If we have a dynamical system for a vector of scalar variables $x_t$: $$\dot x_t=f(x_t)$$  Then the jacobian is the matrix of partial derivatives $$J(x_t)=Df(x_t)$$  Let's say we have a fixed point $x_t^*$: $f(x_t^*)=0$.   Then what is the (intuitive) interpretation of $|J(x_t^*)|$? and of $sign |J(x_t^*)|$?

Can someone explain what exactly the Jacobian matrix is (specifically in its application to dynamical systems) and maybe give an example of how to compute it? It really confuses me...and I haven't been able to find any good resources online.


I can not start pdfLaTeX from TeXMaker in Windows 7. I try Quick Building with Pdflatex+Viewer but I'm getting the error: "Could not start the command". I have installed TexLive 2013.   I added the bin filepath to my enviromental PATH variable and I am able to run pdfLaTeX and all other commands from cmd without problems. I also tried specifying the full path in texmaker as: C:\texlive\2013\bin\win32\pdflatex.exe but the same error pops up. Am I missing something?

I just downloaded and installed Texmaker. I've never used any (La)TeX before.  When I click the Run button with an arrow next to "Quick build" I get an error saying "Could not start the command". Why? What do I need to do?


My mom bought some toys from a woman with a very sick son. They had yet to find out what was wrong with him. The toys have sat in an unheated detached garage for more than 2 months. Will they be safe for an infant to play with? Some are electronic, so it is hard to get them completely sanitized.

I work at a nursery and I have a hard time managing the toys that the kids play with. I watch them put things in their mouths, cough and sneeze on the toys, and throw everything on the ground. Even though I see all of these things, it is hard to find the time to clean all of the toys, simply because there are too many and I do not have that much time. Any input would be appreciated!


The family is eating home roasted chicken tonight. I cut into it, and found this bright green "line". What is it?

I smoked a whole chicken. When I cut into the breast I found this:    What is it and is my chicken ruined?


how to prevent (programmatically) a java application from starting if it's not in a predefined directory?  Example:  I have application.jar and I want to make it runnable only if it's located in             "C:\runnable" directory else the application will exit.  any ideas?

My code runs inside a JAR file, say foo.jar, and I need to know, in the code, in which folder the running foo.jar is.  So, if foo.jar is in C:\FOO\, I want to get that path no matter what my current working directory is.


How do you get a tool to break a specific block in adventure mod, like on maps?

I am trying to make an axe for my capture the flag game called "Flag Breaker" so when players enter the arena they are in adventure mode but using flag breaker they can break the flag. I've looked into can break but the with the command I have come up with under "CanDestroy" it just says MissingNo which I assume means missing number. I have tried to use block id in place of the word Banner but it still just says MissingNo. If someone could tell me the proper structure for using can break on colored banners (Red and Blue) that would be great  I am on a 1.12.2 minecraft server


Inline
 elements are not positioning themselves within their parent div. It is ok when I set overflow:auto on the parent div but not without it.    Please help me understand it, how they are getting out of their parent.   Here is my code:    body {   margin: 0;   padding: 0; }  div {   background-color: black;   color: red;   padding-top: 2px;   padding-bottom: 2px; }  li {   display: inline;   float: right; }  ul {   list-style-type: none; }
BUSINESS NAME

HOME

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ABOUT

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Although elements like
s normally grow to fit their contents, using the float property can cause a startling problem for CSS newbies: If floated elements have non-floated parent elements, the parent will collapse. For example:

Div 1

Div 2

    The parent div in this example will not expand to contain its floated children - it will appear to have height: 0. How do you solve this problem? I would like to create an exhaustive list of solutions here. If you're aware of cross-browser compatibility issues, please point them out. Solution 1 Float the parent.

Div 1

Div 2

    Pros: Semantic code. Cons: You may not always want the parent floated. Even if you do, do you float the parents' parent, and so on? Must you float every ancestor element? Solution 2 Give the parent an explicit height.

Div 1

Div 2

    Pros: Semantic code. Cons: Not flexible - if the content changes or the browser is resized, the layout will break. Solution 3 Append a "spacer" element inside the parent element, like this:

Div 1

Div 2

    Pros: Straightforward to code. Cons: Not semantic; the spacer div exists only as a layout hack. Solution 4 Set parent to overflow: auto.

Div 1

Div 2

    Pros: Doesn't require extra div. Cons: Seems like a hack - that's not the overflow property's stated purpose. Comments? Other suggestions?


I am having difficulties in providing the following proof: If $a_1, \dots, a_n$ are all positive, show that: $$ \prod_{k=1}^{n}(1+a_k) \leq \sum_{k=1}^{n+1}\frac{S^{k-1}}{(k-1)!} $$ where $S = \sum_{k=1}^{n}a_k$

Let $x_1$, $x_2$, $\ldots$, $x_n$ be positive real numbers, and let $$S=x_1+x_2+\cdots+x_n.$$ Prove that $$(1+x_1)(1+x_2)\cdots(1+x_n)\leq 1+S+\frac{S^2}{2!}+\frac{S^3}{3!}+\cdots+\frac{S^n}{n!}.$$  My first thought is about using induction. For $n=1$, $LHS=1+x_1\leq1+S=RHS$. Now I suppose that this inequality holds true for $n=k$; that is, $$(1+x_1)(1+x_2)\cdots(1+x_k)\leq 1+S+\frac{S^2}{2!}+\frac{S^3}{3!}+\cdots +\frac{S^k}{k!}.$$ And here I am stuck. I can't really see how I can find the relation between when $n=k$ and $n=k+1$. Perhaps induction may not be the way?  Any hints or suggestions will be much appreciated. Thanks.


When I tried to join a discussion in Area 51, the system said I had to log in.   So I clicked on the link to log in, and logged in. Then I tried to join the discussion in Area 51 again, and the system still said I had to log in.  What should I do?

I can login to Area 51 using my Google account, and everything seems fine at first. Until I try to participate, such as answering a question, voting, or creating a new question. At this point the login bar shows me as not logged in, and I am asked to create an account or login again. But when I do I get the crashed flying saucer error. Login works fine on other StackExchange communities. I tried different browsers, clearing cache, clearing cookies, loging out from Google itself, creating another account - no avail. Has anyone else seen this?


Calling the method:  Log.i("MY_TAG 0 =", String.valueOf(findViewById(R.id.listView))); allUsers(host, json, login, this);   My method:  private static void allUsers(String host, String json, String login, Activity activity) {     ListView lv1 = activity.findViewById(R.id.listView);      Log.i("MY_TAG 1 =", String.valueOf(activity));     Log.i("MY_TAG 2 =", String.valueOf(lv1));     Log.i("MY_TAG 3 =", String.valueOf(activity.findViewById(R.id.listView)));      new AsyncTask<Void, String, String>() {         @Override         protected String doInBackground(Void... params) {             return Http.sendMsg(host, json);         }         @Override         protected void onPostExecute(String s) {             super.onPostExecute(s);             AllUsersJson allUsersJson = new Gson().fromJson(s, AllUsersJson.class);             GetAllUsersAdapter myAdapter = new GetAllUsersAdapter(allUsersJson, activity.getApplicationContext(), login);             ListView lv2 = activity.findViewById(R.id.listView);             Log.i("MY_TAG 4 =", String.valueOf(lv1));             Log.i("MY_TAG 5 =", String.valueOf(lv2));             lv2.setAdapter(myAdapter);         }     }.execute(); }   Logs:  MY_TAG 0 =: android.widget.ListView{1255189 VFED.VC.. .F....ID 0,0-1080,1584 #7f080071 app:id/listView} MY_TAG 1 =: myzabbix.sadrutdin.zaynukov.com.testzabbix.NavDrawerActivity@231f1a MY_TAG 2 =: android.widget.ListView{1255189 VFED.VC.. .F....ID 0,0-1080,1584 #7f080071 app:id/listView} MY_TAG 3 =: android.widget.ListView{1255189 VFED.VC.. .F....ID 0,0-1080,1584 #7f080071 app:id/listView} MY_TAG 4 =: android.widget.ListView{1255189 VFED.VC.. ......ID 0,0-1080,1584 #7f080071 app:id/listView} MY_TAG 5 =: null   Replace lv2.setAdapter(myAdapter); by lv1.setAdapter(myAdapter);  Result:  MY_TAG 0 =: null MY_TAG 1 =: myzabbix.sadrutdin.zaynukov.com.testzabbix.NavDrawerActivity@ce89be3 MY_TAG 2 =: null MY_TAG 3 =: null MY_TAG 4 =: null MY_TAG 5 =: null   The strangest thing is that an identical method works without problems. I tried all the options, but apparently I do not understand something in Android ...

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 am currently using    \usepackage{biblatex}   and I have two different  .bib files:  First_bib_File.bib Second_bib_File.bib   The following command does not work  \addbibresource{First_bib_File.bib ,  Second_bib_File.bib}   What alternative command should I use to simultaneously use the two .bib files?

