There are a number of Stack Exchange sister sites. I have a hard time signing up with them. I'm presented with three options:   Sign up using Google Sign up using Facebook Sign up using Stack Exchange   I have a Stack Exchange ID, so that's what I want to use.  On filling in my existing name, email, and password (confirmed), I am presented with the puzzling message:     We already have an account with that email address.   If the email is correct, try recovering your account.   Huh? Of course I have an account with that email address. That's what I'm trying to use!  I'm using the right email, the right password. Why do I have to enter any of that? I'm logged into three SE sites right now! Why do I have to type my password twice, and above all, why do I have to "recover my account", which I never lost?  My workaround has been to "recover my account". That means changing my password with all of my existing SE accounts.

For most OpenID options, it doesn't much matter if you pick the "Sign up" versus the "Log in" tab on the sign in page.  Whether you have an account on the site or not, it just does the right thing. Not so if you are using the Stack Exchange OpenID service:    (Bonus bug: the reCAPTCHA box is a bit too wide for the expanded "Sign up using Stack Exchange" container.)  Since we already have collected an email and password (well, two copies of the password), could we not check to see if they match and automagically log the user into their SE OpenID?  If not, the error needs to be reworded somehow to explain that while the email might have been used to create a Stack Exchange OpenID, that doesn't mean they can't log in with that OpenID to create an account.  Counterintuitively, they need to use the  even if they've never had an account there before.  The  link adds to the confusion since it sends an email that leads off with:     Someone requested an account recovery on The Workplace Stack Exchange for jericson@stackexchange.com, but we don't have an account on this site that matches this email address.   (For people with accounts on other sites and/or Stack Exchange OpenIDs, this paragraph is followed by other instructions that would probably work if followed. By that time I imagine many users are at wit's end.)  To simplify: If a user already has a Stack Exchange OpenID (likely because they have an account on another site) they should be able to use the  to sign up for an account or there should be clear instructions on what to do next if they fail.


Disclaimer - I'm not a mathematician, I'm a dirty physicist.  My work often involves performing calculus on various things without thinking about what I'm doing too much (I leave the proof of various identities etc for the pure mathematicians to worry about).  However I've often noticed that mathematicians get a little upset when I do tricks such as treating the differential $\frac{\text{d}y}{\text{d}x}$ as if it were a fraction.  The simplest example I can think of is how I think about the chain rule: $$\frac{\text{d}y}{\text{d}x} = \frac{\text{d}y}{\text{d}u}\frac{\text{d}u}{\text{d}x}$$ In my head, I imagine the $\text{d}u$ terms cancelling, which is why this works.  Indeed, this is how I'll explain to others how to use the chain rule when asked about it.  My question is the following:  Is is dangerous to think about differentials in this way?  After all, one of the very first examples of calculus I've ever seen (back when I was a baby in high-school) was the derivative of $y=x^2$ calculated from first principles in the following way:     \begin{align} y&=x^2\\ y+\delta y&=(x+\delta x)^2\\ y+\delta y&=x^2+2x\delta x+\delta x^2\\ \require{cancel}\cancel{x^2}+\delta y&=\cancel{x^2}+2x\delta x+\delta x^2\\ \delta y&=2x\delta x+\delta x^2\\ \frac{\delta y}{\delta x}&=2x+\delta x\\ \text{Now let }&\delta x\rightarrow0\text{ leaving}\\ \frac{\delta y}{\delta x}&=2x\\ \frac{\text{d}y}{\text{d}x}&=2x \end{align}   And to me, this is just treating $\frac{\delta y}{\delta x}$ as a fraction.  I know that technically you're doing $0/0$ if you think about it, but are there any examples where treating $\text{d}y/\text{d}x$ is really inappropriate?

In the book Thomas's Calculus (11th edition) it is mentioned (Section 3.8 pg 225) that the derivative $dy/dx$ is not a ratio. Couldn't it be interpreted as a ratio, because according to the formula $dy = f'(x)dx$ we are able to plug in values for $dx$ and calculate a $dy$ (differential). Then if we rearrange we get $dy/dx$ which could be seen as a ratio.   I wonder if the author says this because $dx$ is an independent variable, and $dy$ is a dependent variable, for $dy/dx$ to be a ratio both variables need to be independent.. maybe?


This semester I both took a computer vision and a computer graphics seminar. But only now before the exams I realize that there seems to be a fundamental difference between projection in both topics.   In computer vision we learned the math to map an object point from 3D to a plane using a 4x3 matrix, which seems logical to me:  |u|   |p_11 p_12 p_13 p_14|   |X| |v| = |p_21 p_22 p_23 p_24| x |Y| |w|   |p_31 p_32 p_33 p_34|   |Z|                               |1|   However in computer graphics one usually uses a 4x4-matrix. The very nice explanation on  has a picture depicting the outcome of said transformation: it depicts a unit-cube containing the transformed objects (distorted according to the projection).   But a unit-cube certainly isn't what is rendered on to the flat 2D screen. Is there something going on internally that just isn't mentioned? Why is this done?

To translate a vector by 10 unit in the X direction, why do we have to use a matrix?    We can just add 10 to the mat[0][0], and we got the same result too.


I am bench-marking the execution time of solving matrices , and i cant get more then ~200x200, i should go probably 1500x1500 or close to that. I am running this on VS .   #include <stdlib.h> #include <stdio.h> #include "lapacke.h" #include "lapacke_config.h" #include <time.h>  /* Auxiliary routines prototypes */ extern void print_matrix(lapack_complex_double *a, int m, int n); extern void generate_matrix(lapack_complex_double * matrix, int w, int h);  /* Parameters */ #define N 179  /* Main program */ int main() {     clock_t t;     /* Locals */     lapack_int n = N,info;     lapack_int ipiv[N];     lapack_complex_double a[N*N];     lapack_complex_double b[N*N];      FILE* fp1 = fopen("complexNumsLog.txt", "w");      int w = 1, h = 1, h2 = 1, i = 0, j = 0;        for(i = 1; i <= N; i++){         for(j = 1; j <= N; j++){             w = i;             h = i;             h2 = j;              generate_matrix(a, w, h);             generate_matrix(b, w, h2);              // print_matrix(a, w, h);             // print_matrix(b, w, h2);              // getchar();                t = clock();             info = LAPACKE_zgesv(LAPACK_ROW_MAJOR, w, h2, a, h, ipiv, b, h2);             t = clock() - t;              fprintf(fp1, "Matrix A: %3dx%3d ", w, h);             fprintf(fp1, "Matrix B: %3dx%3d ", w, h2);             fprintf(fp1, "%3d milliseconds %2.3f seconds\n",t,((float)t)/CLOCKS_PER_SEC);              /* Check for the exact singularity */             if( info > 0 ) {                 printf( "The diagonal element of the triangular factor of A,\n" );                 printf( "U(%i,%i) is zero, so that A is singular;\n", info, info );                 printf( "the solution could not be computed.\n" );                 getchar();                 exit( 1 );             }         }         printf("%d\n", i);     }     getchar();     exit( 0 ); }   void print_matrix(lapack_complex_double* a, int m, int n) {     int i, j;     for( i = 0; i < m; i++ ) {         for( j = 0; j < n; j++ )             printf( " (%6.2f,%6.2f)", a[i*m+j].real, a[i*m+j].imag );         printf( "\n" );     }     printf( "********************************************\n" ); }    void generate_matrix(lapack_complex_double * matrix, int w, int h){     int i,j;     double r;     for(i = 0; i < w; i++){         for(j = 0; j < h; j++){             r = (rand()%1000 - 500)/100.0;             matrix[i*w+j].real = r;             r = (rand()%1000 - 500)/100.0;             matrix[i*w+j].imag = r;;         }     } }

Programming language books explain that value types are created on the stack, and reference types are created on the heap, without explaining what these two things are. I haven't read a clear explanation of this.  I understand what a stack is. But,    Where and what are they (physically in a real computer's memory)? To what extent are they controlled by the OS or language run-time? What is their scope? What determines the size of each of them? What makes one faster?


I googled quite a while in order to find out a comparison that shows the differences in complexity for all STL-Containers on insert/push erase/pop etc. I did not find any. Also not in all of my STL Books. Any hint?  I know some rules of thumb of course. But where is a definition?

Apparently ;-) the standard containers provide some form of guarantees.  What type of guarantees and what exactly are the differences between the different types of container?  Working from  (about ) I have come up with this:  Container Types: ================ Container:     Forward Container         Reverse Container             Random Access Container     Sequence         Front Insert Sequence         Back  Insert Sequence     Associative Container         Simple   Associative Container         Pair     Associative Container         Sorted   Associative Container         Multiple Associative Container  Container Types mapped to Standard Containers =============================================  std::vector:    Sequence    Back        Sequence                    Forward/Reverse/Random Container std::deque:     Sequence    Front/Back  Sequence                    Forward/Reverse/Random Container std::list:      Sequence    Front/Back  Sequence                    Forward/Reverse Container std::set:       Sorted/Simple/Unique    Associative Container       Forward Container std::map:       Sorted/Pair/Unique      Associative Container       Forward Container std::multiset:  Sorted/Simple/Multiple  Associative Container       Forward Container std::multimap:  Sorted/Pair/Multiple    Associative Container       Forward Container   Container Guarantees: =====================                                                                                Simp                                                                                or                           For   Rev  Rand        Front  Back  Assoc        Sort   Mult                     Cont: Cont: Cont Cont: Sequ: Sequ:  Sequ: Cont:        Cont:  Cont: Copy    Const:      O(n) Fill    Const:                             O(n) begin()             O(1) end()               O(1) rbegin()                        O(1) rend()                          O(1) front()                                    O(1) push_front()                                     O(1) pop_front()                                      O(1) push_back()                                             O(1) pop_back()                                              O(1) Insert()                                                                          O(ln(n)) Insert: fill                               O(n) Insert: range                              O(n)                                   O(kln(n)+n) size()              O(n) swap()              O(1) erase key                                                     O(ln(n)) erase element                                                 O(1) erase range                                                   O(ln(n)+S) count()                                                       O(log(n)+k) find()                                                        O(ln(n)) equal range                                                   O(ln(n)) Lower Bound/Upper Bound                                                    O(ln(n)) Equality                  O(n) InEquality                O(n) Element Access                       O(1)


I first implement following functions in the same .cpp file as the main(). Everything works perfectly. But I met some problem when I tried to define them in a header file and implement them in a separate .cpp file.  These are my original code:  template <class T> //implement the sum function of one single container double sum(const T& source){...}  //explicit specialization for map template<> double sum<map<string, double>>(const map<string,double>& source){...}  template <class T> //implement the sum function for two iterators double sum( const class T::const_iterator& start,  const class T::const_iterator& end){...}  //explicit specialization for map (sum function of iterator) template<> double sum<map<string, double>>(const map<string, double>::const_iterator& start,const map<string, double>::const_iterator& end){...}  void main(){...}   Then I remove the implementation of the functions and define them in a header file:  template <class T> //implement the sum function of one single container double sum(const T& source);  //explicit specialization for map template<> double sum<map<string, double>>(const map<string,double>& source);  template <class T> //implement the sum function for two iterators double sum( const class T::const_iterator& start,  const class T::const_iterator& end);  //explicit specialization for map (sum function of iterator) template<> double sum<map<string, double>>(const map<string, double>::const_iterator& start,const map<string, double>::const_iterator& end);   and implement them in a .cpp file.  Then when I include both of the header file and cpp file, and run the project:  main(){...}   I received error message like:  sum.obj : error LNK2005: "double __cdecl sum<class std::map<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >....   Can anyone give a hint what I might have done wrong?   Many thanks!

