This is kind of a conceptual thing I have wondered from time to time. What I am trying to describe is when a user can provide some sort of input to software that will result in some action being taken, but that ability is not obvious and there is no affordance presented to suggest it.  I have just run into a particularly good example of this in Adobe Acrobat XI. I am making a fillable PDF form, and I had opened a properties dialog for one of the (many) fields. I accidentally discovered that if I press the Enter key in this dialog, the result is that it stays up, but now shows properties for the next field in the tab order.  For instance, in the dialog below, pressing the Enter key will not close the dialog, but rather change its "focus" to Text26.    Is there a formal term in UX/HCI theory for this situation? Thanks!

We're building an app that has an element that performs some specific set of actions. The element itself is new, and tests are very conclusive: for the target the app is directed to, the affordance is clear (while for other targets, it's not, but this is basic in Gibson's theory).  So I'm writing the documentation for the app, and came to the part where I have to describe this element, and I was simply explaining the fact that affordances had yet to be discovered but test are conclusive, providing all the theoretical background and testing results at hand. Then I thought that instead of having to re-create the wheel, I could simply include existing research on the concept of "yet to be discovered affordances" itself (assuming it exists).   Note: Of course I'm aware about Nielsen's UX Discoverability and Gaver's False affordances concepts, so this NOT what I'm asking. In some way, I think it's the state previous to UX Discoverability.   Anyways, maybe it's just that I can't think the proper words, but my question is "Is there a concept for "yet to be discovered" affordances?"


I have a lightning component similar to:  <aura:component>     <aura:handler name="myevent" action="{!c.myRerender}" />      <lightning:recordViewForm recordId="{!v.recordId}" objectApiName="MyObj__c" /> </aura:component>   How can I get my <lightning:recordViewform> to reload? Usinge.force:refreshView` is not a viable answer as it reloads other things as well.

I have two lightning component placed on one page lightning app. First Component have refresh icon and I set onclick action to refresh Component $A.get('e.force:refreshView').fire(); but this event refresh the whole page instead of First component.  how can refresh only one component on page not all the page ?


I have been trying to set up Ubuntu to dual boot but after the install the GRUB2 bootloader is not starting. I tried boot repair but still nothing happening.  The link for the boot repair information is: .  Can anyone tell me what I'm doing wrong?

I installed Ubuntu 14.04 onto my Acer Aspire E15. The PC has a 500 Gigabyte HDD.   During the installation it divided the HDD into separate partitions. However every time I turn on the PC it goes directly into Windows 8.1. It doesn't allow you the opportunity to select which OS you want to use.   Question 1: How do I set the PC so it will allow me to select the OS?  Question 2: And if #1 isn't possible. How to I remove Ubuntu from the PC and recover the partition for Windows


By the Strum theory it is easy to see that the equation $\tan(\alpha)=\alpha$ has not complex roots and it's real roots occur at zero and near $(2n+1)\pi/2,\ n\in Z^{+}$.  I am interesting to know that is there any other way to see that the above equation has not complex roots?

I have calculated the real and imaginary parts of $\dfrac{\sin z}z.$ I've obtained  $$\begin{eqnarray} \frac{\sin z}z&=&\frac{\sin(x+iy)}{(x+iy)}\\ &=& \frac{\sin(x)\cosh(y)+i\cos(x)\sinh(y)}{x+iy}\\ &=& \frac{x\sin(x)\cosh(y)+y\cos(x)\sinh(y)}{x^2+y^2}+i\frac{x\cos(x)\sinh(y)-y\sin(x)\cosh(y)}{x^2+y^2}. \end{eqnarray}$$  Before calculating it, I hoped I could use this in a solution to a certain problem, but I would need to differentiate the real and imaginary parts of $\dfrac{\sin z}z$ with regard to $x$ and $y$. But what I'm getting is very complicated. I understand that it could be that that's just the way it is. But maybe there are some simplifications to be done either in the functions or in their derivatives? I've never really used hyperbolic functions before so I'm not sure I'm not missing something.  Added. The problem I'm working on is the following.     Prove that the solutions of the equation $$\tan z=z$$ are all real.   I will sketch the solution I know here.  It can be calculated that  $$\tan(x+iy)=\frac{\sin(2x)}{\cos(2x)+\cosh(2y)}+i\frac{\sinh(2y)}{\cos(2x)+\cosh(2y)}.$$  Plugging this to the equation, we get  $$\begin{eqnarray} x&=&\frac{\sin(2x)}{\cos(2x)+\cosh(2y)}\\ y&=&\frac{\sinh(2y)}{\cos(2x)+\cosh(2y)}. \end{eqnarray}$$  From this we can get   $$\sin(2x)\cdot2y=\sinh(2y)\cdot2x.$$  By plotting the functions $\sin,$ $\mathrm{id}$ and $\sinh$ (and proving the right inequalities we can see from the plots), we can see that this is only possible when $xy=0$. But when we plug $x=0$ to the second equation, we can show that the only solution is $y=0$, which ends the proof.  What strikes me in this solution is the fact that $\dfrac{\sin z}z$ is used. (Not explicitly in my statement.) This function has another connection to the problem:     The non-zero solutions of the equation $\tan z=z$ are exactly the zeros of the derivative of $\dfrac{\sin z}z.$   This is easy to prove. I wondered if there shouldn't be a solution to the problem which uses this fact, given that $\dfrac{\sin z}z$ appears in the solution I know.


I normally use the following method to determine the free/used space within each file of a database:  Select *, fileproperty(name, 'SpaceUsed') as Used From dbo.sysfiles   This returns total and used space in pages, which I then multiply by 8 to get KB (or divide by 128.0 to get MB).  I found another script than instead uses DBCC showfilestats and dbcc sqlperf(logspace) to return the TotalExtents and UsedExtents, which can then be multiplied by 64 to get KB (or divided by 16.0 to get MB).  Ignoring the extra columns, will these two always give identical values for free/total space? What about sp_spaceused?  Does their accuracy both depend on a recent DBCC UPDATEUSAGE?  Is there another, better method for determining used/free space? (I need this script to work on SQL 2000, 2005, and 2008 servers)  Partially related: Can you have a partially-allocated extent? (only 3 of the 8 pages within an extent are allocated, for example)

We are using 6 databases in total for an application, and we can only share 4TB of space among all 6 auto-grow databases (via SAN storage).  I'd like to write a query (report) for a single database indicating the "Currently allocated space" and "Available free space" attributes under the Tasks > Shrink > Database option in SQL Server Management Studio.  Then I'd like to convert those numbers to TB and total each database to get a rough estimate of how much space we have left.  Can these fields be accessed via a T-SQL query?  If so, what would the query look like?


I want to setup a cronjob for PHP script in ubuntu  I have a script just I want to know how to set it.  * 3 * * * /var/www/html/booking_cron.php

Often, crontab scripts are not executed on schedule or as expected. There are numerous reasons for that:   wrong crontab notation permissions problem environment variables   This community wiki aims to aggregate the top reasons for crontab scripts not being executed as expected. Write each reason in a separate answer.  Please include one reason per answer - details about why it's not executed - and fix(es) for that one reason.  Please write only cron-specific issues, e.g. commands that execute as expected from the shell but execute erroneously by cron.


I have an app in which I can open camera and take a photo and to save gallery. When I click on button to open camera its works. If I click the back button on the phone without taking a photo, my application is stopped. How can I solve this problem ?      Button camera = (Button) findViewById(R.id.camer);     camera.setOnClickListener(new View.OnClickListener() {          @Override         public void onClick(View arg0) {             Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);             startActivityForResult(cameraIntent, CAMERA_PIC_REQUEST);           }     });      send.setOnClickListener(new OnClickListener() {          @Override         public void onClick(View arg0) {              Intent i = new Intent(Intent.ACTION_SEND);               //Log.d("URI@!@#!#!@##!", Uri.fromFile(pic).toString() + "   " + pic.exists());             if (pic != null) {                 i.putExtra(Intent.EXTRA_STREAM, Uri.fromFile(pic));             }              i.setType("image/jpg");              startActivity(Intent.createChooser(i, "Share you on the jobing"));         }     });   }  protected void onActivityResult(int requestCode, int resultCode, Intent data) {     if (requestCode == CAMERA_PIC_REQUEST) {         thumbnail = (Bitmap) data.getExtras().get("data");         image = (ImageView) findViewById(R.id.imageToUpload);          image.setImageBitmap(thumbnail);           try {             File root = Environment.getDataDirectory();             if (root.canWrite()) {                 pic = new File(root, "pic.jpg");                 FileOutputStream out = new FileOutputStream(pic);                 thumbnail.compress(CompressFormat.JPEG, 100, out);                 out.flush();                 out.close();             }          } catch (IOException e) {             Log.e("BROKEN", "Could not write file " + e.getMessage());         }      }  }      Caused by: java.lang.NullPointerException: Attempt to invoke virtual   method 'android.os.Bundle android.content.Intent.getExtras()' on a   null object reference

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'm on exchange in the UK for 9 months and have only lived here for a month right now. I was planning to travel around Europe during Christmas. (I have a Chinese passport and have lived in Canada for 5 years before this and am going back to Canada after the exchange term if that's relevant)   I understand they require the applicant to be in the UK for at least 3 months but that would be a bit late for Christmas break.   According to ,     To apply for a Schengen visa from the UK you must be a UK resident for at least three months. If this condition is not fulfilled, the Consulate of your country of preference will hardly take the application into consideration.   It only says "hardly considered" but didn't say it'll definitely be rejected. I think I have pretty good reasons to apply from the UK but not sure if it's worth a try.   So I was wondering if anyone has ever got a Schengen visa from a country where you've lived in for less than 3 months or has been in a similar situation?

I'm a citizen of country A who would like to apply for a Schengen visa at a consulate in country B. When is this possible?


I remember watching a film on TV in roughly 1989. It would have been a German production broadcasted on Austrian ORF, or any production but in german synchronized version. It was in color, not subtitled, depicting a contemporary earth society and environment. Not sure about the length, say one hour. Not a serial. The story revolves around a pickle-sized cucumber interstellar spaceship (no, not with a rat rib cage exoskeleton) with humanoid crew of at least one female and one male. They could make sections of the cucumber skin translucent for windows. They were explorers, and made contact with what I believe to remember, human children; in the end they got themselves in a position where they were in danger and had to lam to their homeworld. The homeworld was a sentient tree in space, with white dendrites, quite like those on Pandora. There was a philosophical backstory and a morale, of which I remember nothing concrete. What is the name of that movie, and if it is based on a novel or short story, which?

A very long time ago, possibly late 70s or early 80s, I remember seeing a one-off science fiction drama on British BBC TV. It was about an expedition to an alien planet to get help for a space station which was running out of oxygen.  The alien planet was, of course, Earth. The crew were about a centimetre high. It was all live action and I suspect the programme was a showcase for miniature photography. They land their shuttle (which looks very much like a courgette) in someone's garden, and there are various adventures. The ones I remember are:   encountering some dropped jelly babies and thinking they're idols made by the natives. flying around on weirdly insectile flying bikes. discovering a discarded battery in a puddle and getting into trouble from the chemicals. I think they get attacked by a rat at some point?   Eventually they discover that there's a light-resistent coating on their courgette-ship, and if it gets stripped off then it will generate its own oxygen. They take off to take the good news home, and the programme ended with them approaching the station, floating in space --- which is a tree.  Does anyone know what this is?


