explain xkcd - User contributions [en]

1188: Bonding

2021-10-14T13:48:02Z

108.162.221.75:

{{comic
| number = 1188
| date = March 20, 2013
| title = Bonding
| image = bonding.png
| titletext = I'm trying to build character, but Eclipse is really confusing.
}}

==Explanation==
This is {{w|source code}} written in the {{w|Java (programming language)|Java programming language}} which models a parent and a child playing a {{w|Catch (game)|game of catch}}. Normally this game is played with the parent throwing a ball to their child, who catches it and throws it back, and repeated back-and-forth. The comic title "Bonding" refers to the {{w|Paternal bond|building of relationship}} between the parent and the child. The joke lies in the puns using the words <code>try</code>, <code>throw</code>, <code>catch</code>, and <code>Throwable</code>. These can refer to actions in the real-life game, but are also keywords in the Java language that are used for {{w|exception handling}}, a method of signaling error conditions and responding to them. Also, the terms "parent" and "child" are usually interpreted more abstractly in programming, as generic terms used in hierarchical {{w|Data structure|data structures}}.

The program, as written, will {{w|Recursion (computer science)|recursively}} call the <code>aim</code> method alternately on the parent and the child indefinitely, causing each to take turns throwing and catching the <code>Ball</code> object. Note that unlike the real game, this program actually has the same person both throwing and catch the same ball on their turn. The ball is passed onto the other person by ''aiming'' it at them, which causes the person to both throw and catch the ball, and ''aim'' it back, perpetuating the cycle. This program will also eventually crash with a {{w|stack overflow}} error.

The title text refers to the [http://www.eclipse.org/ Eclipse IDE], which is a tool commonly used to develop software in Java. "Building character" is something that you would expect a parent to do, in order to instill in his child positive traits, such as confidence and athleticism. This is possibly a reference to {{w|Calvin_and_Hobbes|Calvin and Hobbes}}, where Calvin's dad often encourages him to build character in a number of ways, including playing baseball. This is made more likely by other references combining technology with Calvin and Hobbes, such as xkcd comics [[409: Electric Skateboard (Double Comic)]], [[702: Snow Tracking]] and [[1002: Game AIs]]. However, here, "build" might also be a play on the term of "{{w|Software build|building}}" a program, while "{{w|Character_(computing)|character}}" refers to a data type in programming languages. It may also refer to the common notion that programming in C++ or Java builds character due to their powerful but sometimes finicky libraries.

===Program description===
To compile this {{w|Java_(programming_language)|Java}} source code, the two [http://docs.oracle.com/javase/tutorial/java/javaOO/classdecl.html classes] would need to be in a .java file.
The program defines two classes (types of objects):
#The Ball class [http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html extends] [http://docs.oracle.com/javase/7/docs/api/java/lang/Throwable.html Throwable], making it possible to use an instance of Ball in [http://docs.oracle.com/javase/tutorial/essential/exceptions/handling.html exception handling]. In English, this means "a Ball is a kind of Throwable object".
#The P class, representing a Person, which contains the following members (attributes):
#*a [http://docs.oracle.com/javase/tutorial/java/javaOO/variables.html class variable] 'target' to point to another P to aim a Ball at.
#*a [http://docs.oracle.com/javase/tutorial/java/javaOO/constructors.html constructor] 'P' (in Java the constructor always has the same name as the class) used to create an instance of P and initialize its state (with a target). The keyword [http://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html this] refers to the current instance of P.
#*a [http://docs.oracle.com/javase/tutorial/java/javaOO/methods.html method] 'aim' that takes an instance of Ball named 'ball' as a parameter. This contains the code to actually throw, catch, and pass the ball onto the target.
#*a [http://docs.oracle.com/javase/tutorial/java/javaOO/classvars.html static] method 'main' which is called when executing this class. This is the code that sets up the game and starts the process.

The program executes in the following order:
#The static main method is called. It sets up the game by doing the following:
##An instance of P named 'parent' is created without a target ({{w|Nullable_type|null}}) using the 'new' keyword.
##Another instance of P named 'child' is created with 'parent' as its target.
##The parent's target is assigned to be the child. Unlike with 'child', setting the parent's target could not be done at the moment when 'parent' was created because its target (the child) has not yet been created at the time. This is why the code for parent and child don't look alike despite this being a symmetrical setup.
#The game begins by having the parent aim a new instance of Ball.
#The aim method first sets up a [http://docs.oracle.com/javase/tutorial/essential/exceptions/try.html try] block to handle exceptions. A "try" block is required in Java in order to "catch" later.
#Next, the Ball instance 'ball' is [http://docs.oracle.com/javase/tutorial/essential/exceptions/throwing.html thrown]. This signals an exception situation and triggers the [http://docs.oracle.com/javase/tutorial/essential/exceptions/catch.html catch] block below.
#In the catch block, the aim method of the target of the P instance is called with the Ball instance (now referred to as 'b').
#The target now executes its own aim method, which is the same code continuing from step 3 except with the current class instance ('this') and its target switched between the parent and the child.

