing with a caption beneath it.]
:Select a thrower

:*You
:*An NFL Quarterback
:*George Washington
:*Pikachu
:*Carly Rae Jepsen
:*Thor, God of Thunder
:*Chris Hemsworth
:*A squirrel

:Select an object to be thrown
:*You
:*A microwave oven
:*A basketball
:*A blender
:*A gold bar
:*A wedding cake
:*A ping-pong ball
:*An acorn
:*Thor's Hammer
:*A javelin
:*George Washington
:*Pikachu
:*A car
:*A silver dollar (spinning)
:*A silver dollar (tumbling)
:*A squirrel

:[Below the two windows is the result of the animation that will happen when a selection has been made. An animation of the selected thrower throwing (or failing to throw) the selected object is shown, and the object's traveling distance is measured out both in meters (SI units) and in some other unit in brackets below. If the distance is not too long compared to the size of the object and thrower, then both can be seen, and in case the object is soft it may break from the throw.]

:[In the pre-selected version, George Washington throws a microwave oven, which ends up several meters from him lying on a corner broken with its wire lying beneath it. The distance is given under the ruler along which the throw has occurred, with markings for approximately every meter. In this case, there are seven steps even though the distance is above 7 meters:]
:7.76 meters
:(25.46 feet)

:[Clicking on "You" in the thrower box opens a new window over the above described comic parts. some of the comic can still be seen including the thrower and his item, and a new throw occurs every time something is changed in this new window. It is a customization box with several options shown below.]

:Your Name
:____You_____ [can be changed]

:Height
:5.8 ft [number can be changed; ft can be changed to m]

:Mass
:160 lb [number can be changed; lb can be changed to kg]

:Athleticism
:[Below is a scale showing Black Hat, the character depicting You with a knit cap, George Washington, and a person with goggles and a helmet. A marker is set at You, but can be changed. Below the characters are descriptions.]
:Black Hat: Moving objects around is for suckers.
:Minimal
:You: I'm in decent shape and have pretty good form.
:Decent
:George Washington: I'm so good at throwing they made me president.
:Extremely High
:Goggles: I use a time machine to train for 36 hours a day.
:Champion Athlete

:[Once done the box can be clicking on a cross at the top right or just clicking outside the window on the comic behind it. Now the thrower you (and the object you) will have the weight, length and strength chosen and will be able to throw (or be thrown) with these stats. ]

==Trivia==
*The comic refers to Thor as the character from the Marvel comics and movies (and other media), who is himself a reference to the ancient Norse god. In Marvel Cinematic Universe movies, Thor is played by Chris Hemsworth.
*Thor's hammer, Mjölnir, bears an enchantment that prevents any living being from lifting it unless they are "worthy." This is reflected in the simulation by giving Mjölnir a mass of 2,000 kg.
**In-universe, Thor's hammer weighs [https://urbandud.files.wordpress.com/2011/08/detail-128-thors-hammer.jpg?w=550 42.3 pounds].
*The option to customize your own character was added to the comic later.
*Due to a bug, the calculations for the customized person ('you') are incorrect when the mass is specified in pounds
*When the comic came out there was a mistake so the item to be thrown was named the same as the thrower, except for the coins and for when Pikachu and George Washington tried to throw themselves in which case it for instance said:
**How far could George Washington throw himself?
**But if he picked another object it would write:
***How far could George Washington throw George Washington?

{{comic discussion}}

[[Category:Comics with animation]] 
[[Category:Dynamic comics]]
[[Category:Interactive comics]]
[[Category:Physics]] 
[[Category:American football]] 
[[Category:Comics featuring politicians]] 
[[Category:Pokémon]]
[[Category:Comics featuring real people]] 
[[Category:Religion]] 
[[Category:Squirrels]]
[[Category:Food]] 
[[Category:Basketball]]
[[Category:Sport]] 
[[Category:Book promotion]]
[[Category:How To]]

77: Bored with the Internet

2019-08-31T18:16:49Z

162.158.114.82: /* Transcript */ fix typo in Hairy’s name

{{comic
| number = 77
| date = March 17, 2006
| title = Bored with the Internet
| image = bored_with_the_internet.jpg
| titletext = I used to do this all the time.
}}
==Explanation==
A character who has hair (not to be confused with [[Hairy]]) suggests to [[Black Hat]] that he is wasting his life on the Internet, and they should go explore the world. They appear to walk a great distance, through what appears to be a swamp or perhaps a forest in winter, across a plain, and down to a river valley. Despite traveling so far and through such varied landscapes, in the last panel, one of the characters admits that all he can think about is what a great Livejournal post their trip would make. It appears that the plan to get the Internet off their mind has failed.

{{w|Livejournal}} is a website on which users can make accounts and, effectively, blog, although the site is designed around the premise that the blogs ought to be used as personal journals, with the ability to privatize the journal or only let certain friends see certain entries. Livejournal was an early social network and an early blog platform, and was a good way for people to let others know what was going on in their lives. As of 2017, Livejournal still exists, although sites like Facebook and Twitter have become far more powerful and popular sites for sharing one's daily life.

Unlike most of his appearances (especially later ones), Black Hat does not exhibit any of his signature [[Classhole]] tendencies.

The title text suggests that [[Randall Munroe|Randall]] has overcome a tendency to think about how he will document what he has been doing, rather than concentrate on the thing itself.

==Transcript==
:[Black Hat and Hairy are talking in a room with a computer on.]
:Hairy: I feel like I'm wasting my life on the internet. Let's walk around the world.
:Black Hat: Sounds good.
:[The two men are shown walking through trees.]
:[The two men are shown walking on flat stretch, with mountains in the distance.]
:[The two men are shown in a magnificent canyon. They stand, silently looking at the scene.]
:Hairy: And yet all I can think is, "This will make for a great LiveJournal entry."

==Trivia==
*Livejournal was the site where Randall presented his comics before starting xkcd.

*The Image behind the banner on the xkcd site is from the first panel of this comic, showing only the characters and the desk.

{{comic discussion}}
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Hairy]]
[[Category:Comics with color]]
[[Category:Internet]]
[[Category:Footer comics]]

Talk:2178: Expiration Date High Score

2019-07-22T20:06:35Z

162.158.114.82: /* FOOD SCIENCE */

If we assume this comic is contemporary, i.e. the year she found the beans is 2019, it makes Randall's girlfriend/wife 37 years old.[[Special:Contributions/141.101.84.64|141.101.84.64]] 05:25, 19 July 2019 (UTC)
:Well... it makes Megan 37 years old. There is nothing here to strongly suggest that cueball and her are Randall and his gf/wife. --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 05:54, 19 July 2019 (UTC)
::Well, to be exact it makes Megan 37 years, 13 days, 12 hours, 7 minutes, 13.3 seconds old (rounded to the nearest tenth of a second). This is based on 900/24.3 = 37.0370 (...) That would make her born on July 6, 1982 (if we work back from the date of publication of the comic). But to be realistic I guess she was probably rounding the score to the nearest decimal, rather than writing 24.32432... (i.e. 900/37), in which case I'm wrong. Either way, spurious accuracy is fun!! [[Special:Contributions/172.68.10.4|172.68.10.4]] 19:07, 20 July 2019 (UTC)

What about #933? [[Special:Contributions/172.68.38.88|172.68.38.88]] 21:35, 19 July 2019 (UTC)
: I think it's pretty clear that the title text varies from comic to comic. Sometimes it's clearly a character's voice. Sometimes it makes more sense as a narrator's voice. Sometimes it's clearly talking about Randall's life. I realize that this site tends to attribute the title text to Randall's voice, but personally, I consider it an unattributed voice. Sometimes it's him, sometimes it's more of a narrator or character voice. Similarly, the actions in the comics are sometimes clearly influenced by events in Randall's life, but they're also clearly not other times. If it turned out that he made Megan 37 because his wife is 37, that wouldn't surprise me, but neither would it surprise me if he did something different, because he does that on a regular basis. (In other words, without additional evidence or supporting information, I think it's weird to state as a fact that the traits of various characters are, in fact, traits of Randall and his friends and family.) [[User:Mootstrap|Mootstrap]] ([[User talk:Mootstrap|talk]]) 02:38, 20 July 2019 (UTC)
:: Yes. I'm not RM but if I were I'd just write in a pretty number that has no meaning at all just to be done with the comic. [[Special:Contributions/172.68.58.65|172.68.58.65]] 03:58, 20 July 2019 (UTC)

When I was working at a gas station, someone brought in a propane tank which had expired in 1963 (or so). If 1963 and using this scheme, my score would be 96.6.
[[Special:Contributions/172.69.33.251|172.69.33.251]] 06:02, 19 July 2019 (UTC)
: Did you buy the propane tank, though? --[[Special:Contributions/162.158.114.52|162.158.114.52]] 07:09, 22 July 2019 (UTC)