Is is possible to get references from a paper? For example, given that paper A cites paper B, C and D, i wanna to extract Bibtex of B, C and D from A. Is is possible to do this conveniently? Thank you for any help!  EDIT: A more concrete example: I have paper A which cites many other papers such as B, C and D. I wanna some ways to directly get bibtex of all these cited papers in paper A.

How can I convert a .bbl file to a .bib file. I  lost my .bib file but I still have my .bbl file. Now , I need to add more references to my .bbl file according to a specific format which I need to produce using Bibtex, so how can I convert my .bbl file to a .bib file so I can add the new references according to the format.  Thanks for any insight.


Why do I keep getting updates requests that are identical? I install them and restart only to find "another update is ready to install".

For the last week whenever I shutdown my Windows 7 Home Premium laptop, I get the yellow shield telling me I have updates (both updates are shown below my question). I shutdown the system, the updates download and install. The next time I shutdown my system, the exact thing happens again, with the same updates. So far I have run the Microsoft Mr. Fixit tool no success, uninstalled and repaired both the .NET Framework 4 extended and the .NET Framework 4 Client Profile, with no success. Any suggestions? First update:  Update for Microsoft .NET Framework 4 on XP, Server 2003, Vista, Windows 7, Server 2008, Server 2008 R2 for x64 (KB2600217) Download size: 32.2 MB You may need to restart your computer for this update to take effect. Update type: Recommended This update addresses stability, reliability, and performance issues in Microsoft .NET Framework 4. After you install this item, you may have to restart your computer.


I have FbApp class public class FbApp{ private FbServiceActivity fbServiceActivity;   public FbApp(){ fbServiceActivity = new FbServiceActivity(); }  public void highestActivityMenu() {     System.out.println("menu"); }  public void start(){ fbServiceActivity.highestActivity(); }  FbServiceActivity class public class FbServiceActivity { private FbApp fbApp;  public FbServiceActivity(){ //not connected to the question }  public void highestActivity() { //some code     fbApp.highestActivityMenu(); //some code }  In by code I call start() at the beginning. Program starts and works up to fbApp.highestActivityMenu(). The error is NullPointerException.


I have no idea what kind of grammar this is.      No sooner do I sit at the foot of my bed than one of the beginning trainees comes to the door.   How can they use do I in that sentence and still not end it with a question mark?.

Possible Duplicate:          Is there some rule governing the following, or similar, subject-auxiliary inversions (*"Rarely they do see the light of day", *"Never I have been so insulted")?     In fancy sit-down restaurants, you can order a large meal and halfway through the main course, take a little dead cockroach or a piece of glass out of your pocket and place it deftly on the plate. Jump up astonished and summon the headwaiter. "Never have I been so insulted. I could have been poisoned" you scream slapping down the napkin. You can refuse to pay and leave, or let the waiter talk you into having a brand new meal on the house for this terrible inconvenience. ()      Rarely do they see the light of day; it's generally judged to be in no one's commercial interest that they should. Just occasionally, however, like a seemingly dormant volcano, they explode into the open. ()


I need to figure out a way to dissolve a polygon in Python using other modules besides ArcPy. I've been using the Python GDAL/OGR for merging shapefiles but I don't see anything to dissolve a polygon. I've been looking into Shapley, Fiona and Pyshp.  I also don't want to use qgis, as importing the qgis.core module gives my script problems.   Any ideas?  **EDIT I'm trying the Fiona approach but am having a hard time configuring it. I installed a .whl of it and it appears to install but when I run something it crashes Python saying   'This application has requested the Runtime to terminate it in an unusual way'  When I try to update the module in Pycharm, I get an error 'gdal version is not defined'

I have been trying to create a function that does basically the same thing that the QGIS "dissolve" function. I thought it would be super easy but well apparently not. So from what I have gathered around, the use of fiona with shapely should be the best option here. I just began to mess around with vector files so this world is pretty new to me and python as well.  For these example, I am working with a county shapefile founded here  So here are some piece of code I gathered but can't find a way to make them work together  For now my best method is the following based on : . It works fine and I get a list of the 52 states as Shapely geometry. Please feel free to comment if there is a more straight forward way to do this part.  from osgeo import ogr from shapely.wkb import loads from numpy import asarray from shapely.ops import cascaded_union  ds = ogr.Open('counties.shp') layer = ds.GetLayer(0)  #create a list of unique states identifier to be able #to loop through them later STATEFP_list = [] for i in range(0 , layer.GetFeatureCount()) :     feature = layer.GetFeature(i)     statefp = feature.GetField('STATEFP')     STATEFP_list.append(statefp)  STATEFP_list = set(STATEFP_list)  #Create a list of merged polygons = states  #to be written to file polygons = []  #do the actual dissolving based on STATEFP #and append polygons for i in STATEFP_list :      county_to_merge = []     layer.SetAttributeFilter("STATEFP = '%s'" %i )      #I am not too sure why "while 1" but it works      while 1:         f = layer.GetNextFeature()         if f is None: break         g = f.geometry()         county_to_merge.append(loads(g.ExportToWkb()))      u = cascaded_union(county_to_merge)     polygons.append(u)  #And now I am totally stuck, I have no idea how to write  #this list of shapely geometry into a shapefile using the #same properties that my source.   So the writing is really not straight forward from what I have seen, I really just want the same shapefile only with the country dissolve into states, I don't even need much of the attribute table but I am curious to see how you can pass it on from the source to the new created shapefile.  I found many pieces of code for writing with fiona but I am never able to make it work with my data. Example from  :  from shapely.geometry import mapping, Polygon import fiona  # Here's an example Shapely geometry poly = Polygon([(0, 0), (0, 1), (1, 1), (0, 0)])  # Define a polygon feature geometry with one attribute schema = {     'geometry': 'Polygon',     'properties': {'id': 'int'}, }  # Write a new Shapefile with fiona.open('my_shp2.shp', 'w', 'ESRI Shapefile', schema) as c:     ## If there are multiple geometries, put the "for" loop here     c.write({         'geometry': mapping(poly),         'properties': {'id': 123},     })   The problem here is how to do the same with a list of geometry and how to recreate the same properties than the source.


I am an Indian working in Central Government and have applied for an Italian tourist visa for 17 days (to visit Rome-florence-paris-Vience-Rome-India). But my visa application got rejected with the reason "information submitted regarding the justification for the purpose and condition of intended stay is not reliable".  I have already submitted my original tickets to and from Italy and online hotel bookings, my salary slip, form 16 of the last 3 years, bank statement showing a good amount, nOC form employer and all the other relevant documents. May I know what the reason of refusal is and how I can get it corrected?

Schengen refusal formulae can be difficult to understand sometimes.  Sometimes an applicant receives a refusal with:       Justification for the purpose and conditions of the intended stay was not reliable.     often accompanied by:       Your intention to leave the territory of the Member States before the expiry of the visa applied for could not be ascertained.   What is meant by this refusal reason?  What are they trying to say?


Consider $A$ a unital $C^*$ algebra, I want to show that the spectral radius  $r(a)$ satisfies the following: $$r(a) = \inf_{b\in \operatorname{Inv}(A)}\|bab^{-1}\|$$ where $\operatorname{Inv}(A)$ is the set of invertible elements in $A$.  So far I can only see one direction, namely $r(a) \leq  \inf_{b\in \operatorname{Inv}(A)}\|bab^{-1}\|$. I wondering how to prove the other direction.   Thank you very much for the help.

Let $A$ be a unital $C^*$-algebra and $a\in A$ such that $r(a) < 1$. Define b  = $(\sum_{n=0}^\infty (a^*)^n a^n)^{1/2}$. We can prove that $b\geq e$ and that $b$ is invertible. I want to show $\| b a b^{-1} \| < 1$.   From the definition of $b$ we see that $a^* b^2 a = b^2-e$ and we know $r(bab^{-1}) = r(a) <1$.   So it suffices to prove $r(b a b^{-1}) = \| b a b^{-1} \|$. It can follow from the fact $c = ba b^{-1}$ is a normal element... I don't know how to prove it (I have tried to compare $c^* c$ and $c c^*$...).    Context: The question appears in Murphy's book, page 74.   I have managed to prove the first part. The second part of the question is to prove $$r(a)= \inf_{c\in Inv(A)}\{\|cac^{-1} \| \}$$ It's easy to see $$r(a) \leq \inf_{c\in Inv(A)}\{\|cac^{-1} \| \}$$ But I can't prove $$r(a) \geq \inf_{c\in Inv(A)}\{\|cac^{-1} \| \}$$ If we have had $r(a) = \|b a b^{-1} \|$ then it was obvious... But this is not true, so how we can prove this inequality?


Images:   I was going to change out this outlet.  It was previously all shoved together in a back-wire type outlet (The kind you just stab in). Was going to replace with a new side-wire outlet, but wasn't expecting 6 total wires.  For now, I've just pig-tailed the 3 live wires together, & the 3 neutral wires together, so that the next several outlets down work (crucially, the refrigerator's outlet doesn't work unless these are all connected).  Couple questions:   So I'd just pigtail in 2 more wires - 1 white wire to the 3 neutral wires, and 1 black wire to the 3 live wires, then connect those to single posts in the new outlet? Is this not...excessively crowded in that electrical box? Is that OK? Anything else I'm missing that means I'm going to burn down my house?   Thanks,

I'm redoing some of the outlets in our house, as they are pretty loose. Some of these have been really easy, but I came across one today where there were 3 hots and 3 neutrals. All 3 were going into the quick-connects in a outlet which looks like this:     Don't mind the destruction on the quick-connect in the picture, as I broke that taking the wires off and am not re-using this outlet. My new outlets look like:    For my other installations I've been using the screws on the side rather than the quick-connects, but since I had 3 hots/3 neutrals I figured I'd try to put 4 on the screws and the other 2 in the little quick connect holes. However, this plan doesn't work because it seems that the wire is too large for the quick connect holes on my new outlets (maybe a 14 gauge vs 12 gauge difference? )  What do I do in this situation? Do I nut two of the hots and 2 of the neutrals together? If so, can I determine the exact type of nut I need with my wire stripper (AWG of the bare wire correspond to the gauge of the wire or do I need to include insulation?).  Edit: A picture of the sides of the outlet I'm replacing, in which it looks like the tabs are present:


This is probably not the most important thing, but since uservoice is closed, here's a feature request.  The syntax highlighter for code blocks really screws up on PostScript code, making it essentially less readable then unhighlited code (and that's pretty hard with Postcript). And, after all, PostScript is a programming language :-)  What do you think?  Edit: Looking closer, it would go a long way if the prettyfier would at least recognize the precent symbol as a comment starter.  On a side note: To the right of this input box it says     If your question is about this   website, ask it on   meta.stackoverflow.com instead.   This could lead to a mental infinite recursion.

I noticed that sometimes my code gets highlighted in different colors when rendered.   What is syntax highlighting? How does it work? Why isn't my code being highlighted correctly? How do I report a bug or request a new language? How do I use syntax highlighting? What languages are currently available on Stack Exchange?


