..."Can" is more likely when you are addressing a particular person. "Can" expresses ability, so we tend to make some sort of appraisal of whether the person being addressed actually has that ability. When addressing a general audience, some of them may be so unimaginative that they cannot imagine whatever it is. "Could" is far less assertive,...  I've seen many native speakers use this sort of "when + present participle" construction where the subject of the main clause does not match with that of the dependent clause. Isn't this a case of dangling modifier? Or unlike "after + present participle" and "before + present participle", the construction "when + present participle" is an exception?

My case here is that I was writing something for school, and my teacher explained an error which I really can't see. She referred to articles about "dangling participles", which was previously unknown to me. I find it hard to relate the examples I've found about it to my situation. So this is a text I've written and the bold part is where the problem arises: (You could read only the bold part if you please)  Wandering, and lost in his thoughts, there is a deep despair occupying the mind of this man. He is barely aware of his surroundings, except for those few moments when the loud blissful voices break through the protective barriers, developed by his immense sadness and grave frustration, into his mind. ”How can they all possibly be so happy?” he thinks to himself. Staring blindly, with his head low, as he walks in a slow pace, whispering ”Mary, Mary, my Mary,” over and over again. Yesterday was her funeral. She had passed away from a severe type of cancer, at a relatively young age. It was his wife. They had been together since high school and were greatly attached to each other. Having spent nearly half his life by her side, we cannot but imagine his grief. Indeed, he could hardly picture a life without her. So, alone he roams in the midst of all the seemingly incessant cheering and noises, drowned by his sorrow.  Her comments on that part was:  we is slightly out of place here – see my comment below These few sentences are about him and his emotions, so ‘we’ seems out of place. If the sentence starts: ‘Having spent nearly half his life by her side’, the reader expects it to continue: ‘he’. After all we have not spent half our lives by her side.  Is she right? If so, could anyone try to explain why?


Hi I have a question about getting the names of properties of an object.  The context  I am retrieving some data from a database which I am trying to get the column headings from. I am carrying out an ajax request to get the data as JSON.   The code  var tableHeaders = "noHeaders"; var columns = []; $( document ).ready( function( $ ) {     $.ajax({         "url": 'ajaxScripts/getDynamicData.php',         "success": function(json) {              tableHeaders = "";             parsedData = JSON.parse(json);              $.each(parsedData[0], function(i, val){                 console.log(parsedData[0]);                 tableHeaders += "<th>" + val + "</th>";                 columns.push(val);             });              $("#headings").append(tableHeaders);             //$("#tableDiv").find("table thead tr").append(tableHeaders);              $('#demotable').DataTable({                 dom: "Bfrtip",                 data: parsedData,                 columns: columns             });         }     }); });   Table Sample  Name | Age | DOB | Height | Weight | Address | Hair Colour | Eye Colour    Steve| 24  | 22/11/1994 ...   The data gets returned as an array of Objects so I want to be able to retrieve the unique properties of those objects - The column headers (Name, Age, DOB etc)

Say I create an object thus:  var myObject =         {"ircEvent": "PRIVMSG", "method": "newURI", "regex": "^http://.*"};   What is the best way to retrieve a list of the property names? i.e. I would like to end up with some variable 'keys' such that:  keys == ["ircEvent", "method", "regex"]


Is it possible to record recent files operation? By operations i mean moving, renaming, deleting, creating etc. Not full log with seeks and stuff.

time is a brilliant command if you want to figure out how much CPU time a given command takes.  I am looking for something similar that can list the files being accessed by a program and its children. Either in real time or as a report afterwards.  Currently I use:  #!/bin/bash  strace -ff -e trace=file "$@" 2>&1 | perl -ne 's/^[^"]+"(([^\\"]|\\[\\"nt])*)".*/$1/ && print'   but its fails if the command to run involves sudo. It is not very intelligent (it would be nice if it could only list files existing or that had permission problems or group them into files that are read and files that are written). Also strace is slow, so it would be good with a faster choice.


How long will this apple compote keep in the fridge?

How do I know if a given food or ingredient I have is still good, or if I should discard it?  How can I best preserve a food or ingredient?     This broad question is intended as a "general reference" question to quickly answer many how long will food keep for? questions. Please feel free to edit this question to expand and clarify as needed.


I consider a very large non homogeneous cloud of dust in isolation. No external gravitational interactions. It is initially completely still and start collapsing under the its own gravity.  Can the separate gravitational collapse of denser subparts, interacting with the rest of the cloud, induce spinning motion in some of these subparts?  To avoid consideration of limit conditions, the cloud may be considered infinite.  I am interested in an answer primarily in Newtonian mechanics. But if relativity can change the answer, that is interesting too, as a complement.  The same goes for quantum mechanics (though I doubt it is compatible with my stillness hypothesis). BUT, my primary interest is pure Newtonian mechanics.  I did some research on the site, and this question has not been asked or answered previously with the explicit precondition of initial stillness of everything, i.e. lack of any relative motion between any two parts of any size.  My prime motivation for asking it is that all questions regarding motion and (angular) momentum seems to be answered somewhat tautogically by: there is this motion because there is that motion, exchanging this for that here and there.  Of course. collapse does create motion. So the question is really about spinning motion and orbital motion.  My own belief, though I do not have the math to prove it formally, is that lack of homogeneity is enough to cause the emergence of angular momentum in equal opposite amount in different parts of the cloud, so that the total angular momentum remains null.

In an older question from June 2011, , apparently revived by the system, a user is asking about the origin of the rotation of celestial bodies.  The  (with 17 votes) states the following:     When things collapse under their own gravity in space (i.e. clouds of gas and dust), any small amount of asymmetry in the collapse will be enough start it spinning.   And then it goes on saying:     Even if it spins by a tiny amount, as it collapses, angular momentum     conservation will mean it spins more and more quickly.   Is all this really correct?  I could try to ask in a comment to the answer. I actually did. But the author is no longer registered.  Hence I am asking it as a question.  But that is not the end of the story. As I was about to ask my question, I looked for other relevant questions, and there are some. I did not make an exaustive survey, but I did not find one that had satisfactory answers:    (december 2011) has just one accepted answer (0 votes) stating essentially that the solar system has angular momentum because it started from a cloud that had angular momentum. No comment.  (july 2011) is questionning about everything from galaxies to electrons. The answers are of a much higher quality, but while they seem to justify the possiblility of spin and angular momentum (and its conservation), there are not clear on how it appears, at least for celestial bodies.  (june 2013): That was my own very naive first question on this site. It is related but does not directly address spin.   One answer I found is that momentum appear from bodies in relative motion past each other. Nice, but not really an answer: where did they get their relative speed to begin with. Unfortunately the answer is: from the angular momentum of larger structures they belong to (well, it can be more comples). So this is just chicken and egg explanation. But how did it get started?  Note that my question is not a duplicate, since it is primarily whether the above statements are correct, which is not considered in these other questions.  Furthermore, these questions are fairly old, and given that none had received answers that seem to answer the question of the origine of existence of celestial angular momentum (not in a way I can understand anyway), it may be appropriate to attempt restarting the process, with the above discussion to motivate that an answer should explain the physical mechanism that started the existence of spin of celestial bodies.


I am reading the proof of the following theorem from Apostol's Introduction to Analytic Number Theory.  Theorem 1.2 Given any two integers a and b, there is a common divisor $d$ of a and b of the form $d=ax+by$, where $x$ and $y$ are integers. Moreover, every common divisor of $a$ and $b$ divides this $d$.  I'm stuck on the first step. The author used induction on $n$, where $n=a+b$ and assumed that the theorem has been proved for $0,1,2, \cdots, n-1$. I think the induction on $n$ should be an independent process where $n$ should be independent on other variables such as $a$ and $b$ here. For example, when we prove that binomial theorem: $$(x+y)^n=\sum_{k=0}^n\binom{n}{k}x^{n-k}y^k=\sum_{k=0}^n\binom{n}{k}x^ky^{n-k}$$ We would use the induction on $n$, and assume this equality holds for $0,1,2, \cdots, n-1$. However, $a,b$ are all constants, not relevant to $n$. What's wrong with my thought? For reference, the following is the whole proof from the book:  Here is a possible relevant: .

I've done proofs in discrete mathematics, but I'm still at the stage where proofs with more than a few steps make me uncomfortable.  From Apostol's Mathematical Analysis [2nd Ed.] on page 5, we have     Theorem 1.6. Every pair of integers $a$ and $b$ has a common divisor $d$ of the form   $$ d = ax + by $$   where $x$ and $y$ are integers. Moreover, every common divisor of $a$ and $b$ divides this $d$.   The proof (with my questions throughout) goes as follows:     Proof. First assume that $a \geq 0, b \geq 0$ and use induction on $n = a + b$. If $n = 0$ then $a = b = 0$, and we can take $d = 0$ with $x = y = 0$. Assume, then, that the theorem has been proved for $0, 1, 2, ..., n - 1$.   I am a little confused about taking $n$ to be $a + b$, since it's not obvious that all pairs $\{a, b\}$ would be covered by induction for all combinations of $a, b \in \mathbb{Z}$.     By symmetry, we can assume $a \geq b$. If $b = 0$ take $d = a, x = 1, y = 0$.   OK.     If $b \geq 1$ we can apply the induction hypothesis to $a - b$ and $b$, since their sum is $a = n - b \leq n - 1$. Hence there is a common divisor $d$ of $a - b$ and $b$ of the form $d = (a - b)x + by$.   I'm going to let $a' = a - b$, let $b' = b$ and let $d' = a'x + b'y$. (I wish Apostol did something like this to make his proofs clearer.)  I don't understand this logical step. Why does the fact that $a' + b' \leq n - 1$ imply that $d'$ exists and is a common divisor of $a'$ and $b'$? This seems like a huge leap.     This $d$ also divides $(a - b) + b = a$, so $d$ is a common divisor of $a$ and $b$ and we have $d = ax + (y-x)b$, a linear combination of $a$ and $b$.   At this point I am clueless. Why does $d$ divide $a$ and why does this imply it also divides $b$? And where does Apostol get $y-x$ from??     To complete the proof we need to show that every common divisor divides $d$. Since a common divisor divides $a$ and $b$, it also divides the linear combination $ax + (y-x)b = d$. This completes the proof if $a \geq 0$ and $b \geq 0$. If one or both of $a$ and $b$ is negative, apply the result just proved to $|a|$ and $|b|$.   Why not just do the entire proof with absolute values from the beginning?    Soft question: is it normal for authors to be very terse and not explain or give motivation for any steps? How do you go about trying to understand proofs that require a higher level of intuition than you currently have?


