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How do I make a textbox that only accepts numbers? Ubuntu Software (Software Center) Crash - Ubuntu 16.04 Novel about a teleportation device and a con artist alien I read two (maybe three) books about a protagonist who communicates with an alien who provides the instructions on how to create a device to teleport. The device is flawed in that it purposefully uses more energy (much more) by taking it from the rotation of the Earth.  The main character and two others continue to fight, commit intrigue, etc. The alien then uses them to recruit other races to do the same thing. Does Thanos's choice make any sense? So we know from Infinity War that Thanos was collecting all the Infinity Stones to basically solve the problems brought about by overpopulation on many planets.  But does it make any sense? He could've just easily increased the resources or changed the area or taken appropriate measure to handle that situation. As far as I know, collecting all the Infinity Stones gives the user limitless power and control over the universe in the MCU.  Is Thanos just a mass murderer or is there something I'm missing? A very easy probability problem but opinions diverge greatly. Need some help. The question itself is a very easy one:     Somebody has got two kids, one of whom is a girl. Then what's the probability that he's got at least one boy?   My answer is that, since he's already got a girl, then "he's got at least one boy" amounts to "the other kid is a boy", whose probability is apparently $\frac{1}{2}$. But my friends argue that the probability should be $\frac23$: they say this is a binomial distribution, all the possible cases are (girl,girl),(girl,boy),(boy,girl) which yields that the probability is two cases out of three and is thus $\frac23$. But I think this is totally unacceptable. I don't think it is a binomial distribution at all, at least not what my friends explained to me. However, I just can't disuade them of their opinion, nor can I prove that I am wrong. So what on earth is the probability? and why? Any help is appreciated. Thanks in advance. Esp. Can anybody show why my explanation is wrong? Isn't it that whether the other kid is a boy or a girl a 50/50 event?  EDIT: Thanks for all the help you provided for me, and special thanks will go to @HammyTheGreek and @KSmarts, who have made it clear to me that there is in fact some ambiguity in my statement in this problem. As is pointed in  ,two distinct interpretation of the statement "one of whom is a girl" that gives rise to ambiguity:     From all families with two children, at least one of whom is a boy, a family is chosen at random. This would yield the answer of 1/3.   From all families with two children, one child is selected at random, and the sex of that child is specified to be a boy. This would yield an answer of 1/2. I was just awarded +100 reputation on all of my Stack Exchange accounts.  What is this bonus for? It simply says "Association Bonus" on my reputation overview.  Also:   What privileges does the association bonus grant users? Can I lose the association bonus? Does it make my reputation 101 everywhere? Can I earn the association bonus on sites I haven't joined yet? Does it matter which site I earn the 200 reputation on? Will I get an association bonus every time my reputation on a site crosses 200 points? Does the association bonus allow me to answer protected questions? Does the association bonus count towards the reputation cap? Can I get the association bonus if I only have a profile on one site? What else is there to know about the association bonus? This has just dawned on me that if you're writing an operating system then what are you writing it on? I ask this as I am reading a microprocessor fundamentals book from 1980 and this question popped in to my head:   How was the first microprocessor chip programmed?  The answer may be obvious but its bugging me. I have a function with the same name, but with different signature in a base and derived classes. When I am trying to use the base class's function in another class that inherits from the derived, I receive an error. See the following code:  class A {     public:     void foo(string s){}; };  class B : public A {     public:     int foo(int i){}; };  class C : public B {     public:     void bar()     {         string s;         foo(s);     } };   I receive the following error from the gcc compiler:  In member function `void C::bar()': no matching function for call to `C::foo(std::string&amp;)' candidates are: int B::foo(int)   If I remove int foo(int i){}; from class B, or if I rename it from foo1, everything works fine.   What's the problem with this? I want to do something like:  MyObject myObj = GetMyObj(); // Create and fill a new object MyObject newObj = myObj.Clone();   And then make changes to the new object that are not reflected in the original object.  I don't often need this functionality, so when it's been necessary, I've resorted to creating a new object and then copying each property individually, but it always leaves me with the feeling that there is a better or more elegant way of handling the situation.  How can I clone or deep copy an object so that the cloned object can be modified without any changes being reflected in the original object? In the United States, we say that someone lives on a street, whereas I've noticed that British people say in. For instance:     Bubba lives on Washington Street.   Colin lives in Cavendish Avenue.   I believe we both would use at when a number is given. For instance:     Bubba lives at 16 Washington Street.   Colin lives at 7 Cavendish Avenue.   I don't think it matters if it's a road, avenue, street, circle, or lane — as far as I know, in America, we always live on a street. Does it vary in British English, or is it always in? If it varies, what are the rules? I have looked at other questions on this site (e.g. "why does space expansion affect matter") but can't find the answer I am looking for.  