Propane tanks do not "expire", that is they do not go bad with time, and you do not need to throw them out after the date. The date on these tanks is when they need to be inspected for damage, as mandated by Federal and state laws. If the tank passes inspection a new date in put on and you can keep using the tank (propane suppliers can legally keep refilling it.) [[User:Godzilla|Godzilla]] ([[User talk:Godzilla|talk]]) 13:40, 19 July 2019 (UTC)

: Except that it <q>must be something ''you'' purchased</q> so you can't use that one in the contest. Unless you then purchased it from whoever brought it in… I don't see any rule requiring that the item be new (or otherwise not-yet-expired) when you purchase it, so can we buy old things from other people in order to inflate our score (potentially over 100)? [[Special:Contributions/172.69.42.76|172.69.42.76]] 06:18, 19 July 2019 (UTC)
::That also circumvents the argument "we moved since 2010". If you buy the apartment with kitchen and all equipment, you also purchased the expired item... --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 06:20, 19 July 2019 (UTC)
:::I think that part in the title text is referring to "how did we manage to not come across all of our expired items when we moved" rather than "this item was here before me moved in". Some very disorganised people might actually pack up and move all of the items (e.g. food) in their house without first checking or even noticing if it is expired. [[Special:Contributions/141.101.98.64|141.101.98.64]] 10:52, 19 July 2019 (UTC)
::::That was my initial thought too, that she either did it without of noticing, or did not notice it on purpose, to at some point reach this score. But the loophole, good 'ol 42.76 brought up, put this idea up, as an alternative.--[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 10:56, 19 July 2019 (UTC)
:The rules say that the item must be something you, personally '''''purchased'''''...so did they BUY the pickles from Megan's mom? I'd want to see a receipt or something! (And if the pickles were dated to 1978, Megan (whom we've established is 37 years old was not born when the pickles were dated...so for sure, this is cheating! [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 13:36, 19 July 2019 (UTC)
::They clearly attribute the pickle score to Megan's mum, not to Megan.[[User:Bischoff|Bischoff]] ([[User talk:Bischoff|talk]]) 13:42, 19 July 2019 (UTC)
:::Yeah - that makes more sense. I had initially read it as these were pickles MADE by her mum and given to Megan - not pickles that her mum purchased. Sadly, we can't work backwards from the 2030 date that Megan needs to wait until in order to beat that score to figure out her mom's age because we don't know on what year her mum discovered the ancient pickles. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 13:48, 19 July 2019 (UTC)

There is one caveat to Megan's strategy: since the fraction (year you found item - year item expired)/(your age when you found it) converges to one as time goes on regardless whether the numerator is bigger than the denominator, as long as the item expired before the year of your birth, postponing the discovery reduces your score (considerably).

Her mom's pickles could still have had an expiration date before 1978 - according to [https://www.smithsonianmag.com/smart-news/sell-and-best-dates-food-are-basically-made-hard-get-rid-180950304/ this article] they were around in the 1950s and on store shelves by 1970. If they were home-canned she could also have dated them herself. --[[Special:Contributions/172.68.174.22|172.68.174.22]] 17:56, 19 July 2019 (UTC)

:Perishable foods had expiration dates in the 1970s at least (maybe earlier in some countries and some stores). But non-perishable foods did NOT had dates until the 2000's or later. A home canned jar of pickles could have a hand written date, but this would be the date it was canned, not an expiration date. Because anyone in the 1970s who knew how to can would know if they did it right the food would not go bad. If they did the canning wrong they would not need a expiration date to know this, they would know in a few weeks, by looking through the mason jar at the food inside. Or by looking at the food and glass spread around the pantry after the jar exploded. So Megan's mom could have a loaf of bread with a 1978 date, but not a jar of pickles. [[User:Godzilla|Godzilla]] ([[User talk:Godzilla|talk]]) 18:17, 19 July 2019 (UTC)

I hereby fervently protest against the age-discriminating rules. [[Special:Contributions/141.101.105.240|141.101.105.240]] 09:25, 22 July 2019 (UTC)
:Hear, hear! A 1-year-expired item shouldn't count 10 times more for a 10-year-old as for a 100-year-old.[[Special:Contributions/162.158.126.34|162.158.126.34]] 17:55, 22 July 2019 (UTC)

== FOOD SCIENCE ==

''"Since then many countries introduced laws and regulations requiring companies to put expiration dates on perishable goods. In some instances this can have the negative effect of people throwing out good food by blindly following the suggested expiration date. This behaviour can incentivise companies to adjust the expiration date so that people will re-buy the products sooner."''

Since science and the truth are a big part of both xkcd.com and explainxkcd.com, I think it is important this explanation includes how/why food goes bad, and why expiration dates on jars/cans of food do not serve to protect people from eating bad food. If no one else gets to it first I'll try to type this explanation when I get a chance.

Until then I don't think the explanation should say "...many countries introduced laws and regulations requiring companies to put expiration dates on perishable goods." Although this is true, it is also true many companies put expiration on non-perishable products even through there is no law requiring them to do so. Like cosmetics and jars of pickles. [[User:Godzilla|Godzilla]] ([[User talk:Godzilla|talk]]) 13:54, 19 July 2019 (UTC)

:To be fair, many items are labelled "Best Before" or "Sell By" - implying that the food item will be edible for at least some time beyond that date. Actual expiration dates on preserved food items do seem to be rarer. There are cases of canned food items from the early 1900's still being in good shape after 100+ years - and those would not have had any expiration date. But one issue is that back then, cans were made by soldering sheets of tin together - and the lead in the solder slowly leaches into the food making it unsafe to eat even though the food itself seems well-preserved. So for potential high scores, we should look to: [http://mentalfloss.com/article/555075/11-oldest-foods-and-beverages-ever-discovered The 11 oldest foods and beverages ever discovered] - except that they'd not have any kind of formal expiration date. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 14:10, 19 July 2019 (UTC)

: "it is also true many companies put expiration on non-perishable products" <- I especially like the "best before" date on salt. Bonus points if the box has a description of how the salt has been in a mine for over millions of years... --[[Special:Contributions/162.158.114.52|162.158.114.52]] 07:13, 22 July 2019 (UTC)

The legal requirements of "expiration dates" for food are less stringent than many believe. In the USA, under FDA regulations, only baby formula cannot legally be sold after its expiration date. Wording like "use by" and "sell by" is not legally binding... more like "guidelines", as Capt. Barbossa would say. [[Special:Contributions/172.68.34.64|172.68.34.64]] 15:57, 19 July 2019 (UTC)

I think the point that needs to be made in the explanation is both the items in the comic (a can of beans and a jar of pickles) do not go bad with time but in fact remain edible indefinitely.

Food going bad, in the sense that it will make you sick if you eat it, is most often caused by harmful bacteria growing in the food. Less often caused by fungi or yeast growing in the food and creating a poisonous substance, like methanol (wood alcohol.) The process of canning food involves boiling it to kill all possible pathogens, then sealing it in a can/jar while the food is still hot, with no air bubble. As long as this process is done correctly, as long as the jar lid has an air tight seal, and as long at the can is not punctured or gets a hole rusted through, no bacteria/virus/yeast/fungi can get in and the food can not spoil. Some food may discolor over time in the jar/can, or the texture may change, but it can not go bad in a way that makes it unsafe to eat.

If the canning process is done incorrectly and bacteria/fungi/yeast is sealed in the can/jar, the food goes bad in a few weeks, not years. Gases given off by the decomposition process often cause the can to swell, or the normal concave jar lid to bulge upwards. Sometimes the internal gas pressure is enough to burst the can/jar, as used to happen to people who canned at home using mason jars. If it does not burst, you are still going the know the food has gone bad the minute you open the can/jar, even without looking inside.

The above facts are more important then who/how/why expiration dates get put on which products. [[User:Godzilla|Godzilla]] ([[User talk:Godzilla|talk]]) 17:13, 19 July 2019 (UTC)

SO my mom's fridge! When I was a kid, my brother had a buddy who would put on his best game show announcer voice and say "It's time for Search... For... Fungus!", then check the fridge for OLD things. Hysterical, laughed our heads off, and helped us out by getting rid of the old stuff, LOL! Me and her recently cleaned her fridge, and similarly found some pre-move items. LOL! [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 06:53, 20 July 2019 (UTC)

All Aussies can win this game with their personal vegemite jar. And they're still EATING it. [[Special:Contributions/108.162.249.124|108.162.249.124]] 09:35, 20 July 2019 (UTC)

Canned food is first put into the can and sealed and then heated up to around 60~80 degrees Celsius. After it cools down, the label is placed on it. - sirKitKat
[[Special:Contributions/162.158.234.112|162.158.234.112]] 06:06, 21 July 2019 (UTC)

So, cool story, if the food is older than you are, your score will decline as you age. If you're older than the food, your score will increase ~ logarithmically.