I want to select and rotate multiple metaballs (ie. an arm) but without success. Instead the individual objects happens to rotate around their corresponding centerpoints.     Even parenting wont do.  Have I missed something?  Translating multiple metaballs, though, (grabbing to move) works fine and expected.

today i run into another problem. i dont know how i have done it (probably i clicked sth what i should not click) - anyway - since that moment my objects are behaving totally different when i try to rotate them. the objects are now rotating around the pivot point but they keep their alignment - not sure if i am clear. eg. if u would rotate a plane which is lies flat on the ground it makes the rotation but the faces of the plane would still be up and dont which shouldn't be the case with the "normal" rotation that i know. so i want to understand what i have done (because this kind of rotation could be also usefull sometimes for me) and how can i return it in the case it happens again.


I've used this code to select the duplicate rows, it went right,   SELECT name, COUNT(name)    FROM emp  GROUP BY name  HAVING COUNT>1;   But it doesn't help me in deleting the same selected rows....  DELETE emp   WHERE name IN ( SELECT name, COUNT(name)                     FROM emp                    GROUP BY name                   HAVING COUNT >1);

I'm testing something in Oracle and populated a table with some sample data, but in the process I accidentally loaded duplicate records, so now I can't create a primary key using some of the columns.  How can I delete all duplicate rows and leave only one of them?


Im doing fyp on sabah & saraawak map. it came without prj file. i manage projected it and its allign to each other. but now i think the map is too small. as in the whole continent is within few hundred meters.    What is wrong here?

I have a Shapefile but its coordinate system is Unknown, and there is no *.prj file.   How can I identify it now?


I have a list of objects which I want to sort. But I have three different conditions. That is why I have this code:  Collections.sort(myList, new Comparator<MyObject>() {     @Override     public int compare(MyObject o1, MyObject o2) {         // my code     } });   Three times. First sorting all elements with condition x to the bottom of the list. Then a second time sorting all elements with condition y to the bottom and again for condition z.  Now I wonder how I could combine multiple conditions in one compare-method. So I don't have to do this three times.  Edit: To be more clear about the conditions. I want to sort all objects that have the criteria x to the bottom of the list. If an element fulfills criteria y it should be even below x and the same applies analog for z.

Assume you have some objects which have several fields they can be compared by:  public class Person {      private String firstName;     private String lastName;     private String age;      /* Constructors */      /* Methods */  }   So in this example, when you ask if:  a.compareTo(b) > 0   you might be asking if a's last name comes before b's, or if a is older than b, etc...  What is the cleanest way to enable multiple comparison between these kinds of objects without adding unnecessary clutter or overhead?   java.lang.Comparable interface allows comparison by one field only Adding numerous compare methods (i.e. compareByFirstName(), compareByAge(), etc...) is cluttered in my opinion.   So what is the best way to go about this?


How do you prove that a determinant is a linear transformation using the properties: $T(cx)=cT(x)$ and $T(u+v)=T(u)+T(v)$?  For instance, if you had a $3\times3$ matrix: $(1,1,2)+(x,y,z)+(1,2,1)$, how would you prove that taking its determinant with respect to the vector $(x,y,z)$ is a linear transformation?

I am trying to understand (intuitive explanation will be fine) why determinant is a multilinear function and therefore to learn how elementary row operation affect the determinant.  I understand that it has something to do with the definition of determinant by permutations, due to permutation being a bijection, in each product of the determinant there is just one entry from each row, but what's next?


Why do most of the physical equations have $\frac{1}{4\pi}$ as constants? I have seen that many equations have $\frac{1}{4\pi}$ as constants like Coulomb, pendulum problems, etc. Can anyone tell me why is like this?

I mean to ask why there is $4\pi$ present in force equations governing electricity? Though all objects in universe are not spherical and circular, the constant of proportionality in both equations contain $4\pi$. Why?


Is it possible to prove  $f: \mathbb{R} \to \mathbb{R}$ is continuous everywhere iff it is sequentially continuous everywhere  without the axiom of choice?

In my introductory Analysis course, we learned two definitions of continuity. $(1)$ A function $f:E \to \mathbb{C}$ is continuous at $a$ if every sequence $(z_n) \in E$ such that $z_n \to a$ satisfies $f(z_n) \to f(a)$. $(2)$ A function $f:E \to \mathbb{C}$ is continuous at $a$ if $\forall \varepsilon>0, \exists \delta >0:\forall z \in E, |z-a|<\delta \implies |f(z)-f(a)|<\varepsilon$. The implication $(2)\implies(1)$ is trivial (though I will happily post a proof if there is sufficient interest).  The proof of the implication $(1)\implies(2)$ is worth remarking on, though. Proof that $(1)\implies(2)$: Suppose on the contrary that $\exists \varepsilon>0:\forall \delta>0, \exists z \in E:\left (|z-a|<\delta \; \mathrm{and} \; |f(z)-f(a)|\ge \varepsilon\right )$.  Let $A_n$ be the set $\{z\in E:|z-a|<\frac{1}{n} \; \mathrm{ and }\; |f(z)-f(a)|\ge\varepsilon\}$.  Now use the Axiom of Choice to construct a sequence $(z_n)$ with $z_n \in A_n \; \forall n \in \mathbb{N}$.  But now $a-\frac{1}{n}<z_n<a+\frac{1}{n}\; \forall n \in \mathbb{N}$ so $z_n \to a$.  So $f(z_n) \to f(a)$.  But $|f(z_n)-f(a)|\ge\varepsilon\; \forall n \in \mathbb{N}$, which is a contradiction. You will have noticed that the above proof uses the Axiom of Choice (the lecturer didn't explicitly spell out the dependence, but it's definitely there).  My question is: is it possible to prove that $(1) \implies (2)$ without using the Axiom of Choice.  I strongly suspect that it isn't.  In that case, can anyone prove that we have to use the Axiom of Choice?  I can think of three ways to do this: (A) Show that $\left( (1) \implies (2)\right)\implies \mathrm{AC}$.  I suspect that this statement is untrue. This is definitely untrue, as Arthur points out, because I only used the axiom of countable choice, which is strictly weaker than AC. (B) Show that $(1)\implies (2)$ is equivalent to some other statement known to require the Axiom of Choice (the obvious example being the well-ordering of the real numbers). (C) Construct or show the existence of a model of ZF in which there exist sequences which satisfy $(1)$ but not $(2)$. Of course, if anyone can think of another way, I would be very interested to hear about it. One final note - I am aware that very many theorems in Analysis use the Axiom of Choice in one way or another, and that this is just one example of such a theorem.  If there exists a model of ZF like the one described in (C), is the study of Analysis in that model interesting?


I have different paths in a column like below:   'E:/R_Process/R_Input_UDM//Greater Europe/CEW Hub/Austria/Toothpaste/Variant Data/AUSTRIA_SHG_VARIANT_8.csv' 'E:/R_Process/R_Input_UDM//Greater Europe/CEW Hub/Austria/ManualTB/Variant Data/AUSTRIA_SHG_VARIANT_7.csv' 'E:/R_Process/R_Input_UDM//Greater Europe/CEW Hub/Austria/MouthWash/Variant Data/AUSTRIA_SHG_VARIANT_9.csv'   I want Toothpaste from 1st path, ManualTB from 2nd, and MouthWash from 3rd.  There are many more paths around 30 every from every paths I want the word from 7th slash.  How can I do this using regex?

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


I'm making a LED beatbox (). I'm using 8 LEDs (5 millimeters, I don't know if this helps) and my power source is 12 VDC 800 mA. Do I need to add a resistor? If yes, which one should I use?

I'm trying to work out what value resistor to use in a LED circuit. The equation I'd use to do this is:  $$ R = \frac{V_{cc} - V_f}{I_f} $$  Seems logical, and makes complete sense. The answers to the question  confirm this too.  I have the following LEDs:   \$ V_f = 3.3V \$ \$ I_{f_{typ}} = 20mA \$   Using a 5V power supply:   \$ V_{cc} = 5V \$   Plugging these into the above equation gives:  $$ \begin{eqnarray} R & = & \frac{V_{cc} - V_f}{I_f} \\   & = & \frac{5V - 3.3V}{20mA} \\   & = & 85\Omega \end{eqnarray} $$  All good so far.  However, if I use the calculator at , that gives me 100Ω. If I use the ElectroDroid app on my phone, that gives me 85Ω.  So, I assume that the linear1 calculator is using a different method of calculating this resistor value; is there some better way of doing this?


I'm trying to run Ubuntu off of a USB. The exact error message read as follows:  SYSLINUX 6.03 EDD 2014-10-06 Copyright (C) 1994-2014 H. Peter Anvin et al  Failed to load ldlinux.c32 Boot failed: please change disks and press a key to continue.   I followed these instructions (multiple times, same result) to create the USB stick:   I followed these instructions for booting the computer:   I used a brand-new 16GB USB 3.0 from PNY. I installed it using a Windows 7 Dell laptop (BIOS), which was unable to boot it from the USB. I tried booting it on a Windows 10 Dell desktop (BIOS) with the same result. I was using the latest LTS ISO from Ubuntu.com (ubuntu-16.04.3-desktop-amd64).  I tried writing in the ISO image mode multiple times with the same result before trying the DD image mode, which threw a "corrupt file" error and then wiped the USB entirely blank, so I slow-formatted it in FAT32 on my next attempt (instead of the instruction's usual "quick format" option).  Some people said they had success copying ldlinux.c32, libcom32.c32, and libutil.c32 to the root directory, but that didn't change a thing for me. I tried formatting the USB as NTFS as well as FAT32. Same result. Some people said that FAT16 fixed it for them, but that wasn't an option in Rufus.  I'm totally lost! Here I was, trying to learn Linux, and I'm unable to even boot it! Help, please?  EDIT: Not sure why it's being marked as duplicate. The questions it's supposedly identical to have nothing to do with this specific error message.