So here is my question: One often hears talk of space expanding when we talk about the speed of galaxies relative to ours. Why, if space is expanding, does matter not also expand? If a circle is drawn on balloon (2d plane), and the balloon expands, then the circle also expands. If matter is an object with 3 spatial dimensions, then when those 3 dimensions expand, so should the object.  If that was the case, we wouldn't see the universe as expanding at all, because we would be expanding (spatially) with it.  I have a few potential answers for this, which raise their own problems:   Fundamental particles are 'point sized' objects. They cannot expand because they do not have spatial dimension to begin with. The problem with this is that while the particles would not expand, the space between them would, leading to a point where the 3 non-gravity forces would no longer hold matter together due to distance Fundamental particles are curled up in additional dimensions a la string theory. These dimensions are not expanding. Same problems as 1, with the added problem of being a bit unsatisfying. The answer seems to be (from Marek in the previous question) that the gravitational force is so much weaker than the other forces that large (macro) objects move apart, but small (micro) objects stay together. However, this simple explanation seems to imply that expansion of space is a 'force' that can be overcome by a greater one. That doesn't sound right to me. Say, I have a script that gets called with this line: ./myscript -vfd ./foo/bar/someFile -o /fizz/someOtherFile  or this one: ./myscript -v -f -d -o /fizz/someOtherFile ./foo/bar/someFile   What's the accepted way of parsing this such that in each case (or some combination of the two) $v, $f, and  $d will all be set to true and $outFile will be equal to /fizz/someOtherFile? I'm trying to find the complex roots of $z^3 + \bar{z} = 0$ using De Moivre.  Some suggested multiplying both sides by z first, but that seems wrong to me as it would add a root ( and I wouldn't know which root was the extra ).  I noticed that $z=a+bi$ and there exists $\theta$ such that the trigonometric representation of $z$ is $\left ( \sqrt{a^2+b^2} \right )\left ( \cos \theta + i \sin \theta \right )$ .  It seems that $-\bar{z} = -\left ( \sqrt{a^2+b^2} \right )\left ( \cos (-\theta) + i \sin (-\theta) \right )$  However, my trig is pretty rusty and I'm not quite sure where to go from here. I have 24 accounts, how can I delete them all in one go? Is there a way to delete all stack exchange accounts at the same time?  I also want to remove all traces of my posts on the site. Is that possible?   Will I have to delete all of my posts manually?  Can I use the stack exchange API for this? 32-bit vs. 64-bit systems What are the differences between 32-bit and 64-bit systems?  If you have used both of them, what kind of sharp differences have you experienced?   Would it be a problem to use 32-bit programs on 64-bit systems in some cases? Probability that a quadratic polynomial with random coefficients has real roots How do hashes really ensure uniqueness? This might seem an impractical and unnecessary conversation, but I feel it's something I need to clarify. Especially, as I just got my first developer job in a blockchain startup.  So hashes are said to generate the same thing for any information it sees, and it's only a one-way interaction.   As far as I understand, hashes are just long alphanumeric strings. If one computes hashes across all documents, keys, information, files, etc, over and over again- it's simply a matter of time until the same combination comes up again for different information (applying it across all possible contexts)? This might be an impractical test given size and possibility, yes, but is it this that makes hashes powerful, that it's practically impossible to recreate a hash that for any foreseeable endeavor it's fine, or is there some element that I'm missing that reduces even that extremely low probability to zero? Is there any design constraint that prevents a very powerful computer to back-calculate the original data from a hash? Or is it simply that the design is so complex that it's simply a futile exercise to dream of such a large computer required for this task? What's stopping a hacker or malicious middle man to hack open the software program or library that creates this "hash" and then use that library to create hashes of his/her own or mislabel some target company's hash with his/her own pointing to their version of the file? Especially since many applications, languages, and developers use hashing independently. Whichever is most weakly secured, we can use that to take on the rest?   Any resources are also appreciated. I wonder about the foundations of set theory and my question can be stated in some related forms:   If we base Zermelo–Fraenkel set theory on first order logic, does that mean first order logic is not allowed to contain the notion of sets? The axioms of Zermelo–Fraenkel set theory seem to already expect the notion of a set to be defined. Is there are pre-definition of what we are dealing with? And where? In set theory, if a function is defined as a set using tuples, why or how does first order logic and the axioms of Zermelo–Fraenkel set theory contain parameter dependend properties $\psi(u_1,u_2,q,...)$, which basically are functions? How to use IDM on Mozilla Firefox Quantum I want to use Internet Download Manager for downloading on Firefox. According to this  it can be done with the extension called Flashgot. But Flashgot does not work on new Firefox Quantum. However, I found  that can be used to interrupt browser's downloading jobs by redirecting these jobs to an external download manager like Internet Download Manager (IDM). But I don't know how to integrate IDM with this new extension. I wrote IDM's location (/.wine/drive_c/Program Files (x86)/Internet Download Manager/IDMan.exe) in the box that says "Path to the executable" but when I try to download something, an error is appearing.     The preference page of the extension        The error that is appearing while trying to download files     How can I make it work? Thanks beforehand! Expansion of $(1+\sqrt{2})^n$