I'm very new to blender so this might be an easy fix, but I have a little problem with the model of my guitar. Here's what I'm working with right now:  But when I add the subdivision surface modifier, the tops go crazy, the big flat faces are not completely flat any more, and there's something wrong with the top and bottom of that carved out part... I would also like to make the edge of that less sharp but I haven't found a good way yet.  For reference, here's a picture of the guitar I'm trying to recreate:  What would you suggest to improve my model? Thanks for the help!

My problem is simple. I think that the strange deformations on the top are there because there are so many vertices in one face. How do I fix this while maintaining nice topology?  Although I triangulated the top polygon, the problem still persists.


In reviewing low quality posts, I cannot see a .  It was closed as:    The available options are as follows.

Related:    I recently noticed something: The off topic subreason chosen by flaggers doesn't make any difference at all. Specifically, the subreason chosen is not shown to close voters.  Besides, as the "other" reason is unavailable, a lot of cases that aren't covered by the custom off topic reasons aren't flaggable unless you use a moderator flag (which is less useful as it doesn't go into the review queues). This is a gap in the workflow, and not entirely intuitive for flaggers.  I propose that we give the flaggers one close off topic reason (and one migration reason)? It seems like the backend already treats custom close flags as the same.  The most obvious objection here (to me) is that it removes part of the usefulness of the close reasons -- the fact that, for flaggers and VTCers, it's much easier to determine whether or not the question should be closed.   However, this can be solved by nesting the close reasons under the description of a  generic "Does not fit the topic" close reason.    Alternatively, just give flaggers an extra default close reason "This question does not appear to be about $Topic, within the scope defined in the help center."


Reinhardt's shield blocks most enemy projectiles and bullets but there are certain attacks which can go right through it. Which attacks ignore Reinhardt's shield?

Reinhardt's main strength is his shielding abilities and the protection he provides for his team, but Are there any abilities that cannot be blocked by Reinhardt's barrier field?


I want to measure the RPM of a motor that I am controlling using a STM32 and some driver chip.. My understanding is that I have to measure the time between 2 hall signal and calculate the speed (RPM).  The question is, how can I start a timer and restart it on each hall signal interrupt. I tried to study the timers but the amount of things to learn are huge...  I mean for my case, what mode should I run a timer? I think there are input direct capture, output captures, etc...  Here is my interrupt code:  void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) {     if(GPIO_Pin == GPIO_PIN_4 || GPIO_Pin == GPIO_PIN_5 || GPIO_Pin == GPIO_PIN_6) {         commutate();     } }

I need to measure the speed of a rotating motor fitted to an encoder disc with 20 slots. The LM393 based sensor is kept at the right place, so that encoder disc rotates in between the sensing part.  I think, I would need three timers provided by STM32 board: one to provide PWM(TIM4), second(TIM1) to measure the time of (1000msec~1sec) and third timer(TIM2) to measure the number of pulses received from encoder disc in 1 sec.   TIM1's counter period(Auto-reload register) is fixed to 1000 and frequency to 1000Hz. TIM2'S frequency is same as PWM frequency-10kHz. Sensor output is connected to PC15 and PWM to PD12.   The code below uses HAL library. I have doubt about how to use these two timers/counters inside the while loop, which HAL library functions to use here and how to use. Also should the code for PWM control and speed calculation be put in same loop.  int main(void) {         volatile GPIO_PinState level; // stores input state from PC15, sensor output is connected to PC15         uint16_t dutycycle=70;         int speed=0;                  //speed variable         int constant=(2*3*1)/20;      //roughly circumference/20 slots    /* Reset of all peripherals, Initializes the Flash interface and the Systick. */   HAL_Init();   /* Configure the system clock */   SystemClock_Config();   /* Initialize all configured peripherals */   MX_GPIO_Init();   MX_TIM1_Init();       //for measuring 1 second   MX_TIM4_Init();       //for PWM   MX_TIM2_Init();      //for counting output pulses from PC15 pin    HAL_TIM_PWM_Start(&htim4,TIM_CHANNEL_1);    //Start PWM signal   level=HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_15); //HAL function is called to read pin status    while (1)   {               counter1=__HAL_TIM_GetCounter(&tim2);               speed=(counter1)*(constant);          //speed variable, counter 1 related to TIM2                htim4.Instance->CCR1=dutycycle;   //setting the duty cycle of PWM signal             HAL_Delay(1000);dutycycle+=10;    //1 sec delay and then increases dutycyle by 10%             if(dutycycle==90)dutycycle=50;    //resets to 50% duty cycle   }   Development board is STM32F407, CubeMX is the source code generator and IDE is Eclipse. OS is Linux(Ubuntu 15.04).  Kindly suggest.


Suppose $G$ is a finite group, whose cardinal is $2n$. $H$ is a subgroup of $G$, whose cardinal is $n$. Show that $H$ is a normal group of $G$.  I think I should start with Lagrange, but that's all I can think of.

I have been going through some material on elementary group theory () and in one place it states:  A subgroup which contains half of all elements, i.e. for which $|G|=2|H|$, is a normal subgroup.  Where a subgroup $H\subset G$ is called a normal subgroup if $gHg^{-1}=H~\forall g\in G$. How would I go about proving this? Sorry if the answer exists somewhere, but I tried searching and could not find it.


What happened to ?  Now when I visit a Stack Exchange site as an anonymous user, I can't find a feedback button. Where did it go?

I first noticed this a while back. But it has yet to resolve itself.  When I click on the  in the 10k tools, it hangs for a while.Then it gives me an error message:


I.e. is it the O(1) scheduler, the CFS scheduler, or an older one?

I'm not quite sure if stackoverflow or serverfault is the forum to use for this question, but ill try here.  Is there some command I can use or a file I can check in order to find out which process scheduler I'm using on my Linux system? I am not looking for the I/O scheduler, but the process scheduler, and please, do not refer to guides or howtos for what a scheduler is, what I'm simply asking is if there is a command or file I can run/check to see this. I could check the doc for my kernel but again I'm just wondering if there is a command or file i can check.  I might have been a little redundant above but that's because the posts I've seen people seem to confuse process scheduler with the i/o scheduler, and they don't seem to answer the actual question, just provide links to what a scheduler is which is not what I'm after here, so apologies if the above comments sounded rude.


When I look through the display, I see always a small grey circle at the same place. Also in the picture it's the same circle. When I change the lens, the circle is still there. So I assume it's something with the sensor. Has the sensor an error?  What could happened (spot wasn't always there)?  Is there a way to fix that (I used the lens cleaning program)?  Warranty case?   Thanks  Here is an example:

I seem to have to dust-like speck on my Sony Cybershot S950's lens, but it appears randomly every few pictures. Could something be going bad internally?


For the longest time I have wanted to find music similar to these two songs, but I have never known the name of the style, or any other way of finding more:      View comments for song info in MusicBrainz.org, Last.fm & RateYourMusic.com     View comments for song info in MusicBrainz.org, Last.fm & Spotify    Maybe someone here can point me in the right direction!

I'm having a hard time collecting music I'm interested in through genre. Do I have any options to look for similar music based on a recording / song name?  For example, when browsing a video tagged Music on Youtube, Youtube presents a "Youtube mix":    But there does not seem to be any known service for this.


My daughter is 14 months old and her appetite has not been any better since she turned almost 11 months old i want to say. Its been an on going struggle at home. She will drink her bottle more often than she will eat. In addition when she's with her babysitter she will eat whatever the lady makes her (ex.: cheerios with milk, pieces of chicken, soup, rice, mashed potatoes etc.) I've tries giving her the same and she just won't eat…its a constant fight.   However if it's not a cracker or a couple cheerios for her to eat with her hands she will not eat. If she sees me eating a bag of chips she will ask for some - but I simply cannot give her something that does not benefit her health as a growing baby. And what she does eat isn't enough - at most it will be two or three bites of her food or mine. Other than that I am unable to get her to take anymore bites or mouthfuls.  Now she's 14 months and the struggle continues. Even if she sees me eat - she will look, smack her lips but when I offer her food she turns away. If I attempt to feed her she tightens her jaw shut and presses her lips closed. Or she'll press her lips and make a spitting sound to show me she refuses to eat.   I've tried different things from finger foods to changing her food to making the same food her babysitter feeds her. Moreover she has lost weight but still seems very energetic and playful as usual. At this point I have no clue what else to do?   Sorry but the solutions to a similar questions simply do not work for me. Therefore I need a BETTER solution. Thanks!

My son (currently 23 months old) attends an in-home daycare 5 days a week.  The daycare provider cooks homemade meals for the kids, and provides snacks.  By every report she gives, our son gives her absolutely no trouble when it comes to eating whatever she presents him.  However, my wife and I are unable to get him to even taste most of the food we prepare, or even food we get at restaurants.  He has a small selection (of rather eclectic diversity) of foods that he will gladly eat, and a few other foods that he will generally be willing to taste (e.g. anything that looks like ground beef, or is wrapped in a tortilla, he'll generally take at least a bite out of).  However, the vast majority of foods, when offered to him, will result in him saying "no!" and turning his head away.  Usually there is a small smile on his lips when he does this.  With some persistence, we can sometimes get a small amount of it past his lips, but usually only because repeated attempts seems to turn it into a game for him, and I can sneak in a tiny mouthful while he's laughing.  Typically, we'll offer him a small amount of whatever we're eating.  When he refuses to try it, we'll then give him something else that we know he likes (chicken nuggets, hot dogs, baked beans, unsweetened apple sauce, just about any kind of soup, grilled cheese, homemade pizzas, etc.).  However, we'd really like him to at least try whatever we're eating.  We've tried not offering anything else, and he simply will ignore the food and want to go and play (my wife is not comfortable letting him go without any food, so eventually he will get a snack, or some milk, some time after dinner is over).  We've tried enforcing "you can't leave until you at least try a bite".  That results in massive melt-downs that are wholly atypical for him.  Our longest foray down that road lasted over 45 minutes, ending with him sobbing uncontrollably after coming out of a short time-out.  I feel that he may simply be too young for "you can't leave until you at least try a bite".  At the same time, it seems pretty clear that not trying food has become a game he plays with us.  He doesn't have any problem at daycare, but that may also be because he sees the other, older kids eating, and wants to emulate them.  What is the best way to get him to try new foods?  Edit to clarify:  The issue is not that he is refusing to eat meals, and is instead eating only snacks.  He is refusing to try some meals, but eats others.  He's not refusing to eat dinner, and instead eating a dish of ice cream.  He's refusing to taste pork chop, but will eat a bowl of vegetable soup; he's turning up his nose at a hamburger to eat a taco (with veggies); or he's pushing away fish sticks to enjoy a homemade whole-wheat pizza with bbq chicken, onions, and green peppers.