I have a bootable pendrive containing Ubuntu GNOME 16.10 (amd64) on it, and I installed it on my pc with no problems. But when I tried installing it on a pc in my college, it said "failed to load ldlinux.c32". After a while, I found out that that pc was 32bit. Could this be the reason that the installation wasn't working?


Here is the error Caused by: java.lang.NullPointerException     at be.bpost.viv.service.impl.UD10ReportGeneratorServiceBean.enterData(UD10ReportGeneratorServiceBean.java:187) [viv-batch-ejb.jar:]     at be.bpost.viv.service.impl.UD10ReportGeneratorServiceBean.createWorkBook(UD10ReportGeneratorServiceBean.java:96) [viv-batch-ejb.jar:]     at be.bpost.viv.service.impl.UD10ReportGeneratorServiceBean.generate(UD10ReportGeneratorServiceBean.java:78) [viv-batch-ejb.jar:]     at be.bpost.viv.service.impl.UD10ReportGeneratorServiceBean.generateUpdateReport(UD10ReportGeneratorServiceBean.java:72) [viv-batch-ejb.jar:]  This is the line where I have error row.getCell(UD10ReportColumns.REGISTER_MAIL_BALANCE.index()).setCellValue(line.getRegisterMailBalance() == null ? 0 : line.getRegisterMailBalance());   private Integer          registerMailBalance = 0;

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 discovered something funny today: all domains *.localhost.yarf.nl resolve to 127.0.0.1.    What is this? Where is this documented? I can not find references to it ...   Here some examples:  » dig aaa.localhost.yarf.nl  ; <<>> DiG 9.11.3-1ubuntu1.5-Ubuntu <<>> aaa.localhost.yarf.nl ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18392 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1  ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;aaa.localhost.yarf.nl.         IN      A  ;; ANSWER SECTION: aaa.localhost.yarf.nl.  3244    IN      A       127.0.0.1  ;; Query time: 0 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Thu Mar 21 07:26:40 CET 2019 ;; MSG SIZE  rcvd: 66   And:  » dig whatisthis.localhost.yarf.nl  ; <<>> DiG 9.11.3-1ubuntu1.5-Ubuntu <<>> whatisthis.localhost.yarf.nl ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27196 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1  ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;whatisthis.localhost.yarf.nl.  IN      A  ;; ANSWER SECTION: whatisthis.localhost.yarf.nl. 3600 IN   A       127.0.0.1  ;; Query time: 55 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Thu Mar 21 07:26:52 CET 2019 ;; MSG SIZE  rcvd: 73   But:  » dig whatisthis.yarf.nl  ; <<>> DiG 9.11.3-1ubuntu1.5-Ubuntu <<>> whatisthis.yarf.nl ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 24959 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1  ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;whatisthis.yarf.nl.            IN      A  ;; AUTHORITY SECTION: yarf.nl.                300     IN      SOA     ns091.auroradns.eu. admin.auroradns.eu. 2019011601 86400 7200 604800 300  ;; Query time: 38 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Thu Mar 21 07:26:59 CET 2019 ;; MSG SIZE  rcvd: 107   And:  » dig yarf.nl  ; <<>> DiG 9.11.3-1ubuntu1.5-Ubuntu <<>> yarf.nl ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13207 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1  ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;yarf.nl.                       IN      A  ;; ANSWER SECTION: yarf.nl.                3600    IN      A       5.157.81.33  ;; Query time: 33 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Thu Mar 21 07:27:06 CET 2019 ;; MSG SIZE  rcvd: 52

I was  about Server-Side Request Forgery. In that article the attacker found that 127.0.0.1 was open to the internet. The victim then blocked 127.0.0.1, but because many other IPs and apparently also some domains are also resolved to to that, including the mysterious localtest.me, he was able to bypass a weak text-based filter.    What is so special about localtest.me? Are there others? (And how to find them?)     UPDATE   I found:   Apparently someone decided to register that domain in a funny way, for testing purposes:     Here’s how it works. The entire domain name localtest.me—and all   wildcard entries—point to 127.0.0.1. So without any changes to your   host file you can immediate start testing with a local URL.   However, I'm still not sure how you can register an external domain to a local one. This is confusing as a tracert localtest.me never even leaves the machine. How is this handled on the low level?  I then  and elsewhere:   lvh.me  vcap.me fuf.me - IPv4 and IPv6 ulh.us 127-0-0-1.org.uk ratchetlocal.com smackaho.st 42foo.com beweb.com yoogle.com ortkut.com feacebook.com   And in   on Stack Overflow.


There is left padding missing for the text, but the right padding is perfect in the Winter Bash notification bar (I mark as red line in the picture):

When opting out the Winter Bash the top bar popup related to snowflake looks like this for me:    Is it intentional that there are no horizontal margins for popup content?


I have a body in 3D-space and I would like to calculate the rotation axis when the body moves from A to B. I know the location (x, y and z) and the orientation (rx, ry and rz (axis angles)) at both A and B.  I have read about Rodriguez' rotation formula and know how to find the axis of rotation, but how can I incorporate the translation components as well?  Any help is appreciated!   /Daniel

Assume I have 3 original points in a 3D object (in 3D space) as A1=<xa,ya,za>, A2=<xa,ya,za>, and A3=<xa,ya,za>. The 3D object is moved and rotated in the 3D space, and the destination points in that object become B1=<xb,yb,zb>, B2=<xb,yb,zb>, and B3=<xb,yb,zb>.   How can I compute the transformation matrix and following that, the degree of rotation in each axis? Basically, I need a matrix that if applied to all points, I get the displaced object.


After some years of enthusiasm about Stack Overflow and other Stack Exchange sites, admiring the politeness of the communities and the effectiveness of the whole system, I finally stumbled upon a serious problem, and decided to make a complaint to the staff. In this page , I've read about what to do in that case, of course after having made the other recommended actions. I wrote a message using the "Contact" link "at the bottom of any page", as stated. Two months have passed, and still nothing is happened, not even a signal that someone did read my complaint. I then searched for some other way, and found this page:  where there is a list of people that should "help you out, really". In their profile page you can find their email addresses. I wrote an email to three of them, leaving some day between each one. Again, no replies, no signals that someone has even received my messages. Now I wonder: are these people really interested in user's feedback, or at least interested in ensuring that no abuses or other serious problems grow in their communities? This is question 1. Question 2: Are those email addresses fake or what? Are they supplied just to give the impression that someone cares about users? Question 3: What can I do now? Should I sit in peace and leave? Or is there still something I can try, once again? --- update --- It has been suggested that this question:  could be the right answer. I think no, because it is 3 years old and it does not suggest what to do other than wait for a week. I've read that there are, these days, new efforts in improving exactly these kinds of problems. I am referring, for example, at the tag "status-review". Moreover, I want to understand better what the Community Team does (): I wrote an email to some of them, but nobody replied. Wouldn't it better, at least, to inform the user with something like "we received your email but we have no time to examine it: please be patient"? Now I have the doubt that the mail system does not work, but it seems more probable that the CM really does not reply.

So I had a dispute with the moderators at a specific SE site. As a result, I got suspended there. As per SE guidelines, I pressed the "Contact us" button and wrote to the higher powers to appeal.  That was 5-6 weeks ago. There was zero feedback, neither positive, nor negative, not even "it's in progress, please wait".  So what is this "contact us" thing supposed to do? Is it a placebo to make me feel better while being routed to dev/null?  What is the normal time it takes to process a "contact us" message?  Notes:   As far as I remember, I did not contact the team before. I'm a longtime user of multiple SE sites and never had any problems except for that one site. I'm pretty sure my form was submitted. I didn't make screenshots or anything, because I did not think I would need them in a post like this. I didn't expect a super-fast reply either, so I wasn't wondering after a week or two.


My Ryanair flight will arrive in Paris at 21:00. Is it still possible to catch the bus? The return flight is also in the morning at 08:00. Are there buses from Paris at 05:00 ?  What are the operating hours for the buses between the airport and the center of Paris? Is there any timetable for the buses?

Paris has 3 airports (Orly, Roissy, Beauvais), what are the options to go to or to come from there?  (There is also Vatry (XCR) but there is very few flights and i see the shuttle system is currently off.)


Suppose every day an agent randomly exhibits one of two behaviours (behaviourA or behaviourB), and the probabilities of exhibiting behaviourA and behaviourB are unknown.  After n days, we will have a sample of n days' data.   Suppose n = 1000, and we have witnessed behaviourA 800 times and behaviourB 200 times, we could estimate the probability of behaviourA as 80% and probability of behaviourB as 20%.   Question  How do we measure how confident we are of these probabilities, and does that change when the sample size is small?   Example with small sample size  Suppose n = 10 with 8 x behaviourA and 2 x behaviourB, then the probabilities would be identical, but we couldn't be as confident in our estimations of those probabilities as we could with n=1000. My guess is that we need some way of penalising the small sample size, but I am not sure how to accomplish that.

I have a random sample of Bernoulli random variables $X_1 ... X_N$, where $X_i$ are i.i.d. r.v. and $P(X_i = 1) = p$, and $p$ is an unknown parameter.  Obviously, one can find an estimate for $p$: $\hat{p}:=(X_1+\dots+X_N)/N$.  My question is how can I build a confidence interval for $p$?