I would like to use multiple .bib files for my article, such as file1.bib, file2.bib. However, I would like my references not to be separated (such as "Primary sources", "Secondary sources", etc.). These bibliographies just need to be merged into one. One way to do this is to copy-paste these .bib files into one .bib file, and this would solve the problem. However, I would like to keep it split into several .bib files, by topic (file1.bib contains articles on topic1, file2.bib contains articles on topic2, and so on). I tried to do \bibliographystyle{alpha}  \bibliography{file1} \bibliography{file2}  but this just gives me the same bibliography twice!


I'm using NGINX and I have ssl cert for example.com And I don't have ssl cert for www.example.com.  In brief: I tried to configure NGINX to redirect from all the www requests to non-www (from **http**://www.example.com and **https**://www.example.com to https://example.com). Nevertheless I used a tone of different answers to more or less similiar questions, I get either no result or the server stops answering :(  That was the problem in general, now I'll dive into details:  Now my NGINX config looks like:  upstream puma_example_production {    server unix:/var/www/example/shared/tmp/sockets/puma.sock fail_timeout=0; }  #server { #    listen 80; #    listen 443 ssl; #    server_name www.example.com; #    return 301 https://example.com$request_uri; #}   server {   listen 80;   listen 443 ssl;   ssl on;   ssl_certificate /var/certs/ssl.crt;   ssl_certificate_key /var/certs/sslkey.key;    server_name example.com;   root /var/www/example/current/public;   try_files $uri/index.html $uri @puma_example_production;    client_max_body_size 4G;   keepalive_timeout 10;    error_page 500 502 504 /500.html;   error_page 503 @503;    # return   301 https://example.com$request_uri;    location @puma_example_production {     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;     proxy_set_header Host $host;     proxy_redirect off;     proxy_set_header Upgrade $http_upgrade;     proxy_set_header Connection "Upgrade";     proxy_set_header X-Forwarded-Proto https;     proxy_pass http://puma_example_production;     # limit_req zone=one;     access_log /var/www/example/shared/log/nginx.access.log;     error_log /var/www/example/shared/log/nginx.error.log;   }    location ^~ /assets/ {     gzip_static on;     expires max;     add_header Cache-Control public;   }    location = /50x.html {     root html;   }    location = /404.html {     root html;   }    location @503 {     error_page 405 = /system/maintenance.html;     if (-f $document_root/system/maintenance.html) {       rewrite ^(.*)$ /system/maintenance.html break;     }     rewrite ^(.*)$ /503.html break;   }    if ($request_method !~ ^(GET|HEAD|PUT|PATCH|POST|DELETE|OPTIONS)$ ){     return 405;   }    if (-f $document_root/system/maintenance.html) {     return 503;   } }   I commented the lines with approaches which cause errors. Now  I have proper server work for non-www requests, but with www requests I get browser warning that I have no ssl cert (NET::ERR_CERT_COMMON_NAME_INVALID) (and that's true).  I hope that there's the right way to redirect from www to non-www. Could youhelp me out, please?

I am not much familiar with server configurations, please help me on this issue:  I have a Debian8 server and a SSL certificate, the SSL certificate only for My non-www domain so I would like to redirect all of www request into non-www, by below htaccess code its working for some browsers but not working for some other  On Chrome: Successfully redirecting http://www.example.com or http://example.com request into https://example.com this is what I want for all browsers.  On Mozilla: Redirecting http://www.example.com request into https://www.example.com and stopped working with INSECURE CONNECTION error. I think from here browser checking first for SSL certificate of www and stop before non-www redirect.   Following is my .htaccess to redirect www to non www with https, is anything I missed on .htaccess? or any other solution through DNS or with help of apache default ssl.conf.  RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC] RewriteRule ^(.*)$ https://%1/$1 [R=301,L]  RewriteCond %{HTTPS} !on RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]   My SSL certificate is  and I followed this tutorial to install  you could see there is only one domain prompting that is non-www, no option for setting SSL certificate for www. If I could get a SSL certificate for www then also I can solve the issue.


You take the blue pill - the story ends, you wake up in your bed and believe whatever you want to believe.   Why was Neo offered blue pill when he could simply walk out of the door to believe whatever he wanted to believe? What does blue pill do?

During the first meeting between Neo and Morpheus in The Matrix, Morpheus states that if Neo takes the blue pill,  Does this mean that the blue pill acts as a selective amnesiac? A program to make Neo feel as though he dreamed the meeting, similar to his experience of having a bug implanted by the Agents? Would it include something that makes him no longer of interest to the Agents? Since, technically, all that Neo has to do, if he refuses Morpheus' offer, is get up and leave the room, why have a blue pill at all?


There are some question arising from my animal companion. We are using the Unearthed Arcana version of the ranger and I chose the beast master. I have this wolf and I can ride it because I’m small (I’m a mousefolk if you’re wondering).   When I’m riding my animal companion, can my wolf attack using her bite?   Also, bonus question, can I attack with melee and ranged weapons while riding my wolf?  Thanks for the help in advance!

This came up in my session tonight. My players all had the cash to buy war horses and outfit them, I ruled that they're readily available in Neverwinter which they were near for their last adventure.   However, there are two bits of text that I'm trying to piece together and figure out how they work. The first is the following from the mounted combat text:     It moves as you direct it, and it has only three action options: Dash, Disengage and Dodge (PHB 198)   Does this mean that you cannot under any circumstances use your mount's attack (such as the Warhorse's Trampling Charge/Hooves attack)?  Reading the next section it really seems to come down to whether or not a Warhorse is considered an intelligent mount or not, answers should address this.


I've only seen this icon in Twitch streams, so assume it's something to do with Twitch, but again have only seen this in DOTA2 streams!  Any ideas what it is?

What is the Icon above Spell Steal? And how come I don't have that on my DotA?


So any of ya'll that don't know      Harry marries Ginny   But I was wondering what was the 1st sign that Harry showed feelings for Ginny.

In the earlier HP books it's pretty clear that Harry and Ginny get on quite well as friends (and that she's rather smitten with him) but I'm struggling to identify when and why Harry started to like Ginny in a romantic fashion..  I feel like it is simply presumed that Harry suddenly likes Ginny Weasley back, but do the books actually describe when and why he started to like her that way?  No speculation, please. Canon answers only.


If someone takes a decision, can someone tell me where they intend to take it? Call me old fashioned or conservative if you like but I was always taught to make a decision and once it's been done it's made.  I do not intend to take it anywhere. Verbally speaking there is a great difference between take and make..........just as there is a difference between stick and put.  Does anyone have any glue?

What is the difference between make decision and take decision? When to use the one and when the other?


Basically, I'm trying to get my set definition to look exactly like the image.  But when I do \Set{w \in { 0,1 } \mid (long definition) }, the text just goes off the right edge of the page and neither the brackets nor the | adjust to fit the long contents.

I was wondering what the proper LaTeX code would be to display something like this:    You don't have to include the mathematical symbols, what is important is the structure.


I create two same zero lists. Yet the results are different when the lists are assigned to same values. Here are my code and result.  code:  m1 = [[0] * 4] * 4 m2 = [[0 for j in range(4)] for i in range(4)] m1[0][1] = 1 m2[0][1] = 1 print('m1:', m1) print('m2:', m2)   result:  m1: [[0, 1, 0, 0], [0, 1, 0, 0], [0, 1, 0, 0], [0, 1, 0, 0]] m2: [[0, 1, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]   Or maybe the two lists are not the "same"? Any help would be appreciated.

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


How Software Testing Engineer should act in environment where requirements are very frequently changing? Big tasks appear suddenly so tester doesn't perform them in a proper way. Developers do what wasn't expected and stories are done just before demo. How processes are usually fixed?

If requirements are likely to change frequently during development. Although a complete change in requirement is possible, most of the time, it is the technical details that are subject to change. e.g. the intent of the requirement or behavior of the feature is the same but implementation details can change. In this case: as a QA, what can be done if requirements are changing continuously and the company follows Agile model?


I recently tried to change the default brightness of my ubuntu by echoing values to /sys/class/backlight/acpi_video0/brightness, and installing xbacklight, as suggested by answers to other questions. However, after booting ubuntu after doing the above, the screen just went blank.  After further checking, I found /sys/class/backlight folder is empty, and I have not been able to add a folder even under root permissions.

Is it possible to set the default display brightness so you don't have to re-adjust it everytime you reboot? My laptop display is killing my eyes at the login screen already because it starts at 100% brightness every time.


I am trying to find the conjugacy classes of the Dihedral group $D_{12}=\{e,a,a^2,a^3,a^4,a^5,b,ba,ba^2,ba^3,ba^4,ba^5\}$   where $a^6=b^2=e$ and $ab=ba^5$. I know that one of the conjugacy classes will be $C_e=\{e\}$ but I don't understand how you find the others. All help appreciated.

I'm trying to understand this proof and I can follow it up the the second last paragraph where it states what happens if n is odd/even. I don't understand why there is just one conjugacy class when n is odd and two when n is even.    Help much appreciated, thanks!