I am about to submit my research article in a Mathematics journal and the online system is asking to mention three Referee/Reviewer names. Should I take the consent of a few experts in my topic before I enlist three expert names as referees, by individually mailing them? I think, I should take. Any suggestions and advice regarding the question, please?

Some journals require the author to propose potential reviewers. Should I just propose reviewers and let the editor contact them? Or should I first contact the potential reviewers myself and ask if they agree?


In the MCU movie Thor, Odin says that Thor's hammer "has no equal as a weapon to destroy, or as a tool to build."  We see it used as a weapon plenty of times throughout the MCU's run, but I don't think I've ever seen it used as "a tool to build."  Has it ever been employed as a tool, in the movies or the comics?

In the movie Thor (2011), while he was about to crown Thor as the next king of Asgard, Allfather Odin describes the mighty hammer Mjolnir as the following:      So long entrusted with this mighty hammer, Mjolnir. Forged in the heart of a dying star, from the sacred metal of Uru. Only one may ift it. Only one is worthy. Who wields this hammer commands the lightning and the storm. Its power has no equal -- as a weapon, to destroy, or as a tool, to build. It is a fit companion for a King.   We know Mjolnir as a weapon of destruction but are there references where it is used to build something?


I'm scaling my rectangle in object mode as suggested, and then insetting two faces in edit mode. Yet the inset is still uneven. I can only guess it's because I'm using decimals. I'm scaling thus: x: 2.92 y: 6.2 z: 0.35  If it really isn't possible to inset this evenly, what are the alternatives to getting an accurate inset?

I seem to have screwed up something that allows you to inset evenly, I think I have tried every combination of settings in inset and pivot center and even is far from even.  I tried uninstalling and re installing blender 2.71 and get the same result.  The image attached is a simple default cube that I tried to inset evenly.  I have also attached the blend file link  help??


I'm trying to update my system with the habitual sequence of codes:  $ sudo apt-get update $ sudo apt-get upgrade   But when the first code finishes, it appears the follow message:  W: Fail to search http://ppa.launchpad.net/fossfreedom/packagefixes/ubuntu/dists/vivid/main/binary-amd64/Packages  404  Not Found W: Fail to search http://ppa.launchpad.net/fossfreedom/packagefixes/ubuntu/dists/vivid/main/binary-i386/Packages  404  Not Found   And appears some other messages too, but the site don't allow me to post more than 2 links with my reputation points.  I use the Ubuntu 15.04 vivid, Kernel Linux 3.19.0-15-generic, MATE 1.8.2. I tried a sort of things, like update the /etc/apt//sources.list, and use the banish 404, but none of them was in success. If someone could help me, it would be great. Thank you very much.

PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?


I have JDBC Class and Servlet class separately in 2 packages. I try to fetch data from an HTML form and insert it into a table. This is the Servlet class code to fetch data   public void doPost(HttpServletRequest request, HttpServletResponse response)                      throws ServletException, IOException {      String userName = request.getParameter("UserName");     String password = request.getParameter("Password");     String country = request.getParameter("Country");     String address = request.getParameter("Address");     String gender = request.getParameter("Gender");     String years = request.getParameter("Years");     String bDate = request.getParameter("BirthDate");     Boolean hasCar = null;      if (request.getParameter("Car")!= null){         hasCar = true;     }else{         hasCar = false;         }   and this is the method in JDBC class to insert data   public static void insertData(User user){           String sql = "insert into users values (1,?,?,?,?,?,?,?,?)";         PreparedStatement ps = null;         String userName = user.getUserName();         String password = user.getPassword();         String address = user.getAddress();         String country = user.getCountry();         String gender = user.getGender();         int years = Integer.parseInt(user.getYears());         String bbd = user.getBDate();         Date bDate = null;     try {         bDate = (Date) new SimpleDateFormat("dd/MM/yyyy").parse(bbd);     } catch (ParseException e) {         e.printStackTrace();     }     boolean hasCar = user.isHasCar();         try {             ps.setString(1, userName);             ps.setString(2, password);             ps.setString(3, country);             ps.setString(4, address);             ps.setString(5, gender);             ps.setInt(6, years);             ps.setDate(7, bDate);             ps.setBoolean(8, hasCar);               ps = conn.prepareStatement(sql);             ps.executeUpdate(sql);          } catch (SQLException e) {             e.printStackTrace();         }   I created an object from class user in Servlet class and passed it to JDBC method and redirect into another html page       User user = new User(userName, password, country, address, gender, years, bDate, hasCar);     JDBCClass.insertData(user); response.sendRedirect("Home.html");   but it throws java.lang.nullpointerexception  What is wrong?

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


How can I write a double closed path integral? I have searched and I have found only single closed loop integral.

I have some code which uses the \oiint symbol. However there are many packages that provide this command. Most of for special fonts. I am using lmodern however and want a package that provides the symbol matching to lmodern.  I have found so far wasysym with option [integrals], mathabx and esint package.


I've been recently working on rewriting my school assignments from C++ to Java, to which I'm still a beginner. I made this class:  package ThreeDimensionalController;  import ThreeDimensionalShape.*; import java.util.Deque;  public class ThreeDimensionalController {     private Deque<ThreeDimensionalShape> setOf3DShapes;     public void displayVolume() {         for( ThreeDimensionalShape s : setOf3DShapes)  System.out.println(s.volume());     }     public void displayArea() {         for (ThreeDimensionalShape s : setOf3DShapes)  System.out.println(s.area());     }     public void add(ThreeDimensionalShape shape) {         setOf3DShapes.push(shape);     } }   and the problem is with method called "add", it doesn't compile - NullPointerException and I do know why, but can't figure out how to deal with it. The ThreeDimensionalShape class is an abstract class, that is extended by 3 other classes called Cone, Cylinder and Cube. I wanted it to work like this:  threedimensionalcontroller.add(new Cone(...));   How do I fix it, so that it works?  @Edit: The NullPointerException is solved, thank you everyone!


I am trying to modify the line of a phpmyadmin configuration file, precisely, the file /etc/phpmyadmin/config.inc.php, in the line on the database server, where I need to change it with a bash instruction. I tried to do it with the sed and awk commands, but I still have no results.  The line that I want to modify is the following:  $cfg['Servers'][$i]['host'] = $dbserver;   For the following value:  $cfg['Servers'][$i]['host'] = '192.168.0.10';

In my bash script I have an external (received from user) string, which I should use in sed pattern.  REPLACE="<funny characters here>" sed "s/KEYWORD/$REPLACE/g"   How can I escape the $REPLACE string so it would be safely accepted by sed as a literal replacement?  NOTE: The KEYWORD is a dumb substring with no matches etc. It is not supplied by user.


Is there a way to discover when my Android OS was installed? In other word: what is the age of the SO running in my phone (since the last FW upgrade)?  I have root access and I prefer not installing any extra apps to this task (altough, if it is the only way, I may install one). I already have a Terminal Emulator App.  I looked into "Settings -> About phone" and there is a counter since the last reboot, which is not what I want.  I am running Android 4.0.4 on a Sony Xperia P.

Is there any way to know when I flashed my last custom ROM?  Atleast a smart way to find the approximate date/time using some logs deep down in my android would be good.


THIS IS NOT A DUPLICATE. The other question was about merging two accounts, my problem is to add a login for all the StackExchange sites I visit.  I was logging in with OpenID, but now that it's gone, I added an email/password to my Stack Overflow account (at  ) and it seems to work, I can now log in at Stack Overflow and have my old account (), with my questions and so on.  But it doesn't work for other Stack Exchange sites. At Server Fault, I now have a new account () with all history for the older account () lost. How can I reconnect to the old account (and the other Stack Exchange accounts), now that OpenID is gone?

I accidentally posted a question without being logged in. Is there a way to associate that question with my account?   For more information, visit "" in the .   a.k.a. How can you link a registered account to a cookie-based account? a.k.a. How do I merge an unregistered account with a registered account a.k.a. Merging users a.k.a. How do I associate anonymous questions I’ve asked with my registered account? a.k.a. Is there a way to claim an unregistered user? (in case anyone searches with those terms)


When I run cd / && ls I see some directories in which I know the purpose of, and then others I don't.  Here are the directories I do not know the functions of: /etc /opt /private  What do all of these do? Thanks in advance.  Edit: I also see some empty folders, like /cores. Are they safe to remove?

What does and should go into /opt/ and what should/does go into /usr/?  My understanding is that /usr/ used to be for user home directories, but since they exist in /Users/ - what is the purpose now?  Is there a manual or guide to what all of the built-in directories should be used for?  Like what is /home/, or /net/?


The following piece of code :   int main() { float a=0.7; printf("%.10f %.10f\n",0.7, a); return 0; }   gives 0.7000000000 0.6999999881 as answer while the following piece of code :   int main() { float a=1.7; printf("%.10f %.10f\n",1.7, a); return 0; }   gives 1.7000000000 1.7000000477 as output.   Why is that in the first case upon printing a I got a value less than 0.7 and in the second case more than 1.7?

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


In the third isomorphism theorem, we are given a chain of normal subgroups $K \unlhd N \unlhd G$, and the statement of the theorem says that there is an isomorphism $$ G/N \cong \left(G/K \right)/ \left( N/K \right)$$ which is given by $gN \mapsto gK\left(N/K \right)$. My confusion arises from the fact that I don't actually know what the objects are in the codomain of the isomorphism. Is there even any way to concretely write them down? To me, it looks like we are "multiplying" (or doing whatever the binary operation might be) a coset by a set of cosets, which is hurting my brain if I'm being honest.