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


I want to interpolate temperature for a surface defined by three coordinates: longitude, latitude and altitude. I know one option is to use universal kriging on two dimensions and use altitude as a regressor. ¿is there a way to perform ordinary kriging on three dimensions with the gstat package in R? ¿what option (3d ordinary kriging or 2d universal kriging) is likely to produce more accurate interpolation results?

I would like to see the difference of including DEM in interpolation from without. Some studies on climate data interpolation suggest that interpolation performs better with DEM. How do I do this in ArcGIS 10.2?


When I was younger (and stupider) I did the quest Taking Sides but I choose Stormcloaks. Now I regret that decision very very much because I have to attack Whiterun. I'm playing on Xbox360, is there any way to join the Imperials?

This is my first time through playing Elder Scrolls and initially I grabbed every quest that has come available...  At first I thought I wanted to be part of the Imperial Legion but I feel like I picked the wrong side and am now regretting my choice.  So...is there any way to un-join the Legion and join up with the Stormcloaks, or will I have to wait and join them next time?


Suppose we have a monochromatic light beam. We put an obstacle between source and observer and remove it repeatedly by certain frequency such that observer sees an oscillating intensity of light. Will the observer see different frequencies or only the original frequency? Does the energy-time uncertainty principle apply in this case?

My textbook and the following extract from feynman's lectures present the same idea regarding wavetrains and uncertainty in their wavelengths. Why is it that a wavetrain confined to some space has an uncertainty in its wavelength or the wave number? Is not a confined wave-train equivalent to a burst of successive pulses which can have a definite wavelength according to their origin or nature of origin.   Next, i understand that the De Broglie relation relates the uncertainty in wavelength to the uncertainty in momentum but what links the finiteness of the wave-train to the uncertainty in position?


When a user does not fill his "about me" section in his profile, the following sentence appears:     Apparently, this user prefers to keep an air of mystery about them.   To my knowledge (which are restricted I admit), it should be     Apparently, this user prefers to keep an air of mystery about him/himself.   I'm pretty sure that I'm wrong, however I really don't understand the use of plural in "them".  Could you please explain me the underlying grammar rule that justifies such a term? Also, I'd be happy to know if replacing them by him or himself would be correct.

Is there a pronoun I can use as a gender-neutral pronoun when referring back to a singular noun phrase?  Each student should save his questions until the end. Each student should save her questions until the end.


I cant find this information anywhere. please help

Service  since Mar 29th. It looks like all the new applicants are allowed to reserve appointment with USCIS for biometrics (see: )  Did anyone successfully finish biometric process at USCIS post Mar 29th? Sometimes the website does not get updated, leaving people in the dark.  This information will help the affected people to plan.


Why output for this code is Class A I expected to see "Class AAA"  #include <iostream>     using namespace std;  class A {     public:     A(){}     virtual int Method1(int a, int b){cout << "Class A" << endl; return a+b;    } };  class AA:public A {     public:     AA(){}     int Method1(int a, int b){cout << "Class AA" << endl; return a*b;} };  class AAA:public A {     public:     AAA(){}     int Method1(int a, int b){cout << "Class AAA" << endl; return a/b;} };  class B { public:    B(){}    B(A a):obj(&a){}    int Method2(int a, int b){ return obj->Method1(a,b);}  private:     A *obj; };  int main() {     A *a = new AAA();     B *b = new B(*a);     b->Method2(2,1);     return 0; }   I have new AAA object passed to class B and assigned to  *obj. What is wrong with this ?  Best Regards,

Someone mentioned it in the IRC as the slicing problem.


The daily email I receive regarding new Python questions on SO arrived today and had a link to a google drive document called "banana_features.csv". I've never seen this email come with a link/attachment before and it just seems odd...   Not sure if this is a bug SE side or some artefact of the content of the digest doing it... any clues?  Screen shot of the first 20 rows if it's of any use:

What in all actually is this PDF attachment doing with the newsletter?    I'm fairly confident that this also came from Stack Exchange, so would someone care to enlighten me as to what's going on?  I admit I'm rusty at reading mail headers, but the sources seem to line up just fine.  Delivered-To: --REDACTED-- Received: by 10.229.68.6 with SMTP id t6csp224071qci;         Fri, 20 Mar 2015 12:28:47 -0700 (PDT) X-Received: by 10.55.31.97 with SMTP id f94mr119580342qkf.10.1426879727323;         Fri, 20 Mar 2015 12:28:47 -0700 (PDT) Return-Path: <do-not-reply@stackexchange.com> Received: from mx-out.stackexchange.com (mx-out.stackexchange.com. [198.252.206.125])         by mx.google.com with ESMTPS id i90si5136899qge.83.2015.03.20.12.28.46         for <--REDACTED-->         (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);         Fri, 20 Mar 2015 12:28:47 -0700 (PDT) Received-SPF: pass (google.com: domain of do-not-reply@stackexchange.com designates 198.252.206.125 as permitted sender) client-ip=198.252.206.125; Authentication-Results: mx.google.com;        spf=pass (google.com: domain of do-not-reply@stackexchange.com designates 198.252.206.125 as permitted sender) smtp.mail=do-not-reply@stackexchange.com;        dkim=pass header.i=@stackexchange.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=stackexchange.com; s=dk;     h=Content-Type:Message-ID:Date:Subject:Reply-To:To:From:MIME-Version; bh=1OWPTURI/S9xuD+By0vS6qm84rNbZTEnVTBe0n3jV2Q=;     b=VEwIjIH/yuaj1DiAJMIuXOs8vPo1fhJOHhM7v9IWtvRozVyDnMzZBeFVsaAiUDSmsMrXb8sH3X0TU2a94KkuzByGyong8s4pRn6CridgSwOJuQ1OLhN/zSNiSu00rPENBxFhmiABN0PNx8m6S8OZHwMMPob6SzQUm5IK1JsjFxY=; Received: from [10.7.2.15] (helo=[10.7.2.101])     by mx-out.stackexchange.com with esmtp (Exim 4.72)     (envelope-from <do-not-reply@stackexchange.com>)     id 1YZ0VC-0006l0-SY     for --REDACTED--; Fri, 20 Mar 2015 17:14:30 +0000 MIME-Version: 1.0 X-Mailer: MailBee.NET 7.0.4.334 From: "Stack Exchange" <do-not-reply@stackexchange.com> To: --REDACTED-- Reply-To: do-not-reply@stackexchange.com Subject: Super User Weekly Newsletter - Friday, March 20, 2015 Date: Fri, 20 Mar 2015 17:14:30 +0000 Message-ID: <2.9e47a33dae2ecd6e7599@NY-WEB01> Content-Type: multipart/alternative;


I'm using Python 3 and working with title strings that have a bracketed tag with a pair of names separated by a +. Like this: [John+Alice] A title here.  I've been using the regex expression re.search('\[(.+)\]', title) to get the tag [John+Alice], which is fine, but it's a problem when encountering a title with more than one bracketed tag:  [John+Alice] [Hayley + Serene] Another title.   That gives me [John+Alice] [Hayley + Serene], when I would prefer [John+Alice] and [Hayley + Serene].   How can I modify the regex to give me all bracketed tags that have + between [ and ]? Thanks.

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


This is my first post in Blender. I'm currently working on this sugarcane's project, But The rendering result cause a lot of noise or flicking issues. can any one give me a advise? I got turn on Denoising and 120 Samples. much appreciated if you guys could give me a hand. thanks    Below is the test rendering link. please have a look.

I know that this question is a bit old or maybe overdone, but I'm running the latest edition of Blender and when I use the Cycles engine I get really fuzzy results and I can't find a simple, non-compromising solution to the quality.  I don't know exactly what I'm doing wrong here, but I'm sure others share my frustration.  Leaving everything in default settings, I started a new project and switched to the Cycles render.  I duplicated the cube and set colors for two Diffuse BSDF shaders, then went ahead and made walls and a floor all sharing the same diffuse shader.  I made two windows to emit blue light.  The screenshot has gaps between the walls because of the setup:  I'm aware that it's considered very incomplete and many have come to terms with some amount of noise, but is this normal?  Furthermore, with default settings or not, I can't change the amount of noise produced.  Supposedly, using "progressively refine" in the rendering tab should make it refine itself indefinitely, however Cycles only counts to 10 refines and then stops, creating a render which is a pixel-perfect match of the ordinary rendering method when it's completed.  I understand that there are tricks that can be used to reduce noise, but at the cost of extra processing time and usually small quality conflicts, like blurring.  My question essentially boils down to is this Cycles' current limit?


Currently, I'm working with Python 3.4. How could I avoid .pyc or .pyo files (__pycache__) without editing the commandline?  The following command works perfectly Using terminal: python3 -B something.py  But these are not working in Python 3 (or are they??):  import os  os.environ['PYTHONDONTWRITEBYTECODE'] = "whatever"   according to the , if it is set to a non-empty string, it should work. But I couldn't.  What am I missing?

Can I run the python interpreter without generating the compiled .pyc files?


I have the following  class Test{      public Inner x;      public static void main(String[] args){          Test t = new Test();         t.bar(t.x);      }      public Test(){         x = new Inner();         System.out.println("X = "+x.val);     }      public void bar(Inner a){         x.val = 2;         System.out.println("a = "+a.val);         a = new Inner(5);         System.out.println("a = "+a.val);         System.out.println("X = "+this.x.val);     }      class Inner{         public int val;         public Inner(){val=0;}         public Inner(int i){val=i;}     } }   I am concerned why the program tells me that my class's inner object and passed-in object are the same, but when I change the passed object to a new one, they are suddenly not the same. I thought java passed by pointers, and thus changing the pointer location of "a" in my bar method would likewise change the pointer location of "x", which was passed in.