I am implementing machine learning algorithm for multiclass classification problem in R programming. The problem is that when I predict the accuracy I am getting around 90% accuracy but when I calculate the AUC score I am getting more than 1. Will the AUC support multi-class classification?  Which is the better approach to consider the evaluation metric of machine learning model for multi class classification?  Below is my code   library(dplyr) smp_size <- floor(0.80 * nrow(New_data)) set.seed(123) train_ind <- sample(seq_len(nrow(New_data)), size = smp_size) train <- New_data[train_ind, ] test <- New_data[-train_ind, ]  train_features <- train[,-ncol(train)] train_labels <- train[,ncol(train)] test_features <- test[,-ncol(test)] test_labels <- test[,ncol(test)]  library(e1071) library(rpart) library(mlbench) svm.model <- svm(as.factor(train$labels) ~ ., data = train,cross = 10) class(svm.model) summary(svm.model) print(svm.model) svm_pred <- predict(svm.model,test_features)  length(svm_pred) length(test_labels) table(pred = svm_pred, true = t(test_labels)) conf_matrix <- table(svm_pred, test_labels) conf_matrix   library(MLmetrics) Accuracy(svm_pred, test_labels) AUC(svm_pred, test_labels)   Output:  > conf_matrix         test_labels svm_pred    0    1    2    3    4        0  896   75   50   18   28        1   71  919   28   13   16        2    7    6  112    1    9        3   31   44   12 1023    2        4    1    5    9    0   55 > library(MLmetrics) > Accuracy(svm_pred, test_labels) [1] 0.8758379 > AUC(svm_pred, test_labels) [1] 1.047074

I'm wondering how to calculate precision and recall measures for multiclass multilabel classification, i.e. classification where there are more than two labels, and where each instance can have multiple labels?


In one rig I have this but in the other I don't.    Well basically I was doing a minecraft gfx when I accidentaly deleted this bar thing, could anyone help get it back?!

I accidentally opened too many menus (or windows) and I want to reset them to default.  It is really annoying, and effecting my animation.  Thanks


I've been trying like crazy to get my composite node setup to render the exploding objects (pass index 1) and I really can't understand why my ID Mask won't render them.  Instead it renders the entire thing in a bluish green hue.  I just want the objects with a pass index of 1 to look like that.  It's been difficult to get any answers via pictures since my node setup is pretty big so I will provide a link to download the .blend file so you can see the nodes more clearly.

I'm trying to make the render have an effect where the stars (which are exploded fragments) have a glowing glare-like effect and the other objects (i.e. film reel and cubes) are their natural colors.  However, despite having made the star objects all a pass index of 1 and the rest 0 by default, everything seems to render a green glowing effect that's supposed to be only for the objects with a pass index of 1.  To illustrate:  This is the render of the image naturally (I rendered at very low quality but it's just for demonstration purposes):    And this is with the composite nodes:    So in essence I want the objects in the the first render I showed to keep those colors, but the stars to have the colors of the green glowing effect.  As you can see from the 2nd picture everything has the green effect.  My node setup is pretty big so I will provide a link to download the  so you can see the nodes more clearly.


Consider the following scenario:   User A writes a comment to User B, or answers the question of User B. This could ping user B, i.e. (s)he would see the comment in his inbox. However, User B is not logged in at the time. The ping is made deleted:   the answer of User A (to User B's question) is deleted the comment of User A (to User B's post, or by mentioning @UserB) is deleted the post which is commented by User A, is deleted (but not the comment)  After that, User B logs in.   Will he see the ping in his/her inbox?  If User B is a 10k+ user, in theory (s)he would see User A's answer, and also his comment, if it wasn't deleted. If User B is a diamond moderator, (s)he could even see User A's deleted comment.  I think, the most logical way would be, if User B would see the ping if and only if (s)he could see the post or comment addressed to him(she). But how does it actually work?

Assuming the following, not entirely hypothetical exchange of comments:  User A: user B is a moron Moderator C: @userA insulting other users is not acceptable, ...  Moderator C also deleted the comment from user A, as it was clearly offensive. Does User A get a notification for the reply of moderator C if the target comment is removed? Does it matter if the moderator removes the comment before or after writing their own comment reply?


I am repeating my question posed in another thread because I can now offer greater clarity in the form of a picture cropped from a Google Earth shot of the actual street location. A second reason for repeating the exercise is that Google Earth revealed that the paved area I need to name actually has the shape of a polyp - or the circular head of a polyp. A third reason is that despite the highly appreciated suggestions, I don't yet have a workable name for the street area in the shape of a polyp head (when photographed from the air, or from a satellite). I would like to write the following sentence: "I walked across the [ ... descriptive and acceptable name for the polyp head ...] to my neighbour across street." Please help!    Looking forward very much to possible replies.

I used to own a house located in a modern suburban street with a circular protuberance, a circular paved (tarred) surface appended to the paved street it was part of. Four houses with their gardens were positioned around this circular paved street area. The number of properties in the street was thus increased by three. The point of entry into the circular paved area had the width of the street. This drive-in entry area could have accommodated one property. By serving as the entrance to the circular paved area, it allowed three extra properties to be erected. What is the name of such a circular paved street area?


How do i change directory to the directory with my python script in? So far I figured out I should use os.chdir and sys.argv[0]. I'm sure there is a better way then to write my own function to parse argv[0].

cd is the shell command to change the working directory. How do I change the current working directory in Python?


This is not a repeat of another post, as I am having a specific problem which is really annoying me.   I am getting an error saying that there is a character that is not supposed to be there in my command, but I can't find it.  Command:   /setblock -248 33 642 command_block 0 replace {Command:"testfor @a[score_craft_min=1] {Inventory:[{id:"minecraft:cobblestone"}]}"}

I need help with a specific command that I am using in a new game that I am creating inside of Minecraft. The command is:  /give @p sign 1 0 {BlockEntityTag:{Text1:"{"text":" [MF2]","color":"gold","clickEvent": {"action":"run_command","value":"tellraw @a [""{"text":"[MF2]  ","color":"gold"},{"selector":"@p","color":"dark_aqua"},{"text":" is now an admin of the server!","color":"white"}]"}}",Text3:"{"text":"Click to join Admin","color":"dark_aqua","clickEvent": {"action":"run_command","value":"scoreboard teams join admin @p"}}"},display: {Name:"Custom Sign"}}   If I take out the /tellraw command then the command works fine, but I need the command in there to announce to the game that a new admin has joined.  With the tellraw command, the error message is the following:  Data tag parsing failed: Unexpected token 't' at: text":" [MF2]","color":"gold","clickEvent":{"action":"run_command","value":"tellraw @a [""{"text":"[MF2] ","color":"gold"}, {"selector":"@p","color":"dark_aqua"},{"text":" is now an admin  of the server!","color":"white"}]"}}",Text3:"{"text":"Click to join Admin","color":"dark_aqua","clickEvent": {"action":"run_command","value":"scoreboard teams join admin @p"}}"   If anyone knows how to fix this, please let me know.


I work with openlayers and geoserver. I'm searching for code that when I click on a point of a layer on the map, a popup window appears that contains information from the database (postgres) for this point.   Can you help me please?

I tried to display data with popup from Geoserver or Postgres to my map, but it dosen't work at all. Can anyone please help me? I used this code:      function Info(e)          {                 if (e.features && e.features.length)                  {                      //console.log(e.features[0].attributes);                     var popupId = e.xy.x + "," + e.xy.y;                     var popup = popups[popupId];                     if (!popup || !popup.map) {                     popup = new OpenLayers.Popup.FramedCloud(                     popupId,                      map.getLonLatFromPixel(e.xy),                     null,                     " ",                     null,                     true,                     function(e) {                         delete popups[this.id];                         this.hide();                         OpenLayers.Event.stop(e);                     }                 );                 popups[popupId] = popup;                 map.addPopup(popup, true);                 }                popup.setContentHTML(popup.contentHTML + "nom_user:" +e.features[0].attributes.nomservice +" region_user :"+ e.features[0].attributes.region);             popup.show();                                    }       selectcltr = {         click: new OpenLayers.Control.WMSGetFeatureInfo({             url: 'http://localhost/geoserver/wms',              title: 'Identify features by clicking',             layers: [ser],             queryVisible: true         }),         hover: new OpenLayers.Control.WMSGetFeatureInfo({             url: 'http://localhost/geoserver/wms',              title: 'Identify features by clicking',             layers: [ser],             hover: true,             // defining a custom format options here             formatOptions: {                 typeName: 'projet',                  featureNS: 'http://www.openplans.org/topp'             },             queryVisible: true         })     }


I would like to construct a diagram which is a variation of the middle third Cantor set as described by:  Suppose we start off with the unit interval $[0,1]$; let us call it $A_0$. Next, remove the segment $(1/4,3/4)$ and then repeat the process on the two intervals $[0,1,4]$ and $[3/4,1]$ which make up $A_1$. In doing so we obtain $A_2=[0,1]\setminus \{ (1/16,3/16)\cup(13/16,15/16) \}$. We define the set $A$ by repeating process ad infinitum and so $A= \cap_{k=0}^{\infty} A_k$.  I would like this diagram to look something like this (my middle third Cantor diagram):    I do not know nothing anything about constructing these diagrams.

I am trying to draw a cantor set in LaTeX and I am having issues doing this. I am trying multiple \put commands, but they just go to the right of one another. Does anyone know how to do this?  Any help would be much appreciated.


I've a DIV, inside that i've Iframe. In that Iframe i'm loading the Html page. So I want to apply the css for that Html page.

I have a simple page that has some iframe sections (to display RSS links). How can I apply the same CSS format from the main page to the page displayed in the iframe?