==Transcript==
class Ball extends Throwable {}
class P{
P target;
P(P target) {
this.target = target;
}
void aim (Ball ball) {
try {
throw ball;
}
catch (Ball b) {
target.aim(b);
}
}
public static void main(String[] args) {
P parent = new P(null);
P child = new P(parent);
parent.target = child;
parent.aim(new Ball());
}
}

{{comic discussion}}
[[Category:Programming]]

2528: Flag Map Sabotage

2021-10-14T13:45:19Z

108.162.221.75:

{{comic
| number = 2528
| date = October 13, 2021
| title = Flag Map Sabotage
| image = flag_map_sabotage.png
| titletext = Delaware hopes to explore the western edge of areas marked with the Belgian flag, once the tornadoes die down.
}}

==Explanation==
{{incomplete|Created by a GOD-EMPEROR OF GREATER DELAWARE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

The comic refers to a type of map that colors countries using the national flag designs; see [https://i.pinimg.com/originals/41/0f/36/410f3661d1cee3b255b82a111f99d242.jpg here] for such a map of Europe. Randall proposes a new flag which, if adopted by a country, would sabotage such a map by sneaking in what would appear to be the legend for the whole map. This trick is reminiscent of [[327: Exploits of a Mom]], with Mrs. Robert's son Robert'); DROP TABLE Students;-. If the overall map were then interpreted according to the legend, much of the earth's land mass would appear as Greater Delaware (because red is a very common flag color). It should be noted that there are several ways map makers could counter the sabotage, e.g. by adding a real legend to cover the fake legend included in the new flag.

Given the layout of the proposed flag, this could be an attempt at a new flag of USA (although the text mentions "our new country"). This would seamlessly attach to both Canada's area colored in the red-white-red vertical stripes, and to Mexico's area colored in the green-white-red pattern. The bottom of Randall's flag even makes an attempt to narrow down the white stripe at the bottom, to make such connection with Mexico possible.

The title text refers to the flag of Belgium, which consists of three vertical stripes in the order black, yellow, and red. The western part of Belgium would, according to the legend, be unexplored, while the eastern part would be Greater Delaware. The middle would therefore be a tornado zone separating the unexplored area from Greater Delaware. Depending on how the flags are aligned it would be possible to explore from the south. The north is not viable as rebel forces would be present.

Also, because Belgium is the northern neighbor of France, whose flag is made of vertical stripes with Blue-White-Red, the French Greater Delaware may be conveniently located to help said exploration.

This is not the first time Randall has made a flag for a new country! See [[1815: Flag]]

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[A flag displays a white country-shaped area surrounded by a red field. Inside the shape sits a map legend.]

:Map Legend
:[Bright blue rectangle] Disputed territory
:[Green rectangle] Newly independent
:[Blue rectangle] Demilitarized zone
:[Yellow rectangle] Tornado warning
:[Dark blue rectangle] Held by rebel forces
:[Red rectangle] Greater Delaware
:[Black rectangle] Unexplored

:[Caption below panel]
:Our new country's flag sabotages those maps where geographic areas are colored in with flag patterns.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Maps]]
[[Category:Sabotage]]

Talk:509: Induced Current

2015-08-13T14:18:37Z

108.162.221.75:

I slightly disagree with the run-through of the "hopes to see it tested on mythbusters, and then scaled up to astronomical proportions" bit. Perhaps refine the first part by ending with something like "...in order to give them enough myths to be worth filming another series". The latter (a reference to the title-text, I assume) should then be dealt with in a separate para by explaining that Mythbusters ''tests'' myths experimentally, but that even the basic "use an LHC to get black holes" idea isn't going to be practically replicatable by them, let alone being able to replicate the possibility (or impossibility) of said black holes consuming the Earth. Unless TV budgets and resources are somewhat more capable than I imagine they are... [[Special:Contributions/178.107.63.150|178.107.63.150]] 21:41, 5 June 2013 (UTC)

I think the title text is also referring to the second half of the Mythbusters’ “replicate the circumstances, then duplicate the results” method. Basically, the Mythbusters would see what it ''would'' take to destroy the world (and, in the process, actually do so). Maybe they could get help from [http://qntm.org/destroy Sam Hughes] [[Special:Contributions/199.27.128.87|199.27.128.87]] 08:14, 20 July 2014 (UTC)