I have a group $G=\mathbb{Z}_{36}$ with normal subgroups $K$ and $H$, where $H$ is also a normal subgroup of $K$. What I'm really supposed to find is a bijection between $G/K$ and $(G/H)/(K/H)$ by using the third isomorphism theorem. I have already calculated $G/K$, $G/H$ and $K/H$, but I do not really know how to calculate $(G/H)/(K/H)$. Say that one of the elements in $G/H$ is $\{0,18\}$ and one of the elements in $K/H$ is $\{0,18\}$. Will one of the elements in $(G/H)/(K/H)$ be as follows? $$\{0,18\}+\{0,18\} = \{0+0,18+18\}=\{0,36\}=\{0\}$$ Another way I'm thinking it's possible to caluclate is $$\{0,18\}+\{0,18\} = \{0+0,0+18,18+0,18+18\}=\{0,18,18,36\}=\{0,18\}$$ Is any of these a correct way of calculating an element in $(G/H)/(K/H)$?


Find this limit,and if you can, do it without derivates or integrals or l'Hospital , just using the fundamental limits of functions. $$\lim_{x\to1} \left( \frac{x}{x-1} - \frac{1}{\ln(x)} \right)$$

Find: $$\lim\limits_{x \to 1} \left( {\frac{x}{{x - 1}} - \frac{1}{{\ln x}}} \right) $$  Without using L'Hospital or Taylor approximations  Thanks in advance


Instale Ubuntu 18.04 en mi PC, luego de haber tenido Windows10, instale un nuevo kernel pero sigue sin buscar redes, solo funciona mediante una red cableada La salida del comando  lspci -nnk | grep 0280 -A3 es la siguiente Network controller [0280]: Realtek Semiconductor Co., Ltd. Device [10ec:d723]   Subsystem: Hewlett-Packard Company Device [103c:8319] y la salida de el comando uname -r es la siguiente : 4.15.0-91-generic gracias, espero respuestas Google translate: Install Ubuntu 18.04 on my PC, after having Windows 10, install a new kernel but still not looking for (WiFi?) networks, it only works through a wired network The output of the lspci -nnk | grep 0280 -A3 is the following: Network controller [0280]: Realtek Semiconductor Co., Ltd. Device [10ec: d723]  Subsystem: Hewlett-Packard Company Device [103c: 8319]  and the output of the uname -r command is as follows: 4.15.0-91-generic  thanks, I wait for answers

How do I install Wi-Fi drivers for Realtek RTL8723DE device in Ubuntu 16.04?  lspci -v | grep -i network 02:00.0 Network controller: Realtek Semiconductor Co., Ltd. Device d723


Pretty simple, I am trying to change the runlevel. Everything I find online points me to the file located in:  /etc/init/rc-sysinit.conf   Here I have tried changing the "DEFAULT_RUNLEVEL" to 3 or anything else and it makes no difference (the original value was 2 which didn't make much sense either). No matter what, my machine boots fully and when I check the runlevel command, I see "N 5" as the result every time.  How do I change the runlevel? I would rather not override it through grub or some other workaround mechanism. And I am not looking for how to disable X specifically.  All the instructions I was finding online were a bit old, did something change with 16.04?

Is it possible to disable X at boot time? I'm setting up a server so it would be nice if it wouldn't load the graphical interface every time I boot.


Hi i am working on Codecademy exercise 9/15. The goal is to create a scrabble function that takes a string as input then returns a score for that word.   They give you a dictionary to start off with and this is what I have so far after searching for "how to loop through a dictionary and add values" on google.  score = {"a": 1, "c": 3, "b": 3, "e": 1, "d": 2, "g": 2,           "f": 4, "i": 1, "h": 4, "k": 5, "j": 8, "m": 3,           "l": 1, "o": 1, "n": 1, "q": 10, "p": 3, "s": 1,           "r": 1, "u": 1, "t": 1, "w": 4, "v": 4, "y": 4,           "x": 8, "z": 10}     1) total = 0 # takes your input word value and saves it to total    2) def scrabble_score(x):       # defining function name  3)     for i in score.values(): # loops through score            4)         total += i           # sums up your input key value 5)     return i    this code keeps throwing a local variable total error.  does this mean that the total variable does not work with the scrabble_score(x) function?

The following code works as expected in both Python 2.5 and 3.0:  a, b, c = (1, 2, 3)  print(a, b, c)  def test():     print(a)     print(b)     print(c)    # (A)     #c+=1       # (B) test()   However, when I uncomment line (B), I get an UnboundLocalError: 'c' not assigned at line (A). The values of a and b are printed correctly. This has me completely baffled for two reasons:   Why is there a runtime error thrown at line (A) because of a later statement on line (B)? Why are variables a and b printed as expected, while c raises an error?   The only explanation I can come up with is that a local variable c is created by the assignment c+=1, which takes precedent over the "global" variable c even before the local variable is created. Of course, it doesn't make sense for a variable to "steal" scope before it exists.  Could someone please explain this behavior?


I am taking an undergraduate course in computer science an is in the first year of my college. I like mathematics and am willing to learn Linear Algebra first and then move on to Abstract Algebra and further into Topology ,Computational Geometry and other parts like Number Theory,Probability and Discrete Mathematics.  Now my friend in an undergraduate course in Mathematics told me that their professor has recommended "Finite Dimensional vector Spaces" by Halmos for the first course in Algebra. I found that book to be a bit tough. So I coupled it with Sheldon Axler's "Linear Algebra done Right" looking for more basic explanations or background knowledge. But my friend says that he has heard that Axler's book is not good and lacks in providing proper concept.   Which book is going to be good for backing up Halmos. It is not that I am unable to understand. But I feel that I need more background knowledge. Which book should I read to get that background knowledge. Am I doing things wrong ? Should I restart learning Linear Algebra from the beginning ?   I am a pretty much beginner in abstract mathematics. Please help.

I plan to self-study linear algebra this summer. I am sorta already familiar with vectors, vector spaces and subspaces and I am really interested in everything about matrices (diagonalization, ...), linear maps and their matrix representation and eigenvectors and eigenvalues. I am looking for a book that handles every of the aforementioned topics in details. I also want to build a solid basis of the mathematical way of thinking to get ready to an exciting abstract algebra next semester, so my main aim is to work on proofs for somehow hard problems. I got Lang's "Intro. to Linear Algebra" and it is too easy, superficial.  Can you advise me a good book for all of the above? Please take into consideration that it is for self-study, so that it' gotta work on its own. Thanks.


Can sombebody help me with the following question?  I'm trying to study the Fermat´s equation $X^{n}+Y^{n}=Z^{n}$ over some non-conmutative rings such as $M_{n\times n}(\mathbb{Z})$. Are there solutions? What are all the solutions? On the other hand: it would be interesting study that equation over the ring $\mathbb{H}$ of Hamilton's quaternions?   I want to write my first paper on some Diophantine equations on different rings, specially different from $\mathbb{Z}$

I was wonderwing about a matrix equation (in some way similar to a very well known theorem :P).  Find all positive integers $n,m$ such that there exists $X$, $Y$, $Z$ matrices $n\times n$, non-singular, such that: $$X^m+Y^m=Z^m$$  Disclaimer: $X$, $Y$, $Z$ must have integer entries. Also, they may have an inverse which is not necessarily in $\mathbb{Z}^{n\times n}$.  I made some approachs (I don't know how to spoil, so if you want to think it yourself stop reading):  As my intuition says to me that there will always be solutions for $n>1$, then, it suffices to show there will be solutions for $n=2$ and $n=3$ (because then you can form a matrix composed by matrices $2\times 2$ and $3\times 3$ in its diagonal).  I showed that for all $m$ odd, and $n=2$ there is a solution.   Can someone give me a hand with the other cases? I would be very grateful.


I want to retopo an object so I tried using the Xray option to make my new mesh appear in the viewport in front of others. However I don't want to be able to see on my new mesh faces that are facing away from the camera or are behind other faces as it's making the process pretty hard. How can I do this?

I'm doing retopology and find it convenient to turn on xray for the object I am building. However, I now see ngons facing away from me as well. It's hard to navigate.  I would also like to set the display type to wire (like in image below). This way the original mesh isn't hidden and I can easily create new geometry around eyes, nose and mouth without hiding them.  I guess a mirror modifier could help along the x-axis since I can eliminate that half of the mesh. But I would like it even better if I didn't see the back of the skull when working on the face.


I’ve tried reinstalling it. I’ve tried opening the GRUB menu and all that. All I see when I boot up is a black screen and my cursor. I can move my cursor but thats the extent of everything.

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


How to prove that if $V$ is a finite dimensional inner product space and $W$ a subspace of $V$, if $P$ is projection map ($P^2=P$) having $W$ as its range and is such that $\|Px\| \leq \|x\|$ for all $x \in V$, then $P$ is orthogonal projection of $V$ onto $W$.

Seems like I , I think I am missing something important.     Let $V$ be an $n$ dimensional inner product space ($n \geq 1$), and $T\colon\mathbf{V}\to\mathbf{V}$ be a linear transformation such that:         $T^2 = T$   $||T(a)|| \leq ||a||$ for every vector $a$ in $\mathbf{V}$;         Prove that a subspace $U \subseteq V$ exist, such that $T$ is the orthogonal projection on $U$.   Now, I know these things:   The fact hat $T^2 = T$ guarantees that $T$ is indeed a projection, so I need to prove that T is an orthogonal projection (I guess this is where $||T(a)|| \leq ||a||$ kicks in). To do this I can prove that:   For every $v$ in $ImT^{\perp}$, $T(v) = 0$ Alternatively, I can prove that for every $v$ in $ImT$ and $u$ in $KerT$, $(v,u)=0$. $T$ is  (according to Wikipedia) The matrix $A = [T]_{E}$ when $E$ is an orthonormal basis, is hermitian (this is equivalent to the previous point). What else?    I've been thinking about it for quite some time now, and I'm pretty sure there is something big I'm missing, again. I just don't know how to use the data to prove any of these things.  Thanks!


When i run below code   <script>      var name = "Hello moorthi";     var myArray = name.split(' ');      setTimeout(function(){       var nameDisplay='';       try {         for (var names in myArray){            nameDisplay += myArray[names].toUpperCase()+' ';         }         alert(nameDisplay);       }       catch(err){         console.log(err.message);       }     },     1000);   </script>   getting undefined is not a function error in chrome, can help me why this happening?

I've been told not to use for...in with arrays in JavaScript. Why not?