If $ p + q + r = 10 $, find the number of possible combinations satisfying the equation. ( $p,q,r ≥ 0$)    PS - As suggested by Brian Moehring, I used the 'stars and bars' method.   We need the sum as $10$. We have to add $1$ ten times, to get 10. If we add two bars i.e., we are dividing them into p, q and r. So now in total there are $10 \ 1's$ and $2$ bars. We have to find the number of ways to arrange those $2$ bars in $12$ places. Hence, there are $\binom{12}{2}$ ways of selecting $p,\ q$ and $r$ to satisfy the equation.

I realize that this question has been asked multiple times and I do not really want to know how to do it, I understand how to solve it, my issue is somehow I have used the distribution and I am not getting the right answer.  Method of Solving: I solved this in the first go by directly applying the distribution formula that is $$\binom {n+r-1}{r-1} $$ By using, $n = 10, r= 3$ we get, $$\binom{12}{2} = 66$$ however the answer given is $$\binom{12}{3} = 220$$ Next, I tried to solve by taking multiple cases that is, setting any variable, $x,y$ or $z$ to values from $0,1,2,3...10$, so for example if $x = 0$ then we get, $$y+z=10$$ now it is simple enough to distribute this even without the formula, we get $$\Bigl((0,10),(1,9),(2,8)(3,7),(4,6)\Bigl) \cdot 2,(5,5)$$ which gives us $11$ cases, that can be verified using the formula $$P_0 = \binom{11}{1}.$$ Now taking cases till $x=10$ we get, the final result as $$\sum _{n=0} ^{n=10} P_n = 11+ 10 + 9 + 8+ \ldots +1 = 66$$ Please tell me where I am going wrong or of it simply a case of the answer in the text being wrong, and if the second method is correct.


I've been using CentOS 7 and its kernel version is 3.10. To check Kernel Version, I typed 'uname -r' and command showed 3.10.0-957.1.3.el7.x86_64  As far as I know, MemAvailable metric was introduced to Linux kernel version 3.14.  But, I ran /proc/meminfo and this command showed MemAvailable metric.   MemTotal:       3880620 kB MemFree:        3440980 kB MemAvailable:   3473820 kB   Why did my linux show MemAvailable metric? My Linux kernel is below 3.14

The standard files/tools that report memory seem to have different formats on different Linux distributions. For example, on Arch and Ubuntu.   Arch  $ free               total        used        free      shared  buff/cache   available Mem:        8169312     3870392     2648348       97884     1650572     4110336 Swap:      16777212      389588    16387624   $ head /proc/meminfo  MemTotal:        8169312 kB MemFree:         2625668 kB MemAvailable:    4088520 kB Buffers:          239688 kB Cached:          1224520 kB SwapCached:        17452 kB Active:          4074548 kB Inactive:        1035716 kB Active(anon):    3247948 kB Inactive(anon):   497684 kB  Ubuntu  $ free              total       used       free     shared    buffers     cached Mem:      80642828   69076080   11566748    3063796     150688   58358264 -/+ buffers/cache:   10567128   70075700 Swap:     20971516    5828472   15143044   $ head /proc/meminfo  MemTotal:       80642828 kB MemFree:        11565936 kB Buffers:          150688 kB Cached:         58358264 kB SwapCached:      2173912 kB Active:         27305364 kB Inactive:       40004480 kB Active(anon):    7584320 kB Inactive(anon):  4280400 kB Active(file):   19721044 kB    So, how can I portably (across Linux distros only) and reliably get the amount of memory—excluding swap—that is available for my software to use at a particular time? Presumably that's what's shown as "available" and "MemAvailable" in the output of free and cat /proc/meminfo in Arch but how do I get the same in Ubuntu or another distribution?


I need to show by contour integration that $$\int_0^\infty \frac{(\log x)^2}{x^2+x+1} dx = \frac{16}{81}\sqrt 3 \pi^2$$ I usually approach a contour integral involving $\log x$ by considering a semi-circular contour indented at $0$. But here the other straight arm doesn't simplify due to odd $x$ in denominator. Can somebody help me how to proceed?

I was thinking this integral : $$I(\lambda)=\int_0^{\infty}\frac{\ln ^2x}{x^2+\lambda x+\lambda ^2}\text{d}x$$ What I do is use a Reciprocal subsitution, easy to show that: $$I(\lambda)=\int_0^{\infty}\frac{\ln ^2x}{\lambda ^2x^2+\lambda x+1}\text{d}x =\frac{1}{\lambda}\int_0^{\infty}\frac{(\ln x-\ln \lambda)^2}{x^2+x+1}\text{d}x \\ =\frac{\ln ^2\lambda}{\lambda}\int_0^{\infty}\frac{1}{x^2+x+1}\text{d}x+\frac{1}{\lambda}\int_0^{\infty}\frac{\ln ^2x}{x^2+x+1}\text{d}x \\ =\frac{\ln ^2\lambda}{\lambda}\frac{2\pi}{3\sqrt{3}}+\frac{2}{\lambda}\int_0^1\frac{\ln ^2x}{x^2+x+1}\text{d}x$$ But I hav no idea on process the remaining integral:( Anyone knows how to solve it?  THX guys! I came with another method might work for this: Recall the handy GF $$\frac{1}{x^2+x+1}=\frac{2}{\sqrt{3}}\sum_{k=0}^{\infty}\sin \left(\frac{2\pi}{3}\left(k+1\right)\right)x^k$$ Then we have :  $$\int_0^1\frac{\ln ^2x}{x^2+x+1}\text{d}x=\frac{2}{\sqrt{3}}\sum_{k=0}^{\infty}\frac{2}{\left(k+1\right)^3}\sin \left(\frac{2\pi}{3}\left(k+1\right)\right)x^k$$ With $$\sum_{k=1}^{\infty}\frac{\sin (kx)}{k^3}=\frac{\pi ^2}{6}x-\frac{\pi}{4}x^2+\frac{x^3}{12}$$ What can we arrived?


I have an external hard drive. macOS automatically saves files like ".Trash" and ".DS_Store" ".fseventsd". I was able to delete some files using the terminal. However, ".Trash" remained, which I cannot remove. What should I do? root@home Volume # sudo rm -rf .Trashes rm: .Trashes: Operation not permitted root@home Volume #

I use OS X Mavericks and have some company storage drives mounted (using smb or cfs). (smb://username@address.path.toserver.com/directory/data). When I work with files on the drive or copy files to the drive, some hidden files are created. Most of these files start with dot-dash ._ and then the filename of the original file, like:  ._test001.png ._test002.png ._test003.png   And most of the times, the famous ._.DS_Store and .DS_Store are also there.  On my Mac, these . dot items are invisible, but my windows colleagues do see these files. How can I prevent OS X from making these strange invisible files?  On  (and other internet sources) you can find a 'defaults write' to disable the creation of .DS_Store files on your network drives. But this does not work in Mavericks:  defaults write com.apple.desktopservices DSDontWriteNetworkStores -bool true   For now I use this oneliner, but doing a rm -rf does feel wrong in this case.  find . -type f -name "._*" -exec rm "{}" \;   Edit: I don't want to delete the files or exclude them from copying. I want them not to be created in the first place.  Edit: I prefer a 'native' OS X solution over third party apps.  Edit: This questions has two answers, one for the ._ files and one for the .DS_Store files. The bounty is rewarded for dot_clean, this native command line app cleans all ._ files. Unfortunately is does not clear the .DS_Store files, this can effectively be done with Asepsis. Asepsis stores .DS_Stores in a fixed location, and not in the folder itself.


First of all, I think this is not a variable address copying issue. I have this code : x = [1, 1, 0, 0] b_u = [[0.2 for _ in range(3)]] * 4 for i in range(4):     # The problem is on line below. This line copying new value to the whole column.     b_u[i][0] = (2 * x[i]) / (1 + sum(x)) print(b_u)  And you can see whats happening in lines below : # b_u : # Before loop : [[0.2, 0.2, 0.2], [0.2, 0.2, 0.2], [0.2, 0.2, 0.2], [0.2, 0.2, 0.2]] # Expected : [[0.67, 0.2, 0.2], [0.67, 0.2, 0.2], [0, 0.2, 0.2], [0, 0.2, 0.2]] # After loop : [[0.0, 0.2, 0.2], [0.0, 0.2, 0.2], [0.0, 0.2, 0.2], [0.0, 0.2, 0.2]]  Where am I mistaken? Is it a typo?