Two interesting historical examples are [http://en.wikipedia.org/wiki/Solar_storm_of_1859 the solar flare of 1859] in which telegraph wires had enough induced voltage to cause sparks on the telegraph poles, and [http://en.wikipedia.org/wiki/March_1989_geomagnetic_storm the geomagnetic storm of 1989], which caused the power grid in Quebec, Canada to fail. The latter demonstrates that in this modern era we are certainly not immune to such "outlandish" scenarios.[[Special:Contributions/108.162.219.160|108.162.219.160]] 01:16, 16 February 2015 (UTC)

Wait. If you tell Beret Guy that doesn't that make it more likely to happen since physics conforms to his simplistic understanding of it around him?
[[Special:Contributions/108.162.221.75|108.162.221.75]] 14:18, 13 August 2015 (UTC)

Talk:1563: Synonym Movies

2015-08-12T10:46:29Z

108.162.221.75:

Space Trip would probably be Star Trek, right?
[[Special:Contributions/141.101.98.166|141.101.98.166]] 05:17, 12 August 2015 (UTC)

Is this supposed to be related to "Thing explainer"? But then there are words like government, and Vulcan...
--[[User:Zzyss|Zzyss]] ([[User talk:Zzyss|talk]]) 06:51, 12 August 2015 (UTC)
:No I do not think so. It is not simple words, just different words with he same meaning --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:29, 12 August 2015 (UTC)

Funny, I would've said "''The Sword Wizard'''s Are''' Back''"... I've always interpreted that instance of ''Jedi'' as being plural.
--[[User:Vor0nwe|vor0nwe]] ([[User talk:Vor0nwe|talk]]) 08:04, 12 August 2015 (UTC)
:It could refer to Luke, the only Jedi alive at the end of the movie... --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:29, 12 August 2015 (UTC)
: In German the title is "Rückkehr der Jedi-Ritter" which would translate back into "Return of the Jedi Knights" - Plural. So it is/was naturally plural for me, too. But, of course, German movie titles are no reference to the actual meaning. Since some years we occasionally use English titles in Germany, too. But somehow they are different to the original English titles... (No worry: Star Wars is Star Wars - but even that was translated in the 70's to "Krieg der Sterne") [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 09:50, 12 August 2015 (UTC)

Wikipedia does note that Czar had become a title equivalent to King by the 19th Century, so perhaps that ought to be mentioned regarding "We Have a Czar Again."

Gaaaah! Power and force are not synonyms! Power and force-velocity are! Edit:thx whoever [[Special:Contributions/108.162.221.75|108.162.221.75]] 10:41, 12 August 2015 (UTC)

Talk:1563: Synonym Movies

2015-08-12T10:41:56Z

108.162.221.75:

Space Trip would probably be Star Trek, right?
[[Special:Contributions/141.101.98.166|141.101.98.166]] 05:17, 12 August 2015 (UTC)

Is this supposed to be related to "Thing explainer"? But then there are words like government, and Vulcan...
--[[User:Zzyss|Zzyss]] ([[User talk:Zzyss|talk]]) 06:51, 12 August 2015 (UTC)
:No I do not think so. It is not simple words, just different words with he same meaning --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:29, 12 August 2015 (UTC)

Funny, I would've said "''The Sword Wizard'''s Are''' Back''"... I've always interpreted that instance of ''Jedi'' as being plural.
--[[User:Vor0nwe|vor0nwe]] ([[User talk:Vor0nwe|talk]]) 08:04, 12 August 2015 (UTC)
:It could refer to Luke, the only Jedi alive at the end of the movie... --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:29, 12 August 2015 (UTC)
: In German the title is "Rückkehr der Jedi-Ritter" which would translate back into "Return of the Jedi Knights" - Plural. So it is/was naturally plural for me, too. But, of course, German movie titles are no reference to the actual meaning. Since some years we occasionally use English titles in Germany, too. But somehow they are different to the original English titles... (No worry: Star Wars is Star Wars - but even that was translated in the 70's to "Krieg der Sterne") [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 09:50, 12 August 2015 (UTC)

Wikipedia does note that Czar had become a title equivalent to King by the 19th Century, so perhaps that ought to be mentioned regarding "We Have a Czar Again."

Gaaaah! Power and force are not synonyms! Power and force-velocity are! [[Special:Contributions/108.162.221.75|108.162.221.75]] 10:41, 12 August 2015 (UTC)

177: Alice and Bob

2014-01-29T13:27:02Z

108.162.221.75: /* "Commic" to "Comic" */

{{comic
| number = 177
| date = October 30, 2006
| title = Alice and Bob
| image = alice_and_bob.png
| titletext = Yet one more reason I'm barred from speaking at crypto conferences.
}}

==Explanation==
Any good cryptography presentation will include at least one story about {{w|Alice and Bob}}. They are the canonical "protagonists" of the crypto world, frequently used in illustrations to demonstrate how a cryptographic system works. (The names were mostly chosen to abbreviate to A and B, as well as being of different genders so that they can be distinguished by pronouns alone.)