If the food is older than you, you are still living with your parents, so it isn't your house, and your score doesn't count ;)
[[Special:Contributions/162.158.114.82|162.158.114.82]] 20:06, 22 July 2019 (UTC)

666: Silent Hammer

2019-07-09T21:44:21Z

162.158.114.82: grammar; removed trivia section, which was redundant to the explanation and irrelevant in itself

{{comic
| number =666
| date =November 23, 2009
| title =Silent Hammer
| image =silent_hammer.png
| titletext ='I bet he'll keep quiet for a couple weeks and then-- wait, did you nail a piece of scrap wood to my antique table a moment ago?'
}}
==Explanation==
[[Black Hat]] has created a set of tools that work in complete silence so that he can go to the house of the chairman of the {{w|The Skeptics Society|American Skeptics Society}} late at night, do some rearranging of walls and moving of windows, just to screw with him in typical Black Hat fashion. A {{w|skeptic}} is someone who questions knowledge, facts and beliefs, especially of supernatural phenomena like the existence of {{w|poltergeists}} which Black Hat is trying to imitate with his rearranging and scratching noises.

The American Skeptics Society is a non-profit organization dedicated to promoting skeptical and critical thinking in education and public discourse. The executive director and chief editor of the {{w|Skeptic_(U.S._magazine)|Skeptic Magazine}}, {{w|Michael Shermer}}, is a leading proponent of skepticism, and has written many books and articles debunking pseudoscience, fringe science, quack medicine, alien abductions, conspiracy theories and [[373|supernatural phenomena]]. The [http://www.skeptic.com Skeptic Society website] and Skeptic magazine feature a lot of material debunking anecdotal accounts of these phenomena, explaining how events like "hauntings" could have occurred without supernatural intervention.

One of the premises of modern skepticism is that the supernatural is not rejected out of hand; if someone came up with a proper scientific hypothesis that predicted something supernatural and that hypothesis was proven beyond reasonable doubt, a skeptic would accept that the supernatural thing in question was probably correct.

In the title text [[Cueball]] realizes that Black Hat has (probably intentionally) ruined his antique table by demonstrating his silent hammer.

Black Hat's tools are seen in two boxes labelled "drills" and "non-drills", likely a reference to the phrase "this is not a drill", used to differentiate an emergency situation from a practice of procedure for such.

The particularly evil nature of this comic (even for Black Hat) might be because this is comic number 666, which is the "number of the beast".

==Transcript==
:[Black Hat is hammering something on a table.]
:Cueball: What—
:Black Hat: Silent hammer. I've made a set of silent tools.
:Cueball: Why?
:Hammer: ''woosh woosh woosh''

:Black Hat: Stealth carpentry. Breaking into a house at night and moving windows, adjusting walls, etc.
:[He takes his silent hammer over to a tool bench with other things on it. Two boxes underneath are labeled "Drills" and "Non-Drills."]

:Black Hat, narrating: After a week or so of questioning his own sanity, the owner will stay up to watch the house at night. I'll make scratching noises in the walls, pipe in knockout gas, move him up to his bed, and never bother him again.
:[The events he's describing are shown in two mini-panels below.]

:[Zoom in on Black Hat, with Cueball off-panel to the left.]
:Cueball, off-panel: Nice prank, I guess, but what's the point?
:Black Hat: Check out the owner's card, on the table.
:Cueball, off-panel: Chair of the American Skeptics Society? Oh, god.
:Black Hat: Yeah, this doesn't end well for him.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Black Hat]]

Talk:1951: Super Bowl Watch Party

2018-02-06T08:41:47Z

162.158.114.82:

Which one is Megan? The description refers to Megan coming in but also Megan predicting the cut, but the comic clearly shows two different people.L

soooo 17776 but on the viewer’s end
(The above comment was unsigned)

Now I want to see this! Could someone set up an Internet livestream? (For some definitions of “live” anyway) ;) [[User:PotatoGod|PotatoGod]] ([[User talk:PotatoGod|talk]]) 22:25, 5 February 2018 (UTC)
: Working on it ;)
: EDIT: Done, check it out! https://yearlongsuperbowl.com/ [[User:Okofish|Okofish]] ([[User talk:Okofish|talk]]) 00:10, 6 February 2018 (UTC)
Love it!! [[Special:Contributions/162.158.114.82|162.158.114.82]] 08:41, 6 February 2018 (UTC)

What gluttons for punishment. Professional sports games with all that commentary, colour, etc. is long as it is.
[[Special:Contributions/108.162.216.220|108.162.216.220]] 06:19, 6 February 2018 (UTC) Gene Wirchenko genew@telus.net

Talk:1951: Super Bowl Watch Party

2018-02-06T08:41:20Z

162.158.114.82:

Talk:1951: Super Bowl Watch Party

2018-02-06T08:40:44Z

162.158.114.82:

Which one is Megan? The description refers to Megan coming in but also Megan predicting the cut, but the comic clearly shows two different people.L

soooo 17776 but on the viewer’s end
(The above comment was unsigned)

Now I want to see this! Could someone set up an Internet livestream? (For some definitions of “live” anyway) ;) [[User:PotatoGod|PotatoGod]] ([[User talk:PotatoGod|talk]]) 22:25, 5 February 2018 (UTC)
: Working on it ;)
: EDIT: Done, check it out! https://yearlongsuperbowl.com/ [[User:Okofish|Okofish]] ([[User talk:Okofish|talk]]) 00:10, 6 February 2018 (UTC)
Love it!!

What gluttons for punishment. Professional sports games with all that commentary, colour, etc. is long as it is.
[[Special:Contributions/108.162.216.220|108.162.216.220]] 06:19, 6 February 2018 (UTC) Gene Wirchenko genew@telus.net

1497: New Products

2017-10-23T09:33:39Z

162.158.114.82: /* Explanation */ added "Facebook is evil"

{{comic
| number = 1497
| date = March 11, 2015
| title = New Products
| image = new products.png
| titletext = If you ever hear "Wait, is that Kim Dotcom's new project? I'm really excited about it and already signed up, although I'm a little nervous about whether everyone should hand over control of their medical...", it's time to dig a bunker in your backyard.
}}
==Explanation==
This comic points out an apparent paradox in product performance: Many products that are [https://www.google.com/search?q=No+wireless+Less+space+than+a+nomad+Lame criticized by techies when first announced] go on to great success, and many that are heavily hyped are total flops. The product in question may be a reference to the {{w|Apple Watch}}, which was announced around the time of this comic's release.

{| class="wikitable"
! If they say...
! Explanation
! Example
|-
|"It doesn't do anything new"
|A product that "doesn't do anything new" may still be successful for a variety of reasons. It may in fact do something new that the engineers and programmers are overlooking, or it may simply be a better presentation of an older idea that so far hasn't caught on among the general public. This latter category is the completion of the life-cycle mentioned later in the comic, those products whose "ideas will show up in something successful."
|{{w|iPod}}, {{w|iPad}}
|-
|"Why would anyone want that?"
|If engineers and programmers can't figure out why anyone would want a product, it may be because the applications are highly avant-garde or niche (though that could make it hard for the product to be a mass success). Alternatively, engineers and programmers themselves often don't share the tastes and priorities of non-technical people, and are therefore unable to understand and accurately assess the appeal that a product will have to the masses.
|{{w|Twitter}}, {{w|MacBook Air}}
|-
|"Really exciting"
|rowspan="2"|Products that are "really exciting" to engineers and programmers, so much so that they have already pre-ordered them, may fail to succeed for various reasons, such as:
*The product is excellent, but costs too much for mass audiences.
*The product has an unintuitive interface or strange aesthetics, which techies are willing to "live with", but regular people are not.
*The product has bad marketing; the masses never "get" how good the product is.
*The product turns out to be "nerd bait" or {{w|vaporware}}, offering visionary ideas that aren't actually feasible yet.
When a later product is based on the same ideas, but without the mistakes, it will be worth billions. Then the techies will say "it doesn't do anything new".
|{{w|NeXT}}
|-
|"I've already preordered one"
|[http://arstechnica.com/gadgets/2014/07/how-one-kickstarter-project-squandered-3-5-million/ myIDkey]
{{w|Ubuntu_Edge}}
|-
|"Wait, are you talking about <unfamiliar person's name>'s new project?"
|If a product's developer's name is well-known among engineers and programmers, but not among the general public, that's usually not a good sign. Quite likely, the developer is someone who goes a step further than those in the previous category, not just announcing something cool and exciting they can't follow through on, but doing so ''knowing'' that they can't follow through yet still taking people's money. The state may press criminal charges against them (for fraud or such), or the angry investors may sue to get their money back.
|{{w|Shawn Fanning}}
|-
|"I would never put <company> in charge of managing my <whatever>"
|If engineers' and programmers' only objection is that they don't like the company behind the product, that's basically a tacit admission that there's nothing else wrong with it. For the average consumer, the perks of a groundbreaking new product outweigh whatever problems they may have with the company behind it. This category also relates to the numerous privacy concerns raised about the devices and software of certain companies, and the way people tend to get riled up about these issues and then forget about them once it becomes too inconvenient. For instance, a few months ago, in the aftermath of Facebook releasing its Messenger app, it would not be uncommon to hear people say "I would never put Facebook in charge of managing my network connectivity/phone calls/camera". However, 6 months later and barely anyone is complaining anymore, and within another year or so even the most hardline of privacy advocates will probably give in.
|[https://www.google.com/search?q=apple+OR+google+OR+microsoft+OR+amazon+OR+facebook+"is+evil" take your pick]
|}

The title text imagines a product that fits into the second, third and fourth categories:
* "Wait, is that Kim Dotcom's new project?" — third category
* "I'm really excited about it and already signed up." — both options from the second category
* "Although I'm a little nervous about whether everyone should hand over control of their medical..." — fourth category

{{w|Kim Dotcom}} is a controversial entrepreneur and [http://www.ibtimes.co.uk/who-kim-dotcom-timeline-his-life-1442384 convicted fraud]. He {{w|Kim Dotcom#Personal life|changed his surname}} to "Dotcom" because of the {{w|Dot-com bubble|dot-com stock market bubble}} that made him a millionaire. He fits perfectly into the mold of someone well-known to programmers and engineers (as well as New Zealanders), but perhaps not so much to your average Joe.