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


when I'm trying to update through terminal I'm getting the following error:  E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?   I am not sure if it is due to virus or any other reason.

I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this?


Prove by induction that $\forall x \in \mathbb{R}, x \geq -1, \forall n \in \mathbb{N},n \geq 0$ that $$(1+x)^n \geq 1+nx$$ First of all I have a problem with x being a real number, how can I use induction over a real number? Can I simply assume that it holds for all $y \in [-1,x]$ and then show that it also holds for $x + \epsilon, \epsilon \in \mathbb{R},\epsilon \gt 0$?  If that were possible I would try to prove over n. Prove the base case for n, use induction over x and then prove the induction step over n.  But I have some problems with the induction step over n.  Assuming that it works for all $l \in \mathbb{N}, l \leq n-1$. I need to show $$(1+x)^n=(1+x)^{n-1}(1+x) \geq 1+(n-1)x+x$$ which basically results in showing that $$z(1+x) \geq z + x$$ for some quantity z, correct?  But then I'd get $$zx \geq x$$, which would obviously depend on the value of z.  I'm kind of confused at this point, any help would be appreciated.

I'm asked to used induction to prove Bernoulli's Inequality: If $1+x>0$, then $(1+x)^n\geq 1+nx$ for all $n\in\mathbb{N}$. This what I have so far:  Let $n=1$. Then $1+x\geq 1+x$. This is true. Now assume that the proposed inequality holds for some arbitrary $k$, namely that $$1+x>0\implies (1+x)^k\geq 1+kx,~\forall~k\in\mathbb{N}\setminus\{1\}$$ is true. We want to show that the proposed inequality holds for $k+1$. Thus multiplication of $(1+x)$ on each side of the above inequality produces the following result: $$(1+x)(1+x)^k\geq (1+kx)(1+x)\implies (1+x)^{k+1}\geq 1+x+kx+kx^2\cdots\cdots\cdots$$  I'm not sure where to go from here.


Let $P \subset \mathbb{N}$ be a finite index set and suppose that there is a partial function $f:P \to P$, which is undefined for some strict subset of $P$. Then, suppose I have a function $g: P \to \{ 0, 1 \}$ defined as $$ g(i) =  \begin{cases} 0 & f(i) \text{ is undefined} \\ 1 & f(i) \text{ is defined.} \end{cases} $$ What is the formally correct way to denote these predicates? Could $\not \exists f(i)$ and $\exists f(i)$ work?

Consider a partial function $f$ that is defined only for a few values of its domain (my exact use case is $\delta$ transition functions in automata). One can 'complete' it by saying $$g(x)=0\iff f(x) \text{ is not defined.}$$  Is there a symbol to mean "undefined"? Would it be correct, or accurate, to write $\nexists f(x)$?


Background: I have a game, the game uses an ArrayList to store tile data. There are several subclass's like TileLadder, TileFan, etc...  The Issue: When I go to replace the tile with a new class (ie. replace an Air Tile with a fan tile) It doesn't show the change   Here is the placeTile method:  public void placeTile(int x,int y,Tile tile) {         Tile replace = getTile(x,y);         replace = tile; }   This is odd, shouldn't this automatically set the 'replace' tile class with the new tile, thus changing what is rendered?   Notes: 1. getTile() method is works 100% of the time. 2. The entire map is tiled, there are air tiles which are not rendered.  3. Some tiles have there own subclass (ex. TileFan) for specific functions. Tiles like Grass do not.   A few other methods that might prove helpful:  public void deleteTile(Tile tile) {     if(tile!=null) { tile.getMetadata().setTag(EnumTileTag.Non_Solid);             tile.getMetadata().setType(EnumTile.AIR);             tile.image = Sprites.TILE_AIR;         }            }   public Tile getTile(int x,int y) {     Tile toReturn = null;     x  = x / 2;      y  = y / 2;     x -= Camera.OFFX;     y -= Camera.OFFY;     for(Tile tile : tiles) {         if(tile.getCollision().contains(x,y)) {             return tile;         }     }      return toReturn; }   Thank you for reading my question and I hope you understand it, please ask me for any extra information, I have tried to be as detailed as possible in my explanation, hopefully this is an easy fix. ;)


This huge dock appears when I press the Windows key:   I already have plank installed, I just want others dock to be completely removed, I already run a command to remove the default dock, I don't know what the heck is this appearing here, this is very frustrating.

After I installed plank as my dock panel, I removed the default Ubuntu dock by running    sudo apt-get remove gnome-shell-extension-ubuntu-dock   Then Ubuntu dock is not on my desktop anymore, but when I open the application menu or Activities overview it is there, how can I hide it?  Removed dock shows on the left:


Using Oracle SQL.   COL1        COL2                COL3    COL4 2017-12-01  2017-12-01 02:00    296.82  161 2017-12-01  2017-12-01 06:00    287.25  158 2017-12-01  2017-12-01 10:00    290.3   157 2017-12-01  2017-12-01 14:00    345.58  157 2017-12-01  2017-12-01 18:00    285.13  156 2017-12-01  2017-12-01 22:00    287.68  158 2017-12-02  2017-12-02 02:00    306.5   164 2017-12-02  2017-12-02 06:00    315.79  166 2017-12-02  2017-12-02 10:00    307.59  164   What I need to do is get the MAX(COL3) from each day but I need the other values out of the row as well....I can group by COL1 but I'm having issues returning the other values COL2 and COL4 from the row as well.   Almost there however this is not working It is saying that the from is in a bad location.....  SELECT *,MAX(VDC) OVER (PARTITION BY DATETHE) from (select  trunc(x.lvl) "DATETHE", energy_metrics_pdu.WATTS_READING "PDU", case energy_metrics_pdu.watts_reading when 0 then NULL else round(energy_metrics_vdc.watts_reading/energy_metrics_pdu.WATTS_READING,2) END "RATIO", energy_metrics_vdc.watts_reading "VDC" from (  SELECT to_date('01-DEC-2017','DD-MON-YYYY') + (level/24)-0  lvl         FROM dual         CONNECT BY LEVEL <= (5*24)-1 ) x          LEFT JOIN energy_metrics_pdu on to_char(x.lvl, 'YYYY-MM-DD HH24') = to_char(energy_metrics_pdu.READING_DATE, 'YYYY-MM-DD HH24')          LEFT join energy_metrics_vdc on to_char(x.lvl, 'YYYY-MM-DD HH24')||':00' = to_char(energy_metrics_vdc.READING_DATE, 'YYYY-MM-DD HH24:MI')         where energy_metrics_pdu.watts_reading IS NOT NULL  order by "DATETHE" ASC          );    Any suggestions...

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


I was trying to learn something else then i encounter with the following code.   class point{}; point p_; new (&p_) point(w.p_);   What does third line expression do, and what is intended ? Does it helps us to save time while copying or something. And is p_ somehow allocated dinamically? // I'm so confused.  The place I encountered ->>   //Second page of the document.

Has anyone here ever used C++'s "placement new"? If so, what for? It looks to me like it would only be useful on memory-mapped hardware.


Possibly a simple / daft question so apologies in advance...  Suppose I have several independent observations of a continuous variable, like height. The observations are grouped, and I would like to test whether the groups have significantly different distributions. If the groups are nominal I would use a one-way ANOVA, if continuous I would use a mixed-model, but what should I use if the groups are ordinal but not at regular intervals?  For example, for the continuous variable "height", nominal groups might be English people vs Swedish people vs French people --> ANOVA, if the 'groups' are Age --> Mixed model, but if the groups are, say, "Self-reported weekly exercise", or "eating your greens", where ordinal categories might be: not at all, mild, moderate, lots, what would people suggest?

I am trying to analyze data based on a sample size of around 50 and would appreciate advice on which statistical test would be most appropriate. Participants, on a single questionnaire, were asked to complete two different sections. Variable 1: rating Likert items on a scale from 1-5 (strongly agree to disagree). Variable 2: rating Likert items of a validated tool on a scale of 1-9, which is averaged to obtain a single number.  My research question is: Do those who 'agree' with the statement in the first section significantly differ in terms of their scores on the variable 2, compared to those who 'disagree'? (ex. Do participants tend to 'agree' with "I like to read books for pleasure." have higher IQs (variable 2) than those who 'disagree'?)  I was advised by a colleague to run a one-way ANOVA with variable 1 (categorical) as IV and variable 2 (continuous) as DV.   Question 1: My independent variable is the three groups: 'agree', 'neutral', and 'disagree.' (I combined strongly agree with agree because of low frequencies and likewise for strongly disagree and disagree.) However, there are many more participants in the 'agree' category than in the 'disagree' category. The distribution is, on average, around 44 agrees, 3 neutrals, and 3 disagrees. Do the (very) unequal sample sizes prevent me from performing ANOVA, or any other tests? Which test would be most appropriate for this analysis?  Question 2: I would like to run analyses on all of the Likert items, which is more than 10 statements. (ex. Seeing how IQs correlate with agreement to many statements including “I like to read books for pleasure,” “I watch a lot of TV,” “I exercise more than 30 minutes each week,” etc.) I was planning to do a Bonferroni correction to adjust for the multiple tests. Would this be correct, and help make my analyses more robust? Note: The continuous data are not normally distributed (there is negative skewness), but I seem to be able to correct the skewness using logarithmic transformation.  Any advice or suggestions for papers to read would be appreciated. Thank you!


Given these two array:         $name=array("alice","ken","wendy");  $frequent=array(3,6,9);                                          I try to combine it like  $data = array($name=>$frequent);   but it fails. Anyone can help?  I want this:  $data = array(       'alice' => 3,       'ken' => 6,       'wendy' => 9,  );

I've got two arrays of the same size.  I'd like to merge the two so the values of one are the key indexes of the new array, and the values of the new array are the values of the other.  Right now I'm just looping through the arrays and creating the new array manually, but I have a feeling there is a much more elegant way to go about this.  I don't see any array functions for this purpose, but maybe I missed something?  Is there a simple way to this along these lines?  $mapped_array = mapkeys($array_with_keys, $array_with_values);


I am currently preparing lots of las files for analysis and am wondering about the easiest way to share the results on my intranet.   Are there any cool web application for displaying and navigating within las point clouds?