I will soon be published at a peer-reviewed journal and this is my first publication in my career. My concern is that I'm Asian descent and have an extremely common last name, and personally I do not wish to be identified with my legal last name at all.  On the other hand, my Asian first name is relatively unique. Also, I've been going by an English nickname since I moved to US, and all the people I know knows me as my nickname since I always introduce myself with it in person and in my resume.  So, I thought I would choose my publishing name that is unique and personal to be  not this:  [legal first name] [legal last name]  but this:  [daily-used nick name] [legal first name].  I thought about adding my nickname as middle name, but this still results in tons of same names due to my last name.  The question is, would this be considered a good idea if I will always use this for publishing from now on? Or would it cause any big troubles in future career, such as employers having a difficulty with identifying my work or other issues? Are there any potential issues with this style of pseudonym?  I read other similar posts about publishing in pseudonym, but the closest I could find to my question was this:

I've recently embarked on my PhD studies (cancer, structural biology) and have yet to publish. Currently, there are some 200 papers in my name and several thousand under my surname. Because of this, I am considering switching my surname to an old, rare, surname in my family, which is only used by one active researcher.  My question is this: are there any reasonable alternatives that does not include legally changing my name? I personally don't mind changing it, but the old surname happens to be "noble", and may come off as quite pretentious. I would be able to change to another, less pretentious, surname, but in terms of rareness, no alternative comes close.   In short, what are my alternatives?


The leaderboard banners seem to always have the same size. Setting this with CSS would allow the ads to load later than the page content without having the content move around or scroll position change.

There is a usability problem when you visit a site on which ads are being served.  The top banner ad doesn't render immediately, and then when it does, it causes the rest of the page below it to jump down by just about the amount that e.g. attempting to click on the downvote arrow ends up clicking on the upvote arrow.  This is easy to fix if you notice, but if you were planning to click somewhere else, you will miss by rather a large distance.  This is annoying and hardly serves any useful purpose, and in the worst case could lead to you clicking on something you really didn't want to click.  I don't know enough about the underlying technology to propose a fix, but a thing which used to work already in the 1990s was to reserve space for an image if you could tell in advance how large it was going to be.  Banner ads typically have this property, and so I'm imagining this should be possible.  Examining the page source reveals an iframe element with width="0" and height="0" attributes which seems like precisely the wrong thing here, but like I said, I probably don't understand this well enough.  Frustratingly, the image block my browser offers doesn't help at all; the jump happens even if the image is not displayed (at least in Chrome on Mac).  Some sites which have this annoying behavior are  and  but it depends on your privileges on these sites and ads are not served 100% of the time even then.  The particular use case for me is to flag obvious spam quickly; I basically never do anything else on the Drupal site, for example, and so probably will never earn enough rep there to not see the ads.  When spam is dead obvious, you really want to be able to just flag it and move on.


I need to know how I can install skype-4.3.0.37.tar.bz2 in Ubuntu 14.04.

Note: The legacy Skype for Linux application (v4.*) is now discontinued and was removed from Canonical’s partner repositories, so this question and its answers are obsolete. Please refer to  of our .  Skype 4.3 is just released with considerable improvements. As a regular Skype user I want to use the latest Skype on my Ubuntu 14.04, but there is no updates from Update Manager. Even in Skype website only Skype 4.3 is available only for Ubuntu 12.04. Is there anyway to use this latest Skype on Ubuntu 14.04 or how much we have to wait for the update?


Evaluation of the limit $$\lim_{n\rightarrow \infty}\sum^{n}_{k=1}\left(\sqrt{1+\frac{k}{n^2}}-1\right).$$   I don't understand how can I start the above problem because Riemann sums and integrals are not applicable here.  It seems that we can solve it using  the Squeeze theorem, but I don't understand which inequality I have to use. Help required, thanks.

$$\lim_{n\rightarrow\infty}\sum_{k=1}^n\left(\sqrt{1+\frac{k}{n^2}}-1\right)$$   Note that $\forall x\ge 0, \sqrt{x}-1\le\sqrt{1+x}-1\le x$ Then $$\sum_{k=1}^n\left(\sqrt{\frac{k}{n^2}}-1\right)\le S_n\le \sum_{k=1}^n\frac{k}{n^2}=\frac{1}{2}-\frac{1}{2n}$$  How do I evaluate the sum on the left?


Let $f : [1, \infty) \to [1, \infty)$ be a function such that $f(x) = x(1 + \ln x)$. Prove that $f$ is bijective and then calculate: $$\lim_{x \to \infty} \frac{f^{-1}(x) \ln x}{x}$$  I have no difficulties in proving that $f$ is bijective, but I can't calculate the limit. I've tried using l'Hospital's rule but got nothing meaningful.  Thank you in advance!

For any real number $a \geq 1$ let $f(a)$ denote the real solution of the equation $x(1+\ln x)=a$ then the    question is to find out $$ \lim_{a \to \infty} \frac{f(a)\ln a}{a}$$.  It is clear that if we denote $h(a)$ by $h(a)=a(1+\ln a)$ then $f(a)$ is the inverse function of $h(a)$. Also $f(a)$ is increasing function in its domain. Also the limit persuades using lhospital's but I cannot see how to apply it here. Thanks.


I read the following statement in a exercise, which I don't think is correct:  $NM=I \rightarrow MN=I$, where $M,N$ are real square matrix of finite size.  However, I cannot think of a counter-example to this.

If $A$ and $B$ are square matrices such that $AB = I$, where $I$ is the identity matrix, show that $BA = I$.    I do not understand anything more than the following.   Elementary row operations. Linear dependence. Row reduced forms and their relations with the original matrix.   If the entries of the matrix are not from a mathematical structure which supports commutativity, what can we say about this problem?  P.S.: Please avoid using the transpose and/or inverse of a matrix.


I recently submitted an . In very short order it has been downvoted to the point where it appears on the rogues gallery of downvoted questions (i.e. the last page of questions sorted by votes, with 50 per page). It also has by far the worst net-votes-to-total-views rating of all questions on that last page, which could be worst of all questions. Finally, although I can't see up/down vote totals for other questions with my rep, the fact that the question only has one upvote probably puts it in the running for worst up/down vote ratio amongst high net-downvoted questions.  While there are a few questions on the last page that might cause me to view my membership there as a badge of honor (e.g. ), I would, if possible, like to "improve the question". After all, that's how the system is supposed to work, right? I know I shouldn't radically change the question as that would violate SE's rules of integrity, but wanted to get your thoughts on the reasonableness of any of the following:   Change the title to fit MSO's convention of highlighting the key change under discussion rather than the twisted form of maintaining the status quo that is there now (ironically done in an attempt to avoid controversy) Remove the update about "agreement voting" not being allowed for discussion questions on the grounds that people don't like being lectured to, particularly from a relative newcomer and particularly about something that's been accepted practice for a long time Add an update which summarizes all the reasons why the embedded idea was a bad one Include a link to the popular  to emphasize that I've read that post as part of my research Leave the question alone and let it die, on the grounds that any more modifications at this point would be viewed as pandering and would be considered unwelcome

I wrote a question about blocking certain characters in passwords. It became tremendously unpopular, and it seemed like everyone wanted to rain on my parade every day.  Eventually, I "got it," agreed completely with what people were saying to me, and just wanted to withdraw my question so that my reputation didn't slide even further downhill.  Unfortunately, the system is designed such that I can't withdraw my question or redeem myself. Instead, I just get daily reputation attacks. That's a terrible system, and it needs to be changed.


i am running a test suite, and my test case extends the following base class:  public class BaseTestSuite {     public static final Logger log = LogManager.getLogger(C2630.class.getName());     public WebDriver driver;     public String baseURL;     public LoginPageFactory loginPage;     public DashboardPageFactory dashboardPage;     public MerchantsPageFactory merchantsPage;     public MerchantDashboardPageFactory merchantDashboard;     public PayPagesPageFactory payPage;     public LaunchPageFactory launchPage;     public HubPayPagePageFactory hubPayPage;     public TransactionCompletePageFactory transactionCompletePage;       @BeforeSuite     public void beforeSuite() {         baseURL = "myWebsite.com";         System.setProperty("webdriver.chrome.driver", "D:/Automation/chrome driver/chromedriver.exe");         driver = new ChromeDriver();         // Maximize the browser's window         driver.manage().window().maximize();         driver.manage().timeouts().implicitlyWait(20, TimeUnit.SECONDS);         loginPage = new LoginPageFactory(driver);         dashboardPage = new DashboardPageFactory(driver);         merchantsPage = new MerchantsPageFactory(driver);         merchantDashboard = new MerchantDashboardPageFactory(driver);         payPage = new PayPagesPageFactory(driver);         launchPage = new LaunchPageFactory(driver);         hubPayPage = new HubPayPagePageFactory(driver);         transactionCompletePage = new TransactionCompletePageFactory(driver);     }      @BeforeClass     public void beforeClass() {         driver.get(baseURL);     }  }   The first test case runs fine when going through Before Suite and Before Class, however when the second test case begins, i want to redirect it to the MyWebsite.com so that it begins on the homepage but i get an error when it runs that line and it skips the whole test. any ideas would help, thank you!  here is the exception  java.lang.NullPointerException     at testClasses.C2631.TestCase(C2631.java:12)     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)     at java.lang.reflect.Method.invoke(Unknown Source)     at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:108)     at org.testng.internal.Invoker.invokeMethod(Invoker.java:661)     at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:869)     at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1193)     at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:126)     at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)     at org.testng.TestRunner.privateRun(TestRunner.java:744)     at org.testng.TestRunner.run(TestRunner.java:602)     at org.testng.SuiteRunner.runTest(SuiteRunner.java:380)     at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:375)     at org.testng.SuiteRunner.privateRun(SuiteRunner.java:340)     at org.testng.SuiteRunner.run(SuiteRunner.java:289)     at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)     at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)     at org.testng.TestNG.runSuitesSequentially(TestNG.java:1301)     at org.testng.TestNG.runSuitesLocally(TestNG.java:1226)     at org.testng.TestNG.runSuites(TestNG.java:1144)     at org.testng.TestNG.run(TestNG.java:1115)     at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:114)     at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:251)     at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:77)

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I was planning to try play Skyrim on the PC again. The first time I played, I find the menu system extremely annoying. Especially with regards to cycling/swapping through weapons.   It seems to be a common idiom in PC games to cycle through available weapons with the mouse wheel. Is it possible in Skyrim to do so, with the help of some mods perhaps?  Cheers.