Taken together, these imply that an untrustworthy and potentially malicious company has an exciting new idea that may eventually come out in successful form, gains control of a large amount of medical information, but ultimately result in lawsuits not just from investors but from misled consumers (category 3). Because the initial release will be a flop (category 2), there is some time to prepare before the successful use of this idea becomes a reality (also category 2), at which point that or some other company will gain control of a large amount of people's medical something (category 4). Once this happens you could expect dramatic repercussions; this is why the title text suggests to dig a bunker while there is still time.

==Transcript==
:'''Predicting the success or failure of a new product'''
:based on what engineers and programmers are saying about it

:[A two-column table illustrating this. The headings are actually standing above the table.]
:{| class="wikitable alternance"
! If they say...
! It means...
|-
| "It doesn't do anything new"
|rowspan="2"|The product will be 
a gigantic success.
|-
| "Why would anyone want that?"
|-
| "Really exciting"
|rowspan="2"| The product will be a flop. 
Years later, its ideas will 
show up in something successful.
|-
|"I've already preorded one"
|-
| "Wait, are you talking about 
<unfamiliar person's name>'s 
new project?"
| The product could be 
a scam and may result 
in arrests or lawsuits.
|-
| "I would never put 
<company> in charge of 
managing my <whatever>."
| Within five years, they will.
|}

==Trivia==
*There is a typo in the comic: "preorded" should have been "preordered".

{{comic discussion}}
[[Category:Charts]]
[[Category:Comics featuring real people‏‎]]

1313: Regex Golf

2017-04-18T10:08:18Z

162.158.114.82: +List of unique last names matched by each expression

{{comic
| number = 1313
| date = January 6, 2014
| title = Regex Golf
| image = regex_golf.png
| titletext = <nowiki>/bu|[rn]t|[coy]e|[mtg]a|j|iso|n[hl]|[ae]d|lev|sh|[lnd]i|[po]o|ls/ matches the last names of elected US presidents but not their opponents.</nowiki>
}}

==Explanation==
The comic talks about {{w|regular expressions}}, which are a way to specify textual patterns. Given a regular expression, one can search for the pattern it specifies inside a text string. If the pattern is found, it's said that the pattern "matches" the string; if it's not found, it's said it doesn't match.

The title of the comic and the first panel is based on "[http://regex.alf.nu/ regex golf]", which is a discipline of "{{w|code golf}}", a game in which programmers attempt to solve a given programming problem using as few characters as possible, analogous to the number of {{w|golf}} shots it takes to reach the goal. In regex golfing, the programmer is given two sets of text fragments, and s?he tries to write the shortest possible regular expression which would match all elements of one set, while at the same time not matching any element from the other set.

The regex golf challenge Megan faces consists of matching all subtitles of (then extant) ''{{w|Star Wars}}'' films, while not matching any subtitle of ''{{w|Star Trek}}'' movies. {{w|Subtitle (titling)|Subtitles}} are the secondary titles of the movies, after the ''"Star Trek: "'' or ''"Star Wars Episode N: "''. For example, in ''Star Wars Episode I: The Phantom Menace'', the subtitle is ''The Phantom Menace''. In the first panel, she created a 12-character regex solving the challenge.

Then she moved on to building a tool which would automatically build such a regex for arbitrary lists of text, which could be described as {{w|meta}}- regex golfing. But as she has lost this tool, she needs to search through her files and chooses a tool called "{{w|grep}}" to find it. This implies that she needs a regular expression that would find any code that appears to be a regex golf generator, which leads to another "meta-" layer of abstraction. At the end, Megan notes this sequence of meta-meta-... might go to infinity and Cueball quips that she now has "infinite problems" as a result of her efforts; Megan retorts that she already had "infinite problems" because she's geeky enough to run meta-versions of programs on themselves, and stubborn enough to continue on until she fails, to the exclusion of all else. This also seems to be a reference to a famous quote (see also ''[[1171: Perl Problems]]''):

<blockquote>''Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.''</blockquote>

===Regular expressions===
The first regex Megan uses is <code>/m | [tn]|b/</code>, said to match ''Star Wars'' subtitles but not ''Star Trek''.

The forward slashes <code>/</code> just mark the start and end of the regex. The <code>|</code> character means "or", so the regex matches any string that contains the patterns "<code>m </code>", "<code> [tn]</code>" or "<code>b</code>" (including the spaces). The square brackets match one of the enclosed characters, meaning that "<code> [tn]</code>" matches either "<code> t</code>" or "<code> n</code>". The regex is apparently case-insensitive, because it wouldn't work otherwise.

The Star Wars subtitles match the parts of the regex in the following way:
*"The Phantom Menace" is matched by "<code>m </code>".
*"Attack of the Clones" is matched by "<code> [tn]</code>".
*"Revenge of the Sith" is matched by "<code> [tn]</code>".
*"A New Hope" is matched by "<code> [tn]</code>".
*"The Empire Strikes Back" is matched by "<code>b</code>".
*"Return of the Jedi" is matched by "<code> [tn]</code>".
Note that if one included the animated film "Star Wars: The Clone Wars" it would not be matched by "<code> [tn]</code>" because the T is the start of the subtitle and is not preceded by a space. (The string also will likely fail to match some or all of the upcoming post-Disney-acquisition Star Wars films, which the comic predates; it definitely does not match the first two such films, 2015's "The Force Awakens" and 2017's "The Last Jedi")

On the other hand, none of the Star Trek subtitles contains an M followed by a space, a T or an N preceded by a space, or any B, so the regex does not match any of them. Note that in the original series all subtitles start with a "T" but it's the first character so it's not preceded by a space.

Here is the list that Megan probably used:
*Original series:
**The Motion Picture
**The Wrath of Khan
**The Search For Spock
**The Voyage Home
**The Final Frontier
**The Undiscovered Country
*The Next Generation:
**Generations
**First Contact
**Insurrection
**Nemesis
*Reboot series:
**''the one without a subtitle''
**Into Darkness
**''Beyond''

Note that ''Star Trek: Beyond'' was released after this comic and matches the regex, so the pattern doesn't work any more.

In the last panel "and beyond" Megan uses the regular expression <code>/(meta-)*regex golf/</code> to describe her problem. <code>*</code> means "zero or more" of the preceding character/group (parentheses <code>()</code> group characters). So this regex matches "regex golf", "meta-regex golf", "meta-meta-regex golf", etc. In a way this is regex golf in itself, matching all levels of meta-regex golf while not matching anything else.

In the title text, there is a long regex that is the solution of another regex golf challenge: matching the last names of all elected US presidents but not their opponents. Note that the list of opponents include some people who were previously or later became presidents, or whose last name matches that of another person who was president, so taken literally this is impossible. To make this work the list of opponents must exclude any names of presidents. The regular expression itself works in a very similar way to the Star Wars/Trek one, including several different patterns separated by <code>|</code>. Each elected president matches one pattern while each opponent matches none.