How can I force the pattern of a dashed line to be shifted/modified in such way that it does not start/end with a space?  Simple example:  \documentclass{article} \usepackage{tikz}  \begin{document}  \begin{tikzpicture} \draw coordinate (nw) (0,0) rectangle (4,4) coordinate(se); \path (nw)--coordinate (aux) (se);  \draw[dashed] (nw|-aux)--(aux-|se); \end{tikzpicture}  \end{document}   In the resulting output the line ends with a space.    If se is at (3,3) the line both starts and ends with no space:

Dashed lines differ between TikZ and PSTricks:  PSTricks provides symmetry about the midpoint, and full dashes are guaranteed at each end. Can TikZ be configured to achieve this? (By default TikZ does not provide midpoint symmetry, and truncates the last dash.)   The latex which produced the above sample:  \documentclass[11pt]{standalone} \usepackage{color} \usepackage{tikz} \usepackage{pst-node}  \newcommand{\bookend}{{\color{blue}\rule{1pt}{1ex}}} \newcommand{\tikzdash}[1]{\bookend\tikz[baseline=-.5ex,ultra thick]{\draw[line width=2pt,dash pattern=on 4pt off 2pt] (0,0) -- (#1,0);}\bookend} \newcommand{\pstricksdash}[1]{\bookend\rnode{a}{\rule{0ex}{1ex}}\hspace{#1}\rnode{b}{\rule{0ex}{1ex}}\ncline[linewidth=2pt,linestyle=dashed,dash=4pt 2pt]{a}{b}\bookend}  \begin{document}  \begin{tabular}{cc} \begin{tabular}{l} \\ Ti\emph{k}Z \\[1ex] \tikzdash{30pt} \\ \tikzdash{31pt} \\ \tikzdash{32pt} \\ \tikzdash{33pt} \\ \tikzdash{34pt} \\[2ex] \end{tabular} & \begin{tabular}{l} \\ PSTricks \\[1ex] \pstricksdash{30pt} \\ \pstricksdash{31pt} \\ \pstricksdash{32pt} \\ \pstricksdash{33pt} \\ \pstricksdash{34pt} \\[2ex] \end{tabular} \end{tabular}  \end{document}


How much swap space should I have? I have a 500GB HDD and 6GB RAM.  My specs:     Release 12.04 (precise) 64-bit   Kernel Linux 3.8.0-34-generic   GNOME 3.4.2   Memory: 5.7 GiB Processor: Intel® Core™ i3-3227U CPU @ 1.90GHz × 4   I just want to run Steam games smoothly.

For a desktop installation in a new and shiny laptop (let's say 16gb ram and ssd hd), does it make sense to have a swap partition?


While I was working on proofs of functions, the following claim occurred to me that I think it is correct but I could not prove it. Please note that the claim may not be correct since it is just my hypothesis. So my hypothesis is:     Let $A$ be a finite set and $F$, a function $F:A\rightarrow A$.   $F$ is surjective if and only if $F$ is injective.    Here is how I tried to prove it:   $\rightarrow$ Let $X$, $Y$, $Z$ and assume $F(X)=F(Y)$. We need to show that $X=Y$ to prove that $F$ is $1-1$. $F(X)$ and $F(Y)\in A$ and $F$ is surjective then $\text{Img}(F)=A$. $A$ is a finite set then $\text{Img}(F)$ is a finite set.   how can I continue the proof?    $\leftarrow$ We need to show that $A=\text{Img}(F)$ to show that $F$ is surjective but we know that $\text{Img}(F)\subseteq A$ so we need to show $A\subseteq \text{Img}(F)$. Let $x\in A$. We need to show $x\in\text{Img}(F)$. $A=\text{Dom}(F)$ and $x\in\text{Dom}(F)$ and $F$ is function so there exists $y$ such that $F(x)=y$.   And here also I got stuck. Any ideas how to continue the proof if it is right.. I know that I did not use that $A$ is a finite set and $F$ is injective in one way because I do not see where I can use in my proof.

Let S be a finite set.Let F be a surjective function from S to S.  How do I prove that it is injective?


I'm a newbie .htaccess and regex. I have a script that works locally but when I upload it to a live server it causes an infinite loop. How can I fix this? On the site when you load http://subdomain.example.com if you are unauthenticated it takes you to http://subdomain.example.com/auth/ for a login form, else it displays the contents of http://subdomain.example.com/index.php. It works fine locally but when I upload on a live server, it cannot find auth.php so it redirects to the index page and because the user is not authenticated it sends to auth.php thus the infinite loop. When I test my .htaccess from here  the results are as shown below. Please advice. Please help. Thanks.  This is my file  Options +FollowSymLinks -MultiViews -Indexes  <IfModule mod_rewrite.c>    DirectoryIndex index.php    RewriteEngine On    RewriteBase /          # remove php extensions (only for GET method)    RewriteCond %{THE_REQUEST} ^GET\ /(.+)\.php(?:\?|\s) [NC] #This variable is not supported: %{THE_REQUEST}    RewriteCond %{REQUEST_FILENAME} -f #This variable is not supported: %{REQUEST_FILENAME}    RewriteRule ^ %1/? [L,R=301] #This rule was not met because one of the conditions was not met     # don't touch other existing files/folders    RewriteCond %{REQUEST_FILENAME} -f [OR] #This variable is not supported: %{REQUEST_FILENAME}    RewriteCond %{REQUEST_FILENAME} -d [OR] #This variable is not supported: %{REQUEST_FILENAME}    RewriteCond %{ENV:REDIRECT_STATUS} \d #This variable is not supported: %{ENV:REDIRECT_STATUS}    RewriteRule ^ - [L] #This rule was not met because one of the conditions was not met     # force trailing slash    RewriteCond %{DOCUMENT_ROOT}/$1\.php -f #This variable is not supported: %{DOCUMENT_ROOT}/$1\.php    RewriteRule ^(.+?[^/])$ $1/ [L,R=301] #This rule was not met because one of the conditions was not met     RewriteCond %{DOCUMENT_ROOT}/$1.php -f #This variable is not supported: %{DOCUMENT_ROOT}/$1.php    RewriteRule ^([^/]+)/([^/]+)/([^/]+)/?$ $1.php?a=$2&id=$3 [QSA,L]#This rule was not met because one of the conditions was not met     #rewrite path to file eg http://example.com/auth/recover to http://example.com/auth.php?a=recover    RewriteCond %{DOCUMENT_ROOT}/$1.php -f #This variable is not supported: %{DOCUMENT_ROOT}/$1.php    RewriteRule ^([^/]+)/([^/]+)/?$ $1.php?a=$2 [QSA,L] #This rule was not met because one of the conditions was not met     # rewrite extensionless php files    RewriteCond %{DOCUMENT_ROOT}/$1.php -f #This variable is not supported: %{DOCUMENT_ROOT}/$1.php    RewriteRule ^(.+?)/$ $1.php [L] #This rule was not met because one of the conditions was not met     # finally, if not found    RewriteRule . index.php [L] #This rule was met, the new url is http://subdomain.example.com/index.php </IfModule>

This is a  about Apache's mod_rewrite.   Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes such things as:   Changing HTTP to HTTPS (or the other way around) Changing a request to a page which no longer exist to a new replacement. Modifying a URL format (such as ?id=3433 to /id/3433 ) Presenting a different page based on the browser, based on the referrer, based on anything possible under the moon and sun. Anything you want to mess around with URL   Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask!  How can I become an expert at writing mod_rewrite rules?   What is the fundamental format and structure of mod_rewrite rules? What form/flavor of regular expressions do I need to have a solid grasp of? What are the most common mistakes/pitfalls when writing rewrite rules? What is a good method for testing and verifying mod_rewrite rules? Are there SEO or performance implications of mod_rewrite rules I should be aware of? Are there common situations where mod_rewrite might seem like the right tool for the job but isn't? What are some common examples?   A place to test your rules  The  web site is a great place to play around with your rules and test them. It even shows the debug output so you can see what matched and what did not.


I need the code folding property in gedit, and I found online a folding.gedit-plugin online, but it never works.  My gedit is of version 3.2.1, and it is said that the plugin folding.gedit-plugin was made for 2.x version only.     So is there a code folding plugin for gedit of version 3.2.1?  Thanks!

Does anyone know about a way to get code folding in gedit? I've found  in google code, but looks like dead and doesn't work with the latest gedit.


I’m reading  on the subgroup structure of classical subgroups. According to Corollary 2.2 (d), since $8=2^3$ is a prime power of even number $2$, ${\rm PSL}(2,8)$ has a maximal subgroup ${\rm PSL}(2,2)=S_3$. But ${\rm PSL}(2,8)$ has exactly $3$ conjugacy classes of maximal subgroups.  The three non-conjugate maximal subgroups of ${\rm PSL}(2,8)$ are $C_9\rtimes  C_2$, $C_7\rtimes C_2$ and $C_2^3\rtimes C_7$, none of which is $S_3$. I believe I misunderstood something when reading the reference, but I don’t know what that is. Could you give me some help? Any help would be appreciated.

This material is covered in detail in Dickson's "Linear Groups with an exposition of the Galois Field Theory", chapter XXII and Huppert's "Endliche Gruppen", chapter II, paragraph 8. Since I don't speak german and Dickson's treatment often requires deciphering, I was wondering if there is a "modern" account of this somewhere.