I am looking to host lidar data on my own server and give clients the ability to view that data through a web browser as a 3D point cloud (file would be in .las format or equivalent), possibly with the ability to measure features.   Does anyone know of an easy to implement piece of software that can do this?  I am not nessecarily looking for open source, and I would prefer something plug and play because I am not a programmer.


I built a cube under a white point light to build a material using Cycles rendering. When I finished building my material and went to bed after saving the file, the material was kind of white with grey spots.  When I opened the file this morning, the material is pink in color. Note, I have not made any changes at all to any aspect of the file, anywhere. So with it just becoming pink for no apparent reason, I have no idea how it happened or what to do to fix it.

I made a character, and its one of my first times texturing, and I saved my character into a new folder, and when I came back to the model ALL the textures were pink, I used to know what to do, but I stopped texturing, how do I bring my textures back?


Just got a new MacBook with USB 3 ports. I thought it would be able to charge my Nexus 4 phone much faster using USB 3 900 mA current.  However, I haven't seen any improvements compared to charging on a USB 2 port. Obviously, AC chargers can charge way over 500 mA using USB 2 cables.  Which brings me to question: can a (micro) USB 2 cable hooked up to a computer USB 3 port charge a device at 900 mA current, or is it limited by the USB 2 cable to 500 mA?

I have some USB 3.0 ports on my motherboard which can deliver up to 900 mA of current I believe.  If I plug in a USB 2.0 cable, I can still get up to 900 mA right? I have some devices that uses USB charging and outputs from 1A to 2A but I'm not sure if the cable provided is a factor or not since I'm just using a generic USB cable for this.


I need to create at runtime instances of a class that uses generics, like class<T>, without knowing previously the type T they will have, I would like to do something like that:  public Dictionary<Type, object> GenerateLists(List<Type> types) {     Dictionary<Type, object> lists = new Dictionary<Type, object>();      foreach (Type type in types)     {         lists.Add(type, new List<type>()); /* this new List<type>() doesn't work */     }      return lists; }   ...but I can't. I think it is not possible to write in C# inside the generic brackets a type variable. Is there another way to do it?

What's the best way to call a generic method when the type parameter isn't known at compile time, but instead is obtained dynamically at runtime?  Consider the following sample code - inside the Example() method, what's the most concise way to invoke GenericMethod<T>() using the Type stored in the myType variable?  public class Sample {     public void Example(string typeName)     {         Type myType = FindType(typeName);          // What goes here to call GenericMethod<T>()?         GenericMethod<myType>(); // This doesn't work          // What changes to call StaticMethod<T>()?         Sample.StaticMethod<myType>(); // This also doesn't work     }      public void GenericMethod<T>()     {         // ...     }      public static void StaticMethod<T>()     {         //...     } }


Below is my code but it gives me null point error. some please help me out to find out what is the error  package path1;  import org.openqa.selenium.WebDriver; import org.openqa.selenium.firefox.FirefoxDriver; import org.openqa.selenium.firefox.FirefoxProfile; import org.openqa.selenium.firefox.internal.ProfilesIni;  public class New1 {   public static void main(String[] args) {               System.setProperty("webdriv`enter code here`er.gecko.driver", "C://Users/Ramesh/Desktop/Udemy/Selenium/geckodriver.exe");           ProfilesIni profile = new ProfilesIni();      FirefoxProfile testprofile = profile.getProfile("default");     testprofile.setAcceptUntrustedCertificates(true);     testprofile.setAssumeUntrustedCertificateIssuer(true);      WebDriver driver = new FirefoxDriver(testprofile);     driver.get("https://www.w3schools.com/");   }     }

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 have Ubuntu installed on a USB flash drive.  It works fairly well.  But every time I exit the system, it erases all newly created data and settings.  E.g., the add-nos in Firefox are deleted and all the other settings, like bookmarks.  All downloaded files are deleted.  When I boot up the system again, only the original system appears.  How can I get Ubuntu to not delete the settings and newly added data upon exiting the system?

If you are hurrying to reply, System → Administration → StartUp Disk Creator -- no, that's not what I'm talking about.   I want to try Ubuntu 11.04's Unity without touching my existing Ubuntu install.  To do this, I need to install the nVidia drivers first (sigh).  To do this, I need changes to persist a reboot.  To do this, I need to really install Ubuntu on a USB key.  How do you do that?    What I tried   I tried to make a USB key from , then boot from it, then choose "Install Ubuntu." The installer refused to install to the installation media itself. I tried, from my installed copy of Ubuntu:  sudo kvm /dev/sdb --cdrom .cache/testdrive/iso/ubuntu_natty-desktop-i386.iso   ...but the installer didn't detect the disk properly.


How do I get the Yongnuo YN560 III flash to work with a canon eos 4000d camera?

The external Flash is not showing up in the configuration Menu when using Pixel TF-321 hot shoe. Is this the wrong adapter for that camera, as there is no X connection? I want to trigger a studio flash via sync connection. Can you recommend me a working hot shoe? Thanks!


Given a set X, using java how do I pick two random items from it so that i could maybe increment one item and decrement the other at the same time. Thank you in advance.

How do I pick a random element from a set? I'm particularly interested in picking a random element from a HashSet or a LinkedHashSet, in Java. Solutions for other languages are also welcome.


My friend and I are working in Riyadh. We are Filipino by nationality and passport. We have Schengen visas because we will be travelling around Schengen territories. On our return to Saudi Arabia, we will leave from Berlin, Germany and fly to London Heathrow for a 16-hour layover before the flight to Riyadh.  Are we able to go outside the airport during the layover in the UK? What visa do we need to be able to tour a bit before our next flight?

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


This command does not give time & date when command was executed. Is this possible to check date & time  with history command or other command.  $ history     1  cd /strswork/strsapp/applications     2  ll     3  cd UM1     4  ll     5  cd DEV/oldlogs     6  ls -ltr     7  cd ..     8  ls -ltr     9  tail -10 log.txt    10  more log.txt

I would like to keep timestamps on the commands logged in my Bash $HISTFILE, is it possible?  I did not manage to set it up using man bash as an information source.   My other options are as follows:  function thebanana() {   local -r -a bash_commands=(     "ls"     # ... more coconut commands   )   for bash_command in "${bash_commands[@]}"; do     printf "${bash_command}"     printf ":"   done } export HISTFILE=banana export HISTIGNORE="$(thebanana)" export HISTSIZE=999999 export HISTFILESIZE=999999999 export HISTCONTROL=ignoredups:erasedups   I should have mentioned I am on OS X Mountain Lion (sigh). uname -a gives me:  Darwin CoconutMac.local 12.2.0 Darwin Kernel Version 12.2.0: Sat Aug 25 00:48:52 PDT 2012; root:xnu-2050.18.24~1/RELEASE_X86_64 x86_64   and echo $BASH_VERSION gives me:  3.2.48(1)-release   Tried adding this:  export HISTTIMEFORMAT='%b %d %I:%M:%S %p '   and it only prefixes this kind of timestamps to commands:  #1349057791   I try echoing back the variable (echo $HISTTIMEFORMAT), it has the right value.  Interesting!  I even removed .profile completely to debug this. Still only funny timestamps:  #1349058320   I don't know how to further troubleshoot this... :(  Solution: I was using a script that reads the $HISTFILE directly, not the history built-in so the epoch-based timestamp (secs since Coordinated Universal Time (UTC) of January 1, 1970) was not being translated using the date formatting string. Plain-old history works fine, I'll use that instead.


Mac OS 10.13.16 Python 3.7 PyCharm    I was going through a tutorial for this guessing game and I came across something I thought was weird. On line 18 I call on the guess variable, which I though was a Local Variable under the for loop created above it, let's me call on it as if it were a Global. I though if a var is declared within a function or loop it makes it a local. Can someone help explain this to me.   import random print("Hello what is your name?") name = input() print("Well " + name + " I am thinking of a number between 1 and 20") secretNumber = random.randint(1,20)  for guessesTaken in range(1, 7):     print("Take a guess.")     guess = int(input())     if guess < secretNumber:         print("Sorry to low")     elif guess > secretNumber:         print("Sorry to high")     else:         break   if guess == secretNumber:     print("Great job " + name + ". You guessed my number in " + str(guessesTaken) + " moves.") else:     print("Sorry the number I was thinking of is " + str(secretNumber))

What exactly are the Python scoping rules?  If I have some code:  code1 class Foo:    code2    def spam.....       code3       for code4..:        code5        x()   Where is x found?  Some possible choices include the list below:   In the enclosing source file In the class namespace In the function definition In the for loop index variable Inside the for loop   Also there is the context during execution, when the function spam is passed somewhere else. And maybe  pass a bit differently?  There must be a simple reference or algorithm somewhere.  It's a confusing world for intermediate Python programmers.


In orden to avoid overfitting, how I can choose the correct amount of epochs? I should be create 3 splits (train, valid and test) for each fold??

Assume that you found the optimal hyperparameters of a neural network (e.g. a multi layer feed forward NN) with k-fold cross validation in a grid search. Lets assume you have varied the number of epochs and got the optimal epoch number as a result.  Now you want to train the network for the optimal number of epochs on the whole data used for CV. In my opinion following problem arises: When using a constant mini batch size, number of iterations varies for datasets of different size - so your optimal epoch number found for the smaller training split in the CV can not be applied to training with the whole CV data. Am I missing something here? Right at the moment I can not find a proper solution for finding the optimal training epochs for my NN. I searched the net for some time now, but could not find an answer.  P.S. I only described the problem after the inner loop of nested CV, but the same problem arises after the outer loop (training the model on ALL data, not only on CV data for putting the model to production).


Is the usage of 'would have been' correct in this sentence below?     The only time I believe we exchanged physical pleasantries would have been at the 70th birthday dinner hosted in honour of your mother-in-law, Erelu Ojuolape Ojora at The Eko Hotel and Suites in Lagos some years back.   Read more at:

What is the meaning of would, and which tense is it used in the following sentences?  For example,   That would be Ram calling. I'll answer it. (the meaning of would and which tense is used) The guy on the phone had southern accent. That would be Tom. (the meaning of would and which tense is used) “We saw a police helicopter overhead yesterday morning.” “Really? They would have been looking for those bank robbers.” (the meaning of would and which tense is used) You would have to say/do that. (Why is would used here? What happens to the meaning if would is removed?) John said he didn't steal any money. Well, he would, wouldn't he ? (Why is would used here?)   Why is would used in sentences 1, 2, and 3 to mean "presumption" instead of using other modals, such as: must and should? Does the meaning change if used others?   Can we use will, must, should and could in the place of would, without changing the meaning of sentences?   What kind of meanings would it make if they (will, must, should, and could) are used in the place of would?     I'd be grateful if you could answer me.