I want to return all values of 2D array. How I can return it if I use get method with String type?  public class Data { private final String[][] table; public Data(){     table = new String[][] {{"ID", "NAME"},                          {"101", "A"},                          {"102", "B"},                          {"103", "C"},                          {"104", "D"},                          {"105", "E"}}; }  public String[][] get(){     for (int i = 0; i < table.length; i++) {         for (int j = 0; j < table[i].length; j++) {             table[i][j] = table[i][j];         }     }     return table; }  public void displayMessage(){     System.out.println(get()); }   }

In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the  of the array, as defined by Object.toString():  int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray);     // prints something like '[I@3343c8b3'   But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:  // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5]  // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob]


I'm sure I'm just be being a n00b here, but the size value for my particle systems seems to be missing. It should be right there next to mass under physics, right?   Any help is much appreciated.

I am sure that beside Mass there used to be a particle size and size random setting here in previous versions of blender, but on 2.79a, I can't seem to find it?   Did I accidentally change a setting somewhere that turned it off  or did they remove it?    I know that I can use the Normal setting under velocity to control the size, but I am not sure how I can make the size random without randomizing the rotation also.


Using elementary row operations, a matrix A $\in \mathrm{R}^{n \times n} $ can be reduced to a Row-Reduced Echelon (RRE) form. Using the RRE form of A, the bases of Nullspace and Range can be obtained. The RRE form of A is a triangular (almost diagonal) form of A and is row-equivalent to A. If we are able to get a simple form of A, why do we need to get eigenvalues and diagonalize A ? What is the motivation for having an alternative method to simplify(diagonalize) A ? Why would one choose to diagonalize A using eigen values ?

What is the importance of eigenvalues/eigenvectors?


I was trying to dual boot Ubuntu 18.04.1 LTS alongside Windows 10 on my laptop.  I got the USB and followed the video and everything worked up to where I clicked Try Ubuntu without installing and when the desktop loaded I was not able to use my touchpad. A wireless mouse worked but I was not able to click.   Someone told me      You need to boot the installation media with an additional boot parameter nomodeset and also when booting the installed system until you install the Nvidia proprietary drivers.   I have no clue what the user means by any of this as I am very new to Ubuntu, can someone explain how to do these things and what it means? Thank you in advance.

I'm trying to install Ubuntu 18.04 desktop with Rufus on a computer with the following specs:  CPU: AMD Ryzen 5 2600 MOBO: ASUS Prime B450M-A/CSM RAM: G-Skill Ripjaws DDR4 F4-2400C15D-16GVB GPU: Nvidia GeForce GTX750 PSU: Apexgaming AG-650M SSHD: Seagate Firecuda Compute mATX: Rosewill SCM-01  Basically it boots from the USB (FAT32) and brings up a black error screen with words and numbers. Then it transitions to the purple splash screen with "ubuntu" and 5 dots, however the screen shows various visual glitches depending on which USB port I plug into. When trying to boot the computer, it boots to a black screen with the following error message: ACPI Error: Needed [Integer/String/Buffer], found [Region]    that shows what I mean.


I have a volume element in phase space:  $$ d\omega = \prod _{i=1}^{N}(dq_{i},dp_{i})$$  Now I should show the invariance of this product under canonical transformations. I think first I would have to write down a general equation for the canonical transformation then compute the total differential and plug this into the equation given. My problem is now I can't figure out how the equation for a general canonical transformation would look like. Does anybody have a hint how to start? The proof should be done without the concept of Symplectomorphisms like it was already shown in this question


This is a follow up question to .  Following the answers therein, I was able to install gcc-7.2 by:  sudo add-apt-repository ppa:ubuntu-toolchain-r/test sudo apt-get update sudo apt-get install -y gcc-7   However, after the install, the gcc/g++ command still defaults to 5.4.0  gcc --version gcc (Ubuntu 5.4.0-6ubuntu1~16.04.5) 5.4.0 20160609   Is it possible/safe to have gcc-7 as the default and remove the old gcc-5.x files entirely?    Note that, different from the said duplicate, I'm looking to remove/replace gcc-5.x instead of setting a symlink.

So I have installed gcc-4.4 and gcc-4.3 (same for g++). Now as far as I remember there is a tool in Ubuntu which sets the symlinks for you if you just tell it which version you want. However it does not seem to work in the newest version, which I find disappointing.  root@nexus:~# update-alternatives --config gcc update-alternatives: error: no alternatives for gcc. root@nexus:~# update-alternatives --config cc There is only one alternative in link group cc: /usr/bin/gcc Nothing to configure.   root@nexus:~# dpkg -l | grep gcc | awk '{print $2}' gcc gcc-4.3 gcc-4.3-base gcc-4.3-multilib gcc-4.4 gcc-4.4-base gcc-4.4-multilib gcc-4.5-base gcc-multilib lib32gcc1 libgcc1   Any ideas?


Linux pc 4.15.0-76-generic is show on but not working. Dell inspiron 1521. How to solve this bluetooth problem?  02:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM43142 802.11b/g/n [14e4:4365] (rev 01)     Subsystem: Dell Wireless 1704 802.11n + BT 4.0 [1028:0016]     Kernel driver in use: wl     Kernel modules: bcma, wl Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 005: ID 0c45:64ad Microdia  Bus 001 Device 004: ID 0bda:0129 Realtek Semiconductor Corp. RTS5129 Card Reader Controller Bus 001 Device 003: ID 0a5c:21d7 Broadcom Corp. BCM43142 Bluetooth 4.0 Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 003 Device 002: ID 046d:c535 Logitech, Inc.  Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub [   22.026377] Bluetooth: Core ver 2.22 [   22.026400] Bluetooth: HCI device and connection manager initialized [   22.026404] Bluetooth: HCI socket layer initialized [   22.026406] Bluetooth: L2CAP socket layer initialized [   22.026412] Bluetooth: SCO socket layer initialized [   24.113880] Bluetooth: hci0: BCM: chip id 70 [   24.114825] Bluetooth: hci0: BCM: features 0x06 [   24.130858] Bluetooth: hci0: himanshu-pc [   24.130863] Bluetooth: hci0: BCM (001.001.011) build 0000 [   24.336532] bluetooth hci0: Direct firmware load for brcm/BCM.hcd failed with error -2 [   24.336536] Bluetooth: hci0: BCM: Patch brcm/BCM.hcd not found [   26.364031] Bluetooth: hci0: command 0x1003 tx timeout [   26.364883] Bluetooth: hci0: unexpected event for opcode 0x1003 [   35.978595] Bluetooth: BNEP (Ethernet Emulation) ver 1.3 [   35.978597] Bluetooth: BNEP filters: protocol multicast [   35.978601] Bluetooth: BNEP socket layer initialized [   38.684072] Bluetooth: hci0: command 0x1003 tx timeout [   38.685760] Bluetooth: hci0: unexpected event for opcode 0x1003 [  100.076586] Bluetooth: RFCOMM TTY layer initialized [  100.076592] Bluetooth: RFCOMM socket layer initialized [  100.076601] Bluetooth: RFCOMM ver 1.11 [  166.099911] Bluetooth: hci0: command 0x1003 tx timeout [  166.100849] Bluetooth: hci0: unexpected event for opcode 0x1003

Bluetooth is on but can't find or be found by any other devices.  Output of sudo service bluetooth status:  ● bluetooth.service - Bluetooth service    Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled; vendor preset: enabled)    Active: active (running) since ხუთ 2015-06-04 22:33:18 GET; 13min ago  Main PID: 26678 (bluetoothd)    CGroup: /system.slice/bluetooth.service            └─26678 /usr/sbin/bluetoothd -n  ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPAG ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPHS ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSource ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSink ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPAG ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPHS ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSource ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSink ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Adapter /org/bluez/26678/hci0 has been enabled ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Adapter /org/bluez/26678/hci0 has been enabled   Output of lsusb:  Bus 003 Device 005: ID 0a5c:21d7 Broadcom Corp. BCM43142 Bluetooth 4.0   How can I fix it?


Given any $\beta \in R$, do there exist integers $k,l,m$, and a real number $x$ such that:  $l=4x^{3}m+6x^{2}m^{2}+4xm^{3}-2xm$,  as well as  $x^{4}-x^{2}=k+\beta$ ?

An  can be identified by its  together with isolating intervals with rational bounds for its real and imaginary parts. The degree of an algebraic number is the  of its minimal polynomial. There are known algorithms that allow to easily compute sum and product of algebraic numbers in this representation, raise them to a rational power, extract real and imaginary parts, compare them, or evaluate them numerically to an arbitrary precision.  Is there an efficient algorithm that given an algebraic number $\alpha$ in this representation can decide if $\alpha$ can be represented as a sum or product of algebraic numbers of smaller degree?


Is there any toolbox or app that will support issuing shutdown command via ssh to a rooted android smartphone? Note that I'm not asking  – but to really shut it down / turn it off.

I'm looking for the best / friendliest way to reboot my rooted android 4.1.1 device. I found these solutions so far:   su -c "reboot" - Causes problems with wifi after restart on my device... I read that this can cause a currupt file system in some cases... Doesn't work via ssh for me. toolbox reboot - Same concerns here, but works via ssh. reboot -d 8 -f - causes problems after restart e.g. some apps wont start busybox killall system_server - "Hot Reboot" (not really a system restart) start|stop - Starts/stops Android Runtime (not really a system restart)   What is the device doing exactly when I'm pushing the (hardware) power button? I guess that's the most friendly way.


was flagged by the system as vandalism, because the user had just deleted five of his old junk answers (need 10K rep to see):          Notice that these are all zero-voted and 3 of the 5 questions are closed!  So, I flagged this: "Not vandalism. These are all zero-voted answers on Q's that were either closed or have better answers."  I've flagged this way probably a dozen times, and it's always been found "helpful".  This time, the flag was declined -- meaning that the deletions were vandalism! (The decline-message was the standard "a moderator reviewed your flag, but found no evidence to support it".)  Yet, all 5 answers remain deleted.  Shouldn't they be restored if it was vandalism to delete them?  So, was this vandalism? Was the mod having an off moment? Something else?

I flagged a post and (choose one)   my flag was marked as helpful, yet nothing was done my flag was marked as declined, yet the post was deleted/edited/closed   Why?


What's the difference between <b> and <strong>, <i> and <em> in HTML/XHTML? When should you use each?


Standard cat concatenates files line by line (row by row, if you will). I find myself needing a horizontal cat command more and more often recently; i.e. a command that takes a list of files and concatenates them horizontally, column by column. So far I’ve used ad-hoc workarounds but I’d like to know if there exists a good solution for this.  To clarify, consider the following comparison between cat and hcat of two files:  $ cat a.dat 1.dat a b c d 1 2 3 4 $ hcat -s ' ' a.dat 1.dat a b 1 2 c d 3 4   (Unlike for cat we need to specify a separator since by convention UNIX files don’t have a column separator at the end.)

I am searching for a nice method of merging two or more files line by line using the zipper method (also called late merge). Assuming we have three files, the result should look like this:  line1 file1 line1 file2 line1 file3 line2 file1 line2 file2 line2 file3 ...   EDIT  I wrote a little python script capable of doing this:  #!/usr/bin/python  import sys, itertools  fileList = [] for file in sys.argv[1:]:     f = open(file, "r")     fileList.append(f.read().split("\n"))  for z in itertools.izip_longest(*fileList):     print "\n".join([i for i in z if i is not None])   I still wonder if there is any standard tool or a clever combination of them doing the same thing.