When  I see him quickly change his weapons and spells during combat. When he later goes inside his items, you can see a second smaller arrow next to the weapon that you can quickly change to in combat. How can I set such an alternative so that I can quickly switch weapon?  The screen doesn't seem to intuitively explain what key I need to use to do that...


My Linux system sometimes reaches 90% memory usage.    We are running some Java processes, and top shows overall usage as 45%.  If I stop the running processes, usage reduces to 5-10%. I want to list out which process is consuming so much memory, ideally as a table of process ids next to their memory usage.  How can I do that?

My processor is using a big part of my RAM memory as cache and I want to clean it up because of that; will it prejudice something?


How do I get my Windows 7 system tray to stop showing the Windows 10 upgrade symbol after every restart?  Here's what it looks like:    At every restart, I have to manually go in and set it to "Hide."

This icon showed up in my taskbar notification area today and I cannot seem to get rid of it:    Clicking on it displays the following screen:    So how do I disable or remove the "Get Windows 10" icon?


For a project I want to use wget in a cron to download a data file. In the wget statement, a start- and enddate have to be defined in the following format:   wget --post-data="stns=235&vars=TEMP&start=YYYYMMDDHH&end=YYYYMMDDHH"   Since I want it to be done by a cron job, I would like the start- and enddate to be set automatically. More specific, I would like the startdate to be set to '1 hour ago' and the enddate to 'now'.   There has been a similar question in the post . Here the suggested solution was to put the variables between single quotes, but this did not work. E.g.:  "[...]start='`date -d yesterday +%Y%m%d%H'&end=`date +%Y%m%d%H`"   I simply got the error "Error 400: Bad request" when trying to execute the wget-statement in the terminal.  Thank you.

I want to create a log file for a cron script that has the current hour in the log file name. This is the command I tried to use:  0 * * * * echo hello >> ~/cron-logs/hourly/test`date "+%d"`.log   Unfortunately I get this message when that runs:  /bin/sh: -c: line 0: unexpected EOF while looking for matching ``' /bin/sh: -c: line 1: syntax error: unexpected end of file   I have tried escaping the date part in various ways, but without much luck. Is it possible to make this happen in-line in a crontab file or do I need to create a shell script to do this?


I have following files with names like:  Selection_Test_from_120118_1140118.txt Selection_Test_from_monthly_120118_1140118.txt   how we can rename both files by removing string from file:  string1 --> Selection_Test.txt (remove "_from_120118_1140118") string2 --> Selection_Test.txt (remove "_from_monthly_120118_1140118")   I want to use parameter expansion method instead of traditional cut command here

I have a directory full of images:  image0001.png image0002.png image0003.png ...   And I would like a one-liner to rename them to (say).  0001.png 0002.png 0003.png ...   How do I do this?


PS D:\LWCSession\LWC> sfdx force:auth:web:login { Error: spawn cmd ENOENT     at Process.ChildProcess._handle.onexit (internal/child_process.js:240:19)     at onErrorNT (internal/child_process.js:415:16)     at process._tickCallback (internal/process/next_tick.js:63:19)   errno: 'ENOENT',   code: 'ENOENT',   syscall: 'spawn cmd',   path: 'cmd',   spawnargs:    [ '/c',      'start',      '""',      '/b',      'https://login.salesforce.com/services/oauth2/authorize?response_type=code^&client_id=PlatformCLI^&redirect_uri=http%3A%2F%2Flocalhost%3A1717%2FOauthRedirect^&state=aee1a7bf19e7^&prompt=login^&scope=refresh_token%20api%20web^&code_challenge=AFdNI-DWiP7RrZdfNgWFWxe3pnXuqpAFkU4CcjXiMDA' ] } { Error: spawn cmd ENOENT     at Process.ChildProcess._handle.onexit (internal/child_process.js:240:19)     at onErrorNT (internal/child_process.js:415:16)     at process._tickCallback (internal/process/next_tick.js:63:19)   errno: 'ENOENT',   code: 'ENOENT',   syscall: 'spawn cmd',   path: 'cmd',   spawnargs:    [ '/c',      'start',      '""',      '/b',      'https://login.salesforce.com/services/oauth2/authorize?response_type=code^&client_id=PlatformCLI^&redirect_uri=http%3A%2F%2Flocalhost%3A1717%2FOauthRedirect^&state=aee1a7bf19e7^&prompt=login^&scope=refresh_token%20api%20web^&code_challenge=AFdNI-DWiP7RrZdfNgWFWxe3pnXuqpAFkU4CcjXiMDA' ] } { Error: spawn cmd ENOENT     at Process.ChildProcess._handle.onexit (internal/child_process.js:240:19)     at onErrorNT (internal/child_process.js:415:16)     at process._tickCallback (internal/process/next_tick.js:63:19)   errno: 'ENOENT',   code: 'ENOENT',   syscall: 'spawn cmd',   path: 'cmd',   spawnargs:    [ '/c',      'start',      '""',      '/b',      'https://login.salesforce.com/services/oauth2/authorize?response_type=code^&client_id=PlatformCLI^&redirect_uri=http%3A%2F%2Flocalhost%3A1717%2FOauthRedirect^&state=aee1a7bf19e7^&prompt=login^&scope=refresh_token%20api%20web^&code_challenge=AFdNI-DWiP7RrZdfNgWFWxe3pnXuqpAFkU4CcjXiMDA' ] } { Error: spawn cmd ENOENT     at Process.ChildProcess._handle.onexit (internal/child_process.js:240:19)     at onErrorNT (internal/child_process.js:415:16)     at process._tickCallback (internal/process/next_tick.js:63:19)   errno: 'ENOENT',   code: 'ENOENT',   syscall: 'spawn cmd',   path: 'cmd',   spawnargs:    [ '/c',      'start',      '""',      '/b',      'https://login.salesforce.com/services/oauth2/authorize?response_type=code^&client_id=PlatformCLI^&redirect_uri=http%3A%2F%2Flocalhost%3A1717%2FOauthRedirect^&state=aee1a7bf19e7^&prompt=login^&scope=refresh_token%20api%20web^&code_challenge=AFdNI-DWiP7RrZdfNgWFWxe3pnXuqpAFkU4CcjXiMDA' ] }

All was working fine till the morning untill, in the afternoon when i tried to run some create LWC commands. Now, no SFDX commands will work, i am getting the following error :   04:30:38.633 sfdx force:lightning:component:create --componentname myComponent2 --outputdir force-app/main/default/aura ERROR running force:lightning:component:create:  Command failed with ENOENT: npm root -g --prefix /Users/padmajasubhash/Documents/SFDX Projects/Surya Practice/.yo-repository --loglevel error spawnSync npm ENOENT 04:30:39.881 sfdx force:lightning:component:create --componentname myComponent2 --outputdir force-app/main/default/aura  ended with exit code 1   Please help.


So basically, I was really desperate when I met this guy. I'm 18. He says he's in Canada right now, and will be back on the 23rd. When he isn't talking about money, he's been really upfront, honest, and genuine. But he offered to help me get a car, and I ended up giving over $2k worth, while he coughed up $1500, and he said he's going to help me pay off the final $2k when he brings the car to me. After, if I no longer want the car, he wants me to sell it at a higher price.   I'm AWARE this was stupid, but it was really convincing and I took a leap of faith. But now he's telling me he doesn't trust his personal assistant anymore or something, and wants to link his company account to mine. He wants me to apply for a credit card, because I haven't established credit yet, and I'm not sure if this is suspicious or what.   Like I said, he's told me he's going to come see me when he gets back to the states. I'm not sure if that will really happen, but he otherwise hasn't shown many signs of being a scammer. Like he is obviously from another country, but he lives in New York. Seems to trade a lot of bitcoin. But his english is good, he's intelligent. For the most part, in my opinion, he seems legit but... I still can't help but feel it's a bit suspicious.

I met a guy on a sugar daddy dating site and we talked, I told him my situation and he said he would help.   He asked for my bank account information and I told him you can use cash app or PayPal to go through. He said his account manager deals with his finances. So I set up an account with a bank that I don’t use so that my primary account isn’t used.  Eventually he was in the process of sending me money and we had agreed on a amount that wasn't crazy. But then he asked for my address and I asked why and he said just wondering. Then said he wanted to send me a surprise for being his baby. Which I didn’t give.  Then later on he sent the money and said he sent me a bonus and that I was supposed to use that to pay his mothers caregiver, which he didn’t mention until after.  I kept questioning him and he was saying that he works in construction and he’s trusting me to carry out the errand. Then he said don’t let him down and I asked him if he was threatening me and he kept saying I need this done but didn’t really answer my question.  Am I being scammed? I’m about to change my password but is this a scam?


I have the following problem:     Let $V$ be a finite dimensional vector space. Let $A$, $B$ be linear maps of $V$ into itself. Assume that $AB = BA$. Show that if $\vec{v}$ is an eigenvector of $A$, with eigenvalue $\lambda$, then $B\vec{v}$ is an eigenvector of $A$ with eigenvalue $\lambda$ also if $B\vec{v} \neq \vec{0}$.   Now, I have to show that if $\vec{v}$ is an eigenvector of $A$ with eigenvalue $\lambda$, then also $B\vec{v}$ with the same eigenvalue.   So I started by assuming $$A\vec{v} = \lambda \vec{v}$$ Then I multiplied both sides by $B$:   $$BA\vec{v} = B \lambda \vec{v}$$ Since $AB = BA$, then $$A(B\vec{v}) = \lambda (B \vec{v})$$ Which should prove what I needed to prove.   Is my proof correct?

I read in G. Strang's Linear Algebra and its Applications that, if $A$ and $B$ are diagonalisable matrices of the form  such that $AB=BA$, then their eigenvector matrices $S_1$ and $S_2$ (such that $A=S_1\Lambda_1S_1^{-1}$ and $B=S_2\Lambda_2 S_2^{-1}$) can be chosen to be equal: $S_1=S_2$.  How can it be proved?  I have found a proof , but it is not clear to me how to see that $C$ is diagonalisable as $DCD^{-1}=Q$. Matrix $C$ obviously is the matrix with the coordinates of $B\mathbf{x}$ with respect to the basis $\{\mathbf{x}_1,...,\mathbf{x}_k\}$ of the eigenspaceof $V_\lambda (A)$, but I do not see how we can know that it is diagonalisable.  Thank you very much for any explanation of the linked proof or other proof!!!  EDIT: Corrected statement of the lemma I am interested in. See comments below by the users whom I thank for what they have noticed.