Say if I had a question that I didn't know where to ask, say,     How does myopia work?   I know it goes somewhere around , but if someone (I) didn't know where to ask that, do we just ask on Meta Stack Exchange and hope for a redirect or something?

If I have a specific question I want to ask about, but I don't know which Stack Exchange site would be on topic for asking that question, where can I ask where to ask that question?  Is there any generic place where we can ask for advice? Is it here?  This is not about a specific question but in general.  For example: "Where should I ask for advice about fishing?", or if I need to know where I should ask "What would be the best fishing rod to fish for salmon?" (regardless of how good/bad these examples are)


Let $R:=\mathbb{C}[X_1,\dots, X_n]$, $a=(a_1,\dots, a_n)\in \mathbb{C}^n$ and $\phi_a:R\rightarrow \mathbb{C}$, $\phi_a(f)=f(a)$. I want to show that $\ker(\phi_a)=(X_1-a_1,\dots, X_n -a_n)$.    I know that to be true for $n=1$ and I also know that $\ker(\phi_a)$  is a maximal ideal in $R$. Moreover, $(X_1-a_1,\dots, X_n -a_n) \subseteq \ker(\phi_a)$ is obvious.  I am note sure if I can do an induction in this case.  Thank you.

I want to prove that the kernel of the evaluation map $s_a : \mathbb{C}[x_1,\dots,x_n] \rightarrow \mathbb{C}, x_i \mapsto a_i$ where $a = (a_1,\dots, a_n) \in \mathbb{C}^n$ is the ideal generated by $\{x_1 - a_1, \dots, x_n - a_n\}$.    The proof in the book first shows it easily for the case $a = 0$, and says that by substitutions of variables $x_i' = x_i - a_i$, you can show it for the rest of the cases.  I know that $f \in \ker s_a$ iff $f(a) = 0$.  And $\phi : \mathbb{C}[x_1,\dots, x_n] \rightarrow \mathbb{C}[x_1 - a_1, \dots, x_n-a_n], x_i \mapsto x_i - a_i$ is a surjective ring homomorphism.  Please give a hint and not the full answer.  Thanks.


How do I find 14^20 mod 33 ?  I tried writing 14^20 as 14^(2+4+8+6) but still no simplification.  Should I just check all the power of 14 mod 33 and hope that some of them give nice numbers (1 or 2)  What is a good method ?

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


I recently purchased a new laptop, and I decided to take the plunge and get Ubuntu 18.04, despite it still being in beta. While there have been a few minor quirks here and there, for the most part it's worked fine for me, and I'm pretty happy for it.  When ubuntu 18.04 is officially released on April 26th, will I have to download it onto a bootable thumb drive and update that way, or will my version be equivalent to the full version as long as I continue to regularly install updates?  In summary, What is the correct way to update from a beta version once the full version has been released?

I installed an Ubuntu alpha or beta and have been keeping it up to date.   So, Should I presume that my system has automatically updated to the next alpha or beta, and will be running the official release when it's finished?


My PostgreSQL database version is  PostgreSQL 9.3.10 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2, 64-bit  In both databases, datestyle is set to"ISO, DMY".    ATTEMPT 1  Query :  insert into station(name , date) values('test' , '21/1/2016')   Error Log:        ERROR:  date/time field value out of range: "21/1/2016" LINE 1: select '21/1/2016'::date                ^ HINT:  Perhaps you need a different "datestyle" setting.  ********** Error **********  ERROR: date/time field value out of range: "21/1/2016" SQL state: 22008 Hint: Perhaps you need a different "datestyle" setting. Character: 8   ATTEMPT 2  Query :    select '21/1/2016'::date   Error log :   ERROR:  date/time field value out of range: "21/1/2016" LINE 1: select '21/1/2016'::date                ^ HINT:  Perhaps you need a different "datestyle" setting.  ********** Error **********  ERROR: date/time field value out of range: "21/1/2016" SQL state: 22008 Hint: Perhaps you need a different "datestyle" setting. Character: 8   On one system it works and on other system it doesn't. Both have Ubuntu and the same PostgreSQL version.  COLLATE SETTINGS ON BOTH SERVERS     Query works successfuly on this server and has below COLLATE setting   show lc_CTYPE   -> C show LC_CoLLATE -> C SHOW lc_time;   -> "en_IN" select '21/1/2016'::date   -> "2016-01-21"      Query Does not Works on this server and has below COLLATE setting   show lc_CTYPE  -> "en_IN" show LC_CoLLATE ->  "en_IN" SHOW lc_time -> "en_IN" select '21/1/2016'::date  -> above error log

How can I set my database to see the 'date' as "MDY" without running:  SET datestyle = "ISO, MDY";   every-time I'm trying to access it? I'm using Postgresql version 9.1, Ubuntu 12.04. My system locale, at the time of the database installation was set to en_CA.utf8 and I recently changed it to en_US.utf8.  show lc_CTYPE   returns: --> "en_CA.UTF-8"  but  show LC_CoLLATE   returns: --> "en_CA.UTF-8"


I don't understand why they locked him in a room with nightlock (kills you fast) what did he do?

At the end of the movie we are shown      a bowl with berries in it and Seneca Crane looked like he was locked in a room with them and was supposed to eat them. Did he eat them?   Why did that happen?


I'm looking for suggestions on how to prove that     Given a function $U: A \subset \mathbb{R}^n \to \mathbb{R}$ with $U \in C^1 $ (therefore continuous) and $A$ a   connected set, $$\nabla U=\bar{0} \,\,\,\,\,\,\, \forall \bar{x} \in A\implies U=\mathrm{constant} \,\,\,\,\,\,\, \forall \bar{x} \in A$$   In particular, how is the condition of $A$ as a connected necessary?

How can I prove the following statement?     Given a function $U: A \subset \mathbb{R}^n \to \mathbb{R}$ with $A$   connected set, $$\nabla U=\bar{0} \,\,\,\,\,\,\, \forall \bar{x} \in A\implies U=\mathrm{constant} \,\,\,\,\,\,\, \forall \bar{x} \in A$$   In particular I do not understand how the condition of $A$ as a connected set is necessary to prove the statement.


I am creating a table using array, and I want one of my columns to be used as the argument of xrightarrow as shown below. To make the code cleaner, I want to avoid having to write xrightarrow for each row of the table. I tried using the functionality of the array package to make the second column the argument of xrightarrow (my feeble attempts are commented out below). Is there any way to make this work, or do I need to repeat the xrightarrow for each row of the table?  \documentclass{article}     \usepackage{amsmath}     \usepackage{array}  \begin{document}  \[     \begin{array}{l@{\qquad}c@{\qquad}l}         Y = \alpha X^{\beta}         & \xrightarrow{X' = \log(X) , Y' = \log(Y)}         & Y' = \log(\alpha) + \beta X' \\         Y = \alpha \exp(\beta X)         & \xrightarrow{Y' = \log(Y)}         & Y' = \log(\alpha) + \beta X     \end{array} \]  %\[ %   \begin{array}{l@{\qquad}>{\xrightarrow}c@{\qquad}l} %       Y = \alpha X^{\beta} %       & X' = \log(X) , Y' = \log(Y) %       & Y' = \log(\alpha) + \beta X' \\ %       Y = \alpha \exp(\beta X) %       & Y' = \log(Y) %       & Y' = \log(\alpha) + \beta X %   \end{array} %\] % %\[ %   \begin{array}{l@{\qquad}>{\xrightarrow{}c<{}}@{\qquad}l} %       Y = \alpha X^{\beta} %       & X' = \log(X) , Y' = \log(Y) %       & Y' = \log(\alpha) + \beta X' \\ %       Y = \alpha \exp(\beta X) %       & Y' = \log(Y) %       & Y' = \log(\alpha) + \beta X %   \end{array} %\]  \end{document}

I want to apply a macro to all the cells of a column with the cell content as the input to the macro. Is this possible?  For example if the cell contents have the word TEST, the macro should take TEST as its argument.


im a beginner at python and i've come across what is probably a simple problem. I want the code below to print the "." x times, each .100 of a second after each other. This is what ive got, but it just prints it all at once after x * .100 seconds. It would also help if you could redirect me to something that explains why it dosnt work or if you explained why it dosnt work.  import time for i in range(x):     print(".", end="")     time.sleep(.100)   Thanks in advance.  PS. If the code is completely wrong please say so.

I'd like to do it in Python. What I'd like to do in this example in C: #include <stdio.h>  int main() {     int i;     for (i=0; i<10; i++) printf(".");     return 0; }  Output: ..........  In Python: >>> for i in range(10): print('.') . . . . . . . . . . >>> print('.', '.', '.', '.', '.', '.', '.', '.', '.', '.') . . . . . . . . . .  In Python print will add a \n or space, how can I avoid that? Now, it's just an example, don't tell me I can first build a string then print it. I'd like to know how to "append" strings to stdout.


Plz help me When we get data from server and save in a string variable, it is store in a variable but cantnot retrive.   public class Profile extends Activity {     ListView list;     Activity act;     String[] username = { "Pankaj", "Aaa" };     TextView name;     JSONObject object;     String url = "http://thinksl.com/taughtable/profile.php?user_email=pank@gmail.com";      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.profile);         list = (ListView) findViewById(R.id.list);         name = (TextView) findViewById(R.id.mailid);         Custom_Profile pro = new Custom_Profile(Profile.this, username);         list.setAdapter(pro);         new Userdata().execute(url);     }      public class Userdata extends AsyncTask<String, Void, String> {         public static final int connection_type = 1500;         Profile p = new Profile();         ProgressDialog dialog;         String resul;         HashMap<String, String> user;          @Override         protected void onPreExecute() {             // TODO Auto-generated method stub             dialog = new ProgressDialog(Profile.this);             dialog.setTitle("Processing");             dialog.setMessage("Loading Data.Please wait....");             dialog.setCancelable(false);             dialog.show();          }          @Override         protected String doInBackground(String... url) {             // TODO Auto-generated method stub             Log.e("result", "Do in background");             HttpParams params = new BasicHttpParams();             HttpConnectionParams.setConnectionTimeout(params, connection_type);             HttpConnectionParams.setSoTimeout(params, connection_type);             HttpClient client = new DefaultHttpClient(params);              ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();             param.add(new BasicNameValuePair("user_email", "pank@gmail.com"));              HttpGet get = new HttpGet(url[0]);             try {                 Log.e("result", "Try");                 HttpResponse response = client.execute(get);                 Log.e("result", "Response" + response);                 HttpEntity entity = response.getEntity();                 String result = EntityUtils.toString(entity);                 Log.e("result", "result" + result);                 JSONObject jobject = new JSONObject(result);                 object = jobject.getJSONObject("userdetail");                 Log.e("result", "result" + object);                  String name = object.getString("user_login");                 int post = object.getInt("month");                 Log.e("name", "name" + name);                 Log.e("name", "post" + post);                 Log.e("result", "result" + resul);                 user = new HashMap<String, String>();                 user.put("name", name);              } catch (IOException e) {                 // TODO Auto-generated catch block                 e.printStackTrace();             } catch (JSONException e) {                 // TODO Auto-generated catch block                 e.printStackTrace();             }              return null;         }          @Override         protected void onPostExecute(String result) {             // TODO Auto-generated method stub             super.onPostExecute(result);             dialog.dismiss();             String s = user.get("name").toString();             p.name.setText(s);          }     } }

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 know that $C^1([a,b])$ is a Banach space with the $C^1$ norm. But is it a Banach space with the usual norm $||f||_\infty=sup|f|$ ? I think it shouldn´t be, but when trying to prove it I always get that it is. Any idea of a Cauchy sequence in $C^1[0,1]$ which is not convergent  ?