Here is a list of elected president and the patterns they match:
{| class="wikitable"
!Number
!President
!Matched expression
|-
|1
|{{w|George Washington|George Washington}}
|<code>sh</code>
|-
|2
|{{w|John Adams|John Adams}}
|<code>[ae]d</code>
|-
|3
|{{w|Thomas Jefferson|Thomas Jefferson}}
|<code>j</code>
|-
|4
|{{w|James Madison|James Madison}}
|<code>[mtg]a</code>
|-
|5
|{{w|James Monroe|James Monroe}}
|<code>[coy]e</code>
|-
|6
|{{w|John Quincy Adams|John Quincy Adams}}
|<code>[ae]d</code>
|-
|7
|{{w|Andrew Jackson|Andrew Jackson}}
|<code>j</code>
|-
|8
|{{w|Martin Van Buren|Martin Van Buren}}
|<code>bu</code>
|-
|9
|{{w|William Henry Harrison|William Henry Harrison}}
|<code>iso</code>
|-
|11
|{{w|James K. Polk|James K. Polk}}
|<code>[po]o</code>
|-
|12
|{{w|Zachary Taylor|Zachary Taylor}}
|<code>[mtg]a</code>
|-
|14
|{{w|Franklin Pierce|Franklin Pierce}}
|<code>[coy]e</code>
|-
|15
|{{w|James Buchanan|James Buchanan}}
|<code>bu</code>
|-
|16
|{{w|Abraham Lincoln|Abraham Lincoln}}
|<code>[lnd]i</code>
|-
|17
|{{w|Andrew Johnson|Andrew Johnson}}
|<code>j</code>
|-
|18
|{{w|Ulysses S. Grant|Ulysses S. Grant}}
|<code>[rn]t</code>
|-
|19
|{{w|Rutherford B. Hayes|Rutherford B. Hayes}}
|<code>[coy]e</code>
|-
|20
|{{w|James A. Garfield|James A. Garfield}}
|<code>[mtg]a</code>
|-
|22
|{{w|Grover Cleveland|Grover Cleveland}}
|<code>lev</code>
|-
|23
|{{w|Benjamin Harrison|Benjamin Harrison}}
|<code>iso</code>
|-
|24
|{{w|Grover Cleveland|Grover Cleveland}}
|<code>lev</code>
|-
|25
|{{w|William McKinley|William McKinley}}
|<code>n[hl]</code>
|-
|26
|{{w|Theodore Roosevelt|Theodore Roosevelt}}
|<code>[po]o</code>
|-
|27
|{{w|William Howard Taft|William Howard Taft}}
|<code>[mtg]a</code>
|-
|28
|{{w|Woodrow Wilson|Woodrow Wilson}}
|<code>ls</code>
|-
|29
|{{w|Warren G. Harding|Warren G. Harding}}
|<code>[lnd]i</code>
|-
|30
|{{w|Calvin Coolidge|Calvin Coolidge}}
|<code>[lnd]i</code>
|-
|31
|{{w|Herbert Hoover|Herbert Hoover}}
|<code>[po]o</code>
|-
|32
|{{w|Franklin D. Roosevelt|Franklin D. Roosevelt}}
|<code>[po]o</code>
|-
|33
|{{w|Harry S. Truman|Harry S. Truman}}
|<code>[mtg]a</code>
|-
|34
|{{w|Dwight D. Eisenhower|Dwight D. Eisenhower}}
|<code>n[hl]</code>
|-
|35
|{{w|John F. Kennedy|John F. Kennedy}}
|<code>[ae]d</code>
|-
|36
|{{w|Lyndon B. Johnson|Lyndon B. Johnson}}
|<code>j</code>
|-
|37
|{{w|Richard Nixon|Richard Nixon}}
|<code>[lnd]i</code>
|-
|39
|{{w|Jimmy Carter|Jimmy Carter}}
|<code>[rn]t</code>
|-
|40
|{{w|Ronald Reagan|Ronald Reagan}}
|<code>[mtg]a</code>
|-
|41
|{{w|George H. W. Bush|George H. W. Bush}}
|<code>bu</code>
|-
|42
|{{w|Bill Clinton|Bill Clinton}}
|<code>[rn]t</code>
|-
|43
|{{w|George W. Bush|George W. Bush}}
|<code>bu</code>
|-
|44
|{{w|Barack Obama|Barack Obama}}
|<code>[mtg]a</code>
|}

Some presidents are missing because they weren't elected but became presidents after the resignation/death of their formers.

And here is a list of how many unique last names are matched by each expression:

{| class="wikitable"
!Expression
!Match count
|-
| bu
| 3
|-
| [rn]t
| 3
|-
| [coy]e
| 3
|-
| [mtg]a
| 7
|-
| j
| 3
|-
| iso
| 1
|-
| n[hl]
| 2
|-
| [ae]d
| 2
|-
| lev
| 1
|-
| sh
| 1
|-
| [lnd]i
| 4
|-
| [po]o
| 3
|-
| ls
| 1
|}

Randall's regular expression must be modified slightly, because it also matches {{w|John C. Fremont|John C. Fremont}}, the runner-up to James Buchanan in 1856, as discussed by {{w|Peter Norvig}} at [http://nbviewer.ipython.org/url/norvig.com/ipython/xkcd1313.ipynb xkcd 1313: Regex Golf]. Note that Norvig provides a small amount of Python code which actually plays regex golf with arbitrary lists, and found a shorter solution than Randall's for the ''Star Wars'' vs ''Star Trek'' game.

The regex does not match Donald Trump, who won over Hillary Clinton in 2016, and thus would need to be updated. The regex does match Hillary Clinton's last name, but because a person with the same last name (Bill Clinton) was president, this does not count as a mistake. There was already a losing opponent called George Clinton who ran in 1792 and 1812.

==Transcript==
:Regex golf:
:[Megan is sitting at a laptop. Cueball is standing behind her.]
:Megan: You try to match one group but not the other.
:Megan: /m | [tn]|b/ matches ''Star Wars'' subtitles but not ''Star Trek''.
:Cueball: Cool.

:Meta-regex golf:
:[A close-up of Megan at her laptop.]
:Megan: So I wrote a program that plays regex golf with arbitrary lists...
:Cueball (offscreen): Uh oh...

:Meta-meta-regex golf:
:[Megan typing at her laptop.]
:Megan: ...But I lost my code, so I'm grepping for files that look like regex golf solvers.
:[Cueball facepalming.]

:...And beyond:
:[Another closeup of Megan at her laptop.]
:Megan: Really, this is all /(meta-)*regex golf/.
:Cueball: Now you have ''infinite'' problems.
:Megan: No, I had those already.

==Trivia==
*There are now at least four comics that reference regular expressions. The other three are: [[208: Regular Expressions]], [[224: Lisp]], and [[1171: Perl Problems]].
*Additionally, regular expressions are mentioned in the title text of [[1277: Ayn Random]].
*A regular expression is used in the [http://what-if.xkcd.com/75/ 75th] post of [[what if?]] to calculate the answer to that week's question.
*Also, Randall mentions [http://regex.alf.nu/ a website with a regexp golf game] he got distracted by while researching for the [http://what-if.xkcd.com/78/ 78th] post of [[what if?]] (which was published one day after this comic).

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Regex]]
[[Category:Star Trek]]

1313: Regex Golf

2017-04-18T09:55:58Z

162.158.114.82: /* Regular expressions */ Clarify Clinton "mistake"

{{comic
| number = 1313
| date = January 6, 2014
| title = Regex Golf
| image = regex_golf.png
| titletext = <nowiki>/bu|[rn]t|[coy]e|[mtg]a|j|iso|n[hl]|[ae]d|lev|sh|[lnd]i|[po]o|ls/ matches the last names of elected US presidents but not their opponents.</nowiki>
}}

==Explanation==
The comic talks about {{w|regular expressions}}, which are a way to specify textual patterns. Given a regular expression, one can search for the pattern it specifies inside a text string. If the pattern is found, it's said that the pattern "matches" the string; if it's not found, it's said it doesn't match.

The title of the comic and the first panel is based on "[http://regex.alf.nu/ regex golf]", which is a discipline of "{{w|code golf}}", a game in which programmers attempt to solve a given programming problem using as few characters as possible, analogous to the number of {{w|golf}} shots it takes to reach the goal. In regex golfing, the programmer is given two sets of text fragments, and s?he tries to write the shortest possible regular expression which would match all elements of one set, while at the same time not matching any element from the other set.

The regex golf challenge Megan faces consists of matching all subtitles of (then extant) ''{{w|Star Wars}}'' films, while not matching any subtitle of ''{{w|Star Trek}}'' movies. {{w|Subtitle (titling)|Subtitles}} are the secondary titles of the movies, after the ''"Star Trek: "'' or ''"Star Wars Episode N: "''. For example, in ''Star Wars Episode I: The Phantom Menace'', the subtitle is ''The Phantom Menace''. In the first panel, she created a 12-character regex solving the challenge.

Then she moved on to building a tool which would automatically build such a regex for arbitrary lists of text, which could be described as {{w|meta}}- regex golfing. But as she has lost this tool, she needs to search through her files and chooses a tool called "{{w|grep}}" to find it. This implies that she needs a regular expression that would find any code that appears to be a regex golf generator, which leads to another "meta-" layer of abstraction. At the end, Megan notes this sequence of meta-meta-... might go to infinity and Cueball quips that she now has "infinite problems" as a result of her efforts; Megan retorts that she already had "infinite problems" because she's geeky enough to run meta-versions of programs on themselves, and stubborn enough to continue on until she fails, to the exclusion of all else. This also seems to be a reference to a famous quote (see also ''[[1171: Perl Problems]]''):

<blockquote>''Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.''</blockquote>

===Regular expressions===
The first regex Megan uses is <code>/m | [tn]|b/</code>, said to match ''Star Wars'' subtitles but not ''Star Trek''.