Hi I am querying about some suggestions regarding latex table placement. In m latex document I have an appendix section at the end of the paper. The appendix contains a couple of tables and a figure no text. I placed mu bibliography before the appendix. That was ok, but the guidelines suggests that I need to place the appendix before the bibliography. I did so, moved the appendix section before bibliography.  But after that the default lace handling mechanism of latex is placing the tables and figures in the appendix in the midst of the references which is not desired. I just want them to appear after the references. How can I force that?

How to influence the position of float environments like figure and table in LaTeX?   This is a general question and should collect useful answers for all users. I hope we can use this as a reference


Okay, so I want to buy a iTunes giftcard for my iPad, but I’m pretty confused. Firsthand, my iPad is from Singapore and I’m in bangladesh right now. Am I able to order a Singaporean giftcard so I can use it here? Or do I have to go to Singapore to redeem my giftcard? I know it’s a pretty stupid question but I’m genuinely confused.

Christmas is coming up, and I'm currently living in a country (UK) that's a completely different iTunes store from my family (US).  So I'm wondering if I can gift things in the iTunes store if I'm in a different country than the recipient.  If I gift something from the UK store, can someone in the US download the items?  I'm not even sure if there's a way for me to go to the US version, let alone try to gift an item from there.


I'm searching for a book, video documentary, or any other source of information to learn Quantum Physics from the beginning. I know almost nothing on physics, so I guess I would need the basics first. And although I can't skip the math, what I'm seeking is more on the theoretical part.   Also I'd love to know how history on this goes. I mean, what Plank did, Einstein, Schrodinger... Things the way they happened.  But of course, anything helps.

I'm really interested in quantum theory and would like to learn all that I can about it. I've followed a few tutorials and read a few books but none satisfied me completely. I'm looking for introductions for beginners which do not depend heavily on linear algebra or calculus, or which provide a soft introduction for the requisite mathematics as they go along.  What are good introductory guides to QM along these lines?


Assuming two medium humanoid types with 5ft reach are the grappler/grappled and the thorn whip pulls the grappler 10ft against their will towards the caster. Does this satisfy the conditions to end a grapple per the final point of the grappled condition, quoted below:     The condition also ends if an effect removes the grappled creature from the reach of the grappler or grappling effect, such as when a creature is hurled away by the thunderwave spell.

A situation came up in my session where a fighter used his Shield Master Shove feature to shove a Giant Crocodile that was currently restraining another PC using it's bite+grapple ability.  I did a quick check at the time and did not find anything related to shove, although in the  condition description it states:     The condition also ends if an effect removes the grappled creature from the reach of the grappler or grappling effect, such as when a creature is hurled away by the thunderwave spell.   I ruled at the time that a shove would count in a similar way to being "hurled away" however I wasn't sure and said I would find more concrete information for the future.  I have searched high and low for somebody else asking this specific question but have yet to find it. I saw some reference to a Jeremy Crawford tweet about involuntary movement and grappling however I am unable to find it.  If a third party "shoves" a creature that is grappling another, does it only shove the grappler away, or does it move both the grappler and grappled?  I drew a diagram:   (; this question relates to if a third party shoves the grappler instead, so it's not a duplicate.)


I have an asset I am selling, and I am using a material that has shaders only Blender has. Is there a way to make the material act as a texture so it can work in other 3D software like 3DS Max and Maya? if it helps, i have the node setup:    I think it has something to do with baking, which I have no idea what it is or how to use it. Oh, forgot to add, it is a procedural leather texture. Is it possible for a material that has no textures to be exported and used in a different software? Would be very helpful.

I created a interior scene and  i don't know how to bake a texture using cycles bake.


We recently discovered that a large, publicly traded corporation purchased a domain that they have pointing to our domain. Both the corporation and the domain are completely unrelated to our type of website. Their domain is now coming up above us in search engines for our main keyword. Their listing in Google looks like our listing (our title, description, etc.) and initially what was happening is that someone would click on that link and surf our site, even though it was their domain in the browser window.   We are now using a 301 redirect. Is that okay or will that hurt us in some way?  We trying to figure out if that is the appropriate action to take, especially since we are unsure what they are attempting to accomplish.  Are they trying to steal our seo somehow, or are they maybe trying to damage our seo reputation, or are they trying to steal login information?  In attempting to research what is going on and what to do about it, I came across   where using a 403 was suggested, but the question about security or motivation of the other party was never answered. Why use a 403 as opposed to a 301? What is going on here?

I have a random domain name which has it's A record going to my dedicated IP. Therefore duplicating content. Is there a way I can disable the domain at IP level maybe in iptables?  I have a .htaccess setup to redirect to the main domain as its always force HTTPS.


Let $a_n$ a decreasing sequence of real positive numbers such that $\sum a_n$ converges then $\lim_{m \to +\infty} ma_m = 0$. I had the following idea but cannot finish it : We know that :  $\sum a_n$ converges absolutely (I do not use it but can be useful for permutations). $\lim_{n \to +\infty} a_n = 0$ $\frac{a_{m+1}}{a_m} \leq 1$ $a_n \geq 0$.  We cannot use the alternating series criteria because of the last point but I thought of using D'Alembert's criteria : if $\lim_{m \to +\infty}$ $\lvert \frac{(m+1)a_{m+1}}{ma_m}\rvert =  \lvert \frac{a_{m+1}}{a_m}+\frac{a_{m+1}}{ma_m}\rvert < 1$ then $\lim_{m \to +\infty} ma_m=0$ but it seems to be not using at all the fact that $\sum a_n$ converges. Is there a way to finish this way or maybe there is some other proof ?

I'm studying for qualifying exams and ran into this problem.  Show that if $\{a_n\}$ is a nonincreasing sequence of positive real numbers such that $\sum_n a_n$ converges, then $\lim_{n \rightarrow \infty} n a_n = 0$.  Using the definition of the limit, this is equivalent to showing \begin{equation} \forall \varepsilon > 0 \; \exists n_0 \text{ such that } |n a_n| < \varepsilon \; \forall n > n_0 \end{equation} or \begin{equation} \forall \varepsilon > 0 \; \exists n_0 \text{ such that } a_n < \frac{\varepsilon}{n} \; \forall n > n_0 \end{equation} Basically, the terms must be bounded by the harmonic series. Thanks, I'm really stuck on this seemingly simple problem!


I'm using unity to pass values to my php script with HTTP GET. I am new to php and just got my script to work, however, I would like to make sure I can protect against SQL Injection. Can someone please look this over and let me know what I need to change in order to protect it?  <?php  $servername = "localhost"; $username = "Test"; $password = "Test"; $dbname = "Test";  $userId = $_GET['userId'];  // Create connection $conn = new mysqli($servername, $username, $password, $dbname); // Check connection if ($conn->connect_error) {     die("Connection failed: " . $conn->connect_error); }   $sql = "SELECT rp FROM RP where userID = '$userId'"; $result = $conn->query($sql);  if ($result->num_rows > 0) {     // output data of each row     while($row = $result->fetch_assoc()) {         //echo "UserID: " . $row["userID"]. " - RP: " . $row["rp"]."
";     echo "RP: " . $row["rp"]."
";     } } else {     echo "0 results"; } $conn->close(); ?>

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


I want to change some package,but in the beginning of the package i need in checking,what compiler use. For example,if i use latex,i want to require one packages,for lualatex i want to require other packages,and for any other compiler i want to require other packages,which i not require for latex and lualatex. Give me please small example,which show,how to check latex,lualatex and any other compilers. Thanks everybody for the help.

How can I detect inside a TeX file which engine (pdftex/xetex/luatex) is used to compile the file? Is there a LaTeX package that provides this functionality?


Any and all help/hints/proofs would be appreciated, I really don't even know where to start.

I know how to prove the fact that $ p$ | ${ p \choose k } $ (when writing it as a fraction, $p$ cannot be divided by any of the $1\times2\times...\times k$ or $1\times2\times...\times(p-k)$ because $p$ is prime).  When I try to apply the same rationale for $ p$ | ${ p^n \choose k } $ I get stumped because $p^n$ is in fact divisible by one of the $k! = 1\times2\times...\times k$, where $0 < k < p^n$.  If we take the example of $2^3$ and $k = 7$, we can easily see that $k! = 1 \times 2 \times ... \times 6 \times 7$, and $2$ clearly divides $2^3$.  How else can I approach this?


Is there any way to restrict accounts to login only once at the same time? Ex. Mike bought a subscription from my website and also lent it to his friend John. What I want to achieve is preventing Mike login if John is already logged in and the opposite. Is this possible?

On a site with premium user account subscriptions, I'd like to be able to limit logins to one computer at a time. The most straightforward way to accomplish this would be to limit by IP, but I haven't had any luck finding a plugin to accomplish this. Does anybody know of one I can use to get this functionality?  Related:


I'm a little bit confused about truth in PHP.  My understanding is that 0 evaluates to false, and non-empty strings (unless the string is "0") evaluate to true.  This is as I expect:  var_dump((bool) 0);              // prints "boolean false" var_dump((bool) 'someString');   // prints "boolean true"   But then I am surprised by the following result:  var_dump((0=='someString'));     // prints "boolean true"   My question is, why does 0=='someString' evaluate to true?

What is the difference between == and ===?  How exactly does the loosely == comparison work? How exactly does the strict === comparison work?  What would be some useful examples?


XXXXX-T480:~$ sudo apt install codelite Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  codelite : Depends: libstdc++6 (>= 9) but 8.3.0-6ubuntu1~18.04.1 is to be installed             Recommends: lldb (>= 3.4) but it is not going to be installed             Recommends: clang-tools but it is not going to be installed E: Unable to correct problems, you have held broken packages.

After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


We are building a dynamic app development platform. Its approaches are directly aligned with the way apps are built using code though it's a complete drag and drop and no code system.   Though developers will relate to the approach instantly, anyone can use the system after going through a couple of hours of video.   My question is which community among the Stack Exchange sites is good for forging Q & A around the tool, and how/what is the process for creating a dedicated tag for it ?   E.g. a developer is creating a specific form using the system and encounters a challenging situation and wants to ask how to implement the specific needed feature. We would like such developers to use SE to ask their qustions. Which SE site should we use for a product such as this?