I want to switch layouts with Print Screen, which conveniently sits under the right thumb on my ThinkPad keyboard. I configure it so in the Keyboard settings and it works! HOWEVER every time I press Print Screen, a giant layout indicator appears in the center of the screen and stays there for a couple of seconds. If the layouts are switched with Shift+PrtSc, then the indicator disappears quickly.  Is there any way to switch layouts without making the indicator appear at all? I'm asking because it used to work well on 15.10.  EDIT: Works, posted an  to .

Since I installed 17.10, when switching language with the assigned keyboard shortcut I get this switcher "window" that obstructs me from typing for a couple of seconds. And yes, a couple of seconds is a huge amount of time when switching languages a lot.      This happens both in X11 and Wayland but doesn't happen (the obstructive window will not appear) when I switch language by clicking on the lang indicator on top bar. Is there any way to tell this window "please go away"?


If $f(x)$ and $g(x)$ are two Riemann Integrable functions on the Interval [a,b] such that $f(x)<g(x)$ on $[a,b]$. Then $\int_a^b f(x)<\int_a^b g(x)$. How can we prove this without using Measure Theory or Lebesgue Integration.

In an exercise session of an analysis course (which covers Riemann integration and differentiation in one dimension rigorously) the following question came up:  Suppose $f$ is strictly positive and integrable (on some compact interval $[a,b]$ on the real line). Can we show that $\int_a^b f > 0$?  The proof by using measure theory and Lebesgue integration is easy, but also beyond the students at this point. So can one do without machinery such as sets of zero measure?    Tools in use: Mean value theorems, fundamental theorem of calculus, Riemann's condition for integrability (upper and lower integral within every epsilon of each other implies integrability), Riemann-Darboux integral, usual integration and differentiation techniques, as well as elementary real analysis in the epsilon-delta style.


I have a parent program that calls a worker console app when and update is found to update the files, this application gets the process ID from the parent via arguments and then calls WaitForExit(). What I wish to know is what would be the best way of then restarting that process, would simply calling Proc.Start() be the best way of doing this? Ex:  static void Main(string[] args) {     if (args.Length == 2)     {         int ParentID = Convert.ToInt16(args[1]);         Process ParentProc = Process.GetProcessById(ParentID);         ParentProc.WaitForExit();         Console.WriteLine(UpdateHandler.GetUpdates(             Path.GetDirectoryName(ParentProc.MainModule.FileName), args[0]));         ParentProc.Start();     }     else         Console.WriteLine("Error: Invalid number of arguments."); }   Or should I create a new process to launch it (I would assume using ParentProc.MainModule.FileName)  I would also like to know if there is a managed way to get the parent process not via arguments?  Thanks :)

I was looking a lot for method to get parent process in .NET, but found only P/Invoke way.


Let $f: X \xrightarrow{} Y $and $A,B \subseteq Y. $ Show that if $A \subseteq B, $ then $f^{-1}(A) \subseteq f^{-1}(B)$   I'm having a tough time getting started with this one so if someone could push me in the right direction, I'd greatly appreciate it.

If $A\subseteq B$ under what conditions is $f^{-1}(A) \subseteq f^{-1}(B)$, where $f^{-1}$ is the preimage, not  the inverse.


$("#dataTable tbody").on("click", "tr", function(event){     alert($(this).text()); });   is this syntax is for tr's which are already on the Page ?  and if not , What is the syntax for future tr's  elements ?

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I do not understand what's going on in these cases:  Math.abs(40.35 * 100) ->4035 Math.abs(40.36 * 100) ->4036 Math.abs(40.37 * 100) ->4036.9999999999995 Math.abs(40.38 * 100) ->4038.0000000000005 Math.abs(40.39 * 100) ->4039   Why does this happen? I though math.abs() returns absolute values (?).  Thank you a lot   EDIT* Thanks for the referencing link, did not find anything like that

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


I created a class, ProcessQueue:  //ProcessQueue.h template<class T> class ProcessQueue{ public:     void addTask(T param);     void clearQueue();     void addSetup(void (*setup)());     void addProcess(void (*process)(T));     void addCleanup(void (*cleanup)());     void setup();     void finish(); private:     //Some private fields and functions that aren't relevant }   addSetup and addCleanup add functions that are performed when setup and finish are called (The function pointers are then stored in a vector, but that shouldn't matter). addProcess should accept a void function that inputs a variable of type T, and addTask adds a variable of type T to a processing queue.  When clearQueue is called, the class iterates over each T that has been added and calls the various "process" functions that have been added to the ProcessQueue.  In another file (kernel.cu), I use a ProcessQueue to process the results of a computation:  (Note that this is part of the host code of the cu file, so it is regular C++. runRecord is simply a c-style struct)  //kernel.cu ProcessQueue<runRecord> queue;  #ifdef PRINTTOFILE queue.addSetup(setupPrintToFile); queue.addProcess(processPrintToFile); queue.addCleanup(cleanupPrintToFile); #endif  #ifdef PRINTRESULTS queue.addProcess(printRecord); #endif  queue.setup();  //Do some computation //Add the results to the ProcessQueue  queue.clearQueue(); queue.finish();   Some other function declarations that may be relevant:  //Various .h files void setupPrintToFile(); void processPrintToFile(runRecord r); void cleanupPrintToFile(); void printRecord(runRecord rec);   When I compile this, I get a few error messages:  1>kernel.cu.obj : error LNK2001: unresolved external symbol "public: void __thiscall ProcessQueue<struct runRecord>::addTask(struct runRecord)" (?addTask@?$ProcessQueue@UrunRecord@@@@QAEXUrunRecord@@@Z) 1>kernel.cu.obj : error LNK2001: unresolved external symbol "public: void __thiscall ProcessQueue<struct runRecord>::clearQueue(void)" (?clearQueue@?$ProcessQueue@UrunRecord@@@@QAEXXZ) 1>kernel.cu.obj : error LNK2001: unresolved external symbol "public: void __thiscall ProcessQueue<struct runRecord>::addSetup(void (__cdecl*)(void))" (?addSetup@?$ProcessQueue@UrunRecord@@@@QAEXP6AXXZ@Z) 1>kernel.cu.obj : error LNK2001: unresolved external symbol "public: void __thiscall ProcessQueue<struct runRecord>::addProcess(void (__cdecl*)(struct runRecord))" (?addProcess@?$ProcessQueue@UrunRecord@@@@QAEXP6AXUrunRecord@@@Z@Z) 1>kernel.cu.obj : error LNK2001: unresolved external symbol "public: void __thiscall ProcessQueue<struct runRecord>::addCleanup(void (__cdecl*)(void))" (?addCleanup@?$ProcessQueue@UrunRecord@@@@QAEXP6AXXZ@Z) 1>kernel.cu.obj : error LNK2001: unresolved external symbol "public: void __thiscall ProcessQueue<struct runRecord>::finish(void)" (?finish@?$ProcessQueue@UrunRecord@@@@QAEXXZ) fatal error LNK1120: 6 unresolved externals   I'm not too sure where the problem is. I've tried changing the template and function declarations, but it doesn't seem to help.  The compiler is nvcc v7.5.

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


I came across a question while buidling schema for my application.  When to use varchar(max) and nvarchar(max). I mean the exact use cases where it should be applied. I have surfed in net too but I was able to get the exact answer.  Could anyone suggest some exact usecase.

Is it just that nvarchar supports multibyte characters? If that is the case, is there really any point, other than storage concerns, to using varchars?


I have installed Tex live 2013 Version 3.1415926 and I want to install the package mdframed.  My first try was to enter in the terminal  tlmgr install mdframed   but the terminal responded to me that I am not allowed to do that. When I entered  sudo tlmgr install mdframed   I gained the message "tlmgr: command not found". So I typed   sudo -i   added the tex path in /root/.bashrc and finally entered  tlmgr install mdframed tlmgr update mdframed   and it worked! But if I compile my latex file the error   ! LaTeX Error: File `mdframed.sty' not found.   remains. Any Idea how to solve it?  EDIT: Output of  kpsewhich mdframed.sty   is  /usr/local/texlive/2013/texmf-dist/tex/latex/mdframed/mdframed.sty

Debian and Ubuntu have very good texlive packaging. But I'd like to use tlmgr to have a more fine-grained control about upgrades and which packages I want to be installed.   So how do I install "vanilla" TeXLive on Debian/Ubuntu?   Also how do I make dpkg aware that I have TeXLive installed?


I have a server with Ubuntu 18.04 installed and it does not have access to the internet. How would I install external drivers and programs if I cannot use  sudo apt get  etc..?

I have a friend who has got a computer that is not connected to the Internet. Is there any way to install software offline easily?


I will use the notation and language of Stichtenoth, Algebraic Function Fields and Codes.  Let $F$ be a function field over a finite field $\mathbb F_q$, $S$ a non empty set of places (possibly infinite) and $O_S$ the holomorphy ring of $S$, i.e., $O_S:=\bigcap_{P\in S} O_P$ (being $O_P$ the valuation ring of the place $P$).  Give necessary and sufficient conditions for $O_S$ to be a Principal Ideal Domain.  Many thanks in advance!  G.


Why in below sentence writer has used past perfect tense i.e. since Daesh had taken?     This was my third trip to Iraq in 10 years and my second since Daesh had taken over several areas of the country.   As per my knowledge we can use present perfect:     This was my third trip to Iraq in 10 years and my second since Daesh has taken over several areas of the country.   Because Iraq is presently in the possession of Daesh.  Or simple past tense here:     This was my third trip to Iraq in 10 years and my second since Daesh taken over several areas of the country.   Because I think there is no need to explain which event happen first and which second.  .

I have never had this problem before. But after seeing some questions posted on ELU, I started to doubt. I have been through links1, pages of grammar books2, a lot of questions3 posted here and ELU. I now still can't seem to understand how the past perfect is exactly used. The references sometimes even contradict each other.  What I had understood so far was      The past perfect is not necessary if we are not 'going back' to the earlier past, and simply moving from one event to another.   but I then saw a lot of other 'rules' including      If the sequence is clear, the past perfect is not needed.   which is slightly different, less 'narrow' and can be applied in more situations than the first ruleA, and      The past perfect is optional only when talking about an action at a specific time.   This is confusing. Can anyone here clarify things out please?    A For example, for  Doing the survey [completed] -> Showing the result      We showed the result of the survey we did.      If the second rule is applied, the sentence above is fine (the sequence is clear), but not if the first rule since we are not moving from any event to the next and possibly even going back.    1  and   2 Practical English Usage (2005) by Michael Swan, Collins Cobuild Student's Grammar (1991). Upper-Intermediate Cutting Edge.  3 including , , ,  etc.


I am anxious to replace an outdoor faucet but sick of it leaking and splashing back on turning on and off. There’s mystery holes above where the hoses connect that causes the leaking. Very confusing... and the amount of paint on it is confusing me on what I can unthread and replace. Very subtle I can make out the number 76-100 8 ? Any intel on replacement parts or procedures appreciated. There’s not much pipe sticking out so I’m hoping to avoid pipe cutting and soldering a new connection.