The forward slashes <code>/</code> just mark the start and end of the regex. The <code>|</code> character means "or", so the regex matches any string that contains the patterns "<code>m </code>", "<code> [tn]</code>" or "<code>b</code>" (including the spaces). The square brackets match one of the enclosed characters, meaning that "<code> [tn]</code>" matches either "<code> t</code>" or "<code> n</code>". The regex is apparently case-insensitive, because it wouldn't work otherwise.

The Star Wars subtitles match the parts of the regex in the following way:
*"The Phantom Menace" is matched by "<code>m </code>".
*"Attack of the Clones" is matched by "<code> [tn]</code>".
*"Revenge of the Sith" is matched by "<code> [tn]</code>".
*"A New Hope" is matched by "<code> [tn]</code>".
*"The Empire Strikes Back" is matched by "<code>b</code>".
*"Return of the Jedi" is matched by "<code> [tn]</code>".
Note that if one included the animated film "Star Wars: The Clone Wars" it would not be matched by "<code> [tn]</code>" because the T is the start of the subtitle and is not preceded by a space. (The string also will likely fail to match some or all of the upcoming post-Disney-acquisition Star Wars films, which the comic predates; it definitely does not match the first two such films, 2015's "The Force Awakens" and 2017's "The Last Jedi")

On the other hand, none of the Star Trek subtitles contains an M followed by a space, a T or an N preceded by a space, or any B, so the regex does not match any of them. Note that in the original series all subtitles start with a "T" but it's the first character so it's not preceded by a space.

Here is the list that Megan probably used:
*Original series:
**The Motion Picture
**The Wrath of Khan
**The Search For Spock
**The Voyage Home
**The Final Frontier
**The Undiscovered Country
*The Next Generation:
**Generations
**First Contact
**Insurrection
**Nemesis
*Reboot series:
**''the one without a subtitle''
**Into Darkness
**''Beyond''

Note that ''Star Trek: Beyond'' was released after this comic and matches the regex, so the pattern doesn't work any more.

In the last panel "and beyond" Megan uses the regular expression <code>/(meta-)*regex golf/</code> to describe her problem. <code>*</code> means "zero or more" of the preceding character/group (parentheses <code>()</code> group characters). So this regex matches "regex golf", "meta-regex golf", "meta-meta-regex golf", etc. In a way this is regex golf in itself, matching all levels of meta-regex golf while not matching anything else.

In the title text, there is a long regex that is the solution of another regex golf challenge: matching the last names of all elected US presidents but not their opponents. Note that the list of opponents include some people who were previously or later became presidents, or whose last name matches that of another person who was president, so taken literally this is impossible. To make this work the list of opponents must exclude any names of presidents. The regular expression itself works in a very similar way to the Star Wars/Trek one, including several different patterns separated by <code>|</code>. Each elected president matches one pattern while each opponent matches none.

Here is a list of elected president and the patterns they match:
{| class="wikitable"
!Number
!President
!Matched expression
|-
|1
|{{w|George Washington|George Washington}}
|<code>sh</code>
|-
|2
|{{w|John Adams|John Adams}}
|<code>[ae]d</code>
|-
|3
|{{w|Thomas Jefferson|Thomas Jefferson}}
|<code>j</code>
|-
|4
|{{w|James Madison|James Madison}}
|<code>[mtg]a</code>
|-
|5
|{{w|James Monroe|James Monroe}}
|<code>[coy]e</code>
|-
|6
|{{w|John Quincy Adams|John Quincy Adams}}
|<code>[ae]d</code>
|-
|7
|{{w|Andrew Jackson|Andrew Jackson}}
|<code>j</code>
|-
|8
|{{w|Martin Van Buren|Martin Van Buren}}
|<code>bu</code>
|-
|9
|{{w|William Henry Harrison|William Henry Harrison}}
|<code>iso</code>
|-
|11
|{{w|James K. Polk|James K. Polk}}
|<code>[po]o</code>
|-
|12
|{{w|Zachary Taylor|Zachary Taylor}}
|<code>[mtg]a</code>
|-
|14
|{{w|Franklin Pierce|Franklin Pierce}}
|<code>[coy]e</code>
|-
|15
|{{w|James Buchanan|James Buchanan}}
|<code>bu</code>
|-
|16
|{{w|Abraham Lincoln|Abraham Lincoln}}
|<code>[lnd]i</code>
|-
|17
|{{w|Andrew Johnson|Andrew Johnson}}
|<code>j</code>
|-
|18
|{{w|Ulysses S. Grant|Ulysses S. Grant}}
|<code>[rn]t</code>
|-
|19
|{{w|Rutherford B. Hayes|Rutherford B. Hayes}}
|<code>[coy]e</code>
|-
|20
|{{w|James A. Garfield|James A. Garfield}}
|<code>[mtg]a</code>
|-
|22
|{{w|Grover Cleveland|Grover Cleveland}}
|<code>lev</code>
|-
|23
|{{w|Benjamin Harrison|Benjamin Harrison}}
|<code>iso</code>
|-
|24
|{{w|Grover Cleveland|Grover Cleveland}}
|<code>lev</code>
|-
|25
|{{w|William McKinley|William McKinley}}
|<code>n[hl]</code>
|-
|26
|{{w|Theodore Roosevelt|Theodore Roosevelt}}
|<code>[po]o</code>
|-
|27
|{{w|William Howard Taft|William Howard Taft}}
|<code>[mtg]a</code>
|-
|28
|{{w|Woodrow Wilson|Woodrow Wilson}}
|<code>ls</code>
|-
|29
|{{w|Warren G. Harding|Warren G. Harding}}
|<code>[lnd]i</code>
|-
|30
|{{w|Calvin Coolidge|Calvin Coolidge}}
|<code>[lnd]i</code>
|-
|31
|{{w|Herbert Hoover|Herbert Hoover}}
|<code>[po]o</code>
|-
|32
|{{w|Franklin D. Roosevelt|Franklin D. Roosevelt}}
|<code>[po]o</code>
|-
|33
|{{w|Harry S. Truman|Harry S. Truman}}
|<code>[mtg]a</code>
|-
|34
|{{w|Dwight D. Eisenhower|Dwight D. Eisenhower}}
|<code>n[hl]</code>
|-
|35
|{{w|John F. Kennedy|John F. Kennedy}}
|<code>[ae]d</code>
|-
|36
|{{w|Lyndon B. Johnson|Lyndon B. Johnson}}
|<code>j</code>
|-
|37
|{{w|Richard Nixon|Richard Nixon}}
|<code>[lnd]i</code>
|-
|39
|{{w|Jimmy Carter|Jimmy Carter}}
|<code>[rn]t</code>
|-
|40
|{{w|Ronald Reagan|Ronald Reagan}}
|<code>[mtg]a</code>
|-
|41
|{{w|George H. W. Bush|George H. W. Bush}}
|<code>bu</code>
|-
|42
|{{w|Bill Clinton|Bill Clinton}}
|<code>[rn]t</code>
|-
|43
|{{w|George W. Bush|George W. Bush}}
|<code>bu</code>
|-
|44
|{{w|Barack Obama|Barack Obama}}
|<code>[mtg]a</code>
|}

Some presidents are missing because they weren't elected but became presidents after the resignation/death of their formers.

Randall's regular expression must be modified slightly, because it also matches {{w|John C. Fremont|John C. Fremont}}, the runner-up to James Buchanan in 1856, as discussed by {{w|Peter Norvig}} at [http://nbviewer.ipython.org/url/norvig.com/ipython/xkcd1313.ipynb xkcd 1313: Regex Golf]. Note that Norvig provides a small amount of Python code which actually plays regex golf with arbitrary lists, and found a shorter solution than Randall's for the ''Star Wars'' vs ''Star Trek'' game.

The regex does not match Donald Trump, who won over Hillary Clinton in 2016, and thus would need to be updated. The regex does match Hillary Clinton's last name, but because a person with the same last name (Bill Clinton) was president, this does not count as a mistake. There was already a losing opponent called George Clinton who ran in 1792 and 1812.

==Transcript==
:Regex golf:
:[Megan is sitting at a laptop. Cueball is standing behind her.]
:Megan: You try to match one group but not the other.
:Megan: /m | [tn]|b/ matches ''Star Wars'' subtitles but not ''Star Trek''.
:Cueball: Cool.

:Meta-regex golf:
:[A close-up of Megan at her laptop.]
:Megan: So I wrote a program that plays regex golf with arbitrary lists...
:Cueball (offscreen): Uh oh...

:Meta-meta-regex golf:
:[Megan typing at her laptop.]
:Megan: ...But I lost my code, so I'm grepping for files that look like regex golf solvers.
:[Cueball facepalming.]

