defining a subclass constructor
What does it mean to "program to an interface"?
How many ways to arrange people on a bench so that no woman sits next to another woman? Why do universal constants have the values they do? This is meant to be a generic question of the type that we get repeatedly on this site, in different versions:        Why do universal constants have the values they do? Can we predict their values theoretically? Do they change over time? How would the world be different if a particular constant had a different value? Function with varying number of For Loops (python) I've heard that i can travel to the US any time before my tourist visa expiry.  Is that true?  (please advise) What is the "Wanna Cry" ransomware's possible impact on Linux users? It's just come to light that there's a $300 ransom you have to pay because ransomware targeting Microsoft Windows has encrypted your data. What steps do Linux users need to protect from this if for example they are using wine?  This ransomware is widely reported to be based on a tool developed by the NSA to hack into computers. The NSA tool was used by a hacker group called the Shadow Brokers. The code can be found in .  Microsoft released a patch (MS17-010) against this vulnerability on March 14, 2017. The mass infection is reported to have begun spreading on April 14th. This is discussed .  As I haven't booted Windows 8.1 in 6 to 8 weeks, can I apply this patch from Ubuntu without booting Windows first? (After research it may be possible ClamAV could report the vulnerability from the Linux side looking into Windows partition but it's unlikely it could apply the patch. The best method would be to reboot into Windows and apply patch MS17-010.)  Individuals and small companies who subscribe to Microsoft Automatic Updates are uninfected. Larger organizations who delay apply patches as they are tested against organization intranets are more likely to be infected.  On May 13, 2017, Microsoft took the extraordinary step of releasing a patch for Windows XP which has been unsupported for 3 years.  No word if wine is doing anything about a security update. It was reported in a comment below that Linux can be infected too when users run .  An  registered a domain name that acted as a kill-switch to the ransomware. I presume the non-existent domain was used by the hackers on their private intranet so they didn't infect themselves.  Next time they will be smarter so don't rely on this current kill-switch. Installing the Microsoft patch, which prevents exploiting a vulnerability in the SMBv1 protocol, is the best method.  On May 14, 2017 Red Hat Linux said they are not affected by "Wanna Cry" ransomware. This might mislead Ubuntu users along with Red Hat, CentOS, ArchLinux and Fedora users. Red Hat supports wine which answers below confirm can be effected. In essence Ubuntu and other Linux distro users googling this issue might be mislead by the Red Hat Linux Support answer .  May 15, 2017 Update. Over the last 48 hours Microsoft released patches called KB4012598 for  to protect against "Wanna Cry" ransomware. These Windows versions are no longer on automatic updates. Although I applied security update MS17-010 on my Windows 8.1 platform yesterday, my old Vista Laptop still needs patch KB4012598 downloaded and manually applied.       Moderator note: This question is not off topic - it asks about whether or not any Linux users need to do any steps for protecting against the risk.      It is perfectly on topic here, because it's relevant to Linux (which Ubuntu is), and it's also relevant for Ubuntu users running Wine or similar compatibility layers, or even VMs on their Ubuntu Linux machines. I have installed a vlc in centos 6.5. I want to run it as root. But I get the following error,      "VLC is not supposed to be run as root. Sorry. If you need to use   real-time priorities and/or privileged TCP ports you can use   vlc-wrapper (make sure it is Set-UID root and cannot be run by   non-trusted users first)." Do we know Snoke predates the Empire? Let $S$ be a finite collection of real numbers (not necessarily distinct). If any element of $S$ is removed then the remaining real numbers can be divided into two collections with same size and same sum ; then is it true that all elements of $S$ are equal ?  (I know the result is true if the &quot;reals&quot; are replaced by &quot;integers&quot;.) Object glitching/dissapearing in render due to parenting problems I have completed my animation but I realised when I render it that one of the propellers blades starts to glitch. On some frames it is in shot and some it is out of shot and this is really strange. These 'blades' are both parented to the same 'propeller' and the 'propeller' is parented to the middle ball. I have baked the animation through so this shouldn't be a problem. These propellers are passive rigid bodies. I have tried to figure out this problem and I just can't get to a solution. I've never had it where a rigid body object glitches out like that in the rendered animation, it's almost like it's jumping, which on the render these frames show the object as invisible. The video attached will show.   If anyone has experienced problems like this or knows an answer to my dilemma that would be greatly appreciated, thanks! A book in which every species on earth was rendered intelligent The 'blurb' on the back of the book was that something had boosted the intelligence of every creature on earth, to the point that at least some animals were on par with humans. I'm not sure if humans were similarly enhanced or just animals. I'm not sure whether it was done by aliens, or a side effect of something humans did, or what.   This book was on the shelves in the mid/late 1980's, so it's nothing more recent than that. Python, Unicode, and the Windows console Does entanglement not immediately contradict the theory of special relativity? Does entanglement not immediately contradict the theory of special relativity? Why are people still so convinced nothing can travel faster than light when we are perfectly aware of something that does? Hi I can compute a Basic Loan Amortization Schedule, But now I'm trying to Calculate a Seasonal Loan Amortization Schedule . So for example A loan starts at January And Will go on for 3 years, with Monthly Payments. Interest is at 3% Annually and is compounded Annually. During the months of September, October, November, December It'll only accumulate Interest But no payments and principal. Principal is 100000. How Do I calculate Payments and interest. Showing that the roots of a polynomial with descending positive coefficients lie in the unit disc. Let $P(z)=a_0+a_1z+\cdots+a_nz^n$ be a polynomial whose coefficients satisfy $$0&lt;a_0&lt;a_1&lt;\cdots&lt;a_n.$$  I want to show that the roots of $P$ live in unit disc. The obvious idea is to use Rouche's theorem, but that doesn't quite work here, at least with the choice $f(z)=a_nz^n, g(z)=$ (the rest).  Any ideas? Find the value of : $\lim_{n\to\infty}\prod_{k=1}^n\cos\left(\frac{ka}{n\sqrt{n}}\right)$ Why are cryptography algorithms not exported to certain countries? There have been strict laws about the export of crypto software to certain countries. I can understand the intent, but never gauged the fact that there is nothing stopping these countries from developing their own crypto software. So why limit the export?   And in light of the recent NSA revelations, of backdoors being engineered into crypto algos, wouldn't the export of such compromised algorithms have helped to unravel secrets? Does an adjective or longer modifier apply to both nouns when they are joined with 'and' [or 'or']? Can you grab the blue shirts and socks?   Is the above sentence stating that both the shirts and the socks are blue? Or only the shirts?  At this stage, I am leaning towards the earlier (only the shirts) — though writing "Can you grab the blue shirts and blue socks?" seems redundant. Generalized Euler sum $\sum_{n=1}^\infty \frac{H_n}{n^q}$ I found the following formula   $$\sum_{n=1}^\infty \frac{H_n}{n^q}= \left(1+\frac{q}{2} \right)\zeta(q+1)-\frac{1}{2}\sum_{k=1}^{q-2}\zeta(k+1)\zeta(q-k)$$  and it is cited that Euler proved the formula above , but how ?  Do there exist other proofs ?  Can we have a general formula for the alternating form   $$\sum_{n=1}^\infty (-1)^{n+1}\frac{H_n}{n^q}$$ How do I profile memory usage in Python? I've recently become interested in algorithms and have begun exploring them by writing a naive implementation and then optimizing it in various ways.  I'm already familiar with the standard Python module for profiling runtime (for most things I've found the timeit magic function in IPython to be sufficient), but I'm also interested in memory usage so I can explore those tradeoffs as well (e.g. the cost of caching a table of previously computed values versus recomputing them as needed). Is there a module that will profile the memory usage of a given function for me? What changed in the Hot Questions sidebar algorithm? I've recently noticed that the hot questions list is now different almost every time I look at it. It used to be static - I.e. I could browse around for half an hour and the items on it would be minimally changed.  Was the algorithm changed? In what way?