There seems to be more than a few computer science/programming Stack Exchange networks (is that the correct term?). Stack Overflow, being the first, has by far the most users, questions, and answers.  What is the reasoning for creating the others, and are there clear guidelines for which kinds of questions should be posted? I can see a large amount of potential overflow, many cases of people not getting a good answer to their question, because the person who has the answer isn't browsing that particular network at the moment.  I understand that they were probably created for organizational purposes, but wouldn't it almost make more sense to just have them as categories under Stack Overflow, keep them separated but still connected, instead of making people have to create multiple 'account's, one for each network?  I am sure there was a very good reason to break them up, but as someone that is new to SE, it can be somewhat intimidating to decide which one to post in to ensure you get a good answer. For example, if I am a computer science student, my first instinct might to be to post in the computer science network, until I see that it literally has 1% of the users as the Stack Overflow network, which still seems to be for programming/computer science related questions.  So my second instinct would then to be to post it into the Stack Overflow site on the basis that I have a significantly higher chance of my question being seen and getting a good answer. Then I notice that there is also a 'programmers' network, and I don't even begin to know where that fits in. I, and I am assuming most people, will probably just post on Stack Overflow to be safe.  My question is, other than the short little description blurb of each one, is there a clear cut set of guidelines which what each network is intended for, what kinds of questions should go to each one, and is anything being done to encourage people to post in these newer, smaller (more specialized?) networks as opposed to just posting in big daddy Stack Overflow?  Now again, this is for computer science/programming/"why isn't this code doing what I want?" related questions, I am not saying that if I had a question about Linux or WordPress or something I would have the same confusion.


Account field and integration__c fields combination of record is have already in case object don't allows duplication if sftype__C checkbox is true otherwise allows if sftype__c is false allows for duplication.  This is my trigger but this is also allows duplicates please check it once  trigger AvoidDuplicateInsertions on Case(before insert,before update){           Set<string> accountname= new Set<string>();          Set<string> integrationto= new Set<string>();            for(Case cas: Trigger.new){             accountname.add(cas.Account.Name);            integrationto.add(cas.IntegrationTo__c);           }         List<Case> duplicatecaseList = [Select id,Case.Account.Name,IntegrationTo__c,SFType__c From Case where Case.Account.Name= :accountname AND IntegrationTo__c =:integrationto];         Set<string > duplicatecaseIds = new Set<string >();         for(Case dup: duplicatecaseList ){            duplicatecaseIds .add(dup.Account.Name);           duplicatecaseIds .add(dup.IntegrationTo__c);         }         for(Case s : Trigger.new){              if(s.Account.Name!=null && s.IntegrationTo__c!=null){                  if(duplicatecaseIds.contains(s.Account.Name) && duplicatecaseIds.contains(s.IntegrationTo__c)){                    if(s.SFType__c = true){                        s.addError('Record already exist with same Service');                   }                  }              }        } }   but this allows duplication please anyone check it once  Thanks In advance

I have taken three fields from case object called AccountName, IntegrationTo__c and SfType__c (checkbox).  I have created one case record with a specific combination of three fields.  For the second time I create a record with that combination, then  display error message only if SfType__c is true in first record otherwise allow  for record creation.  trigger AvoidDuplicate on Case(before insert)  {          set<string> newNameSet = new set<string>();     newNameSet = new set<string>();      set<string> newEmailSet = new set<string>();      set<string> dbNameSet = new set<string>();      set<string> dbEmailSet = new set<string>();      for(Case newLead : trigger.new){          newNameSet.add(newLead.Account.Name);          newEmailSet.add(newLead.IntegrationTo__c);      }      for(Case dbLead : [select id, Case.Account.Name, IntegrationTo__c from Case where IntegrationTo__c IN: newEmailSet OR Case.Account.Name IN: newNameSet]){          dbNameSet.add(dbLead.Account.Name);          dbEmailSet.add(dbLead.IntegrationTo__c);      }      for(Case newLead : trigger.new){          if(dbNameSet.contains(newLead.Account.Name) && dbEmailSet.Contains(newLead.IntegrationTo__c))              newLead.addError('You are inserting Duplicate Case');      }  }   i wrote this this not checking the account field name and integration__c values only with combination of account and integration__c shows error


Many people just assume that simply because The Hobbit is a lighter story than LOTR and the Silmarillion, it's a children's story, but I don't believe Tolkien himself ever said it was made for children.

Tolkien wrote The Hobbit as a story for children. However, I've never seen a specific age mentioned. Did Tolkien intend the story for young children or for teens?   What reading level should a child be at to understand and enjoy The Hobbit?


I am logged into Stack Overflow using Chrome. But once I'm going to another Stack Exchange site, it asks to log in again.   Why? Is it possible to share authority?

I've seen this question asked 3 times, but in none of those threads did I find a satisfactory answer.  I'm not asking about reputation: it makes sense that different sites should have different reputations.  However, consider the StackExchange drop-down menu at the top left of the screen.  When looking through the "Hot questions", the links are often to sister websites of StackExchange (programmers.stackexchange i.e.).  It doesn't make sense to me that if I go to one of those sister sites, I'm no longer logged in.  I feel like it's counterintuitive to click a link to go answer a question, only to find that you can't answer that question until you log in.  What is the reason for this?  Is there an option to do as I'm suggesting?


i'm kind of new in sql, right now I'm trying to get the best average for each group(GRP) and i have this table.      i'm tryng to get something like this, but im not sure how to do it

Table:   UserId, Value, Date.   I want to get the UserId, Value for the max(Date) for each UserId. That is, the Value for each UserId that has the latest date. Is there a way to do this simply in SQL? (Preferably Oracle)  Update: Apologies for any ambiguity: I need to get ALL the UserIds. But for each UserId, only that row where that user has the latest date.


I developed an application for Raspberry Pi with C and C++ and the OpenVG graphic library. Because of certain circumstances, I want change the platform from Raspberry Pi to Windows tablets. I don't really want to change a lot of my current program, so I'd be nice to find a way, just to compile it on Windows. Which C/C++ Compiler should I use on Windows, that also supports a graphic library like OpenVG?

Which OpenVG implementations exists?   What are pros and cons of each of them?  I'm looking for is a highly stable, fast rendering implementations that is still being actively maintained and developed.


I am interested in computing prediction bands for a non-linear regression (log-logistic function with 3 parameters). I have read the Prism help page:  The calculation of the confidence and prediction bands are fairly standard. Read on for the details of how Prism computes prediction and confidence bands of nonlinear regression. First, let's define G|x, which is the gradient of the parameters at a particular value of X and using all the best-fit values of the parameters. The result is a vector, with one element per parameter. For each parameter, it is defined as dY/dP, where Y is the Y value of the curve given the particular value of X and all the best-fit parameter values, and P is one of the parameters.) G'|x is that gradient vector transposed, so it is a column rather than a row of values. Cov is the covariance matrix (inversed Hessian from last iteration). It is a square matrix with the number of rows and columns equal to the number of parameters. Each item in the matrix is the covariance between two parameters. Now compute c = G'|x * Cov * G|x. The result is a single number for any value of X. The confidence and prediction bands are centered on the best fit curve, and extend above and below the curve an equal amount. The confidence bands extend above and below the curve by: = sqrt(c)*sqrt(SS/DF)*CriticalT(Confidence%, DF) The prediction bands extend a further distance above and below the curve, equal to: = sqrt(c+1)*sqrt(SS/DF)*CriticalT(Confidence%, DF)  I also read the topic . But I still do not understand something : how to compute the Hessian matrix. I do not think it is (I do not get values between -1 and 1), but, is it the second-order partial derivatives of my log-logistic function ? In Prism, it refers to the "Hessian from last iteration" while in the topic, it is written "the second derivatives of the likelihood function at your estimates". The likelihood function I use is ( -N / 2 ) * log( sum( ( dat - model ) .^2 ) ) where N is the number of observations, dat is a vector with data being fitted and model is a vector of model values. I do not really understand how it would be possible to do a second order derivatives of this function. Could anyone give me a hand with this ?

The  for Prism gives the following explanation for how it computes the prediction bands for non-linear regression.  Please excuse the long quote, but I am not following the second paragraph (that explains how $G|x$ is defined and $dY/dP$ is computed).  Any help would be greatly appreciated.     The calculation of the confidence and prediction bands are fairly   standard. Read on for the details of how Prism computes prediction and   confidence bands of nonlinear regression.      First, let's define G|x, which is the gradient of the parameters at a   particular value of X and using all the best-fit values of the   parameters. The result is a vector, with one element per parameter.   For each parameter, it is defined as dY/dP, where Y is the Y value of   the curve given the particular value of X and all the best-fit   parameter values, and P is one of the parameters.)      G'|x is that gradient vector transposed, so it is a column rather than   a row of values.       Cov is the covariance matrix (inversed Hessian from last iteration).   It is a square matrix with the number of rows and columns equal to the   number of parameters. Each item in the matrix is the covariance   between two parameters.      Now compute c = G'|x * Cov * G|x. The result is a single number for   any value of X.      The confidence and prediction bands are centered on the best fit   curve, and extend above and below the curve an equal amount.      The confidence bands extend above and below the curve by:    =   sqrt(c)*sqrt(SS/DF)*CriticalT(Confidence%, DF)      The prediction bands extend a further distance above and below the   curve, equal to:    = sqrt(c+1)*sqrt(SS/DF)*CriticalT(Confidence%,   DF)


This may be an odd question, but this is one thing I've always wondered. How does a dragonfly ancestor with early structures that will one day become wings gain any benefit from these useless limbs that don't work?  It seems in an intermediary context like this, that the adaptation would almost fall under a category more along the lines of something vestigial--something defunct.  I understand the creature adapts with no understanding or control of the process, and it takes extremely long periods of time to see any significant changes from one anatomy to another, but it would seem that statistically that would work against the animal, not for it. It's not like the dragonfly goes from the land and water to having fancy new fully operational wings.  The longer a species is stuck with an unhelpful adaptation, the longer they would be exposed and at a disadvantage. There is one way in which I could see this happening, and that is a prolonged series of random mutation in favor a winged route for the insect with no real input from their environment.  We all know that mutation and variation drift (all of which are relatively random) are part of the evolutionary process, but it is often described in more concrete terms, and the creatures in between an ancestor and a descendant have been discovered and described, but often not very well to the public.  The mutant albino bear ancestor being better suited for arctic stealth and eventually becoming the polar bear and diverging from the brown bear is an example given in the new Cosmos that actually could happen overnight. The bear is born with the full adaptation.  Even if the bear weren't instantly white, fur slowly becoming lighter leading to better hiding capability, or having a thicker coat to help it keep warm makes more sense than the precursor to an entire limb like wings or a tail though.  I suppose that it's possible to say the that random mutation is the primary method of evolution, and the apparent improbability of plants and animals surviving with incomplete, underdeveloped adaptations can be answered by realizing that the plants and animals alive today are the cousins of countless species that actually weren't helped by the wings, and some of that is random too.  And with that in mind, it's slightly more obvious, but I'm wondering if there's more to it or something I'm overlooking.  I've struggled to find any discussion about this topic in the literature, which I may have simply missed because it often goes over my head. I'm hoping my conclusion is helpful.