:...And beyond:
:[Another closeup of Megan at her laptop.]
:Megan: Really, this is all /(meta-)*regex golf/.
:Cueball: Now you have ''infinite'' problems.
:Megan: No, I had those already.

==Trivia==
*There are now at least four comics that reference regular expressions. The other three are: [[208: Regular Expressions]], [[224: Lisp]], and [[1171: Perl Problems]].
*Additionally, regular expressions are mentioned in the title text of [[1277: Ayn Random]].
*A regular expression is used in the [http://what-if.xkcd.com/75/ 75th] post of [[what if?]] to calculate the answer to that week's question.
*Also, Randall mentions [http://regex.alf.nu/ a website with a regexp golf game] he got distracted by while researching for the [http://what-if.xkcd.com/78/ 78th] post of [[what if?]] (which was published one day after this comic).

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Regex]]
[[Category:Star Trek]]

1313: Regex Golf

2017-04-18T09:46:58Z

162.158.114.82: /* Regular expressions */ Update to include second Star Wars sequel film

{{comic
| number = 1313
| date = January 6, 2014
| title = Regex Golf
| image = regex_golf.png
| titletext = <nowiki>/bu|[rn]t|[coy]e|[mtg]a|j|iso|n[hl]|[ae]d|lev|sh|[lnd]i|[po]o|ls/ matches the last names of elected US presidents but not their opponents.</nowiki>
}}

==Explanation==
The comic talks about {{w|regular expressions}}, which are a way to specify textual patterns. Given a regular expression, one can search for the pattern it specifies inside a text string. If the pattern is found, it's said that the pattern "matches" the string; if it's not found, it's said it doesn't match.

The title of the comic and the first panel is based on "[http://regex.alf.nu/ regex golf]", which is a discipline of "{{w|code golf}}", a game in which programmers attempt to solve a given programming problem using as few characters as possible, analogous to the number of {{w|golf}} shots it takes to reach the goal. In regex golfing, the programmer is given two sets of text fragments, and s?he tries to write the shortest possible regular expression which would match all elements of one set, while at the same time not matching any element from the other set.

The regex golf challenge Megan faces consists of matching all subtitles of (then extant) ''{{w|Star Wars}}'' films, while not matching any subtitle of ''{{w|Star Trek}}'' movies. {{w|Subtitle (titling)|Subtitles}} are the secondary titles of the movies, after the ''"Star Trek: "'' or ''"Star Wars Episode N: "''. For example, in ''Star Wars Episode I: The Phantom Menace'', the subtitle is ''The Phantom Menace''. In the first panel, she created a 12-character regex solving the challenge.

Then she moved on to building a tool which would automatically build such a regex for arbitrary lists of text, which could be described as {{w|meta}}- regex golfing. But as she has lost this tool, she needs to search through her files and chooses a tool called "{{w|grep}}" to find it. This implies that she needs a regular expression that would find any code that appears to be a regex golf generator, which leads to another "meta-" layer of abstraction. At the end, Megan notes this sequence of meta-meta-... might go to infinity and Cueball quips that she now has "infinite problems" as a result of her efforts; Megan retorts that she already had "infinite problems" because she's geeky enough to run meta-versions of programs on themselves, and stubborn enough to continue on until she fails, to the exclusion of all else. This also seems to be a reference to a famous quote (see also ''[[1171: Perl Problems]]''):

<blockquote>''Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.''</blockquote>

===Regular expressions===
The first regex Megan uses is <code>/m | [tn]|b/</code>, said to match ''Star Wars'' subtitles but not ''Star Trek''.

The forward slashes <code>/</code> just mark the start and end of the regex. The <code>|</code> character means "or", so the regex matches any string that contains the patterns "<code>m </code>", "<code> [tn]</code>" or "<code>b</code>" (including the spaces). The square brackets match one of the enclosed characters, meaning that "<code> [tn]</code>" matches either "<code> t</code>" or "<code> n</code>". The regex is apparently case-insensitive, because it wouldn't work otherwise.

The Star Wars subtitles match the parts of the regex in the following way:
*"The Phantom Menace" is matched by "<code>m </code>".
*"Attack of the Clones" is matched by "<code> [tn]</code>".
*"Revenge of the Sith" is matched by "<code> [tn]</code>".
*"A New Hope" is matched by "<code> [tn]</code>".
*"The Empire Strikes Back" is matched by "<code>b</code>".
*"Return of the Jedi" is matched by "<code> [tn]</code>".
Note that if one included the animated film "Star Wars: The Clone Wars" it would not be matched by "<code> [tn]</code>" because the T is the start of the subtitle and is not preceded by a space. (The string also will likely fail to match some or all of the upcoming post-Disney-acquisition Star Wars films, which the comic predates; it definitely does not match the first two such films, 2015's "The Force Awakens" and 2017's "The Last Jedi")

On the other hand, none of the Star Trek subtitles contains an M followed by a space, a T or an N preceded by a space, or any B, so the regex does not match any of them. Note that in the original series all subtitles start with a "T" but it's the first character so it's not preceded by a space.

Here is the list that Megan probably used:
*Original series:
**The Motion Picture
**The Wrath of Khan
**The Search For Spock
**The Voyage Home
**The Final Frontier
**The Undiscovered Country
*The Next Generation:
**Generations
**First Contact
**Insurrection
**Nemesis
*Reboot series:
**''the one without a subtitle''
**Into Darkness
**''Beyond''

Note that ''Star Trek: Beyond'' was released after this comic and matches the regex, so the pattern doesn't work any more.

In the last panel "and beyond" Megan uses the regular expression <code>/(meta-)*regex golf/</code> to describe her problem. <code>*</code> means "zero or more" of the preceding character/group (parentheses <code>()</code> group characters). So this regex matches "regex golf", "meta-regex golf", "meta-meta-regex golf", etc. In a way this is regex golf in itself, matching all levels of meta-regex golf while not matching anything else.

In the title text, there is a long regex that is the solution of another regex golf challenge: matching the last names of all elected US presidents but not their opponents. Note that the list of opponents include some people who were previously or later became presidents, so taken literally this is impossible. To make this work the list of opponents must exclude anyone who was also president. The regular expression itself works in a very similar way to the Star Wars/Trek one, including several different patterns separated by <code>|</code>. Each elected president matches one pattern while each opponent matches none.

Here is a list of elected president and the patterns they match:
{| class="wikitable"
!Number
!President
!Matched expression
|-
|1
|{{w|George Washington|George Washington}}
|<code>sh</code>
|-
|2
|{{w|John Adams|John Adams}}
|<code>[ae]d</code>
|-
|3
|{{w|Thomas Jefferson|Thomas Jefferson}}
|<code>j</code>
|-
|4
|{{w|James Madison|James Madison}}
|<code>[mtg]a</code>
|-
|5
|{{w|James Monroe|James Monroe}}
|<code>[coy]e</code>
|-
|6
|{{w|John Quincy Adams|John Quincy Adams}}
|<code>[ae]d</code>
|-
|7
|{{w|Andrew Jackson|Andrew Jackson}}
|<code>j</code>
|-
|8
|{{w|Martin Van Buren|Martin Van Buren}}
|<code>bu</code>
|-
|9
|{{w|William Henry Harrison|William Henry Harrison}}
|<code>iso</code>
|-
|11
|{{w|James K. Polk|James K. Polk}}
|<code>[po]o</code>
|-
|12
|{{w|Zachary Taylor|Zachary Taylor}}
|<code>[mtg]a</code>
|-
|14
|{{w|Franklin Pierce|Franklin Pierce}}
|<code>[coy]e</code>
|-
|15
|{{w|James Buchanan|James Buchanan}}
|<code>bu</code>
|-
|16
|{{w|Abraham Lincoln|Abraham Lincoln}}
|<code>[lnd]i</code>
|-
|17
|{{w|Andrew Johnson|Andrew Johnson}}
|<code>j</code>
|-
|18
|{{w|Ulysses S. Grant|Ulysses S. Grant}}
|<code>[rn]t</code>
|-
|19
|{{w|Rutherford B. Hayes|Rutherford B. Hayes}}
|<code>[coy]e</code>
|-
|20
|{{w|James A. Garfield|James A. Garfield}}
|<code>[mtg]a</code>
|-
|22
|{{w|Grover Cleveland|Grover Cleveland}}
|<code>lev</code>
|-
|23
|{{w|Benjamin Harrison|Benjamin Harrison}}
|<code>iso</code>
|-
|24
|{{w|Grover Cleveland|Grover Cleveland}}
|<code>lev</code>
|-
|25
|{{w|William McKinley|William McKinley}}
|<code>n[hl]</code>
|-
|26
|{{w|Theodore Roosevelt|Theodore Roosevelt}}
|<code>[po]o</code>
|-
|27
|{{w|William Howard Taft|William Howard Taft}}
|<code>[mtg]a</code>
|-
|28
|{{w|Woodrow Wilson|Woodrow Wilson}}
|<code>ls</code>
|-
|29
|{{w|Warren G. Harding|Warren G. Harding}}
|<code>[lnd]i</code>
|-
|30
|{{w|Calvin Coolidge|Calvin Coolidge}}
|<code>[lnd]i</code>
|-
|31
|{{w|Herbert Hoover|Herbert Hoover}}
|<code>[po]o</code>
|-
|32
|{{w|Franklin D. Roosevelt|Franklin D. Roosevelt}}
|<code>[po]o</code>
|-
|33
|{{w|Harry S. Truman|Harry S. Truman}}
|<code>[mtg]a</code>
|-
|34
|{{w|Dwight D. Eisenhower|Dwight D. Eisenhower}}
|<code>n[hl]</code>
|-
|35
|{{w|John F. Kennedy|John F. Kennedy}}
|<code>[ae]d</code>
|-
|36
|{{w|Lyndon B. Johnson|Lyndon B. Johnson}}
|<code>j</code>
|-
|37
|{{w|Richard Nixon|Richard Nixon}}
|<code>[lnd]i</code>
|-
|39
|{{w|Jimmy Carter|Jimmy Carter}}
|<code>[rn]t</code>
|-
|40
|{{w|Ronald Reagan|Ronald Reagan}}
|<code>[mtg]a</code>
|-
|41
|{{w|George H. W. Bush|George H. W. Bush}}
|<code>bu</code>
|-
|42
|{{w|Bill Clinton|Bill Clinton}}
|<code>[rn]t</code>
|-
|43
|{{w|George W. Bush|George W. Bush}}
|<code>bu</code>
|-
|44
|{{w|Barack Obama|Barack Obama}}
|<code>[mtg]a</code>
|}