This adapter is attached to an outdoor spigot:    It is near the location of a former hot tub so I believe it has something to do with pressure control. When I attach a hose to it and turn it on if the hose is not flowing (e.g. a closed nozzle at the end) the water leaks (more like squirts, lots of it) from this adapter, it appears to be from the holes and not the connection to the spigot or the hose.  What is this thing? Is there a way to utilize it? I'd like to remove it so I can use this spigot but when I try to unscrew it with a wrench it does not budge - in fact the spigot itself starts to rotate. I wasn't really able to tighten a pipe wrench to the spigot due to the available clearance & pipe width.  There appears to be a rivot on the under side of the adapter but it is difficult to tell, it is somewhat rusted over.  Follow Up  My original concern was water leaking from it when it was used. While a plumber was on site doing a different job I asked him to look at this to see if something was wrong. He said the vacuum breaker wasn't working properly and ended up replacing the entire hose bib (with new vacuum breaker), I presume because he was not able to remove the vacuum breaker as well or it wasn't salvageable. Now no water spews out when it is used.


I like to organize things, and if it was up to me, all the contacts from contacts.google.com would be inside a group. most of them are, but I cannot find the ones that are not. Is there a way to filter my contacts to show this?

Possible Duplicate:          In Google Contacts, I've had Groups set up which look like this: All Contacts.. Family.. School.. Work.. etc.  Each contact I have is assigned to All Contacts. In addition, it is assigned to at least one more Group.  Sometimes when I add contacts, I forgot to bucket them in the respective groups, so I was wondering is there anyway I could do a search for contact that belongs toAll Contact-group, but does not belong to any other group ?


chmod is used to change permissions of files/directories and generally use syntax like - chmod xyz <file-or-directory>  where x, y, z numeric values of permissions for user, group and others but from , I can see 4 numeric values for permission like - sudo chmod 4755 /opt/google/chrome/chrome-sandbox  I'm unable to understand what is that 4th numeric value for. Please help to understand it.

When I install a program, it recommends me to do chmod 4555. Okay, i know about values if I just use three numbers. For example  chmod 555 test-file   will give  -r-xr-xr-x   4 for write, 2 for read and 1 for execute. But, when I do this:  chmod 4555 test-file   it gives me  -r-sr-xr-x   So, x changed to s. What's that mean?


$$x_{n+1} = \frac 12 x_n + \frac 1 {x_n}, x_0 \neq 0$$ $$ a = \frac a2  + \frac 1a \Rightarrow a = \frac {a^2 + 2} {2a} \Rightarrow 2a^2 = a^2 + 2 \Rightarrow a^2 = 2 \Rightarrow a = \pm \sqrt 2$$  If $x_0 > 0$, then any subsequent terms will be positive too. If $x_0 < 0$ , then - negative. Hence, if $x_0 > 0$, then $\lim_{n \rightarrow \infty} x_n = \sqrt 2$. If $x_0 < 0$, then $\lim_{n \rightarrow \infty} x_n = - \sqrt 2$  Is it complete solution? I know that it's correct answer, but may be I missed something in proof?

a) Let $a>0$ and the sequence $x_n$ fulfills $x_1>0$ and $x_{n+1}=\frac{1}{2}(x_n + \frac{a}{x_n})$ for $n \in \mathbb N$. Show that $x_n \rightarrow \sqrt a$ when $n\rightarrow \infty$. I have done it in two ways, but I guess I'm not allowed to use the first one and the second one is incomplete. Can someone please help me?  We already know $x_n \rightarrow \sqrt a$, so we do another step of the iteration and see that $x_{n+1} = \sqrt a$.  Using limit, $x_n \rightarrow x, x_{n+1} \rightarrow x$ (this is the part I think it's incomplete, don't I have to show $x_{n+1} \rightarrow x$, how?), we have that   $$x = \frac x 2 (1 + \frac a {x^2}) \Rightarrow 1 = a/x^2 \Rightarrow x = \sqrt a$$ b) Let the sequence $x_n$ be defined as $x_{n+1}= 1 + \frac 1 {x_n} (n \in \mathbb N), x_1=1$. Show that it converges and calculate its limit. "Tip: Show that sequences $x_{2n}$ and $x_{2n+1}$ monotone convergent to the limit." I didn't understand the tip, how can this help me? Does it make a difference if the number is odd or even? Thanks in advance!


I have in my sql table different kinds of barcodes.   My Barcodes starting with 0 example   05212365489787 0000000290098 0000000000103   I want to remove all starting 0 from my barcodes.   Example result want to be:  5212365489787 290098 103   I found this Code: But i want to update them:  select SUBSTRING(str_col, PATINDEX('%[^0]%', str_col+'.'), LEN(str_col)) from table1   something like that   update table1 set Barcode =(SELECT SUBSTRING(Barcode, PATINDEX('%[^0 ]%', Barcode + ' '), LEN(Barcode)) FROM table1 )   but i get error Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

I am working on a SQL query that reads from a SQLServer database to produce an extract file. One of the  requirements to remove the leading zeroes from a particular field, which is a simple VARCHAR(10) field. So, for example, if the field contains '00001A', the SELECT statement needs to return the data as '1A'.  Is there a way in SQL to easily remove the leading zeroes in this way? I know there is an RTRIM function, but this seems only to remove spaces.


Please tell me that can it be the sign of diffraction? I mean can diffracted rays make this pattern?

So, when I point a laser at a piece of wire (pointed at a specific angle), a circle of light appears on a wall behind it (see image below). I am trying to see why this happens and if there are any readings on this. Could anyone give some tips on what I should search for or any references?   ()  So this is a problem for a physics tournament, but I haven't tried it myself yet. However I have found a video depicting what I mean.


I have exported the PATH but once I switch to a different terminal or reboot Debian, $PATH is reset. Here are the steps I take:  ~$ vim scripts.sh  #!/bin/bash echo "Hello"   I save it as mybash.sh and chmod with 755. Then I move it to my /root/scripts directory.  Then:  ~$ export PATH=$PATH:~/root/scripts   and it works, but once I reboot Debian, close or switch into another terminal, mybash.sh cannot be called.   Why doesn't it store PATH permanently?

This is irritating me. I seen several suggestions (all using different files and syntax) and none of them worked.  How do I set an environment variable for a specific user? I am on debian squeeze. What is the exact syntax I should put in the file to make ABC = "123"?


My UK visa was rejected once in 2013 and twice in 2018. how should I apply again

Over the course of time here on TSE, I have observed individuals whose pattern of visa applications is best described as ''...     serial refusals - Two or more consecutive visa refusals issued by the same regime to the same person. Commonly for the same, or nearly the same, reasons. In some visa regimes Serial refusals can have a cumulative effect wherein the applicant's credibility is increasingly eroded, especially when the application pattern suggests a secondary agenda.   A common thread appears to be the need to visit the destination country (especially Schengen, the USA, or the UK) with a special sense of urgency. Also common in these cases are the following types of questions...   Should I just reapply once again? What are my chances? What can I do to improve my odds in the future? Can I somehow address the previous refusals to avoid them being a burden on all future applications? How can I break the pattern?      NB: This question is intended as a canonical about serial refusals. I have never been personally denied a visa.


I am looking for a program like cat but with syntax highlighting. As an example I would like to display the content of one of my Python script highlighted in the terminal without using a pager like we do with cat filename.py.

Is there a variant of cat that outputs syntax-highlighted lines of code when used on a source file?  An idea: maybe vi[m] or another editor can be asked to dump the syntax-highlighted contents of said files to stdout and exit immediately?


At first I thought if I compress the disk, then I would get extra space. However, after doing the compression I lost 2.5GB. Then, I decompress the whole disk to regain the lost 2.5GB but I lost 1GB more!  I ran disk cleanup and ccleaner but it did not help. I also restart the Tablet PC but it didn't help neither. I have Acer switch 10.

To save some disk space I figured it might be a good idea to compress the VMware vSphere Client I have installed because I almost never use it.  I was surprised to find that it had the exact opposite effect on free disk space. I tracked it down further and found that it is related to compressing the Help folder. The loss of disk space is not reflected in the folder size.  I repeated the compress/decompress cylce three times to make sure another program did not coincidentally take up the disk space. It might be notable that the folder contains a large number of small files (≈ 30k).  Why is that so and can I somehow find other folders that I should decompress to save disk space?    Without compression:     With compression:


I have Python script which has numpy and PIL Python packages installed in virtualenv. But the package which I have installed I want to use in android code. Also want to execute script using button activity.  I have used Jython but seems not working at my end.   Is anyone have an idea that how can I used Python packages within android code?

We are working on an  version and this platform has a nice Python API..  However, there is nothing official about Python on Android, but since  exists, is there a way to let the snake and the robot work together??


Is there any easy way to parse machine generated log files? Here is 1 line from the file that I am trying to read and save to SQL.  import re  mytext='''2018-07-22 08:12:02 Receive DR [SMAC:PI_ID_VOP3_N_K_T] [SVC:vikan2] [ACT:vitp3] [BINF:] [FID:e6f97a4b-c4bc-4aa1-876b-3a5ce40b4cfd] [META:?spp?dl_err=%03%00% 00&] [from:ALERTS] [to:91985] [flags:-1:-1:-1:-1:1] [msg:132:id:e6f97a4b-c4bc-4aa1-876b-3a5ce40b4cfd sub:001 dlvrd:001 submit date:180722070002 done date:1807220 81157 stat:DEL err:000 text:] [udh:0:]  '''  values = re.search(r'SVC:(.*)]', mytext) print (values.groups())   Intead of returning only 'vikan2' it returns a long string...     ('vikan2] [ACT:vitp3] [BINF:]   [FID:e6f97a4b-c4bc-4aa1-876b-3a5ce40b4cfd',)   I am trying to convert the string to dictionary that will look like this...  {'log_date':'2018-07-22 08:12:02', 'log_entry':'Receive DR',      'SMAC': 'PI_ID_VOP3_N_K_T',      'SVC': 'vikan2',      'ACT': 'vitp3',      'BINF': '',      'FID': 'e6f97a4b-c4bc-4aa1-876b-3a5ce40b4cfd',      'META': '?spp?dl_err=%03%00%\n00&',      'from': 'ALERTS',      'to': '91985',      'flags': '-1:-1:-1:-1:1',      'msg': '132:id:e6f97a4b-c4bc-4aa1-876b-3a5ce40b4cfd',      'sub': '001',      'dlvrd': '001',      'submit date': '180722070002',      'done date': '1807220\n81157',      'stat': 'DEL',      'err': '000',      'text': '',      'udh': '0:'}     Update:  1) I am not able to read the "meta" field (i.e. did not return expected string '?spp?dl_err=%03%00%\n00&'  2) I am able to build the dictinoary using this code. But I am sure there must better way to do this.  svc = re.search(r'SVC:(.*?)]', mytext) smc = re.search(r'SMC:(.*?)]', mytext) act = re.search(r'ACT:(.*?)]', mytext) binf = re.search(r'BINF:(.*?)]', mytext) fid = re.search(r'FID:(.*?)]', mytext) from1 = re.search(r'from:(.*?)]', mytext) to1 = re.search(r'to:(.*?)]', mytext) flags = re.search(r'flags:(.*?)]', mytext) msg = re.search(r'msg:(.*?)\s', mytext) sub = re.search(r'sub:(.*?)\s', mytext) dlvrd = re.search(r'dlvrd:(.*?)\s', mytext) submit_date = re.search(r'submit date:(.*?)\s', mytext) done_date = re.search(r'done date:(.*?)\s', mytext) stat = re.search(r'stat:(.*?)\s', mytext) err = re.search(r'err:(.*?)\s', mytext) text = re.search(r'text:(.*?)]', mytext) udh = re.search(r'udh:(.*?)]', mytext)  mydict=dict()  mydict['SVC'] = svc.groups()[0] mydict['SMC'] = smc.groups()[0] mydict['ACT'] = act.groups()[0] mydict['BINF'] = binf.groups()[0] mydict['FID'] = fid.groups()[0] mydict['from'] = from1.groups()[0] mydict['to'] = to1.groups()[0] mydict['flags'] = flags.groups()[0] mydict['msg'] = msg.groups()[0] mydict['sub'] = sub.groups()[0] mydict['dlvrd'] = dlvrd.groups()[0] mydict['submit_date'] = submit_date.groups()[0] mydict['done_date'] = done_date.groups()[0] mydict['stat'] = stat.groups()[0] mydict['err'] = err.groups()[0] mydict['text'] = text.groups()[0] mydict['udh'] = udh.groups()[0]