Given that the mechanism of natural selection is sensitive, how do species survive in an evolutionary midway? The ability to breath in air requires complex protein systems. An animal that is developing these organs would not be able to utilize its function until it fully evolves. While it doesn't, wouldn't the wasted resources used in growing half-developed lungs be.. wasted? Or is all evolution continuous?


In Java you can override the equals and hash method of the HashMap's key object to determine how the hash code is generated and when two key objects should be considered equal.  Is there any Map implementation that allows to define the hash and equals on in the Map class by overriding its hash method (and determining key equality by an equals(key1,key2) method that can be overridden)?  Use case:  Ĺets assume we have a Objects of class GeoData, containing the fields:  country, region, city. We want access two Maps: map x stores the number of inhabitants of each region and map y the number of inhabitants of each city.  To get both informations for a GeoData object we first need to extract country and region from that object, then create a new Object of class X that defines hash and equals considering country and region and use it as key for map x. Additionally we need to do the same with country, region and city. Create a new Object of class Y and use that get the value from map y.  Wouldn't it be easier if we extend a Map implementation for each of these maps x and y and override a hash(GeoData key) and equals(GeoData key1,GeoData key2) method, which would also avoid to create new key objects for every access?  hash(GeoData key) could then either use country and region in map x, or country,region and city in map y for hash code calculation.  UPDATE:  Correctly marked as duplicate.  answer suggesting apache commons-collections AbstractHashMap is what I was looking for.

With a TreeMap it's trivial to provide a custom Comparator, thus overriding the semantics provided by Comparable objects added to the map. HashMaps however cannot be controlled in this manner; the functions providing hash values and equality checks cannot be 'side-loaded'.  I suspect it would be both easy and useful to design an interface and to retrofit this into HashMap (or a new class)? Something like this, except with better names:    interface Hasharator<T> {     int alternativeHashCode(T t);     boolean alternativeEquals(T t1, T t2);   }    class HasharatorMap<K, V> {     HasharatorMap(Hasharator<? super K> hasharator) { ... }   }    class HasharatorSet<T> {     HasharatorSet(Hasharator<? super T> hasharator) { ... }   }   The  problem gets a trivial solution:   new HasharatorMap(String.CASE_INSENSITIVE_EQUALITY);   Would this be doable, or can you see any fundamental problems with this approach?  Is the approach used in any existing (non-JRE) libs? (Tried google, no luck.)  EDIT: Nice workaround presented by hazzen, but I'm afraid this is the workaround I'm trying to avoid... ;)  EDIT: Changed title to no longer mention "Comparator"; I suspect this was a bit confusing.    EDIT: Accepted answer with relation to performance; would love a more specific answer!  EDIT: There is an implementation; see the accepted answer below.  EDIT: Rephrased the first sentence to indicate more clearly that it's the side-loading I'm after (and not ordering; ordering does not belong in HashMap).


I want to run a programme located in C, which can be run using command line using a line as follows  tclsh oommf.tcl avf2odt -average space -axis z -onefile  <filename>.txt  -headers none -ipat *.omf   This is the only thing I need to type in command line.  How can I run it using python?  Please be VERY relevant to the question. I have seen a lot of answers like: you can use 'subprocess' to realize it. However, none of them really solves the problem.

How do you call an external command (as if I'd typed it at the Unix shell or Windows command prompt) from within a Python script?


I'm learning JavaScript and I have a page that displays the result of dividing two user-inputted numbers.  I didn't like that (1 / 3) would fill the whole result box with 3.333333333333..., so I set the result with .toFixed(4). But this has the result of making (4 / 2) return 2.0000 instead of just 2.  So, in order to fix that I check if (answer % 1 == 0), in which case it displays the answer normally, then checks (answer % 0.1 == 0), which displays answer.toFixed(1), and so on, with the final else being .toFixed(4).  This works as intended for some numbers but not for others, and I don't see why or what's going wrong in the cases it doesn't work.  Examples:   (2 / 5) returns 0.4. This satisfies the second condition, (answer % 0.1 == 0), and returns answer.toFixed(1), displaying 0.4. Great. (2 / 10) also works and displays 0.2, and something like (2 / 7) correctly gets pushed to the else and displays 0.2857. (2 / 8) returns 0.25, then incorrectly displays 0.2500 (2 / 20) correctly returns and displays 0.1 (9 / 6) returns 1.5, then incorrectly displays 1.5000 (2 / 4) returns 0.5, but displays 0.5000. It failed all the conditions and jumps to the else sentence, so answer.toFixed(4) is used.   Why does JavaScript consider (0.4 % 0.1 == 0) to be true, but (0.5 % 0.1 == 0) to be false?  This is my current code:  let num1 = parseFloat($("calcInput1").value); let num2 = parseFloat($("calcInput2").value); answer = num1 / num2;  if (answer % 1 == 0) {     document.getElementById("calcResult").value = answer;     alert("answer % 1 == 0"); } else if (answer % 0.1 == 0) {     document.getElementById("calcResult").value = answer.toFixed(1);     alert("answer % 0.1 == 0"); } else if (answer % 0.01 == 0) {     document.getElementById("calcResult").value = answer.toFixed(2);     alert("answer % 0.01 == 0"); } else if (answer % 0.001 == 0) {     document.getElementById("calcResult").value = answer.toFixed(3);     alert("else"); } else {     document.getElementById("calcResult").value = answer.toFixed(4); }

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


Why $f\left(x\right)$ adds a space between f and the opening parenthesis while $f(x)$ does not? Is the space anyhow more correct typesetting for a function? If not, is there a way to remove the space added by \left( or prevent it from appearing?  This came as a huge surprise to me. Sorry if it is a duplicate, but I couldn't find anything similar.  Minimal working example:  \documentclass{article} \usepackage[utf8]{inputenc} \begin{document} $f\left(x\right)$  $f(x)$ \end{document}   Sample output:

For mathematics, is it ever disadvantageous to use \left(  and \right)  in equations?  I can't see any way that doing this would hinder the typesetting, so why isn't () just converted into \left( \right) automatically? This would save a lot of typing.  Cheers!


I'm trying to post a question/answer on StackOverflow and it won't accept any title I give it, saying "This title doesn't meet our quality standards". I've tried every possible wording that makes any sense and I can't post it.  A few titles I've tried:   Enabling Dart button Enabling button in Dart Enabling a button in Dart Enable an element in Dart   ...and 1,000 others I can't remember.

A good title helps your question get the attention it deserves.  What goes into a good title?


For some reason I cant retrieve data from a query to a username with accent marks, but the same data retrieving works perfectly if the user has no accent marks.  This is the PHP query:  $query = "SELECT * FROM [dbo].[Users] WHERE User= 'Róger'"; $result = sqlsrv_query($conn, $query); $row = sqlsrv_fetch_array($result); $UserID = $row['ID']; echo "ID is: " . $UserID;   This is my result on website:  ID is:   This is what i get from var_dump($query);  "SELECT * FROM [dbo].[Users] WHERE User= 'Róger'"   Now, if we change $query from  $query = "SELECT * FROM [dbo].[Users] WHERE User= 'Róger'";   to  $query = "SELECT * FROM [dbo].[Users] WHERE User= 'Robert'";   Then it properly shows up the UserID.   Any ideas?

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I am trying to loading Digest::MD5 from the directory my Perl script is existing in (since I can't install through PPM on my enviroment.) I've tried a bunch of combinations, but what appears to work on Strawberry perl on Windows, but not in Red Hat linux is having a Digest directory with MD5.pm, base.pm, and file.pm in it. Then I am using this code to load the module. use FindBin; use lib "$FindBin::Bin/"; use Digest::MD5 qw(md5_hex);  But I get this error:  Can't locate loadable object for module Digest::MD5 in @INC (@INC contains: /opt/myapp/bin/script/ /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .) at ./app.pl line 21. Compilation failed in require at ./app.pl line 21. BEGIN failed--compilation aborted at ./app.pl line 21.  I'm tired of banging my head on my desk, anyone have any ideas? Edit: This was marked as an exact duplicate of a very different question. This is not about a missing module, it is about including a module directly with a perl script so it can be packaged and installed without installing a module through PPM or CPAN or something.

I get this error:  Can't locate Foo.pm in @INC  Is there an easier way to install it than downloading, untarring, making, etc?


So I am trying to make a model with hand painted textures. I marked some seams and UV unwrapped it to start painting. (maybe i forgot a step?), but then i try to apply it. I don't really know how to apply it. And once I thought i succeeded, but when I opened up the file again it was blanc.   Anyone knows how to do this?

I was following a  on how to use the Texture Paint feature on blender so I could paint on a terrain I am modeling. I was successful to paint the whole terrain with beautiful, exuberant vegetation, and crystalline water running through the valley.  So I saved my file, and I went to sleep. But now I've reopened the file and everything seems like I left it yesterday, except that I can see no texture in the terrain... The weird thing is that the textures i used are still there... I don't understand, I barely understand the interface, please help. I'm not even sure if the texture is there or if it was never "saved" or something...     I am now going through the second part of the tutorial for possible answers but I (and hopefully many more) will be grateful for your help.