Some presidents are missing because they weren't elected but became presidents after the resignation/death of their formers.

After Donald Trump won over Hillary Clinton, this regex would not be possible to update since it would need to match (Bill) and not match (Hillary) Clinton at the same time.

Note also that Randall's regular expression must be modified slightly, because it also matches {{w|John C. Fremont|John C. Fremont}}, the runner-up to James Buchanan in 1856, as discussed by {{w|Peter Norvig}} at [http://nbviewer.ipython.org/url/norvig.com/ipython/xkcd1313.ipynb xkcd 1313: Regex Golf]. Note that Norvig provides a small amount of Python code which actually plays regex golf with arbitrary lists, and found a shorter solution than Randall's for the ''Star Wars'' vs ''Star Trek'' game.

==Transcript==
:Regex golf:
:[Megan is sitting at a laptop. Cueball is standing behind her.]
:Megan: You try to match one group but not the other.
:Megan: /m | [tn]|b/ matches ''Star Wars'' subtitles but not ''Star Trek''.
:Cueball: Cool.

:Meta-regex golf:
:[A close-up of Megan at her laptop.]
:Megan: So I wrote a program that plays regex golf with arbitrary lists...
:Cueball (offscreen): Uh oh...

:Meta-meta-regex golf:
:[Megan typing at her laptop.]
:Megan: ...But I lost my code, so I'm grepping for files that look like regex golf solvers.
:[Cueball facepalming.]

:...And beyond:
:[Another closeup of Megan at her laptop.]
:Megan: Really, this is all /(meta-)*regex golf/.
:Cueball: Now you have ''infinite'' problems.
:Megan: No, I had those already.

==Trivia==
*There are now at least four comics that reference regular expressions. The other three are: [[208: Regular Expressions]], [[224: Lisp]], and [[1171: Perl Problems]].
*Additionally, regular expressions are mentioned in the title text of [[1277: Ayn Random]].
*A regular expression is used in the [http://what-if.xkcd.com/75/ 75th] post of [[what if?]] to calculate the answer to that week's question.
*Also, Randall mentions [http://regex.alf.nu/ a website with a regexp golf game] he got distracted by while researching for the [http://what-if.xkcd.com/78/ 78th] post of [[what if?]] (which was published one day after this comic).

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Regex]]
[[Category:Star Trek]]

Talk:1787: Voice Commands

2017-01-19T13:38:25Z

162.158.114.82:

http://wbic16.xedoloh.com/dvorak.html converts "svat ussupd ;dlh a kdbk" to "okay google send a text"--[[Special:Contributions/162.158.75.10|162.158.75.10]] 16:38, 18 January 2017 (UTC)
Well that's a much easier way of converting it than my method of looking at two keyboards.
[[Special:Contributions/162.158.255.58|162.158.255.58]] 16:42, 18 January 2017 (UTC)

I think that's just for US keyboards. I get different results trying that on a UK QWERTY keyboard [[User:Jdluk|Jdluk]] ([[User talk:Jdluk|talk]]) 16:56, 18 January 2017 (UTC)

:The opposite way of typing QWERTY on Dvorak gives the even less pronounceable "RTAF IRRIN. O.BE A Y.QY". –''TisTheAlmondTavern'', 12:38, 19 January 2017 (UTC)

The QWERTY layout is to slow typists down is an enduring myth. In the early days there were typing competitions (with big prizes) to find the fastest typist and fastest machine. This was won by QWERTY in the English world and AZERTY in the French one. Other languages may vary.

The avoid a clash reason (as users of manual machines know) is shown up by the common Left Right Left sequence of "the" and the many letter pairs in English of "er" which are adjacent left fingers and often caused me jams!

Other layouts and designs may have benefits, but will never become the default - a bit like Esperanto methinks ;-) [[User:RIIW - Ponder it|RIIW - Ponder it]] ([[User talk:RIIW - Ponder it|talk]]) 18:31, 18 January 2017 (UTC)

: "In the early days" typewriters would jam easily, so ''of course'' a layout that for the most part avoided that would be fastest way back then. Just because the layout ''still'' had jamming problems doesn't mean it wouldn't come out on top. Touchtyping (a more recent development than QWERTY) makes QWERTY uncomfortable to use at speed, but the pretty much random nature of the layout makes life easier for spell checking software (a more recent development than Dvorak) than Dvorak. [[Special:Contributions/198.41.238.16|198.41.238.16]] 23:43, 18 January 2017 (UTC)

I have only typed Dvorak since 1991, currently on a TypeMatrix 2030DV. Since I have pretty much forgotten Qwerty, I had to look at my wife's laptop to find the letters. Back and forth looking at the comic, it took me a minute to translate that in Notepad. ;-) I can do about 90 wpm in DV. Friends don't let friends type Qwerty!
[[User:TrueFalcon|TrueFalcon]] ([[User talk:TrueFalcon|talk]]) 17:10, 18 January 2017 (UTC)
* Dvorak? pfft. I use butterflies [[Special:Contributions/108.162.245.160|108.162.245.160]] 23:52, 18 January 2017 (UTC)
* As a fellow Dvorak user, I think comments like these are the reason we keep getting comics about us. [[Special:Contributions/162.158.69.177|162.158.69.177]] 18:03, 18 January 2017 (UTC)
** I can practically guarantee it. Especially since actual studies on the subject suggest it's more ability and practice that improve typing speed rather than what layout is used. --[[User:KingStarscream|KingStarscream]] ([[User talk:KingStarscream|talk]]) 20:16, 18 January 2017 (UTC)

The hovertext should say "vocal cords," right? Not "chords"? [[Special:Contributions/173.245.50.222|173.245.50.222]] 18:20, 18 January 2017 (UTC)

: I've heard there ''are'' people who can sing more than one note at a time - a real vocal chord. [[Special:Contributions/198.41.238.16|198.41.238.16]] 23:47, 18 January 2017 (UTC)

:I suppose it might be a deliberate error, but, yes, "vocal chords" is incorrect: it should be "vocal cords" (i.e. strings), or even more correctly [https://en.wikipedia.org/wiki/Vocal_folds vocal folds]. [[Special:Contributions/141.101.99.173|141.101.99.173]] 09:27, 19 January 2017 (UTC)

: A stenograph (as used by a court stenographer) is a keyboard where one presses several keys at a time, called a chord, so I think the hover text 'vocal chord' is a play on the idea of vocalising several 'keys' at once --[[Special:Contributions/141.101.107.126|141.101.107.126]] 13:01, 19 January 2017 (UTC)

The layout was intended to reduce jams, and was likely a trial and error process in development. The layout does in effect slow down the people of the day some, as for instance so many words are typed by left hand only, but this is likely unintentional. Notice that keys like the "I" and "O" are "together", but in fact are separated by three other key linkages, "K""," and "9", so pressing those didn't cause a jam as frequently when pressed in rapid succession, but nevertheless would have been faster had they been on opposite sides of the keyboard. Another point is that keyboarding was still visual at the time, so this keyboard mechanism never took into account the touch typing method that was developed a decade or so later. [[Special:Contributions/172.68.38.10|172.68.38.10]] 19:27, 18 January 2017 (UTC)

Is this an appropriate time to mention the advantages of MessageEase? No? Nevermind then.