I currently work at a college and we working to make the process of asking student clubs for information easier. We have created a google form for them to submit their member information, but each group has different amounts of members. We need the final list to be one comprehensive list of the student information, but I am not sure how to program Google Sheets to do this. Here is what the results look like:  Here is how we need it to look:  I am not very proficient in programing but I am a quick Learner If someone could set me in the right direction. Here is the form: I have tried using as ArrayFormula and QueryFunction, if someone could explain the correct formula using one of those or anything else, that would be a great help

I'm trying to develop a solution using Google Forms with Google Sheets that will collect Google Forms data and then automatically divide that one form submission's data into multiple rows of data in another sheet.   I've learned how to QUERY data (thanks to many of you on here) from one sheet to another, but I don't know how to automatically divide 1 row of data into multiple rows.  Here is a  in a visual manner (I will not delete it).   Basically, I have one Google form that collects the following.    Teacher Information (header data) Report Name (header data) Class Information (header data) Student#1 Data (record data: Multiple Form Fields) Student#2 Data (record data: Multiple Form Fields) Student#3 Data (record data: Multiple Form Fields) Student#4 Data (record data: Multiple Form Fields) Student#5 Data (record data: Multiple Form Fields)   I need an automated way to convert that single form response (1 row) into multiple rows (5 rows) each with the same 'header data' but with unique record date.   EXAMPLE Form Data  Header Data  -  Record Date (Student #1)  -  Record Date (Student #2)  -  Record Date (Student #3)  -  Record Date (Student #4)  -  Record Date (Student #5)   EXAMPLE Desired Manipulated Data      Header Data  -  Record Date (Student #1)     Header Data  -  Record Date (Student #2)     Header Data  -  Record Date (Student #3)     Header Data  -  Record Date (Student #4)     Header Data  -  Record Date (Student #5)


I know that using the history command I can view my past commands, but:    Is there a way to view the date and time of the execution of those commands?  Or is that kind of information not saved? And if that sort of information is not saved, is there any way to make it so that it does save it so that I can view it later?

Is there any way I can see at what time the commands were executed from the bash history? We can see the order but is there any way I can get the time also?  Bottom-Line: Execution time in the Bash history


I come from a Java background and just started to work on Python. Most of the things are fairly easy to pick up but I am having hard time to understand one thing in the language which I just found out that is called list comprehension. What is this list comprehension in Python? How does this compare with language constructs found in Java? The problem is it's everywhere, nearly all the examples I found here and there use it.  For the following example, allow me to understand how this works.  [x**2 for x in range(10)]   And then there this.  [j + k for j in 'abc' for k in 'def']   Beyond that I also have seen things like this somewhere on Stackoverflow.  (x for x in (0,1,2,3,4))   Also things like this.  total = sum(x+y for x in (0,1,2,3) for y in (0,1,2,3) if x < y)   This started to get messy, could you please help me?

When should you use generator expressions and when should you use list comprehensions in Python?  # Generator expression (x*2 for x in range(256))  # List comprehension [x*2 for x in range(256)]


For those who went through most possible solutions online, I hope this save you from headaches. So a while ago, I had a PDF file that I saved from Google Chrome that had an excessively long name. Little did I know that Windows will mess things up when a certain file name is too long. When I decided to delete the PDF when I'm done with it. It does not budge. Literally No error code/message, No indication, Nothing happened to the file Also when I attempt to change the filename, nothing happened as well. BUT if  I saved the name as it is, it came up with an error message saying it's too long. Tried various methods as well:  uninstall Adobe programs using CMD to delete booting into safe mode using CMD to delete in safe mode changing file extension (result is same as deleting and renaming) archive the file (failed)

Windows seems to have a length limit on file names when trying to delete, though it won't prevent those files from being created.  Our build process creates a number of temporary files (many build off of a WSDL) that run afoul of this limit.  Our ant script is somehow able to delete them when doing a clean, but sometimes I need to delete the workarea directory (where all the temp files go) without actually doing a full clean from ant.  This is the same errors , but the answers there don't really work for me as I'm dealing with a directory, not a file, and I don't always know what specific files or subdirectories are causing the problem.  And I'm trying to avoid any manual process (other than triggering a single command) to actually delete them.  If I try deleting the directory from Explorer I get the error   Cannot delete [file name]: The file name you specified is not valid or too long.   Specify a different file name   Trying Remove-Item in powershell gives the following error:  Remove-Item : The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters. At line:1 char:12 + Remove-Item  <<<< -force -Recurse <directory>   Does anyone know of any tools or easy ways to get around this delete error without having to manually find the problem files and move/rename them?


I have a compaq presario CQ60 With a CRASHED version of Ubuntu Linux, I am not knowledgeable on how to use linux to begin with, let alone fix a computer that keeps repeating " [sdb] asking for cache data failed" And a never ending repeat of it saying  "[sdb] assuming drive cache: write through" Then it hit repeating the asking for cache failed, over and over and over again, the owner before me said this OS is completely crashed, it doesn't load, it goes to the purple page showing Ubuntu and the 4 dots lighting up then immediately goes to a black screen repeating that, I've attached an image showing. I have used another computer to download windows 10 (sigh) onto a flash drive, and I want to install it on this laptop and not have any trace of linux on here, how do I do so?? Like I said it does not give me the option to type or do anything, it's def screwed up..

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


I've answered a question (perhaps not particularly well) here:    I had introduced a step 0, but when the markdown was actually displayed, it renumbered my sequence from 1, which messes up any references to the points in later commentary.  I've worked around this for now, starting, more normally, the list from 1. But is this intentional behaviour?    A simple reproduction here. Note that if you edit this question, you'll see the numbering starts at 0.   Zero One

I see that you can create an ordered list using Markdown notation like the following.  1. line 1 2. line 2 3. line 3 ... N. line N   The Markdown content supports starting each line with any arbitrary number and reorders the list starting with 1. I'd like to start an ordered list with zero. My use case for zero would be in describing capture groups from regular expressions where group zero always returns the entire string. So I'd like to display something like this:  # Groups 0. Entire string 1. The first capture group you were looking for 2. The second capture group 3. The third group with the string I heart Kittens   Markdown instead reorders the group and forces the ordered list to start at 1:    Trying to force the issue with inline HTML:
 or

entire string

 doesn't work either. Any ideas on how I can create ordered list starting with zero?  If it's not possible to do so, then this is a feature-request.


Please point or link me to any official rules (rules as written) on when a character can delay, hold or ready an action for later in a round, instead of going on their initiative. What does a character have to do to delay or hold an action during a round? What actions are characters allowed to take when they delay?

In D&D 4e there was an option to Delay your initiative:     Perform your actions as desired and adjust your initiative to your new   position in the order.   Does this rule to change initiative order still exist in 5th edition? I cannot find it in the PHB.


Does anyone know what this symbol is in my notification bar? I'm guessing it's from a 3rd party app. Please excuse my poor attempt to recreate it. :)

I'm concerned about an app on my child's phone. I saw an app icon in the notification area that looked strange (Andy Android head, slightly tilted as its icon).  How can I find out what app it is from just having seen that icon in the notification bar?


In an interview, what is the correct way to introduce yourself?  Some use "myself" and their name, and some use "I'm ___."  I'm confused about what I use.  Please guide me.

How do we use myself as the only subject of a sentence?   For example I once heard some people saying Myself am to be blamed. Is this grammatically correct? How is it different from I am to be blamed?


When using operator new  we explicitly provide the size of memory to be allocated:      int* arr = new int[100];   But when deleting, we just type delete []arr; How does the compiler/program calculates the size of arr, as we provide no information about it to operator delete?

Foo* set = new Foo[100]; // ... delete [] set;   You don't pass the array's boundaries to delete[]. But where is that information stored? Is it standardised?


Prove without induction that $$\sum_{r=1}^n {n\choose r}(-1)^{r+1}\dfrac{1}{r}=\sum_{r=1}^n \dfrac{1}{r}$$ for $n\geq1$.   I have shown the above using induction. However, I am interested in knowing if we can show it directly without using induction.  This is not entirely trivial, I think, if one is armed only with the very basic ideas of combinatorial identities. This can be proved in at least two different ways: one using induction and the other is by evaluating an integral. However, regarding the second approach, I am quite certain that if not known beforehand which integral to compute to get this equality, it is a hard exercise.  EDIT: In the link claiming to be a duplicate of my question, induction was allowed. I am looking for approaches that use no induction or calculus. So this question is different.

How to establish the following identities without the help of calculus:  For positive integer $n, $ $$\sum_{1\le r\le n}\frac{(-1)^{r-1}\binom nr}r=\sum_{1\le r\le n}\frac1r $$  and  $$\sum_{0\le r\le n}\frac{(-1)^r\binom nr}{4r+1}=\frac{4^n\cdot  n!}{1\cdot5\cdot9\cdots(4n+1)}$$


I just can't drag and drop a partition to the left to increase its size. I have 2 partitions:  1 unallocated 118Go  2 ext4 120 Go    And I want to extend the ext2 to all space but can't extend it by drag and drop:  What can I do? EDIT: Sorry, I couldn't do it because it was mounted! I thought it's was not mounted because the USB was disappearing from my Gnome File Manager when Gparted was started and the USB drive selected. I unmounted it, and then could do it!

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


I've an issue with my Google Cloud compute VM. It's running Ubuntu 14.04, Apache2, PHP and Percona MySQL.  The server won't respond to TCP connections on port 80. I can connect via SSH, and the server appears to be normal.   I found a couple of dodgy looking files which I've attached [Not attached any more], they seem to have been some kind of data gatherers. I've removed the files, and am assuming Google have blocked my instance from it's network for web traffic.  I'm at a bit of a loss as I've no idea where to go from here. The server is being hammered by lots of different IP with requests for these files.  Any advice is much appreciated.  EDIT: This question isn't about how to deal with a compromised server. It's about how to get Google to allow traffic to the VM again. As I've not got any notifications, statuses or anything to go by in my GCC control panels.

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.


