Story about a time traveller who became their own mother and father
Identifying a short story about time travel and paradoxes
Best technique to create oldschool (fake 3D) racing game? What would be a good approach to develop the render system for an oldschool type racing game that uses a pseudo 3D scenery, like for example Outrun or Lotus Esprit Turbo Challenge? There's an endless scrolling road and scenery graphics are placed like billboard items, etc. I think you get the idea.    Are these developed in a similar way like  or is there a different technique behind it? Does the technique has a specific name I could search for on the web? I need to develop something like that in Flash. What is a "slug" in Django? If two functionals have the same kernel, then one is a multiple of the other I would like some help with this exercise.  Suppose that $f_1,\ f_2 \in V^*$ and that $\text{Ker} f_1 = \text{Ker} f_2$. Show that $f_1 = k f_2$ for some scalar $k$.  I expect your suggestions.  Thanks! PHP get number of week for month What happens when a familiar from the Find Familiar spell "dies"? Can we simply rename an app if they are different versions and keep them both? For example, I have Xcode 4.4.1, and now Xcode 4.5 Golden Master (GM) version is available, but it is also called Xcode (when the .dmg is mounted as an disc image, it shows only one app (or folder), called Xcode)  I think the way is just to double click on the .dmg file, and then drag and drop that app into our Applications folder.  But since the current Xcode and Xcode 4.5GM have the same name, can the new one just be renamed and so we can have both versions on our machine?  I was worried that what if the app writes back data to the /Applications/Xcode folder, then the GM version can write unexpected data for the 4.4.1 version.  And will it work with other software, such as Xcode 3.2, Xcode 3.3, or even different versions of Microsoft Office and Adobe Photoshop? Lie algebra of $\left(\begin{smallmatrix}a & b\\ & a^2\end{smallmatrix}\right )$ in $GL_2(\mathbb{R})$ I'm working on the question     Let $G$ be the group of invertible real matrices of the form $\left [\begin{array}{c c}a &amp; b\\ &amp; a^2\end{array}\right ]$. Determine the Lie algebra $L$ of $G$, and compute the bracket on $L$.   I'm familiar with how to derive the Lie algebra for a linear group like $U_n$, $SU_n$, etc. but I'm not sure what to do in a more explicit case like this. What can I do when getting “This question body does not meet our quality standards”? Matching exact string with JavaScript How can I test if a RegEx matches a string exactly?  var r = /a/; r.test("a"); // returns true r.test("ba"); // returns true testExact(r, "ba"); // should return false testExact(r, "a"); // should return true Should one ask generic or specific question? Let's assume that one has some problems with coding or designing specific project. Should one ask general question about techniques, algorithms, generic problem (anonymising the project references), or should one ask about specific problem in specific problem? Or perhaps something in between?  Example:   generic: Cross-browser implementation of “HTTP Streaming” (push) AJAX pattern specific: How to implement AJAX-y 'incremental blame' view in gitweb (git web interface in Perl)?   If one should ask generic questions, how to anonymise problem? If one should ask specific question, how avoid 'homework' syndrome? I'm having the strangest issue since updating to OS X El Capitan. My "Open File" dialogs show the sidebar but all my main (and useful) locations are missing. Take a look at this screenshot. This screenshot shows Keychain Access but this happens in Safari when I'm trying to attach a file to Gmail for example, or uploading an image to Facebook.  What I would like is for the sidebar to show my home directories, such as Desktop, Documents, Downloads, etc.  Help? I am aware of the basics of evolutionary theory, however I don't understand how mutations can add genes over time.   Am I correct in thinking that creatures within the same species who mutate to have an additional gene in their genome would normally be infertile?  Or am I misunderstanding that?  Can someone explain the process of the creation of genetic material through evolution?  Citation to a decent academic paper or book on the matter would be appreciated too. What is an LUT in FPGA? I have gone through various sources... But I am not quite sure what it is.I want an and gate and the logical equivalent is two inputs feeding to one gate and for Y=AB' the logical equivalent is feeding to one not gate and one and gate. But it is the same LUT for both AND and Y=AB'. I think we store the values as desired in the LUT. Someone elaborate on this Lifting idempotents modulo a nilpotent ideal The problem is this:      Suppose $I \subseteq R$ is a nilpotent ideal and there is $r \in R$ with $r \equiv r^2 \pmod I$. Show $r \equiv e \pmod I$ for some $e \in R$ idempotent.   I have spent a few hours rolling around in abstracta with no destination. I believe that if I could write down a concrete example of this, the example could guide me through the abstract definitions and show me where to look for an idempotent in $R$. I have looked at 2x2 matrices and could not find any such examples. Might anybody have one? Fspy add-on not installing Plot construction for a velocity vs position graph. Interpolation for phase-diagram construction? Could someone make the proof into a hinted exercise? Let $(c_n)$ be a sequence of positive numbers.  Could someone make the proof of the inequality  $\displaystyle\limsup_{n\to\infty}\sqrt[n]{c_n}\leq\limsup_{n\to\infty}\frac{c_{n+1}}{c_n}$  into a hinted exercise? What is the main difference between StringBuffer and StringBuilder? Is there any performance issues when deciding on any one of these? Consequence of the Hahn-Banach Theorem From wikipedia's page on the Hahn-Banach Theorem:  If $V$ is a normed vector space with linear subspace $U$ (not necessarily closed) and if $z$ is an element of $V$ not in the closure of $U$, then there exists a continuous linear map $ψ : V → K$ with $ψ(x) = 0$ for all $x$ in $U$, $ψ(z) = 1$, and $||ψ|| = dist(z, U)^{−1}.$  How is this a consequence of the Hahn-Banach Theorem? How to make DNS server propagate faster if you are a site owner? It's often the case that I want to change name servers because my site is messed up.  Well, it takes a very long time for the name server to propagate.  Is there something in DNS, or registrar or anything I can do to speed that up.  Flushing my dns server using  and it rarely works