I have this gigantic ugly string: J0000000: Transaction A0001401 started on 8/22/2008 9:49:29 AM J0000010: Project name: E:\foo.pf J0000011: Job name: MBiek Direct Mail Test J0000020: Document 1 - Completed successfully  I'm trying to extract pieces from it using regex. In this case, I want to grab everything after Project Name up to the part where it says J0000011: (the 11 is going to be a different number every time). Here's the regex I've been playing with: Project name:\s+(.*)\s+J[0-9]{7}:  The problem is that it doesn't stop until it hits the J0000020: at the end. How do I make the regex stop at the first occurrence of J[0-9]{7}?


My google search has unearthed "La Douleur Exquise" but that seems to carry mainly erotic or romantic connotations.  I wonder if there is a term from psychology that is more general, or that refers to the phenomenon of a child who does something only because he has been told not to do it.

What is another way of saying when you take pleasure in doing something that convention says you are not supposed to do ? (ie the word or expression that I am looking for is very similar to saying for example, I take "subversive pleasure" in talking loudly in the library. I am not thinking of "perverse pleasure", though that is an equally good synonym, its just not the one that I can't think of.)


10-15 17:12:24.365 1102-1102/com.example.nurkan.iip E/AndroidRuntime: FATAL EXCEPTION: main                                                                         java.lang.NullPointerException                                                                             at com.example.nurkan.iip.Adapter.DAdapter.getItemCount(DAdapter.java:61)   public class DAdapter extends RecyclerView.Adapter<DAdapter.RecyclerViewHolder> {   Activity activity;  private List<Dannye> heroes;  public DAdapter(Activity activity, List<Dannye> heroes) {     this.heroes = heroes;     this.activity = activity; }  @Override public RecyclerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {     View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_dannye, parent, false);     return new RecyclerViewHolder(view); }  @Override public void onBindViewHolder(final RecyclerViewHolder holder, int position) {      final Dannye dannye = heroes.get(position);     holder.bind(dannye);  }  @Override public int getItemCount() {     return heroes.size(); }   public class RecyclerViewHolder extends RecyclerView.ViewHolder {     private TextView hour;     private TextView urok;     private TextView spes;     private TextView aut;       private RecyclerViewHolder(View itemView) {         super(itemView);         hour = (TextView) itemView.findViewById(R.id.TWhour);         urok = (TextView) itemView.findViewById(R.id.TWlesson);         spes = (TextView) itemView.findViewById(R.id.TWspes);         aut = (TextView) itemView.findViewById(R.id.TWaut);     }      public void bind(Dannye heroModel) {         hour.setText(heroModel.hour);         urok.setText(heroModel.lesson);         spes.setText(heroModel.spes);         aut.setText(heroModel.aut);     } }   }  //проблема в   @Override public int getItemCount() {     return heroes.size(); }

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?


If H is a subgroup of a group G and if every Left Cosets of H are Right Cosets of H, show that H is normal in G   As per the question, consider a left coset $aH$ and a right coset $Hb$ such that $aH=Hb$, $a,b\in G $ and $a\neq b$.  If $a=b$ then H is normal in G, by the definition of normal subgroup.   My question is if $aH=Hb$ then does it imply $a=b$ always? Please answer

Let $G$ be any group, and $H \leq G$ a subgroup.  Suppose that for each $x \in G$, there exists a $y \in G$ such that $xH \subseteq Hy$. In other words, every left coset of $H$ is contained inside some right coset of $H$.  Question: what can we say about $H$? In particular, does this imply that $H$ is normal?  I know that if $G$ is finite, then $H$ must be normal, because then $xH \subseteq Hy$ implies $xH = Hy$, since $|xH| = |Hy|$.


I was just wondering about the line that nothing can surpass the speed of light but if we try to observe it from an accelerating frame.  Does reference frame have any effect on light?

The speed of light is the same in all inertial frames.  Does it change from a non-inertial frame to another? Can it be zero?  If it is not constant in non-inertial frames, is it still bounded from above?


I need to write a simple bash script that kills a python script that is running in a terminal window. I'm assuming it will use kill -PID but I don't know how to get the PID of something based on what's running.  I'm sure this is elementary for someone experienced in bash scripts, but I am very new to the topic.  I appreciate all of your time, thanks so much!

I am running a program in the terminal that I can't escape with Ctrl-C and that I want to kill. How can I find its PID?


I have a 5v dc supply generated from voltage divider and this 5v is used to drive L293d.  But the problem is as soon as 5v supply is given to L293d the voltage drops to less than 2v.  what could be the problem??

Once again I need your help in my project. I have a 4,5v powered circuit. I put a voltage divider with 2 resistors in series to reduce my initial voltage of 4.5 V to 3.4 V (to feed an XBee module).  The issue is that if I do not connect the xbee, the voltage divider reduces the input voltage to the desired voltage(3.4 V), but when I connect the XBee module, the resulting voltage divider voltage drops to a value very low (0.85 V), making the XBee malfunction. Surely it is a basic mistake, I am asking something that is very clear, but I'm newbies.   Basic Circuit:  Vin(4.5 V)-----R2(10 kΩ)---------R1(33 kΩ)--------GROUND                        |                        |                  Vout desired (3.4 V)                        |                        |                       XBee


Can someone please explain Doobly Doo (a Youtube slang for descriprion box below the video) origins in terms of its linguistic origin and author's motive adress a description box that way? I've seen a lot of sources which explain its meaning and first usage. But since it's an original phrase (is it?) I'd really like to know its language roots: does it root to a phrase with similar phonetics (doodle-doo)? I'm trying to figure out if it needs/can be adopted for other languages.  Would really appreciate your help. Thank you!  Best regards, Anthony  UPDATE: Thank you Josh for providing a link to a previous thread on the pharase. It has a point: "doobly doo" sounds like a familiar idiom that's much older than that, used to name something you don't know the name of.'  If it's possible we'll wait for more opinions. Once again only its linguistic roots/possible cultural references etc. Not who and when it first used. The latter is clear.

The word  is used by several different youtube channels as a different word for the youtube description bar. I've seen it used by the  and by .  Who was first to use and invent the term?


I'm trying to insert values to a table, but it kept giving me error msg saying the command not properly ended. I checked again and again, I don't see I miss any comma, semicoma, and the table name is correct (I also checked again and again), all column names are correct and in right order too (I checked it again and again too), and the spell of the command is also correct. So what's wrong with my code?  insert into fruits (fid,fname,quantities) values (1,'apple',3),    (2,'orange',2),    (3,'banana',5);


I need to prove that $\lim \limits_{x \to 1} x^3-4=-3$ with epsilon-delta.  My work  $\forall \varepsilon > 0 ,\exists \space \delta > 0: 0<|x-1|< \delta \implies |x^3-4+3| < \varepsilon$  Working with the consequent:  $|x^3-4+3| <  \varepsilon \iff |x^3-1| < \varepsilon \iff |x-1||x^2+x+1| < \varepsilon$  Multiplying the antecedent by $|x^2+x+1|:$  $|x-1|< \delta$ $/\cdot |x^2+x+1| \iff  |x-1||x^2+x+1|< \delta |x^2+x+1|$  Here i found a relation but i don't know how to proceed, and i don't know if this way is the best way to prove this. Any hints?

Problem: I need to formally prove that $$\lim_{x\to 1} x^3 = 1.$$ My work: This is what I have so far and I'm generally a bit stuck with these proofs from here onwards. Because$$-\epsilon < x^3-1 < \epsilon  =  | x^3-1 | < \epsilon,$$ then $$ -\epsilon < x^3-1 < \epsilon$$ $$-\epsilon+1 < x^3 < \epsilon +1$$ $$ \sqrt[3]{-\epsilon+1}< x < \sqrt[3]{\epsilon+1}.$$ Hoping that what I have done so far is correct. Am I right in thinking that $$ \sqrt[3]{-\epsilon+1}< x < \sqrt[3]{\epsilon+1}$$ is giving me an interval where $x$ is going to give me a $f(x)$ value that falls within the distance $\epsilon$ from the limit on the $y$-axis ? Or is this interval smaller than the $\epsilon$-distance on the $y$-axis?


I want to show that the following series is convergent and determine the corresponding limit value. $$ a(n):=\sum_{k=1}^n \frac{k}{n^2}$$ To show the series converges I used the ratio test: $$\left|\frac{k}{(n+1)^2}\right|\cdot\left|\frac{n}{k}\right|=\frac{n}{(n+1)^2}<1$$ So the series converges. But how can I go on now and calculate the limit value?

We have $$\dfrac{1+2+3+...+ \space n}{n^2}$$  What is the limit of this function as $n \rightarrow \infty$?  My idea:  $$\dfrac{1+2+3+...+ \space n}{n^2} = \dfrac{1}{n^2} + \dfrac{2}{n^2} + ... + \dfrac{n}{n^2} = 0$$  Is this correct?


This is different from similar questions I have found on this site as the code in question doesn't have any operators or brackets before the character limit to split easily on.  I have several long lines in python without operators or brackets before 79 characters.  As an example:  self.caller.parent.parent.parent.caller.parent.bar.ids.actionview.remove_widget(self.caller.parent.parent.parent.caller.parent.bar.ids.actionview.startbutton)   The above line has 72 characters before a bracket, and is within a function definition within a class so therefore with 4-char spacing per nest level, has 81 characters before a bracket.  What is the preferred way of dealing with this?

I have a long line of code that I want to break up among multiple lines. What do I use and what is the syntax?  For example, adding a bunch of strings,  e = 'a' + 'b' + 'c' + 'd'   and have it in two lines like this:  e = 'a' + 'b' +     'c' + 'd'


I signed up for Stack Exchange with my Google account. Stack Exchange gave me a username automatically, like some sort of a user code. Is this username changeable? How can I change it?

How can I change (or remove / reset ) my name on a site in Stack Exchange network?


I want to use a table in my answer. e.g  |-------------|----------------| | ShortCut    | Description    | |-------------|----------------|  I have posted an answer , which requires this kind of formatting.   Is it possible to have such formatting in stackoverflow Questions & answers ?    If yes, How ? If no, why ?   Edit : I tried to use following code directly in editor of SO. But it didn't work for me.

 hello	 hello2

 hello3	 hello4

It seems like a lot of people try to display tables in Stack Overflow questions, but don't do a very good job. Is there Markdown syntax that supports creating a proper table?