Given the normed space $C^1[0,1]$ of differentiable functions with continuous derivatives on $[0,1]$. The norm is defined as $$\|x\| = \max_{[0,1]} |x(t)|$$ I'd like to prove that the given normed space is not a Banach space. In the attempt of solving this problem, I have thought about the possibility to construct a Cauchy sequence in the space which doesn't converge in the space. However until now I haven't got any idea. Then I proceeded to think about constructing an equivalent norm to the given one where the space can be easily proven to be not a Banach space. However, I have got nothing either. Now I'm stuck without a clue. Please give me a hint to a correct direction. Any help is greatly appreciated.


Is it possible to somehow retrieve all metadata for a single custom metadata type via ant or sfdx mdapi ?   I've tried this:  <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <Package xmlns="http://soap.sforce.com/2006/04/metadata">     <types>         <members>Env_Var__mdt.*</members>         <name>CustomMetadata</name>     </types>     <version>45.0</version> </Package>   but it doesn't work...  I know I can get EVERYTHING with <members>*</members> but that's not really helpful...

I'm trying to use the ant migration tool to retrieve all the Custom Metadata records for a single Custom Metadata Type.  However, I can't figure out the syntax.  I would think that something like this would work:    <Package xmlns="http://soap.sforce.com/2006/04/metadata">     <types>         <members>State_Sales_Tax.*</members>         <name>CustomMetadata</name>     </types>     <types>         <members>State_Sales_Tax__mdt</members>         <name>CustomObject</name>     </types>     <version>36.0</version> </Package>   but no dice.


I remember long time ago I had some antivirus on windows which had wile accesses monitor, and could tell you if any process accesses a file.I need to monitor every file in my home folder(or any other) what application does the actions.

Three files have suddenly appeared in my home directory, called "client_state.xml", "lockfile", and "time_stats_log". The last two are empty. I'm wondering how they got there. It's not the first time it has happened, but the last time was weeks ago; I deleted the files and nothing broke or complained. I haven't been able to think of what I was doing at the time reported by stat $filename. Is there any way I can find out where they came from?  Alternatively, is there a way to monitor the home directory (but not sub-directories) for the creation of files?


I'm pretty new to java and have been working on learning how GUI's work. Through some tutorials, I managed to piece together a program to use a text box with the hope to incorporate a calculator I made as my first project. The area I'm focusing on is the button and action listener, where I'm trying to get an extra response when typing in "calc".  I've tried initializing the extra response outside of the program, but because of the string being called inside, I can't get it to work. I also tried calling the string outside but that still didn't work. I have an idea doing anything past this will require separately called functions, but I was hoping to start by figuring out this smaller part first.       static JTextField tf;     static JFrame frame;     static JPanel panel;     static JTextArea ta;     int count;     int num1;     int num2;     int exp;     char operator;     double answer;      static void GUI() {         frame = new JFrame("Thank you for reading this");         panel = new JPanel();         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         frame.setSize(400,400);         JButton button = new JButton("Test");         tf = new JTextField(15);         panel.add(tf);         panel.add(button);          JTextArea ta = new JTextArea();         ta.setEditable(false);          button.addActionListener(new ActionListener(){             public void actionPerformed(ActionEvent e) {                 String text = tf.getText();                 ta.append(text+"\n");                 if(text == "q") {                     ta.append("something random\n");                 }             }         });          frame.getContentPane().add(BorderLayout.CENTER, ta);         frame.getContentPane().add(BorderLayout.SOUTH, panel);         frame.setVisible(true);     }      public static void main(String[] args) {         GUI();     }      @Override     public void actionPerformed(ActionEvent e) {         // TODO Auto-generated method stub      }  }   I'm expecting to see "something random" appear below "calc" when it is typed into the text field. So far I receive nothing with the if statement

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


I just asked a user to separate his two (otherwise good) questions (real-world use) into two separate questions (stack-exchange use). That is, he was doing a single task, and was wondering about two different aspects of it.   This rule can seem arbitrary to users, for whom it is natural to ask for all the help they need with a single task in a single "package". So I am always careful to explain some of the reasoning behind it when I do it. This explaining has some downsides: 1) it takes time, 2) it doesn't look as "official" when it is just a comment, 3) users couldn't have known about it even if they wanted.   My suggestion is to expand the text in  with a heading of "only one problem per question" and explain a bit of the background. This is a low-friction solution (adding some more relevant text to an existing help page), can be linked when needed, and addresses the other concerns too.

The help centre’s  is linked in many prominent places guiding users on how to ask questions. However, with respect to too broad question  contains only the following line:     Your questions should be reasonably scoped. If you can imagine an entire book that answers your question, you’re asking too much.   This fails to capture the case that a question asks multiple questions (that are sufficiently independent to be asked separately) — which is also bad and  but does not necessarily mean that an entire book is needed to answer the questions.  As this is a common problem, I propose that a respective sentence is added to address this issue, e.g., something along the lines of:     Also do not ask multiple questions at once unless you expect their answers to overlap considerably.


I seem to be looking in the wrong direction so perhaps someone can help me.   In my testcase i need to have 1 specific checkbox 'on' at all times, i need some kind of if/else loop imo but can't figure it out. Can someone come to the rescue?

I want to do an if/else test in SELENIUM IDE. If the checkbox is checked the test should run the IF-condition, whereas otherwise it should go into the ELSE. I tried several commands for the TARGET of the IF, but each time it chose the same way regardless of whether the condition pertained or not. So I need to know how to deal with the notation of SELENIUM IDE in this case. Hope anybody can help me by showing me how I can make the condition dependent on a checkbox..


Does anybody know a way to add a command to an item (emerald, stick, other ingredients), then when left or right clicked, it executes a command?

Is there a way so that I make make it when I left click/right click with a certain item it applies an effect? I know that you can apply attributes to wearing armor and things but I want it so when you use the item it applies an effect on your player.  For example, let's say I want something so that when I right click with a certain item (let's say an iron ingot that was given to me) I'll then have a jump boost for 10 seconds. So kinda like a potion in a way.  Is this possible with command blocks/commands/any mods?


I'm locked out of a local database, and the single-user mode option that has worked for me in the past isn't working for me here. I could use some options to try.  It's saying the account is disabled, which I didn't think was even possible for single-user mode.  What I've tried already:  Restarting in single-user mode:  C:\Program Files\Microsoft SQL Server\MSSQL10_50.DBNAME\MSSQL\Binn>net stop MSSQL$DBNAME The SQL Server (DBNAME) service is stopping.. The SQL Server (DBNAME) service was stopped successfully.   C:\Program Files\Microsoft SQL Server\MSSQL10_50.DBNAME\MSSQL\Binn>.\sqlservr -sDBNAME -m -c  [seems to come up]   The login attempt looks like this:  C:\Program Files\Microsoft SQL Server\MSSQL10_50.DBNAME\MSSQL\Binn>sqlcmd -S .\DBNAME Msg 18470, Level 14, State 1, Server MY-PC\DBNAME, Line 1 Login failed for user 'My-PC\sarahg'. Reason: The account is disabled.   Server output:  2012-05-29 15:55:25.11 Logon       Error: 18470, Severity: 14, State: 1. 2012-05-29 15:55:25.11 Logon       Login failed for user 'My-PC\sarahg'. Reason: The account is disabled. [CLIENT: <local machine>]   Restarting in DAC mode:  C:\Program Files\Microsoft SQL Server\MSSQL10_50.DBNAME\MSSQL\Binn>.\sqlservr -sDBNAME -m -c -t 7806 ... blah blah ... 2012-05-29 15:59:05.59 spid6s      Server name is 'MY-PC\DBNAME'. This is an informational message only. No user action is required. 2012-05-29 15:59:05.60 spid9s      Starting up database 'model'. 2012-05-29 15:59:05.60 spid6s      Informational: No full-text supported languages found. 2012-05-29 15:59:05.60 spid6s      Starting up database 'msdb'. 2012-05-29 15:59:05.72 Server      A self-generated certificate was successfully loaded for encryption. 2012-05-29 15:59:05.72 Server      Server is listening on [ 'any' <ipv6> 49201]. 2012-05-29 15:59:05.74 Server      Server is listening on [ 'any' <ipv4> 49201]. 2012-05-29 15:59:05.74 Server      Server local connection provider is ready to accept connection on [ \\.\pipe\SQLLocal\DBNAME ]. 2012-05-29 15:59:05.74 Server      Server named pipe provider is ready to accept connection on [ \\.\pipe\MSSQL$DBNAME\sql\query ].   The login attempt looks like this:  C:\Program Files\Microsoft SQL Server\MSSQL10_50.DBNAME\MSSQL\Binn>sqlcmd -A -S .\DBNAME Msg 18470, Level 14, State 1, Server MY-PC\DBNAME, Line 1 Login failed for user 'Mys-PC\sarahg'. Reason: The account is disabled.   With server log:  2012-05-29 16:00:24.86 Logon       Error: 18470, Severity: 14, State: 1. 2012-05-29 16:00:24.86 Logon       Login failed for user 'Mys-PC\sarahg'. Reason: The account is disabled. [CLIENT: 127.0.0.1]   Any help is very welcome,  -- Sarah

I lost the sa password on a machine, and when I log in to the machine directly using an account in the admin group, SQL Server Management Studio will not allow me to log in using Windows authentication.  My plan was to simply log into the server, connect via Windows Authentication, and reset sa to use a new password. Since I cant' connect via Windows Authentication, this won't work.  How else can I reset the sa password?