I was reading "Classical Recursion Theory" by Odifreddi and it starts with this phrase:      Recall that Classical Recursion Theory is the study of real numbers or, equivalently, functions over the natural numbers.   I come from Computer Science so this was puzzling to me at first. I understand he's referring to the fact that there is a bijection between $\mathbb{N}$ $\rightarrow$ $\mathbb{N}$ and $\mathbb{R}$. I know that |$\mathbb{N}$ $\rightarrow$ $\mathbb{N}$| is greater than |$\mathbb{N}$| (Cantor's diagonal), but how can you find the real $x$ corresponding to a certain function?  I know that given a real $x$ we can construct a function like this: $f(n) =$ the $n$-th digit of $x$. But what is the other way around? We can't use digits in this case, I think, because we have numbers with more than one digit; I don't think changing the digit system would help (I think every digit system has a finite alphabet?) and that way we would link more functions to the same real number.  I know that you can't compute reals in a strict sense (you would need $\infty$ digits) but I was wondering if there was at least some sketch-procedure of how to represent a function with a real number, to have at least logically a glimpse of what is the number $x$ corresponding to a generic function $f$: $\mathbb{N}$ $\rightarrow$ $\mathbb{N}$.

I was comparing the sets $\mathbb{N}^{\mathbb{N}}$ and $\mathbb{R}$ for a fun practice because I didn't know at first that $\mathbb{N}^{\mathbb{N}}$ was uncountable. But how can I compare two uncountable sets and see which has the larger cardinality?


I have hidden input type=file field, and i want to open its select dialog with javascript. I tried to fire click event on this element, but without luck.  Im using mootools.  $('input_id').fireEvent('click');   This is possible at all?

I'd like to make a click event fire on an <input type="file"> tag programmatically.  Just calling click() doesn't seem to do anything or at least it doesn't pop up a file selection dialog.  I've been experimenting with capturing events using listeners and redirecting the event, but I haven't been able to get that to actually perform the event like someone clicked on it.


How can one achieve following in exposed fliters  FILTER ONE (PARENT) FILTER TWO ( CHILD ) FILTER THREE ( GRAND CHILD )..  I dont want SHS or HS,   Please guide.

I have 3 fields ( Exposed filter ) 1 Country 2 State 3 City  When a respective Country is selected in the 1st field, I want the second filter ( Dropdown or autocompete ) to display states of the country selected in the 1st field & when this is done based on the state selection , I want the 3rd field to show only the cities belonging to the state selected in the second field.  How can this be done ? any help ?


I have a WPF app with a MouseWheel event. The operations in this event is quite heavy. So, I would like to execute this event only when the user has stopped scrolling (i.e.: if he doesn't scroll for a given amount of time). In JS, this is quite easy, I can just put the setTimout in a var and then do a clearTimeout on that var if another scroll happened before the execution of that setTimeout (this is quite useful for auto-completion for instance). How can I achieve that in c#?

I am currently making an MP3 player in WPF, and I want to make a slider that will allow the user to seek to a particular position in an MP3 by sliding the slider to the left or right.  I have tried using the ValueChanged event but that triggers every time it's value is changed, so if you drag it across, the event will fire multiple times, I want the event to only fire when the user has finished dragging the slider and Then get the new value.  How can I achieve this?    [Update]  I have found  on MSDN which basically discusses the same thing, and they came up with two "solutions"; either subclassing the Slider or invoking a DispatcherTimer in the ValueChanged event that invokes the action after a timespan.  Can you come up with anything better then the two mentioned above?


I need to supply +9V to three stepper motors on a breadboard with driver carriers (see parts below). Its too much for my raspberry pi to handle, apparently. I was able to power and control a single driver, so I know my setup is good.   I tried using an arduino power supply to drive them (+9V, 0.664A), but when its under load, the voltage seems to drop below +3V and nothing works.  I need to find a power source (not battery) for this. I'd prefer not ordering anything (short on time). Any suggestions, or tips to get the arduino supply to work properly?

Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.


I am receiving email from daily running crontab which executes a php script. I want it to send me email if only it has errors or fails.  How to do that ?  Note: I am using cpanel to add cron job.  Thanks

I finally set up a realistic backup schedule on my data through a shell script, which are handled by cron on tight intervals. Unfortunately, I keep getting empty emails each time the CRON has been executed and not only when things go wrong.   Is it possible to only make CRON send emails when something goes wrong, ie. my TAR doesn't execute as intended?  Here's how my crontab is setup for the moment;  0 */2 * * * /bin/backup.sh 2>&1 | mail -s "Backup status" email@example.com   Thanks a lot!


I came across a list of functions in my calculus textbook whose indefinite integral cannot be found. It was written that the integral $$\int \frac{\sin(x)}{x} dx$$ cannot be evaluated without any explanation as to why.  I did some research over the internet and found out that the definite integral $$\int_{0}^{\infty} \frac{\sin(x)}{x} dx$$ can be evaluated using Laplace transformation and is equal to $\pi /2$. But I still couldn't find answer to my original question. I read somewhere that the integral cannot be expressed using 'elementary functions'. A little help is appreciated, I'm in Calc 1 going advanced than my course but I am sorry if my post shows lack of research. Thank you!

In the past, I've come across statements  along the lines of "function $f(x)$ has no closed form integral", which I assume means that there is no combination of the operations:  addition/subtraction multiplication/division raising to powers and roots trigonometric functions exponential functions logarithmic functions  which when differentiated gives the function $f(x)$. I've heard this said about the function $f(x) = x^x$, for example. What sort of techniques are used to prove statements like this? What is this branch of mathematics called?  Merged with "" by : Sometimes we are told that some functions like $\dfrac{\sin(x)}{x}$ don't have an indefinite integral, or that it can't be expressed in term of other simple functions. I wonder how we can prove that kind of assertion?


I'm learning how to use java XPath API and I got a question about behavior of evaluate() method of XPathExpression class.  I have XML file that contains data about employees. I want to find highest payed employee in form of String, so I write this code:  FileInputStream file = new FileInputStream(new File ("D:\\workspace\\NetCrackerTasks\\src\\ru\\ncedu\\java\\tasks\\emp.xml")); DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder(); Document src = builder.parse(file); XPath xPath = XPathFactory.newInstance().newXPath(); String expression = "/content/emp/employee[not(../employee/sal > xs:decimal(sal))]"; String result = null; XPathExpression expr = null; try {     expr = xPath.compile(expression);     result = expr.evaluate(src); //This throws NullPointerException } catch (XPathExpressionException e) {     e.printStackTrace(); } return result;   When I run this code in Eclipse, expr.evaluate(src) throws NullPointerException.  In documentation on docs.oracle.com() it says that      If source is null, then a NullPointerException is thrown.   I checked my src object and it is not null, and path to xml document is right.  So my question is: why do I get NullPointerException? And isn't there more proper way to get elements of XML document in form of a String that match XPath expression? My XML file looks like this:  <?xml version="1.0" encoding="UTF-8"?> <content      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     xmlns="ns:emp"     xsi:schemaLocation="ns:emp emp.xsd">     <emp>         <employee deptno="10" empno="7369" mgr="7902">             <ename>SMITH</ename>             <job>CLERK</job>             <hiredate>1980-12-17</hiredate>             <sal>800.00</sal>             <comm>0.0</comm>         </employee>         <employee deptno="30" empno="7521" mgr="7698">             <ename>WARD</ename>             <job>SALESMAN</job>             <hiredate>1981-02-22</hiredate>             <sal>1250.00</sal>             <comm>500.00</comm>         </employee>         <employee deptno="20" empno="7566" mgr="7839">             <ename>JONES</ename>             <job>MANAGER</job>             <hiredate>1981-04-02</hiredate>             <sal>2975.00</sal>             <comm>0.0</comm>     </emp> </content>    EDIT: xPath.compile(expression); does not return null and expr is not null when expr.evaluate(src) runs. So NullPointerException is thrown not becuase calling a method on a null object, because object is not null.

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?


Chrome has a feature where if you double click the refresh button, you can empty cache and hard reload. How does chrome empty the cache? I'm well aware that, on a Mac, if you it command+shift+delete, you can clear cookies and cache. However, I don't want to go this route, and I only want to clear the cache. The reason why I want to know how it's being done is because I'd like to attach a keyboard shortcut to it.

I don't know what exactly it's called, by cache refresh I mean, refresh the page after clearing its cache. I don't want to clear the entire browser cache.  I can't seem to cache refresh my pages. In Firefox, I know it to be Shift+Refresh.  In Chrome, I've tried Ctrl+R, Ctrl+Refresh, Alt+Refresh, Shift+Refresh but none of them work.


If we exert force on an object which would be travelling at near light speed, to an extent to make it move greater than speed of light in vacuum, what would happen? If object doesn't move faster than light, what happens to that excess force?  Is this experiment been done? What would happen if we exert force on light travelling at its maximum speed?

A question has recently come up that goes beyond my knowledge of special relativity.  Suppose a pilot has his foot on the gas pedal of a rocket ship and keeps it applied to achieve a constant acceleration, and he has a magical engine that can maintain the thrust needed to accomplish such acceleration even as the vehicle acquires mass.  He measures his acceleration at periodic intervals and sums it up as he goes.  Observers perceive the rocket to increase in speed and gradually approach the speed of light (but never reach it). Two possibilities are being debated for what the pilot observes, and my preference is for the first:   Time dilation gives him the impression that the summation of his readings are approaching light speed at a constant rate, but there is an asymptote involved here even in the inertial frame such that he never actually perceives himself to reach, let alone exceed, $c$, because time slows down to a crawl (as seen from the reference frame) before this can happen. Although to observers he is only approaching $c$, it is possible for the summation of the measurements on his accelerometer to indicate that he has surpassed $c$ and is now traveling faster than light.  From the reference frame he is approaching $c$ and his instruments in the inertial frame tell him that he has surpassed it.   I assume (1) is true beyond a doubt?  If so, is there a straightforward explanation for this?