I am a newbie to composite editing, and I followed this green screen tutorial on youtube: .  I have audio in the VSE synced up also. I have the start frame and end frame starting at a different place (other than frame 1) to cut out unwanted footage. Everything looks great in the Composite Viewer but for some reason it renders black.

In solid mode with Material or Texture, it is shown fine.   But in the Render mode, everything is pitch black. I have a sun, and the Opacity of the scene is set to 100%.    I am new to using Blender, so I have no idea what is wrong. If you could help, I would appreciate it. If you need more information to help me, I would be glad to give it.


Are there any site with database templates for specific purposes? (i.e. a database schema for users and authentication in a webpage) for different databases like Oracle, MySQL...  I have been looking in the Web but I didn't find anything and I think it would be very useful to share this knowledge. What I found are images of schemas that are useful also.

Where can I find ready-to-use database models ?  I don't need a database with data in it, but only schemas (UML diagrams). Perhaps something like the , but much more complex and real world.


I dealing with a domain controller which was recently compromised.  There is no valid backup to recover from.  I'm trying to join a new machine to the domain so that I can promote it and take over the FSMO roles So i can decom the compromised machine, however I cannot get the new machine to join the domain. The error its giving is 'The network path could not be found'.   I noticed that the shares on the DC cannot be accessed when using its local IP (192.168.3.251), either on the DC itself or some other machines on the network.   I can see the shares, however, if i browse to 127.0.0.1.   I have tried resetting the NIC with...     nbtstat -R  nbtstat -RR  netsh int reset all  netsh int ipv4 reset  netsh int ipv6 reset  netsh winsock reset   But that hasnt made any difference.   Any suggestions on what I can do to get the shares working again? Thanks in advance :)

I have a standalone domain controller that was recently compromised. I've isolated it and cleaned it up, but I need to set about replacing it.   I've built a replacement, however when I try and join the domain, I'm getting 'The network path was not found'. It does prompt for credentials, so its like it can see the domain, but after about 30 seconds, it errors.     I've googled the hell out of this and I've tried various things with no success so far.  I believe DCDiag has shed some light on the cause of the issue, however I've not sure where to go from here...   Performing initial setup:  Trying to find home server...  Home Server = {machinename}  [{machinename}] Directory Binding Error 1722: The RPC server is unavailable. This may limit some of the tests that can be performed. * Identified AD Forest. Done gathering initial info.  Testing server: Default-First-Site-Name\{machinename}   Skipping all tests, because server {machinename} is not responding to directory service requests.   Any help or suggestions welcome!


Let $n$ be a natural number and let $\langle n\rangle$ denote the closest integer to $\sqrt n$. Evaluate $$\sum_{n=1}^  \infty \frac{2^{\langle n\rangle}+2^{-\langle n\rangle}}{2^n}$$ I started putting the values of $n$ to see a pattern. It looks like a Geometric Progression but I am unable to sum it. Also, if a better approach exists, please share. Thanks.

How can I obtain the limit of the series     $$\sum_{n=1}^{\infty} \frac{2^{[\sqrt{n}]}+2^{-[\sqrt{n}]}}{2^n}$$   Where $[\ \ ]$ is .


I am looking for a simplified formula for a cubic equation in the form:  $$Ax^3+Bx^2+Cx+D=0$$  That solves for roots $r_1, r_2 $, and $r_3$ when the discriminant is positive and $r$ when it is negative. I am not looking for the complex roots or when the discriminant is zero.  Thanks in Advance,   Zach Hilman

In the first major studies into the magical properties of the complex number and the application to solving the cubic equation, Cardano did the following in around 1539:  He reduced the cubic equation  $ax^3+bx^2+cx+d$  to the form  $x^3=3px+2q$  where $p$ and $q$ are real numbers.   (1). How did Cardano get to this?  There was also another solution to the cubic, discovered before 1926, and it is often referred to as the (del Ferro-)Cardano solution, and is perhaps where Cardano went from in his first reduction. This solution is:  $x=(q+w)^{1/3}+(q-w)^{1/3}$  where $w=\sqrt{(q^2-p^3)}$.  (2). How is the del Ferro-Cardano solution derived?


I am trying to run the code found , but I get the error. I did not find the pgflibrary 'pgflibraryqrr.shapes.openrectangle.code.tex'.....  I put the files in the directory   C:\Program Files (x86)\MiKTeX 2.9\tex\generic\pgf\libraries\shapes  and did a Refresh FNDB in MiKTeX but I could not get the file to compile.  Can you tell me where I need to put the tikzlibraryqrr.shapes.openrectangle.code.tex file?  Thanks.  Here is the original code found :  \documentclass{book} \usepackage[explicit]{titlesec} \usepackage{fourier} \usepackage{tikz} \usepackage{epigraph} \usepgflibrary{qrr.shapes.openrectangle}  \definecolor{mybluei}{RGB}{0,173,239} \definecolor{myblueii}{RGB}{63,200,244} \definecolor{myblueiii}{RGB}{199,234,253}  \tikzset{ mynode/.style={   rounded corners=30pt,   shape=open rectangle,   open rectangle fill=myblueii,   open rectangle sides=#1,   } }  \titleformat{\chapter}[display]   {\normalfont\huge\sffamily}   {}   {20pt}   {%   \begin{tikzpicture}[remember picture,overlay]   \node[     anchor=west,     rectangle,     minimum height=4cm,     text width=\paperwidth,     xshift=-\the\dimexpr\oddsidemargin+1in\relax,     outer sep=0pt,     fill=myblueiii] (titlerect) {};   \node[     anchor=south west,     xshift=2cm,     text width=\textwidth]      at ([yshift=5pt]titlerect.south west) {\fontsize{30}{36}\selectfont#1};   \node[     mynode=nw,     anchor=south east,     fill=myblueii,     inner xsep=1.5cm,     outer sep=0pt,     font=\color{white},     minimum height=30pt]      at (current page.east|-titlerect.north)      {\bfseries\MakeUppercase{\chaptertitlename}\ \thechapter};   \end{tikzpicture}%   } \titleformat{name=\chapter,numberless}[display]   {\normalfont\huge\sffamily}   {}   {20pt}   {%   \begin{tikzpicture}[remember picture,overlay]   \node[     anchor=west,     rectangle,     minimum height=4cm,     text width=\paperwidth,     xshift=-\the\dimexpr\oddsidemargin+1in\relax,     outer sep=0pt,     fill=myblueiii] (titlerect) {};   \node[     anchor=south west,     xshift=2cm,     text width=\textwidth]      at (titlerect.south west) {\Huge#1};   \end{tikzpicture}%   } \titlespacing*{\chapter}   {0pt}{-20pt}{60pt}  \setlength\beforeepigraphskip{1.5\baselineskip} \setlength\afterepigraphskip{2\baselineskip} \setlength\epigraphwidth{6.8cm} \setlength\epigraphrule{0pt} \renewcommand\epigraphsize{\large} \renewcommand\textflush{flushright}  \let\oldepigraph\epigraph \renewcommand\epigraph[2]{%   \oldepigraph{\color{mybluei}\itshape #1}{#2}}   \begin{document}  \chapter{From the Ground Up!} \epigraph{In theory there is no difference \\ between theory and practice. \\ In practice there is.}{Lawrence ``Yogui'' Berra,1925 \\ New York Yankees baseball player} \chapter*{A test unnumbered chapter}  \end{document}

I am trying to run a rather simple code using tikz and a pgf library. My simple code is  \documentclass{book} \usepackage[explicit]{titlesec} \usepackage{fourier} \usepackage{tikz} \usepackage{epigraph} \usepgflibrary{qrr.shapes.openrectangle}  \begin{document}      This is a test document  \end{document}   This code was copied from Gonzalo Medina's answer in . When I run this code I get the error     '!Package pgf Error: I did not find the pgf library qrr.shapes.openrectangle'.   I am using TeXLive-2014 (actually I installed it yesterday) but nonetheless I updated all packages just in case, but that didn't seem to help.  Any idea how to use this specific library and why it cannot be found in the texmf trees?


In my classes, the subject of gerunds and infinitives comes up.  Students find this a confusing and frustrating subject.  They accept that one can say "I like watching movies," or "I like to watch movies," but they will usually ask, "Which one should I use?"  This question makes sense.  I have seen most teachers answer this by saying "It doesn't matter, they both mean th same thing.  Pick one that you like and use it."  I feel that there is a difference and that as native English speakers we intuitively know the difference and will choose the expression that conveys our meaning.  Sometimes, I feel that this choice is language mirroring.  If someone asks you "What do you like doing," you will probably answer with the gerund, "I like watching."  If they ask "What do you like to do," you will probably answer "I like to watch."  However, if you say to someone "Tell me about your interests," the person is free to answer, and some will give the gerund version and others will give the infinitive version.  My feeling is that infinitives express potential and gerunds express active things.  If you say "I like to watch TV." it means that this is something you like but don't really do it that much.  If you say "I like watching TV." it is probably something you do a lot.  On the flip side, you could also interpret "I like watching TV." as you like the activity but it doesn't mean you do it.  "I like mountain climbing," doesn't necessarily mean that I do it, have done it, or will do it.  What are your thoughts on this matter?

Some verbs are followed by ing, e.g. I enjoy swimming. We can't say I enjoy to swim. Likewise, some verbs are followed by to, e.g. I decided to make a plan.   Which particular verbs are followed by ing and to? Can you please provide a list for that?  Moreover, which verbs can be followed by both without having the meaning changed?


In the conversation in the car between Doe, Somerset and Mills we see that Doe justifies the murders of all the people he killed according to the seven sins. But how can he justify killing Tracy?

I recently watched David Fincher's 'Se7en' for a second time. I was thinking about the ending and I am kinda confused.  So clearly John Doe (Kevin Spacey) has a plan of killing seven different people based on . Now, near the end we come to know that John Doe himself is the representation of Envy. He then incites Detective David Mills (Brad Pitt) to kill him and become 'Wrath' in the process, which Mills clearly does. Now we are left with Mills, the representation of wrath, still alive. Detective Somerset (Freeman) tells Mills not to kill John Doe and further says,     If you kill him, he will win.   But doesn't that leave John Doe's plan incomplete? I mean Mills is still alive and I'm pretty sure that he wouldn't be sentenced to death for that and John Doe clearly set out to kill all the seven people. How exactly would John Doe 'win' in this situation?