I have this simple bash script that looks like this:  #!/bin/sh TIMESTAMP=`date "+%Y-%m-%d %H:%M:%S"` echo "$TIMESTAMP restart" /etc/init.d/nginx restart > /usr/local/nginx/logs/restart.log 2>&1   It produces the output in my restart.log like this:  2020-04-17 18:22:30 Restarting nginx (via systemctl): nginx.service.    but the next time the script is run the output line is erased and there is just one line of the last restart instead of it. There is only one line all the time. It looks like it's just "one liner" script, not multiple lines.  Now the question is how do I make it keep all the previous entries like this:  2020-04-17 18:22:30 Restarting nginx (via systemctl): nginx.service. 2020-04-18 19:12:30 Restarting nginx (via systemctl): nginx.service. 2020-04-19 20:02:30 Restarting nginx (via systemctl): nginx.service.   I know it's supposed to be quite simple but I cannot figure it out. Would appreciate any comments / advices / suggestions. Many thanks in advance!

I often see tutorials online that connect various commands with different symbols. For example:  command1 |  command2 command1 &  command2 command1 || command2     command1 && command2   Others seem to be connecting commands to files:  command1  > file1 command1  >> file1   What are these things? What are they called? What do they do? Are there more of them?    .


I'm surprised that I haven't seen anything about this on here (or maybe I missed it). When parsing a CSV file, if there are rows with no data, how can/should that be handled? I'm not talking about blank rows, but empty rows, for example:  ID,Name,Quantity,Price 1,Stuff,2,5 2,Things,1,2.5 ,,, ,,, ,,,   I am using TextFieldParser to handle commas in data, multiple delimiters, etc. The two solutions I've thought of is to either use ReadLine instead of ReadFields, but that would remove the benefits of using the TextFieldParser, I'd assume, because then I'd have to handle commas a different way. The other option would be to iterate through the fields and drop the row if all of the fields are empty. Here's what I have:  dttExcelTable = new DataTable();  using (TextFieldParser parser = new TextFieldParser(fileName)) {     parser.Delimiters = new string[] { ",", "|" };      string[] fields = parser.ReadFields();     if (fields == null)     {        return null;     }     foreach (string columnHeader in fields)     {        dttExcelTable.Columns.Add(columnHeader);     }      while (true)     {         DataRow importedRow = dttExcelTable.NewRow();         fields = parser.ReadFields();         if (fields == null)         {             break;         }         for (int i = 0; i < fields.Length; i++)         {             importedRow[i] = fields[i];         }          foreach (var field in importedRow.ItemArray)         {             if (!string.IsNullOrEmpty(field.ToString()))             {                 dttExcelTable.Rows.Add(importedRow);                 break;             }         }      } }

I'm using C# 2005 and the CSVreader class, all works well apart from when the CSV file contains an empty row at the end:  Example:  1,2,3,4,5 2,3,5,6,7 ,,,,   My program errors as there are no values here, the problem is that not all columns are contain a value so the 2 rows below would be valid.  1,2,,4,5 2,,5,6,7   but an empty row such containing ,,,, would not. A final hurdle is I don't know for sure how many columns there will be.  How would you suggest I test for an empty row?


'cause it doesn't - at least not for beta sites. I just signed up for an account on  and got the following:    Rather than using the Blender.SE favicon/logo (), a blank favicon/logo is shown instead. I did get a favicon/logo on the corresponding page when signing up for Sharepoint.SE, so I'm guessing this is some sort of bug on the beta sites.

I was signing up for Software Recommendations and realized that a unicorn stole their logo! We need to get it back! Really, the logo is missing when you sign up on SR, and I don't know if this is a universal bug or just here. Also, I did get an error a few seconds later (it should be recorded), so it might be related to that. Edit: It is on all betas; it isn't just my problem.    Note to SE team: if needed I can give the URL that has problems... it should show things like what I was trying to sign up with/verification codes, etc. if you want that.


I just saw this comment on an answer ():    The spacing seems strange to me. If you post a comment below this comment as well the indentation drops to one space.  The poster said they added one space to start the comment.

looks shifted to the right now:        But according to the wayback machine :


For any generic random variables $X$ and $Y$, we know that $$X\perp \!\!\! \perp Y \implies \text{Cov}(X,Y)=0\tag{1}$$ but not viceversa.  Now, let us consider two random variables $X$, $Y$, whose joint distribution $(X, Y)$ is normal. Why in this case does it hold true that: $$ X \perp \!\!\! \perp Y \iff \text{Cov}(X,Y)=0\tag{2}$$?  Could you please explicit your reasoning, specifying why normal joint distribution of $X$ and $Y$ is essential for $(2)$ to hold?

Let $X,Y$ be jointly normally distributed and uncorrelated. Why are they independent?


Complete Error:     "Attempt to invoke virtual method 'bolts.Task com.parse.ParseUser.signUpInBackground()' on a null object reference"   I am trying to make a login and sign up button, on clicking it the user must be signed in and if failed then signed up.  Here is my source code:  public void onClickLogInSignUp (View view) {     EditText editTextUsername = (EditText) findViewById(R.id.editTextUsername);     EditText editTextPassword = (EditText) findViewById(R.id.editTextPassword);      username = editTextUsername.getText().toString();     password = editTextPassword.getText().toString();      ParseUser.logInInBackground(username, password, new LogInCallback()     {          @Override         public void done(ParseUser user, ParseException e)         {             Log.i("Parse","Trying to log in ");              if ( e == null )             {                 Log.i("Parse","Log In Successful");                 Log.i("Parse","Redirecting as "+ ParseUser.getCurrentUser().getUsername());                 Toast.makeText(MainActivity.this, "Logged In", Toast.LENGTH_SHORT).show();                 startActivity(new Intent(getApplicationContext(), UserList.class));             }             else             {                 Log.e("Parse","Log In Failed Error - "+e.toString());                 isLogInSuccessful = false;                 ParseUser.getCurrentUser().signUpInBackground();                 ParseUser.getCurrentUser().saveInBackground(new SaveCallback()                 {                     @Override                     public void done(ParseException e)                     {                         ParseUser user = new ParseUser();                         user.setUsername(username);                         user.setPassword(password);                         user.signUpInBackground(new SignUpCallback()                         {                             @Override                             public void done(ParseException e)                             {                                 if (e == null)                                 {                                     startActivity(new Intent(getApplicationContext(), UserList.class));                                     Log.i("Parse","Sign Up Successful");                                     Log.i("Parse","Redirecting as "+ ParseUser.getCurrentUser().getUsername());                                     Toast.makeText(MainActivity.this, "Signed Up", Toast.LENGTH_SHORT).show();                                 }                                 else                                 {                                     Log.e("Parse","Can't log in as well as signup.");                                     Toast.makeText(MainActivity.this, "Can't log in as well as signup.", Toast.LENGTH_SHORT).show();                                 }                             }                         });                      }                 });             }         }     }); }

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?


For context - I am trying to spin up machines in the cloud (Digital Ocean) to speed up rendering compared to my underpowered laptop. Also - using Blender since yesterday. On both machines Blender is version 2.92.0. However the output generated by this command on the exact same file: blender-2.92.0-linux64/blender -b pet_shop.blend -x 1 -E CYCLES -o  //pet_shop -f 1  looked different on the two machines. On my laptop it looked like this:  and on the Digital Ocean machine it looked like this:  Until I copied the preferences from my local machine to the remote one What are the preference settings that result in this?

I made a character, and its one of my first times texturing, and I saved my character into a new folder, and when I came back to the model ALL the textures were pink, I used to know what to do, but I stopped texturing, how do I bring my textures back?


Suppose that $V$ is finite dimensional and $T \in L(V)$. Prove that $T$ is a scalar multiple of the identity if and only if $ST = TS$ for every $S \in L(V)$.  Suppose $T=\lambda I$ for some $\lambda \in \mathbb{F}$, showing $ST = TS$ is straightforward, but I don't know how to prove the converse.

Let $V$ be a finite-dimensional vector space over $F$. Let $T:V \rightarrow V$ be a linear transformation such that $ST=TS$ for all linear transformations $S:V \rightarrow V$. Show that $T = cI_v$ for some $c \in F$.


I have a old setup that I haven't used in a while. When I plug it in and turn it on, I see it light up for a second before dying.  So far I have tested the paperclip method with the psu and it works fine. I have also removed all the ram.   My motherboard has a few Leds and a start/reset button (Asus M6E Motherboard). They all light up. I have tried taking out the cpu and putting it back again.  Is it possible my cpu failed or my motherboard failed? I don't have any other 1150 cpu around to check. Since this is one of my old setups, I want to make it to work again, but I'm not sure if I have to buy a motherboard or cpu.

I have a fairly modern desktop computer, an AMD Athlon II X2 based silent PC, that does not work.  When turned on, it will start physically (all fans are rotating, disks start up...) but not give a signal on any of the graphics ports (DVI, VGA, and HDMI, I tried all three). Also, the reset button does not seem to have any effect.  I have stripped the mainboard bare of all SATA connections, extension cards, and the one 2GB RAM chip to eliminate them as the problem source, but to no avail, so I think it's fair to assume it's either the mainboard or the processor that are at fault.  However, I have neither a replacement mainboard, nor a replacement processor handy to identify which one is broken. The cause of the defect is unknown, so for all I know, it could be both. Therefore, I'm reluctant to buy replacement hardware blindly before knowing more.   Is there any way to further diagnose (or at least get some indication) which component is broken without buying replacement hardware?


I am making a cake that I will frost with avocado frosting. For how many days can I keep cakes/cupcakes frosted with avocado frosting in the fridge?  I use this avocado frosting recipe from Alton Brown:  Ingredients:  8 ounces avocado meat, approximately 2 small to medium  2 teaspoons freshly squeezed lemon juice  1 pound powdered sugar, sifted  1/2 teaspoon lemon extract  Directions  Peel and pit the avocado. Place the avocado into the bowl of a stand mixer fitted with the whisk attachment along with the lemon juice and beat until lightened in color, approximately 2 to 3 minutes. Add the powdered sugar a little at a time and beat until smooth. Add the lemon extract and mix to combine. If not using right away, store in the refrigerator.

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 want to speed up the time it takes for me to be able to drag text in chrome. I have to wait for 2 or 3 seconds to drag text, or else I just end up selecting text again currently. Is there an attribute that controls the time it waits that I can modify in the terminal??