I have a valid Standard Visitor UK visa for several years. But I also must attend a study course for 3 months in the UK, and organisers informed me that I must have a short term student visa. If I reapply for a student visa with this passport my longer Standard Visitor visa can be canceled. And I don't want this. Another reason, is that I need my passport for traveling while having other passport in the UK migration for several weeks waiting for a decision.   I also have a second passport, a different nationality and slightly different name. Can I apply for a student visa with other passport, and have a valid Standard Visitor in different passport simultaneously?   Of course I would submit copies of my two passports with my application. And an officer may see that I, as a person of another nationality, already have a visa, though a different type.

I have a visitor UK visa valid until October 2017.  I also want to apply for a Tier 4 student visa. My studies in the UK start in September 2017.  If I apply for the student visa in June, will they simply issue an overlapping student visa, or will they cancel my visitor visa and I will not be able to come to the UK until September?  I am worried because in a similar situation with Schengen visas, my existing visa was canceled.


I have a problem with forward/backward search in tex. I'm using Miktex, Texniccenter and SumatraPDF and normally the search works just fine. I tried to make a minimal example.  I use one main file (main.tex), where I load my packages, define new commands, etc. and load my single chapter files (1.tex, 2.tex, 3.tex) via \include{}. In some of these files I use tikz-pictures, which are stored in separate tex-files and loaded via \input{*.tex}.  Here is the example:  main.tex:  \documentclass{scrreprt} \usepackage[english]{babel} \usepackage[latin1]{inputenc} \usepackage{tikz}  \begin{document}  \include{1} \include{2} \include{3}  \end{document}   1.tex:  Test 1.1 \input{pic.tex} Test 1.2   2.tex:  Test 2   3.tex:  Test 3   pic.tex:  \begin{tikzpicture}     \shadedraw[top color=yellow,bottom color=black] (0,0) rectangle +(2,1); \end{tikzpicture}   The document compiles just fine and looks the way it is supposed to. But if I try the backward search (clicking in the pdf => jumping to the right line in the tex-file), it does not work for the "Test 2" part (of file 2.tex). I get the error: "no synchronisation info at this point" in SumatraPDF. If I click on "Test 1.1" or "Test 1.2", it directs me to "pic.tex", for whatever reason. Only the backward search used at "Test 3" and the picture itself work correctly.  If I use  \begin{tikzpicture}     \fill[yellow] (0,0) rectangle +(2,1); \end{tikzpicture}   as pic.tex the backward search works just fine.  Any ideas why there is a problem with \shadedraw?  If you need more information, please let me know. Thanks for the help.

I've got a document that compiles without error or warnings (and looks about right) but for some segments of the document synctex doesn't seem to be working.  What could be wrong?  The document consists of one root .tex file which \inputs a bunch of others.  Synctex works for all these sub-documents - except for one.  In practice, this means I can Ctrl-Click in the viewer and find the appropriate spot both in parts of the text before and after this particular subdocument.  Conversely, I can Ctrl-Click in the editor and jump to the right spot in the view in all subdocuments but this one.  However, when I Ctrl-Click on a part of the output corresponding to this particular subdocument I get the following error popup: Cannot read file "E:/emn/uni/Thesis/doc": Access is denied. in the TeXworks viewer.  The path in this error message exists but is a directory: namely the one containing the tex files.   All filenames consist of only latin letters, numbers, and underscores and the extension .tex.  The problematic file is called G2MLVQ_9_Refinements.tex whereas a (working) file is called G2MLVQ_7_Implementation.tex I can't make a small example which fails - small examples don't fail; however the order of files seems to matter, so perhaps something in an earlier file is affecting synctex later on... (once I've isolated this, I'll update the question). Concerns MiKTeX 2.9 and the bundled TeXworks version 0.4.3 r.857.   I'm stumped: what could be going wrong?  Edit: user59152 tried to isolate the error:     It is virtually impossible to create a minimum working example (MWE) for this problem, so I have posted a . You can see the file names at the tops of the windows. The one being edited (Introduction.tex) comes BEFORE the file that can't be opened using inverse search (SourceAndSinkFreeContinuumRVtracking.tex). The screencapture movie confirms that \clearpage restores inverse search capability, but fouls up the layout of the document, so this problem appears to remain unsolved.  I'm using TeXworks version 0.4.4 r.1003 and MikTex 2.9.


The description of the  spell in D&D 5e says:  You touch one object that is no larger than 10 feet in any dimension. Until the spell ends, the object sheds bright light in a 20-foot radius and dim light for an additional 20 feet. (...)  Can I cast the Light cantrip on an 11-foot pole? On one hand, 11 is greater than 10. This would suggest that the answer to my question is "no". On the other hand, I could put an 11-foot pole in a 10×10×10-foot box. This would suggest that the answer is "yes". I don't expect that the success of an adventure will hinge on the answer to this question any time soon, but I would like to understand how dimensions are supposed to work.

In follow up to my question , I would like to find out whether this portion implies shapability and what restrictions are placed on shapeability.  And can the same logic be applied to a possibly game breaking point?     Choose a door, a window, or an area within range that is no larger than a 20 foot cube   It seems that this language implies shapability because the wording is "an area". But does no larger than a 20 foot cube mean no measurement can be larger than 20 feet? Or does it mean the area or volume cannot exceed that of a 20 foot cube? We already know the size can be round or rectangular (windows can be either).


After reading  by Kusalananda I got some sense about what is a variable-attribute, yet I miss what is a "name-reference" (type?) of a variable-attribute, what is it using for, why would one want to use it in a Bash script,   I tried to Google the term "name reference" (without quote marks) but I didn't find a wiki article on this term.

After reading ilkkachu's answer to  I learned on the existence of the declare (with argument -n) shell built in.  help declare brings:     Set variable values and attributes.      Declare variables and give them attributes. If no NAMEs are given,   display the attributes and values of all variables.      -n ... make NAME a reference to the variable named by its value   I ask for a general explanation with an example regarding declare because I don't understand the man. I know what is a variable and expanding it but I still miss the man on declare (variable attribute?).  Maybe you'd like to explain this based on the code by ilkkachu in the answer:  #!/bin/bash function read_and_verify  {     read -p "Please enter value for '$1': " tmp1     read -p "Please repeat the value to verify: " tmp2     if [ "$tmp1" != "$tmp2" ]; then         echo "Values unmatched. Please try again."; return 2     else         declare -n ref="$1"         ref=$tmp1     fi }


The  shows global distribution, and I wonder if there's a way to find out the difference in Gingerbread distribution between say, India and Europe.

We're starting out with some Android development in our company, and I'm working out which  Android versions we should support.    In one of Google's videos from  (22:34 minutes in) there is a pie chart showing roughly a third of users each for Android 1.5, 1.6 and 2.1.    Does anyone have a more up-to-date source for the percentages of active Android devices with each version of the platform?


Galaxy S9: All day, most apps that I open will stop and immediately close. Apps running i the background repeatedly give the message "(app) keeps stopping". I've removed the SD card, and started it in Safe Mode. I also wiped the cache partition and cleared the Chrome cache. I'm using 57.1 GB out of 74, and memory shows 2.3 GB out of 4 used.

Recently, apps that are fine an hour ago now crash when I open them. The crash report message seems to be caused by a null pointer exception (NPE) in com.google.android.trichromelibrary. Apps affected for me:  Gmail Dashlane  Is it just me, or is there actually something wrong with the library? How can I fix these affected apps? Crash report: *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** Build fingerprint: 'Xiaomi/polaris/polaris:10/QKQ1.190828.002/20.9.4:user/release-keys' Revision: '0' ABI: 'arm64' Timestamp: ... pid: ..., tid: ..., name: com.dashlane >>> com.dashlane <<< uid: ... signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0 Cause: null pointer dereference          ...  backtrace:     #00 pc 00000000038621f0 /data/app/ com.google.android.trichromelibrary 438909034-YaxP9ttrIDcQBfleP5vm7Q==/base.apk! libmonochrome_64.so (offset 0x646000) (BuildId: ... )  (click  for the screenshot of the bug report)


When I was in high school, I asked a physics teacher "Why do we use complex to calculate stuff with electricity?" (something along that line) and he said "Because it just happens to work" without further details on WHY it works.  I'm in CS/IT and am not very well-versed in EE or abstract maths (though I know enough of the basics to make some robots simple.) As I learned about EE basics, I've learnt that complex numbers are VERY useful in EE and complex analysis is a must for students of EE.  I know complex numbers work well for calculating stuff in EE, but WHY does it work? In CS, I've learnt about how logic algebra works and why its maths works and have a pretty good fundamental understanding of it. Complex numbers, however, still seem quite abstract to me. "It just works" doesn't sit quite right with me.  So, how and WHY do imaginary numbers work to calculate stuff in EE?  Edit:  I'm well aware that complex numbers are used in EE like . However, what I'm asking is, I think, even more mathematically fundamental. Why do complex numbers work here at all?  They only possible answer to this I've seen so far is because of Euler's Formula:  \begin{equation} \label{Eq:I:22:9} e^{i\theta}=\cos\theta+i\sin\theta. \end{equation}  Is that it? Is that the sole reason complex numbers are used?

I was just wondering how complex numbers can be applied in electrical engineering and why we use complex numbers over regular, real numbers for this application (e.g what capabilities does the complex number have that real numbers do not in electrical engineering)?  I have done some research concerning impedances and understand how they are written in complex form, however I am still confused why complex numbers are necessary in this field over regular numbers.


Today I was unable to open Discord without updating it to the 0.0.2 version. I attempted to install it using the .deb file but when clicking on "install", nothing happened. So I installed it using the .tar.gz file with these commands:  sudo ln -s /usr/share/discord/discord.desktop /usr/share/applications/ sudo ln -s /usr/share/discord/discord.png /usr/share/icons/ sudo ln -s /usr/share/discord/Discord /usr/bin/discord   When I opened the application I just got a blank screen:

How do I install a .deb file via the command line?