Here, Randall casts the story in a different light. Instead of Alice and Bob being perfectly innocent people who just want to communicate in private, Bob is actually having an affair with Alice, and his former partner, upset, cracked the encryption to see what the message contained. Nevertheless, the "gossipy cryptographic protocol specs" all took Alice's side (since the goal of any good crypto system is, of course, to ''succeed'' in this struggle).

The rest of the comic makes a few other allusions to cryptography:

*{{w|Bruce Schneier}} and {{w|Ron Rivest}} are two well-known cryptographers. They have written lots of papers that use Alice and Bob as examples (Alice / Bob fanfic, if you will).
*Public and private keys are two extremely large numbers, chosen such that there's a mathematical relation between them, and yet it's extremely hard (i.e. would take many billions of years) to derive the private key from the public key. They're the basis of {{w|asymmetric cryptography}}. A public-key authenticated signature is a way of cryptographically proving that a certain person created a file, as only that person could have possibly generated that signature. One downside is that anybody who has the public key can verify who a message is from, so it removes plausible deniability; Bob's partner clearly knew that Alice and Bob were communicating, on disks marked by lipstick hearts no less.
*A known-plaintext attack is a type of cryptographic attack where the plaintext (i.e. unencrypted text) of a message is known, and the attacker wants to figure out the keys used to encrypt the message. The woman is saying that she should have known all along that the messages were adulterous in nature.

Finally, in a twist ending, the girlfriend is revealed to be none other than Eve, the ''eave''sdropper, who is also ubiquitous in Alice and Bob stories. Hell hath no fury, indeed.

The title text continues the theme of Randall getting barred from speaking at conferences due to his unusual take on certain topics.

To further spice things up, there are many other characters in the Alice/Bob canon, including Mallory, the ''mal''icious, who wants to actually ''alter'' the message with nefarious intent; Craig, the ''cr''acker, who doesn't particularly care about the message but ''does'' care about the passwords used; plod, a law enforcement officer attempting to access key or data, and Chuck, a third party in the communication who secretly has a villainous intent.

Alice, Bob and Eve is mentioned again in comic: [[1323: Protocol]]

==Transcript==
:[Eve stands in the frame, talking to the reader.]
:Eve: I'm sure you've heard all about this sordid affair in those gossipy cryptographic protocol specs with those busybodies Schneier and Rivest, always taking Alice's side, always labeling me the attacker.
:Eve: Yes, it's true. I broke Bob's private key and extracted the text of her messages. But does anyone realize how much it hurt?
:Eve: He said it was nothing, but everything from the public-key authenticated signatures on the files to the lipstick heart smeared on the disk screamed "Alice."
:Eve: I didn't want to believe. Of course on some level I realized it was a known-plaintext attack. But I couldn't admit it until I saw it for myself.
:[Eve places her hands on her hips.]
:Eve: So before you so quickly label me a third party to the communication, just remember: I loved him first. We had something and she tore it away. She's the attacker, not me. Not Eve.

{{comic discussion}}
[[Category:Romance]]
[[Category:Computers]]
[[Category:Banned from conferences]]

784: Falling Asleep

2014-01-28T20:29:52Z

108.162.221.75: /* Grammar */

{{comic
| number =784
| date =August 25, 2010
| title =Falling Asleep
| image =falling_asleep.png
| titletext =Sweet unintersecting dreams!
}}

==Explanation==
{{incomplete|There was no reason given originally when this comic was listed as today's incomplete explanation - but since then the explanation has been split up in a part about the comic and one about the title text - Maybe it can be considered complete now?}}
The first few panels of this strip seem romantic and sentimental, as it's common to hear that people sleep better next to people they love. The last panel reveals that Cueball and Megan are actually going through some relationship trouble, because Cueball uses her presence as a good reason for leaving this world behind. He does, however, not intend to commit suicide to escape from her and the world; he just wishes to escape by falling asleep.

As the title text reveals, he also wishes to avoid her in his dreams, as he wishes their dreams do not intersect - i.e. he hopes he will not dream of her (and vice versa).

==Transcript==
:[Cueball gets into bed.]
:It's so much easier
:falling asleep

:[Megan is lying in bed, gripping her pillow.]
:With you beside me-

:[Cueball is lying on his back in bed.]
:All the incentive I need

:[Full shot of the bed, Megan is on the left, gripping the pillow, Cueball is as far to the right as possible, nearly falling off, facing away from her.]
:To leave the world behind.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics with color]]
[[Category:Romance]]