Context I am writing a technical document about some piece of mathematics, the tone of which is intended to be formal and academic.  Question Directly after a computation comes a sentence, in which I am unsure how to best position the preposition 'above'. The two alternatives are:     (1) 'The reader should find no difficulty in identifying the six implicit steps in the above computation.'   and     (2) 'The reader should find no difficulty in identifying the six implicit steps in the computation above.'   In this context, is one of these alternatives to be preferred over the other? I am leaning towards alternative (1), but I am no native speaker of English.  Edit  that my question may be a . The suggested duplicate fails to address a context and appears to pertain more to grammar than to formal style. I think my question is different.  Edit 2  alternative (2) be replaced by     (3) 'The reader should find no difficulty in identifying the six implicit steps in the computation shown above.'   I agree with this suggestion; see  of mine. Thus I wonder if one of alternatives (1) and (3) is to be preferred over the other? I still lean towards alternative (1), simply because it consists of one less word.  It has also been suggested I number the relevant computation and thereafter refer to this number. Whereas this is appropriate in many cases, I find it unnatural to do so here. See my  on Carl Witthoft's answer for an explanation.  Edit 3  (in another thread) links to a graph showing which formulation is more common. It suggests alternative (1), and the question is answered.

I frequently see statements that refer to something later in the text that use a phrase such as "the below information". Is it more correct instead to say "the information below" (or "the following information")?


I'm terrified to Google this and I would appreciate if anyone could answer this as gingerly and spoiler-free as possible because I'm not very far in the game and I'd like to experience all of the puzzles on my own. I take exception with this particular quandary because I've spent the last 30 minutes feathering the thumbstick ever-so-slightly in every direction, trying to get this thing to activate, and it won't do it.  I'm getting varying degrees of sparks when I click in the circle, but I can't seem to line it up properly. Is there a different (maybe higher?) perspective that I am supposed to activate it from? Does the circle on the right-hand side need to be fully closed (ie: no chunk cut out in the middle)? Or is it more important that the circle is as circular as possible? The amount of sparks on the various attempts seems to indicate that the latter is more important, but about 300 attempts haven't sealed the deal, and I'm starting to question my sanity :p  Thanks in advance for your help :) The game is really great so far!! I was grinning like a buffoon when I discovered the first symbol for the black obelisks; I thought the game consisted entirely of the little panel puzzles.

In The Witness, I was walking along the coast, and I came upon this:    Now, since I've learned      that mazes can be embedded in the environment,   I see the puzzle here, but I just can't get the pieces to line up well enough.  Standing on the couch and walking all around it doesn't seem to get me a       functional maze.   Where do I need to stand to activate the puzzle successfully?


I'm familiar with the ideal gas law:  $PV = nRT$,  Which is valid for ideal gases. One can move forward and write EOS for non-ideal gases, liquids and gases. But what is the equation of state for a perfect solid. If possible can you provide a refernce for further reading?

There is an Ideal Gas Law, but why isn't there one for liquids or solids? Is it because they are much too hard to predict or that solids and liquids vary drastically in their reaction to temperature and pressure then do gases, thereby nullifying the need for a Law that could apply to all?


I am having some trouble removing the "white lines" from a colored table (where it says 3 and 4).    \documentclass{report}  \usepackage{wrapfig} \usepackage{colortbl} \usepackage{booktabs} \usepackage{multirow} \usepackage{hhline} \usepackage[table,xcdraw]{xcolor} \usepackage{graphicx}  \definecolor{lightgray}{rgb}{0.75,0.75,0.75} \definecolor{darkgray}{rgb} {0.50,0.50,0.50}  \begin{document} \begin{wraptable}[12]{r}[0cm]{5cm}     \vspace{-1cm}     \resizebox{5cm}{!}{         \begin{tabular}{c|c|c}             \hline             \textbf{Binary}    & \textbf{ICDR}      & \textbf{ETDRS}                                             \\ \hline             0                  & 0                  & No DR                                                      \\ \hline             &\cellcolor{lightgray}1                   & \cellcolor{lightgray}Very mild NPDR   \\ \hhline{~|--}              &\cellcolor{lightgray}2                   & \cellcolor{lightgray}Mild NPDR        \\ \hhline{~|--}             &\cellcolor{lightgray}                    & \cellcolor{lightgray}Moderate NPDR    \\ \hhline{~~|-}             &\cellcolor{lightgray}                    & \cellcolor{lightgray}Severe NPDR      \\ \hhline{~~|-}             &\cellcolor{lightgray}\multirow{-3}{*}{3} & \cellcolor{lightgray}Very Severe NPDR \\ \hhline{~|--}             &\cellcolor{darkgray}                     & \cellcolor{darkgray}\begin{tabular}[c]{@{}c@{}}Mild - Moderate\\ PDR\end{tabular}          \\ \hhline{~~|-}             &\cellcolor{darkgray}                     & \cellcolor{darkgray}High-Risk PDR                                                          \\ \hhline{~~|-}             \multirow{-8}{*}{1}&\cellcolor{darkgray} \multirow{-3}{*}{4} & \cellcolor{darkgray}\begin{tabular}[c]{@{}c@{}}Advanced Diabetic\\ Eye Disease\end{tabular}\\ \hhline{---}     \end{tabular}}     \caption{\label{tab:dr_classes}Sample Caption.} \end{wraptable}]  \end{document}   Any information is appreciated.

So I need to make a colored table with multirows, together with the use of partial horizontal lines. I used \cline which does not work: the \cellcolor-command overwrites the line.  told me to change it to \hhline which will not be overwritten by \cellcolor. Instead, \hhline overwrites the color.  To make it more clear:  Without color:  \documentclass{article}  \usepackage{colortbl} \usepackage{multirow}  \begin{document}    \begin{tabular}{|c|c|}     \hline     \bfseries ColumnOne & \bfseries ColumnTwo\\ \hline     First data & 932\\ \hline      & 239\\ \cline{2-2}  % or \hhline{|~|-|}      & 137\\ \cline{2-2}  % or \hhline{|~|-|}     \multirow{-3}{*}{More data} & 319\\ \hline     Last data & 132\\ \hline   \end{tabular}  \end{document}     With color: Using \cline  \documentclass{article}  \usepackage{colortbl} \usepackage{multirow}  \begin{document}    \begin{tabular}{|>{\columncolor{red}}c|>{\columncolor{blue}}c|}     \hline     \bfseries ColumnOne & \bfseries ColumnTwo\\ \hline     First data & 932\\ \hline      & 239\\ \cline{2-2}      & 137\\ \cline{2-2}     \multirow{-3}{*}{More data} & 319\\ \hline     Last data & 132\\ \hline   \end{tabular}  \end{document}    Makes the lines in the right column disappear.  Using \hhline  \documentclass{article}  \usepackage{colortbl} \usepackage{multirow} \usepackage{hhline}  \begin{document}    \begin{tabular}{|>{\columncolor{red}}c|>{\columncolor{blue}}c|}     \hline     \bfseries ColumnOne & \bfseries ColumnTwo\\ \hline     First data & 932\\ \hline      & 239\\ \hhline{|~|-|}      & 137\\ \hhline{|~|-|}     \multirow{-3}{*}{More data} & 319\\ \hline     Last data & 132\\ \hline   \end{tabular}  \end{document}    Creates white lines on the left column.  Is there any possible way on how to resolve this?


Consider the power series $$\sum_{n=1}^\infty\frac{(1+n)^n}{n!}x^n $$ Now the ratio test shows that the given power series converges absolutely $|x|< 1/e$ and diverges for $|x|>1/e$. But all the tests I know(Raabe's test) are failing at $|x|=1/e$.  Any help will be highly apprecieated.

Let    $$a_n = \dfrac{(1+n)^n}{n!}$$   Discuss convergence of the series $\displaystyle \sum a_nx^n$.   I've shown that the series converges absolutely when |x| < 1/e and diverged when |x| > 1/e. I can't seem to determine what happens at |x| = 1/e


The title is not the issue. this issue i already solved by understanding the "immutable and mutable" -thing. But, I wanted to know a bit better about it. What are exactly allow the object to be acceced by another function if i dont tuch him and make shadow of the first one created. I show you with code:  def text():     print x  x = 6 text()   This example whill work well, because i didnt created a new object of immutable. but this:  def text():     print x  text() x = 6   This will not work because the integer is not a global variable.  What is exactly happend when i created a new object without globaled it? to where in the memory this objects goes that allowed me to approach to it by another scope. why its so different then just a global?

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.