I have a very simple code to insert data into database, also checks if already has same data in table  [HTML]        <title>nickname</title>
input nickname
     <form action="foo.php" method="post">         <input type="text" name="nickname" />         <input type="submit">     </form>     [PHP]  //foo.php if(isset($_POST['nickname']) && !empty($_POST['nickname'])) {     $nickname = $_POST['nickname'];      //Object Oriented way     $servername = "localhost";     $username = "root";     $password = "foo_bar";     $dbname = "nickname";      //check connection     $conn = new mysqli($servername, $username, $password, $dbname);      if($conn->connect_error) {         die("cannot connect:".$conn->connect_error);     }      $sql = "SELECT * FROM nickname WHERE nickname='$nickname'";     $result = $conn->query($sql);      if($result->num_rows > 0) {         echo "nickname exists!";     } else {         $sql = "INSERT INTO nickname(nickname) VALUES(".$nickname.")";         $conn->query($sql);         echo "welcome $nickname!";     }      $conn->close();  } else {     echo "please input your nickname"; }   I am still learning how to use MySQL, what am I doing wrong? especially this line  $sql = "INSERT INTO nickname(nickname) VALUES(".$nickname.")"; $conn->query($sql);   the data in the variable is not inserted to table, nothing happens. but if I replace $nickname to plain text the data is inserted.  edit why is this a duplicate? the question is not even about "how to prevent sql injection"

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


For a lack of better word, I used growing and shrinking in the question, but what I really mean is: Are objects that are now in the observable universe passing getting out of range in the future, or are objects that are now outside of the observable universe ever come close enough to pass over into the observable universe? Or both?  Is the number of objects in the observable universe growing or shrinking due to "migration"?

The size of our observable universe must have grown over time in the early universe.  Conversely with the accelerated expansion, I have heard that eventually our observable universe will shrink down to our local group of gravitationally bound galaxies.  So then the observable universe must go through a maximum at some point in time.  When is that and what is that maximum size?


I'd like to brush up on my statistics, but most books are either overly "colourful" or just plain shallow, and certainly far from a Bourbaki-esque style of exposition. Is there any "Graduate Texts in Mathematics"-like book on Statistical Inference that's both good for learning-reviewing and as a reference book?

Anyone can suggest me one or more good books on Statistical Inference (estimators, UMVU estimators, hypothesis testing, UMP test, interval estimators, ANOVA one-way and two-way...) based on rigorous probability/measure theory?  I've checked some classical books on this topic but apparently all start from scratch with an elementary probability theory.


I have a laptop which docks or plugs into 2 large monitors at my desk. When I unplug my laptop, to go to a meeting, it moves all the program windows onto the small laptop screen. Then when I plug it back in at my desk I have to rearrange all the windows again back onto the large monitors.  Is there a way I can keep all the windows positioning? Can you use the desktop feature in Windows to help one do this?

I find this beyond frustrating.  I have two extra screens on my laptop at work. I take my laptop and go home, with no extra screens connected. I come back, dock the laptop, and the windows need to be rearranged again.  Is there a way to get windows (or a utility) to keep track of the overall screen configuration (#, size, resolution), and remember where windows were placed, so when the screen configuration matches again, it puts applications BACK where they were?


If a lens is designated by manufacturer as "designed for crop sensor" (i.e. DC in Sigma, DX in Nikon, DT in Sony), how would that affect the calculation of practical focal length (equivalent focal length for a full frame sensor)?  For example, if I were to purchase a 50mm lens designed for a crop sensor camera, would that given/advertised focal length already be adjusted for the size of the crop sensor, or would I still multiply by 1.5 (so that the 50mm design for crop sensor lens is actually effectively 50*1.5=75mm) to get the effective focal length?

So, I mount a 200mm lens on my Canon 450D. It effectively becomes a 320mm lens. Is this the equivalent of 320mm on a full frame camera? That is, from what I've figured out I get an equivalent field of view but nothing I've read is indicating that I get the magnification to go along with it.  So as my question says in the title, does my crop sensor camera really turn my lens into a longer one (in terms of magnification), or does it just look like it based on the reduced field of view I get?


Android is a kind of Linux. So I would be able to use the commands.  Can I use Linux commands on Android? If I can, how do I?

Android is based on Linux and has a Linux kernel underneath. Is there any way I can use shell commands and interact directly with the Linux system? E.g. A shell app that has access to the Linux system?


For starters, I started studying blender it's been just a couple of weeks.  So, just for fun, I started modeling a key using a torus, a cylinder and a cube, as you can probably figure out by the images below:        It was all fun and games 'till I tried to merge the objects into one using Ctrl+J, weirdly the result was this:    I've tried changing the sequence of selection when I was merging, but it didn't solve the problem. That little thingy still disappeared. I think this error is due to the mirror modifier I used on the last piece of the key, and maybe when I merged it something wasn't compatible.  I also tried adding the same modifier to the other pieces but the result was the same. The last piece in detail can be seen in the link with the screenshots.  If anyone would kindly explain what's going on and hopefully come up with a solution I would be very much appreciated.

Trying to join my meshes to create a single mesh so it is easier for exporting/ However when I click Ctrl+J to join them all of the mirrored meshes disappear and I am left with half a shape.  Any Suggestions?


I am trying to log just errors in Backgroundjobs in Aspnet zero.  I can do it with given example in ;      Configuration.Auditing.Selectors.Add(     new NamedTypeSelector(         "Abp.ApplicationServices",         type => typeof (IApplicationService).IsAssignableFrom(type)     ) );   but when I am trying to do this with Backgroud jobs it doesn't work.   Configuration.Auditing.Selectors.Add(           new NamedTypeSelector(               "BackgroundJobs",               type => typeof(IBackgroundJob<>).IsAssignableFrom(type)           )       );    It works just specific classes;  Configuration.Auditing.Selectors.Add(               new NamedTypeSelector(                   "BackgroundJobs",                   type => typeof(IBackgroundJob<TestClass>).IsAssignableFrom(type)               )           );    What I want is just log all errors occured in classes implemented by IBackgroundJob<>.

example:  public static void DoSomething<K,V>(IDictionary<K,V> items) {    items.Keys.Each(key => {       if (items[key] **is IEnumerable<?>**) { /* do something */ }       else { /* do something else */ } }   Can this be done without using reflection? How do I say IEnumerable in C#? Should I just use IEnumerable since IEnumerable<> implements IEnumerable?


I am using Lubuntu 17.10 and every time I start the computer, after Lubuntu boots it shows this error:  WARNING: Failed to connect to lvmetad. Falling back to device scanning.  /dev/mapper/lubuntu--vg-root: clean, 239554/9674752 files, 19597960/38680576 blocks   When I turn off the computer the same error appears and after that it shows a blue screen and gets stuck in this position (doesn't turn off).

I upgraded my PC to Ubuntu 17.10, and now that I've restarted my PC I get this message:  Failed to connect to lvmetad. Falling back to device scanning. /dev/mapper/ubuntu--vg--root: clean, 500699/15081472 files, 9150222/60315648 blocks   It gets stuck on this.   What's the problem and how can I fix it?


What is the best way to share a free role playing game? I've painstakingly worked to make it easy to understand and play. I'm giving it away to get my works out in the gaming world.

I have been working on a short narrativist system for quite some time now. I intend to offer it freely to anyone interested but I'm not sure about a couple of things:  First, how do I package it? One option is to make a website with the rules. In that case, is making lots of small interconnected pages a good idea? Or is it better to keep it linear and on as few pages as possible? Another option is to make a book-like pdf, possibly using LaTeX. Assuming people go as far as the download page, will they be willing to get the pdf? Is it easier to read?   Second, how do I let other people know? I can't just barge into forums spamming about how great my system is. Should I look for contests or challenges, like the 24Hour RPG? Is there any point to posting on social news/bookmarking sites? Is it good form to contact game review sites and ask them to consider my game?  Feel free to ignore the secondary questions if you want to; they're there only to expose my reasoning thus far and to inspire answers.


Prove Divisibility test for 11  "If you repeatedly subtract the ones digit and get 0, the number is divisible by 11"  Example:   11825 -> 1182 - 5 = 1177  1177 -> 117 - 7 = 110  110 -> 11 - 0 = 11  11 -> 1-1 = 0  Therefore 11825 is divisible by 11. Note 11825 = 1075*11  I was thinking that we let x = $a_ka_{k-1}.....a_1a_0$ where the following $a_i$'s are the digits.

We know that $1331$ is divisible by $11$. As per the $11$ divisibility test, we can say $1331$ is divisible by $11$. However we cannot get any quotient. If we subtract each unit digit in the following way, we can see the quotient when $1331$ is divided by $11$.  $1331 \implies 133 -1= 132$ $132 \implies 13 - 2= 11$ $11 \implies 1-1 = 0$, which is divisible by $11$.  Also the quotient is, arrange, all the subtracted  unit digits (in bold and italic) from bottom to top, we get $121$. Which is quotient. I want to know how this method is working? Please write a proof.


I know about joins in SQL Server.  For example. There are two tables Table1, Table2.   Their table structures are the following.  create table Table1 (id int, Name varchar (10))  create table Table2 (id int, Name varchar (10))   Table1 data as follows:      Id     Name          -------------     1      A             2      B       Table2 data as follows:      Id     Name          -------------     1      A             2      B      3      C   If I execute both below mentioned SQL statements, both outputs will be the same  select * from Table1   left join Table2 on Table1.id = Table2.id  select * from Table2   right join Table1 on Table1.id = Table2.id   Please explain the difference between left and right join in the above SQL statements.

Also how do LEFT JOIN, RIGHT JOIN and FULL JOIN fit in?


I got an e-mail notification of three comments to a question I posted. Now going to look, I see one of the comments, but the other two are not there. Presumably, they were deleted. Since a record is available of revisions to questions and answers, I wonder if there's any way to see comments that have been deleted?

In my notification bar at the top of the page, there's a pretty rude comment about my question, but when I try to look at it, it's already been deleted. I'd really like to be able to respond to that comment (in a polite, professional manner, of course.) Is there any way I can see comments that have been deleted?