Is there any way to disable the delay for text dragging in OS X?  There is a small delay between selecting and dragging text, if you start dragging the text right after you selected it - it will instead re-select the text which can be annoying. Some apps don't have this delay (for example Sublime Text 2/3 where you can drag the text immediately after selecting it) but in most apps you would have to click the left mouse button and hold it for a bit before you can drag the selected text.


I was hoping someone could shed some light on this issue: When I plot a function using something like \addplot+[mark=none,smooth,] (\x,{2 * \x^2 + 4 * \x + 1}); the line of the function does not extend far enough in the window. In other words, how can I expand the domain of the function being plotted?  An example of the plot I am currently creating:

Why does pgfplots plot functions only until x = 5 and y = 5, but not any further?    \documentclass{article}  \usepackage{tikz} \usepackage{pgfplots}  %%%< \usepackage[active,tightpage]{preview} \PreviewEnvironment{tikzpicture} \setlength\PreviewBorder{5pt} %%%>  \begin{document} \begin{tikzpicture} \begin{axis}[samples=100,ymin=0,ymax=10,xmin=0,xmax=20]  \addplot [thick] plot  (\x,  {1/(1 + exp(-0.6*(\x - 12)))}); \addplot plot (\x, {\x});  \end{axis} \end{tikzpicture} \end{document}


I have installed on my laptop Ubuntu 15.04. Today I have closed the lid, the laptop got into suspend mode and I put my laptop in my bag. After 3 hours I  got him out and it was hot as hell! The laptop woke up from suspend by itself and continued to work while was in my backpack. What I can do to prevent this kind of problems?

For a few days, my Ubuntu 12.04 desktop computer has mysteriously been waking up immediately after going to suspend mode.  Since installation, my Ubuntu 12.10 laptop computer has also been resuming immediately after suspend and hibernation.  How to prevent those?


Is is possible for two neutrons to be in a bound state, assuming that they only interact gravitationally?

It is known that there are no diproton or dineutron nuclei.  Does this mean that two protons or neutrons are not actually attracted to each other? Even if the attraction was weak, wouldn't it cause bound states anyway?  Related:


Suppose that $P$ is a monic polynomial of degree $n$ in one variable with real coefficients and $K$ a real number.Then which is /are true?      If $n$ is even and $K>0$ , then there exists $x_0 \in \mathbb{R}$ such that $P(x_0)=Ke^{x_0}$. If $n$ is odd and $K<0$ , then there exists $x_0 \in \mathbb{R}$ such that $P(x_0)=Ke^{x_0}$. For any natural number $n$, and $0<K<1$ then there exists $x_0 \in \mathbb{R}$ such that $P(x_0)=Ke^{x_0}$. If $n$ is odd and $K \in \mathbb{R}$ , then there exists $x_0 \in \mathbb{R}$ such that $P(x_0)=Ke^{x_0}$.     I feel that Rolles Theorem will be helpful but cant apply i. Can i get some help please.

Suppose that $P$ is a monic polynomial of degree $n$ in one variable with real coefficients and $K$ is a real number. Then which of the following statements are necessarily correct ?         If $n$ is even and $K>0$ then there exists $x_0\in \mathbb R$ such that $P(x_0)=Ke^{x_0}$.   If $n$ is odd and $K<0$ , then there exists $x_0 \in \mathbb{R}$ such that $P(x_0)=Ke^{x_0}$.   For any natural number $n$, and $0<K<1$ then there exists $x_0 \in \mathbb{R}$ such that $P(x_0)=Ke^{x_0}$.   If $n$ is odd and $K \in \mathbb R$ , then there exists $x_0 \in \mathbb{R}$ such that $P(x_0)=Ke^{x_0}$.      For (3), consider, $P(x)=x^2+5$. Then , there does not exist $x_0\in \mathbb R$ such that $0<e^{-x_0}P(x_0)<1$. So it is FALSE.  But what about the others ?


To keep all the inputs to a network on the same scale, they are usually normalized so that they end up being represented as number of standard deviations from the mean.  Is this something that needs to be done for the result of trained word embeddings, e.g. vectors from GloVe or word2vec? If so, should I use the mean/variance of only the embeddings, or all the samples in my data set?

After training word vectors with word2vec, is it better to normalize them before using them for some downstream applications? I.e what are the pros/cons of normalizing them?


I spent over ten hours on this, trying many solutions I found on the internet, and feeling stupid... This function just loads an ogg file in a MediaPlayer. It gets the url of the file as a string argument. It first extracts the name of the file and tries to load it from res/raw/, if it exists there, else it gets it from the website.  MediaPlayer player ;  void snd_load(String url) {      String id_snd = url.substring(url.lastIndexOf("/") + 1); // name of the file      try{         player.setDataSource( "android.resource://didi.a8bitpocketwrestlers/res/raw/" + id_snd );     }     catch (Exception e){         Toast.makeText(getApplicationContext(), "can't open file, will try to download it"+"\n"+e , Toast.LENGTH_SHORT).show();         try{ player.setDataSource(url); }         catch (Exception e2){ Toast.makeText(getApplicationContext(), "can't download file"+"\n"+e2 , Toast.LENGTH_SHORT).show(); }     } }   I was getting java.lang.NULLPointerException error for both. I understand now, player was only of type MediaPlayer, it pointed to nothing yet. I was mistaken because there are properties inside so I thought the object existed. I must do either player = new MediaPlayer(); or player = MediaPlayer.create();.  Now I fixed this, I still can't load the file.     04-22 15:31:58.018 130-4150/? E/FileSource: Failed to open file   'android.resource://didi.a8bitpocketwrestlers/snd_title.ogg'. (No such   file or directory) 04-22 15:31:58.018   4087-4099/didi.a8bitpocketwrestlers E/MediaPlayer: error (1,   -2147483648) 04-22 15:31:58.018 4087-4087/didi.a8bitpocketwrestlers E/MediaPlayer: Error (1,-2147483648)   And it stops, it does not display the message and does not try to download it.  With player = MediaPlayer.create(getApplicationContext(), R.raw.snd_title ); it crashes because of my player.prepareAsync(); call. I read that .create already takes care of that and so I can't call .prepareAsync(); nor use .setOnPreparedListener(). This is a problem for me, I need to know when it is ready.  Anyway I must use the name in the variable id_snd, not just snd_title.ogg file, so I changed it for player = MediaPlayer.create(getApplicationContext(), getApplicationContext().getResources().getIdentifier(id_snd, "raw", getApplicationContext().getPackageName()) ); and I get     android.content.res.Resources$NotFoundException:Resource ID #0x0   New version  MediaPlayer player ;  void snd_load(String url) {      String id_snd = url.substring(url.lastIndexOf("/") + 1); // name of the file     id_snd = id_snd.substring( 0 , id_snd.indexOf(".") ) ; // to remove ".ogg" or ".aac"      try{         player = MediaPlayer.create(getApplicationContext(), getApplicationContext().getResources().getIdentifier(id_snd, "raw", getApplicationContext().getPackageName()) );     }     catch (Exception e){         Toast.makeText(getApplicationContext(), "can't open file, will try to download it"+"\n"+e , Toast.LENGTH_SHORT).show();         try{ player = MediaPlayer.create(getApplicationContext(), Uri.parse(url)); }         catch (Exception e2){ Toast.makeText(getApplicationContext(), "can't download file"+"\n"+e2 , Toast.LENGTH_SHORT).show(); }     } }

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?


What will be the effect on a rigid body if two like unequal parallel forces act on the body? Will the body translate or rotate or both? If they rotate, with respect to which point will they rotate?  Here I have mentioned 'Like Unequal Parallel' forces, not 'Unlike Unequal Parallel' forces.

What will be the effect on a rigid body if two unlike unequal parallel forces act on the body? Will the body translate or rotate or both? If they rotate, with respect too which point will they rotate?


I noticed on some test data that queries of the form  SELECT * FROM a JOIN b ON a.x = b.y WHERE [more conditions...];   were returning the same data as queries of the form  SELECT * FROM a,b WHERE a.x = b.y AND [more conditions...];   Intuitively they seem equivalent, but I'm not confident that this is the case.   I prefer the query that uses JOIN as it separates the general structure of the query from the specific business logic of the query. i.e. The conditions in the WHERE section of the query using JOIN are ones that could be parameterized.  In which other ways, if any, are these queries not identical?

Is there any efficiency difference in an explicit vs implicit inner join? For example:  SELECT * FROM table a INNER JOIN table b ON a.id = b.id;   vs.  SELECT a.*, b.* FROM table a, table b WHERE a.id = b.id;


My partner has been asked to submit passport details for a British passport he held in 1998 to support a British citizenship application for his son. He has been unable to locate the expired passport that he used at the time and so we're wondering if there is a way of accessing, at the very least, the passport number.  We're assuming this record might be held with a UK Visa/Immigration Office? Would anyone know if this is possible, and if so, how to go about getting such information? Many thanks.

I'm a British passport holder and need to find out an expired passport's number for a passport I held with a business visa in it. I no longer have the physical copy and speaking to the Passport Office and the Home Office has proved a fruitless exercise. As I spent a period of time in India in 2001, I need to obtain an Indian Police Clearance Check and my old passport number is necessary for this. Any advice please?


i know that exist polynomials formulas in the case of Integers and the Real which define their orders, my question is if such a formula exist in case of Rationals.

I study model theory and I have questions about relations which are definable in a structure or not. I found three examples from exercises and i want to do them:  Is the relation $<$ on $\Bbb{Q}$ definable in the structure $(\Bbb{Q},+,\cdot,0,1)$ that is does there exists a formula $\phi=\phi(x_0,x_1)$ sucht that for all $p,q$ in $\Bbb{Q}$, $p<q$ if and only if $(\Bbb{Q},+,\cdot,0,1)$ realized $\phi[p,q]$ ?  Is the relation $<$ on $\Bbb{Q}$ definable in the structure $(\Bbb{Q},+,0,1)$ ?  Is the relation $+$ on $\Bbb{Q}$ definable in the structure $(\Bbb{Q},<,0,1)$ ?  I have done this already for the integers with the successor function, but I don't know how to do this in this three cases. I think the first relation is definable, but the other two not. Can someone help me? Thank you :)


Today I asked a question on this site regarding inertia, and while reading one of the answers, a question popped up  Why does a body have inertia?  I looked up this site and several others, but could not find any resources.

In  R P Feynman relates a story where his father told him that, even though we know the word "inertia" and what it means, nobody knows why inertia happens. Is that still true?