One of the questions that is inevitably asked on every beta site at some point, often more than once, is a variation of "why haven't we graduated yet?" or "what do we need to do to graduate?".   The whole process around graduation is rather intransparent. I've been a moderator during the whole beta phase until graduation on one site, and I'm a moderator on another beta site that hasn't graduated yet. I've quite a bit more experience with the process than the average SE user, but I still can only guess why certain sites have not graduated yet and why some sites have.  What I know about the process is that in certain unknown intervals the SE community team evaluates a site and makes a decision on whether to graduate it or not. The general requirements are a minimum threshold of activity on the site, the absence of any severe quality issues, a sufficient amount of high-rep users to ensure moderation and a healthy growth trend in traffic.   The feedback from SE on graduation is currently rather minimal, unless someone explicitly asks, there is no feedback at all until graduation. There are exceptions like severe quality issues that jeopardize the existence of the site, but most of the time there is no feedback. Even if someone asks, the answer are often rather vague.  I think that more feedback on graduation would be very useful to the beta sites, and I'd like to propose the following idea on how SE could provide better feedback without too much additional effort.  The first point is that the schedule on when sites are evaluated should be public, or at least available to the moderators. The result of each evaluations should be communicated to the moderators. This doesn't have to be in any polished form, a very simple summary would already be helpful. Even a simple "no major quality problems, nice question volume but not enough high-rep users to moderate, traffic still a bit low" would be a large help. It shouldn't be more additional effort than whatever report is written internally anyway.  I'm proposing to communicate this to the moderators mainly to reduce the additional effort for SE. The internal communication can be less formal, and the moderators can then decide how to inform the community, if it makes sense (if there is no change compared to the last evaluation, that is probably not necessary).

The beta tab of an Area 51 proposal contains the criteria for considering a beta site healthy:  15 questions per day on average 90% answered 150 users with 200+ rep 10 users with 2,000+ rep 5 users with 3,000+ rep 2.5 answers per question 1,500 visits per day  However, as the Robert Cartaino's answer to my question ( states), this is not enough. There are more fuzzy factors taken into account, before deciding, if . So I propose, that we should sit down and try to objectivise that fuzzy criteria and turn them in some numbers. In fact, this is what happens in the minds of SE team, it's only not yet written. For example, the question states the problem with the possible lack of users with moderator privileges after changing from beta to graduate site. That means, that the requirements from Area51 are too loose. We need more people with close privileges (>3000) and at least a few ones with access to moderator tools (>10000). Another factor is the gross size of the site, which makes the critical mass. We could be inspired by , which require at least 40 tags with at least 200 questions in each in order to grand that badge. Maybe 40 tags with 100 questions is too much as graduate criteria, but how about at least 20 with 100 questions? Anyway, I think there's enough SE sites to sum up the experiences and write out the common problems with beta sites and with sites that should become graduated. Writing clear criteria for graduation would not only make the whole process more transparent, but what's more important, they would become the guidelines for each beta community, saying what should we work on to help our children grow up.


I looking for a function that calculate the day difference between two weekdays. Like, for eg.   Monday - Friday = 4  Sunday - Saturday = 6  Thank you!

How do I get the number of days between two dates in JavaScript? For example, given two dates in input boxes:  <input id="first" value="1/1/2000"/> <input id="second" value="1/1/2001"/>  <script>   alert(datediff("day", first, second)); // what goes here? </script>


@FXML private void ekle() throws Exception{        try{         Connection conn2 = dc.getConnection();     pst=conn2.prepareStatement(query_ekle);     pst.setString(1, text_no.getText());     pst.setString(2, text_stok.getText());     pst.setString(3, text_tarih.getText());     pst.setString(4, text_garanti.getText());     pst.setString(5, text_marka.getText());     pst.setString(6, text_model.getText());     pst.setString(7, text_aile.getText());     pst.setString(8, text_hiz.getText());     pst.setString(9, text_bellek.getText());     pst.setString(10, text_cekirdek.getText());     pst.setString(11, text_soket.getText());     pst.setString(12, text_watt.getText());     pst.setString(13, text_ie.getText());     pst.setString(14, text_ug.getText());     pst.execute();     pst.close();     } catch(Exception e){         System.out.println(e);     }  }  ////////////////////////////////////////////////////////////////////  private connect dc = new connect();       Connection conn3; PreparedStatement pst=null;  ////////////////////////////////////////////////////////////////  String query_ekle="INSERT INTO urunler(u_no,u_stok_miktari,u_alindigi_tarih,u_garanti_suresi,u_marka,u_modeli,u_ailesi,"             + "u_hizi,u_bellek,u_cekirdek,u_soket,u_watt,ie_no,ug_no) Values('?','?','?','?','?','?','?','?','?','?','?','?','?','?')";  /////////////////////////////////////////////////////////////////// public class connect {      private String url="jdbc:mysql://localhost:3306/";     private String dbAdi="my_database1";     private String userAdi="root";     private String userPass="14907";      public Connection getConnection() throws Exception{          try{               Class.forName("com.mysql.jdbc.Driver");             Connection connection=(Connection) DriverManager.getConnection(url+dbAdi,userAdi,userPass);             return connection;          }catch(Exception e){              System.out.println(e);          }             return null;         } }  ////////////////////////////////////////////////////////

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


Recently in physics news, scientists have experimentally discovered the so-called . It seems that a quantum mechanical monopole is different from a magnetic monopole. So my question is what exactly is a quantum mechanical monopole and what are the differences between the two if there are any.

As everybody here knows, Maxwell's equation would look more beautiful if a magnetig charge were present. Beyond the aesthetics question, if a single magnetic Dirac monopole would be found, the consequence is that the electric charge would be quantized.  While, I guess, everybody should be happy with the news, my experimentalist background doesn't allow me to understand the experimental setting. I therefore ask for the following advice -- a rather theoretically oriented question.  A recent paper,     Observation of Dirac monopoles in a synthetic magnetic field. M. W. Ray, E. Ruokokoski, S. Kandel, M. Möttönen and D. S. Hall. .   claims to have observed such monopoles.   Can somebody shed light on the theoretical implicacions of this work? Concretely, should we now take care before saying that it's been proven that the electric charge is quantized?


When I try to connect to chat, either Meta or SE chat, I get an "ERR_CONNECTION_REFUSED" error. Using Chrome latest.      Aaaand it's back. Thank you, oh SE dev :)

Chat is down network-wide. Where can I find when it'll be back up?


I'm having some problems with my code. In particular, I get a NullPointerException in the toString() function of the second class.  I tried to solve, but I'm losing my mind. I hope you guys could help me.  Here the code of the two inherent classes.  public class TypeOfArticle implements Serializable {  private int code; private String name; private String description; private Sport sport; private Materials materials;  public TypeOfArticle (int code, String name, String description, Sport sport, Materials materials) {     this.code = code;     this.name = name;     this.description = description;     this.sport = sport;     this.materials = materials; }  public int getCode(){     return this.code; }  public String getName(){     return this.name; }  public String toString(){     return this.name + this.code; } }   And here the second class where appears the error:  NullPointerExcpetion Error on --> this.typeOfArticle.toString() in the toString() function.  public class Article implements Serializable {  private int code; private double price; private Date date; private TypeOfArticle typeOfArticle ;  public Article(int code, double price, Date date, TypeOfArticle typeOfArticle ) {     this.code = code;     this.price = price;     this.date = date;     this.typeOfArticle = typeOfArticle ; }  public TypeOfArticle getTypeOfArticle() {     return this.typeOfArticle ; }  @Override public String toString() {     return this.typeOfArticle.toString() + this.price; } }   Thank you very much to everyone who can help me!


I am trying to find out the differential of $\sin^{-1}x$ using fist principle as follows $$\frac{d}{dx}\left(\sin^{-1}x\right)=\lim_{h\to 0}\frac{\sin^{-1}(x+h)-\sin^{-1}(x)}{h}$$ I got stuck here what is next step to reach $\frac{1}{\sqrt{1-x^2}}$. could somebody help me ? thank you very much

Because $\sin'(x)=\cos(x)$ we can prove that $\arcsin'(x)=\frac{1}{\sqrt{1-x^2}}$. but, by definition we have $$\arcsin'(x)=\lim_{h\to0}\frac{\arcsin(x+h)-\arcsin(x)}{h}\tag{1}$$ therefore, $$\lim_{h\to0}\frac{\arcsin(x+h)-\arcsin(x)}{h}=\frac{1}{\sqrt{1-x^2}}\tag{2}$$ My question: Can we prove $(2)$ without using $(1)$? How?


What is the difference between E and Object types, when referring to the following example?  Example  List interface has two methods, Add(E e) and Remove(Object obj).  How was it decided to use E or Object for each method?  Phrased another way, how would I know whether to use E or Object when writing the header of my own written method?

Why isn't  generic?    Seems like Collection<E> could have boolean remove(E o);   Then, when you accidentally try to remove (for example) Set<String> instead of each individual String from a Collection<String>, it would be a compile time error instead of a debugging problem later.


I need something like a firewall, but instead of restricting network traffic, I want to be able to restrict scripts, applications, and processes in general from being allowed to run/execute in the first place.   Rather than having to constantly keep checking for rogue processes, troubleshooting, and terminating them individually. I just want them to:       a) Die. Quickly, quietly, without manual user intervention.    Or (preferably):        b) Be prevented from ever spawning in the first place.  PS: I don't think the old chmod utility is really appropriate at this level. I think I recall reading about an Apple style .plist/.xml solution for this kind of thing. I don't know enough about it to say if it's the right approach though.