I have looked all over but I can't really find  a clear example of this...  If $\mathbb{Z}_5$ is set $\{0,1,2,3,4\}$ prove that it is a field... I understand that from the table we can see that the set is commutative, associative, and it has an identity. I'm not sure how to show the inverse $-a$ is in $F$, but by the table we can see that for take $2$  is in $F$ then if the inverse exists $-2$ is in $F$, and $2 + (-2) = 0$ but in the table we can see that $2 + 3 = 0$ so then $-2 = 3$? But I am just confused how that is possible, I know maybe it has something to do with mod but not sure how to tie it all together

Check my proof please.  Let $\Bbb Z_p:=\Bbb Z/p\Bbb Z$ be the quotient ring modulo $p$. I want to prove that if $p$ is prime then $\Bbb Z_p$ is a field.  Known facts about the quotient rings of the kind $\Bbb Z_n$ (I dont list all the characteristics of a ring, just some ones):   They are commutative rings with unity. $[0]=[n]$ is the identity of addition or zero. Then $[n]+[a]=[a]$ and $[n]\cdot[a]=[n]$ for all $[a]\in\Bbb Z_n$. $[1]$ is the multiplicative identity or unity. Then $[1]\cdot[a]=[a]$ for all $[a]\in\Bbb Z_n$. The addition is defined as $[a]+[b]=[a+b]$, and the multiplication is defined as $[a]\cdot[b]=[ab]$. $[a]=[b]$ means that exists $z\in\Bbb Z$ such that $a=b+nz$. $|\Bbb Z_p|=p$.   A ring $\Bbb Z_p$ dont have zero divisors, i.e. doesnt exist $[a],[b]\in\Bbb Z_p$ distinct of $[p]$ such that $[a]\cdot[b]=[p]$. Proof by contradiction: suppose that exists such $[a],[b]$ distinct of $[p]$ that are zero divisors. Then exist some $z_j\in\Bbb Z$ such that:  $$(a+pz_1)(b+pz_2)=pz_3\iff ab+pz_4=pz_3\iff ab=pz_5$$  but this is a contradiction with the assumption that $a,b\neq p$ and $p$ prime, so dont exist divisors of zero on any $\Bbb Z_p$.$\Box$  For any $[a]\in\Bbb Z_p$ distinct of $[p]$ exist $[b]$ such that $[a][b]=[1]$. Because $\Bbb Z_p$ dont have zero divisors and is finite for some $[a]\neq[p]$ we have that if $[b]\neq[c]$ then $[a][b]\neq[a][c]$. Proof by contradiction: if $[a][b]=[a][c]$ in the above conditions then  $$[a][c]=[ac]=[ab]=[a][b]\iff ac+pz_1=ab+pz_2\iff a(c-b)=pz_3$$  for some $z_j\in\Bbb Z$. But $pz_3\in[p]$, then $[a][c-b]=[p]$ but because there are no zero divisors in $\Bbb Z_p$ then or $[a]=[p]$ or $[c-b]=[p]$ what contradicts the above conditions.$\Box$  Because $[a][b]\neq[a][c]$ for $[a]\neq[p]$ and $[b]\neq[c]$ then for any $[a]\neq[p]$ we have that  $$[a]\cdot\Bbb Z_p=\Bbb Z_p\implies \exists [b]\in\Bbb Z_p:[a][b]=[1]$$  In other words: every element of $\Bbb Z_p$ but $[p]$ have a multiplicative inverse as stated above.$\Box$  Because $\Bbb Z_p$ is a commutative ring with $[1]\neq[0]$ and have multiplicative inverse for all their elements but $[p]=[0]$ then $\Bbb Z_p$ is a field.$\Box$


Let $K$ be a field and $I=\langle x^2-yz\rangle$. I am trying to prove that $R=K[x,y,z]/\langle x^2-yz\rangle$ is not a UFD.    My idea is that $(I+y)(I+z)=(I+x)^2$. But I am unable to prove that $I+x, I+y$ and $I+z$ are irreducibles in $R$.   How to prove their irreducibility?

I am trying to show that $k[x,y,z]/(xz-y^2)\not\cong k[x,y]$.    The latter is a UFD, so I am trying to show the former is not. Clearly $x$ is not prime, since $x\mid xz$ which implies $x\mid y^2$, but $x\mid y$.      So if I can show that $x$ is irreducible then $k[x,y,z]/(xz-y^2)$ is a not a UFD, because irreducible implies prime in UFDs.    Attempt: Assume $x$ is reduced into $ab$ in $k[x,y,z]/(xz-y^2)$, then we know there exists $c\in k[x,y,z]$ such that $x=ab+c(xz-y^2)$ in $k[x,y,z]$, or more usefully as $x-ab=(xz-y^2)c$. Someone suggested that I write $a,b$ such they are degree at most 1 in $y$, that is, replace every $y^n$ using $xz$. This means the LHS is degree at most 2 in $y$ and the RHS is degree at least two in $y$ in  $x-ab=(xz-y^2)c$. I am not sure where to go from here just by knowing that $c$ has no $y$ terms though. Ultimately I want to show that this forces $x=ab$ in $k[x,y,z]$ which, since $x$ is irreducible there, shows that either $a,b$ is a unit, which means $x$ is irreducible in $k[x,y,z]/(xz-y^2)$.


If we increase the temperature of a volume of air it will rise up but if we look from molecular level, there kinetic energy has just changed but not thier weight so why they rise up and do not go in any other direction?

Why does hot air rise?  I did an experiment:  I made a model of hot air and cool air with marshmallows and toothpicks. The hot air had more volume than the cold air. Then, I weighed it. They both weighed the same, even though they had a different volume.  So I don't understand why does hot air rise?


This might be a very dumb question. I tried to reverse the input number and compare it.If they are same then, the output should be "the number entered is a palindrome" But, I'm getting out for every number like it is a palindrome.   package com.practise.examples;  import java.util.Scanner;  public class Practise  {     public static void main(String[] args) {           Scanner s=new Scanner(System.in);         System.out.println("enter the number to reverse it:\n");         int num=s.nextInt();         int revNum=0;          while(num!=0)         {             revNum=revNum *10;             revNum= revNum+ num%10;             num=num/10;         }         System.out.println("the reverse of the number is: " +revNum);              if(revNum==num)             {                 System.out.println("the number is a palindrome" );              }             else             {                 System.out.println("the number entered is not a palindrome");              }          }     }

How do I check if a number is a palindrome?  Any language. Any algorithm. (except the algorithm of making the number a string and then reversing the string).


I have found that keeping a detailed log of every command I run, from which path I ran it from and which user I sudo'd from, is extremely valuable as the years go by and I'm trying to remember what I did. Some time ago, after browsing various articles on this site as well as others I came up with a solution that works really well.  Here is what I have in my .bashrc:  SUDOUSER=`who am i | awk '{print $1}'` SUDOIP=`who am i | awk '{print $6}'` DT=`date +"%Y%m%d%H%M%S"`  export HISTCONTROL=ignoredups export HISTFILE=~/.history DETAILHISTORY=~/.historydetail  echo $DT $SUDOUSER:$SUDOIP[$$] \|\|\| $(finger $SUDOUSER | head -1) logged in on $(date) \|\|\| >> $DETAILHISTORY export PROMPT_COMMAND='trap "" 1 2 15; DT=`date +"%Y%m%d%H%M%S"`; history -a >(tee -a ~/.bash_history | while read line; do cwd=$(echo "$cwd" | sed "s|$HOME|~|g"); if [[ $line =~ ^#[0-9]*$ ]]       ; then continue; fi; echo "$DT $SUDOUSER:$SUDOIP[$$] {$cwd} $line" >> $DETAILHISTORY; done); if [[ $(history 1) == "cd" ]]; then cwd=$OLDPWD; else cwd=$PWD; fi; trap 1 2 15;'   I get output like this:  20180919150704 MyUsername:(192.168.24.207)[14090280] ||| Login name: MyUsername In real life: MyName logged in on Wed Sep 19 15:07:04 EDT 2018 ||| 20180919150704 MyUsername:(192.168.24.207)[14090280] {~} clear 20180919150708 MyUsername:(192.168.24.207)[14090280] {~} cd user_scripts/ 20180919150708 MyUsername:(192.168.24.207)[14090280] {~/user_scripts} ll 20180919150714 MyUsername:(192.168.24.207)[14090280] {~/user_scripts} cat file.sh 20180919151013 MyUsername:(192.168.24.207)[14090280] {~/user_scripts} cd 20180919151015 MyUsername:(192.168.24.207)[14090280] {~} cat .bashrc   Fantastic! It's saved my sanity so many times.  There is a down side however; every so often, out of the blue I'll get this message:  bash: cannot open named pipe /tmp//sh-np.5ARMam for reading: A system call received an interrupt.   and sometimes I'll get a whole bunch at once:  bash: cannot open named pipe /tmp//sh-np.4QRMal for reading: A system call received an interrupt. bash: cannot open named pipe /tmp//sh-np.zqRMaj for reading: A system call received an interrupt. bash: cannot open named pipe /tmp//sh-np.y7RMai for reading: A system call received an interrupt. bash: cannot open named pipe /tmp//sh-np.6ARMan for reading: A system call received an interrupt.   I don't see any rhyme or reason for it; sometimes it happens when I adjust the size of the putty/terminal window, which I don't understand. This started happening when I added the detailed history logging (and stops when I disabled it).  Can anyone offer any guesses as to what portion of the history logging in PROMPT_COMMAND may be contributing to this issue, and even better how it might be prevented?

I want to generate a sorted list with all 8-digit numbers — from 00000000 to 99999999. I typed in the shell:  f() {  while IFS="" read -r line; do    for i in {0..9}; do         echo "$line$i";    done;  done }  echo | f | f | f | f | f | f | f | f | tee result.txt | wc -l   response is     bash: echo: write error: Interrupted system call bash: echo: write error: Interrupted system call bash: echo: write error: Interrupted system call 99998890   Why have I got these three errors and malformed result.txt ?  I use  GNU bash, version 4.4.12(1)-release (x86_64-pc-linux-gnu)  Debian GNU/Linux 9.6 (stretch)  Linux kernel: 4.19.0 #2 SMP Thu Nov 1 15:31:34 EET 2018 x86_64 GNU/Linux


I have this:  ql_gray='\033[1;30m' ql_magenta='\033[1;35m' ql_cyan='\033[1;36m' ql_orange='\033[1;33m' ql_green='\033[1;32m' ql_no_color='\033[0m'   I use them like so:  echo "${ql_magenta}quicklock: could not acquire lock with name '${qln}'${ql_no_color}."   but I get this:  \033[1;35mquicklock: could not acquire lock with name '/Users/me/.quicklock/locks/_oresoftware.lock'\033[0m.   is there some flag I need to set in order to get control chars to be recognized?  Is there some flag I can check to see if the end user has allowed control chars to be recognized? If they aren't recognized, then I can just set the above to:  ql_gray='' ql_magenta='' ql_cyan='' ql_orange='' ql_green='' ql_no_color=''   I need to support Bash versions 3+.

I'm aware of libraries in languages such as Ruby and Javascript to make colorizing your terminal scripts easier by using color names like "red".  But is there something like this for shell scripts in Bash, or Ksh, or whatever?


Suppose, $K_n$ is a complete simple graph with each edge label $k$. Then its adjacency matrix $A(K_n)$ has all the entries zero along the diagonal, and each non-diagonal entries are $k$.  What  are the eigenvalues or, the spectrum of $K_n$? Is there any known formula for this?

I have the following $n\times n$ matrix:  $$A=\begin{bmatrix} a & b & \ldots & b\\ b & a & \ldots & b\\ \vdots & \vdots & \ddots & \vdots\\ b & b & \ldots & a\end{bmatrix}$$  where $0 < b < a$.  I am interested in the expression for the determinant $\det[A]$ in terms of $a$, $b$ and $n$.  This seems like a trivial problem, as the matrix $A$ has such a nice structure, but my linear algebra skills are pretty rusty and I can't figure it out.  Any help would be appreciated.