Is there a way to block a list of specific apps on macOS?  I have looked up solutions such as Cisdem, but there are some holes in the way it works that I don't like.   Unless you also block Activity Monitor, Terminal, and System Preferences, you can simply quit the Cisdem process or create a new user to get around it. You have to block Activity Monitor, Terminal, and System Preferences to make it work well.   I want to block an app from running or even being installed on my Mac. The app can be installed via the App Store and the web. Not sure how to go about this. Enabling Parental Controls won't work as Administrator privileges are needed.   The specific app I want to block is Apple Configurator.  Any ideas?


Show that $\text{trace}(A)\leq \sqrt{n}\sqrt{\text{trace}(AA^t)}$ where $A$ is in $M_{n}(\mathbb{R}).$  We know that $\text{trace}(A) =\sum_{i}\lambda_i$ where $\lambda_i$ are eigenvalues of $A.$ Then I was wondering if we could show that the eigenvalues of $AA^t$ are $\lambda_i^2$ then we could apply the AM-GM inequality to complete the proof. So we know that $A$ and $A^t$ have the same eigenvalues, but can we use this conclude that $AA^t$ have $\lambda_i^2$ as eigenvalues?

The following definition is needed for my actual question:  For $A, B \in \mathcal{M}_{n \times n}$ define $$  \langle A, B \rangle = \text{Trace}(B^{T}A) = \sum_{j=1}^{n}\sum_{i=1}^{n}b_{ij} \, a_{ij} $$  And here is the actual question:  For $B \in \mathcal{M}_{n \times n}$ show that $$ \text{Trace}(B)^{2} \:\leq\: n \,\text{Trace}(B^{T}B) $$  I know I have to use the Cauchy-Schwarz Inequality, but I wasn't exactly sure how to.  Here is my attempt:  Since I only have one matrix I decided to use the identity matrix $$ \begin{align} \text{Trace}(B)^{2} \:&\leq\: n \,\text{Trace}(B^{T}B) \\ \text{Trace}(I^{T}B)^{2} \:&\leq\: n \, \langle B, B \rangle \\ \langle I_{n}, B \rangle^{2} \:&\leq\: n \, \Vert B \Vert^{2} \\ \langle I_{n}, B \rangle \:&\leq\: \sqrt{n} \, \Vert B \Vert \end{align} $$  I feel like I either did it incorrect, or that I'm close but am missing something.


We know that one irreducible polynomial on $\Bbb{Z}_2[x]$ is  $x^8 + x^4 + x^3 + x + 1$. How to check that it is irreducible? And how to generate irreducible polynomial for any degree?

I am learning about the AES algorithm which uses the finite field ${\mathbb{Z}_2[x]}\over{(p(x))}$, where $p(x)=x^8+x^4+x^3+x+1$.  How do you prove that this polynomial is irreducible? I know that for polynomials of degree $2$ & $3$ you could just check that it has no roots, but how would you do it for this polynomial?


Background: While trying to understand the Standard Model I stumbled on a paper that explained it in very simple terms. I recognized that I don't even understand the quantum mechanical way of the electric force. The paper pictured electromagnetic repulsion by two people on different boats, exchanging a bowling ball, one throwing, one catching. The bowling ball standing for an exchanged photon. That cannot be the whole of the truth, as it wouldn't, not even as a picture, explain the attracting force between two bodies with opposite charges. Now the question: how is electromagnetic repulsion and attraction really modeled in terms of quantum physics? Edit: the duplicates only address repulsion, or are out of reach for what I understand about quantum theory. So I state the missing part explicitly: How is an electron attracted to a positron by the exchange of a photon?

Since Newton's law of gravitation can be gotten out of Einstein's field equatons as an approximation, I was wondering whether the same applies for the electromagnetic force being the exchange of photons. Is there an equation governing the force from the exchange of photons? Are there any links which would show how the Coulomb force comes out of the equations for photon exchange? I know that my question is somewhat similar to the one posted here , but it doesn't really have an answer to my question specifically.


Is a comma or a colon the correct punctuation of the following sentence?     There are plenty of meals from which to choose /// from pasta to steak.   At the break between clauses, denoted by /// it seems a colon is warranted as what comes before is a complete sentence, and what follows is explanatory details and not a complete sentence.   But a comma also makes sense, as it turns the last portion of the sentence into a modifier. But the modifier from pasta to steak would not be modifying the thing that comes immediately before, so it seems to violate that rule.   I see a similar question here:  but that question's modifier clause does not contain the from x to y structure, and as such the answer to that question does not fully apply here. We would not replace the colon with words such as namely, that is, as, for example, for instance, because, as follows, because the word from would make that awkward: options namely from pasta to steak

The author used a comma in the following text; I would have used a colon. Any thoughts?     "She is one of only a few lawyers with the necessary skills to advise on such deals[:][,] a significant achievement for a mid-level attorney."


For a complex frame with several slides that order is alraidy correctly set, I'd like to process only last frame to tune placement details and avoid a long processing time.  \documentclass{beamer} \includeonlyframes{current} \begin{document}  \begin{frame}[label=current]  \begin{itemize}[<+->] \item  \item  \item  \item  \end{itemize}  \end{frame} \end{document}

I have a big latex beamer that uses \alt, \uncover, ... to create "animations".  My goal is to deactivate all these commands temporary (let's say : just use the last state/slide each time there's this kind of thing) to print my document.  Is there a global command to do this or have I to do all this manually (comment manually the commands / or (simpler but still really long) suppress manually pages from the output) ?  Thanks very much in advance for your help.


I'm currently dual booting Ubuntu and Windows 8. Ubuntu is pretty much broken, and everywhere I've looked doesn't have a solution, so I wish to uninstall it. I read that it's possible to uninstall Ubuntu by deleting its partition on Windows. I checked to see what partitions I have, and there are 7 unused partitions, and I'm not sure which one to delete.     Is there any way to know which partition is Ubuntu so I don't delete the wrong one? Can I just delete Disk 0? Disk 1 is full of files that have names (like OEM, EFI, Recovery, etc).

I installed Ubuntu (I had already had Windows 8.1) from USB (I still have live Ubuntu on it). Is there a way I can uninstall Ubuntu in a way that my Windows will remain bootable? All the tutorials I have seen say that uninstalling ubuntu will delete GRUB also so I will need a Windows recovery CD to boot into it, but I don't have one. Is there a solution?


It is possible in Oracle 18c to rename the default sid (XE) in a custom SID? I tryed using Oracle Database Configuration Assistant but having not success. how can i possibly do? Thanks

I needed to change the SID of an Oracle XE database (not the Service Name) to match a production database.  When I tried searching online, most of the pages were describing changing or adding a service name through tnsnames.ora; that's not what I needed to do.


So I have a text block something like below,  #start Line 1 Line 2 Line 3 #end  *--Similar blocks-*   I used this   Regex.Matches(text,@"#start(.*?)#end",RegexOptions.Multiline)   regex for this above block.  The thing is when I try matching this Regex through Notepad++ find options it works, but through C# Regex.Matches function it fails.  I don't know what exactly is the problem. But hope you people can help me ! :)

For example, this regex  (.*)<FooBar>   will match:  abcde<FooBar>   But how do I get it to match across multiple lines?  abcde fghij<FooBar>


As shown in  video, one can easily make a screen recoding of an iOS device (running iOS 11 or later) using the built-in mechanism.  Is there a similar built-in facility available in macOS to record Mac screen?

I've used  before but for company things it's not appropriate since it becomes public. I need something that lets me record my screen and gives me a small well encoded file that I put into dropbox.  What's my options?


I have province table     province_id province_name     1 Abra   2 Bulacan   3 Cagayan   4 Dagupa     and it is connected in 2 fields in person table     person_id person_name currentaddress_province_id provincialaddress_province_id     1 Jepoy 1 2   2 Jeff 3 4     I want to display output like this:     Name Current Province Provincial Province     Jepoy Abra Bulacan   Jeff Cagayan Dagupan     I tried the below code: $query = "SELECT * FROM person LEFT JOIN province ON province.province_id = person.currentaddress_province_id AND person.provincialaddress_province_id ";  $statement = $connect->query($query); $statement->execute(); $count = $statement->rowCount(); $output = '

Name	Current Province	Provincial Province

'; if ($count > 0) {     $result = $statement->fetchAll();     foreach ($result as $row)     {         $output .= '
'.$row["person_name"].'	'.$row["province_name"].'	'.$row["province_name"].'
';     } } $output .= '

'; echo $output;   but this is the result:     Name Current Province Provincial Province     Jepoy Abra Abra   Jeff Cagayan Cagayan

I have 2 tables. One (domains) has domain ids, and domain names (dom_id, dom_url).  the other contains actual data, 2 of which columns require a TO and FROM domain names. So I have 2 columns rev_dom_from and rev_dom_for, both of which store the domain name id, from the domains table.  Simple.  Now I need to actually display both domain names on the webpage. I know how to display one or the other, via the LEFT JOIN domains ON reviews.rev_dom_for = domains.dom_url query, and then you echo out the dom_url, which would echo out the domain name in the rev_dom_for column.  But how would I make it echo out the 2nd domain name, in the dom_rev_from column?


Consider the equation $(x^3-3x^2+4x-2)s(x)+(x^2-1)t(x)=x+1$. How can we find polynomials $s(x), t(x)$ which satisfy this equation? Clearly $x+1$ divides the term involving $t(x)$ but not the first polynomial. If there are solutions then we need $(x+1)$ to divide $s(x)$. I am not sure where to go from here though.

Isn't finding the inverse of $a$, that is, $a'$ in $aa'\equiv1\pmod{m}$ equivalent to solving the diophantine equation $aa'-mb=1$, where the unknowns are $a'$ and $b$? I have seem some answers on this site (where the extended Euclidean Algorithm is mentioned mainly) as well as looked up some books but there is no mention of this. Am I going wrong somewhere or is this a correct method of finding modular inverses? Also can't we find the Bézout's coefficients by solving the corresponding diophantine equation instead of using the extended Euclidean Algorithm?


I'm trying to tar all .log files in /var/log directory. But i need to tar only the files without the directories names i have done this so far : sudo find  /var/log/ -name '*.log' | sudo xargs tar --transform='s!./!!' -rf allcfiles.tar  the output still have the folder names like varlog/file.log varlog/file1.log varlog/x/file2.log  but i need the archive to have the structure of : file.log file1.log file2.log

I'm .taring some files with the path example/super_user/Output.*.  The resulting .tar looks like this:  + example     + super_user           - Output.zip           - Output.xml           - Output.txt   But I want the file to be like the following:  - Output.zip - Output.xml - Output.txt   Do you know how I can achieve this while still being in another directory?


Is it bad style to start a sentence with being or grammatically wrong. It´s a participle right? Still I feel it is just not it?!  Something like:     Being an English teacher means to not only teach a language but also to teach children about different cultures.

My teacher recently marked on my paper not to use a gerund to start a sentence. I have been told by teachers in the past to use that format to vary sentence structure. It seems to make the paper flow better oftentimes. An example:     Learning to confront his problems is an important part of [character's] growth and maturity in the novel.   Is there a grammar rule about this? I haven't ever heard/seen one before.  Edit: It would also be helpful to know of any good examples or arguments I would be able to use when discussing this.


I want too make a character explicitly too shut down mages  and was curious what methods of destroying an arcane focus or component pouch exist. Getting the item away would also work. Unfortunately effects like shatter dont work on held items, is there a spell that would work for this or an item?

Most spells/abilities only allow the targeting of creatures rather than objects.  Of the few that do allow object targeting, most explicitly except "worn or carried" objects.     It ignites flammable objects in the area that aren’t being worn or carried. (Fireball)    or     A nonmagical object that isn't being worn or carried also takes the damage if it's in the spell's area. (Shatter)   What methods do exist to damage or destroy objects that are worn or carried?  I'm looking for spells, abilities, items, or monsters that could achieve this.


I'll try to be clear. I'd like to ask you if you know some books or chapters in textbooks which explaining the "meaning" of some physical phenomena or entities.   I may try to be more specific using an example to explain what i'm looking for. Let's take electrodynamics: we use both fields and potentials to describe the whole spectrum of electromagnetic phenomena. I have this doubt:    which concept is "more real" and fundamental: the field or the potential?  Are the potentials just a useful mathematical escamotage?    It may be banal but i don't know the answer. I read that in modern times the vector potential plays a central role in the theory and it is good to build the theory around it, why? "Just" less mathematical complication or a more physical insight? Maybe I never even thought about some interesting question about the fundamental quantities and therefore I'll never look for those answer.  As other example of what I mean I may say I'd like something in the style of the first chapter $1$ of the Feynman vol. $II$, the chapter 19 on the Principle of Least Action, or the chapter on electromagnetic mass in the same book.  Edit: it's not a duplicate. I didn't ask for an undergraduate electrodynamics course. I asked for a book different in the way it explains stuff and not just about EM, but about physics in general. I made the electrodynamical example to explain what I needed. That question thred that has been put here it's of no help

What books are recommended for an advanced undergraduate course in electrodynamics?


Let's say I have the following empty two dimensional array in Python:  q = [[None]*5]*4   I want to assign a value of 5 to the first row in the first column of q. Instinctively, I do the following:  q[0][0] = 5   However, this produces:   [[5, None, None, None, None],    [5, None, None, None, None],    [5, None, None, None, None],    [5, None, None, None, None]]   The first element of every array is being initialized to 5, where I thought only the first element of the first array would get the update. I have two questions:   Why is Python initializing the first value of every array and not just the first one? Is there a better way to accomplish what I'm trying to do?

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


I'm looking for a way to save a wepgage along with its gifs (). I know how to save a single gif, but my goal is to save the whole webpage (not as a pdf) and its gifs so that, when I open the file, I can see text and gifs. Thank you in advance.

Is there a way to mimic the "Save - as" function in a browser with wget?  When I save a webpage in a browser, I get a folder with the assets(images, js, css) and the index file, which has the page name:  Nov 28 reddit: the front page of the internet_files Nov 28 reddit: the front page of the internet.html   But no matter what, when I use wget, I get something like this:  Nov 28  a.thumbs.redditmedia.com Nov 28  b.thumbs.redditmedia.com Nov 28  m.reddit.com Nov 28  out.reddit.com Nov 28  reddit.com Nov 28  www.reddit.com Nov 28  www.redditstatic.com   I tried using these:  wget -E -H -k -K -p https://reddit.com wget -r -x -mirror https://reddit.com       and came up with this: wget -E -H -k -p -e robots=off https://www.reddit.com  but all of them either made several folders or didn't download everything needed to view the page offline.  How would I set this up?


I was trying to use Elementary interface in my Ubuntu. I also installed elementary-tweaks. I removed everything but I don't know if happened after removed.  Here goes what is happening, I didn't explain well.

I'm trying to hide the app icon from the title bar in GNOME in Ubuntu 18.04. I know there is  asking the same thing but it's from 2011 and I can't find what it requires to find in the shell css. I'm also using the Arc-Dark custom theme.   Here are two examples of what I want to remove:      To be clear, I don't want to resize it to fit, I want to straight away remove it completely.


I want to know which executable gets executed for any command in bash.  Example:     I have firefox installed here /usr/bin/firefox, it is in the $PATH alias browser=firefox alias br=browser   Now I want to type something like getexecutable "br" and it should display /usr/bin/firefox

I've made several aliases for my convenience.But now I need to be helpful by sending a useful command and it is full of aliases.I've tried doing type u but all it returns is   up && ap upgrade -y --show-progress && r && ap check && ap autoclean  These are all aliases in u:  alias a='alias' a ap='apt-get' a r='ap autoremove -y' a up='ap update'


Let M be a (0, 1) matrix; that is, a matrix where each of whose entries is either a 0 or a 1. A line in M is either a row or a column of M. Use Dilworth's theroem to prove that the minimum number of lines containing all the 1's of M is equal to the maximum number of 1's, no two of which are in the same line. I realize this is the Konig's theorem basically. I started the proof out by: Let G be a bipartite graph with vertex bipartition {X, Y} , such that A is an adjacency matrix of graph G, where X is a set of vertices corresponding to the rows of matrix A, and Y is the vertex set corresponding to the columns. Any hint after this would be great! I know we have to introduce the concept of chains and antichains, but how do we connect that with the matrix entries?

An excercise says "deduce Konig's Theorem on bipartite graphs from Dilworth's theorem on posets".   Let G be a bipartite graph, G=(A,B). Order the edges left to right. A maximum antichain is a largest independent set in the graph.   I can see a maximum antichain must have every vertex in G incident with it. But it doesn't follow that every edge is incident with it. That may not be true.   So how does one proceed?


Summary of the problem:  I have two disks re-configured as RAID 1. instead of copying the data to the empty disk, it deleted the data from the non-empty disk.  Here's what happened:  1. In the last few days, I reinstalled Windows 8 twice.  2. I had 2 disks configured as RAID 1 and 1 SSD contained the OS.  3. While reinstalling Windows 8 (1st time) on the SSD, I might have removed the RAID configurations from BIOS.  4. I made changes to the RAID disk.  5. I reinstalled Windows 8.  6. I noticed I see 3 disks (1 SSD, RAID-disk1, RAID-disk2)  7. RAID-disk1 was updated to my last changes (done after installing Windows 8 for the 1st time)  8. RAID-disk2 was updated to BEFORE installing Windows 8.  9. I formatted RAID-disk2  10. I set SATA configuration to RAID in BIOS.  11. After restart, the disks was automatically configured as RAID and with status rebuild.  12. In Windows 8 I get both disks as EMPTY!  How do I restore the data?

I have a harddisk with two partitions: one for windows and one for data. I've reinstalled windows on the first partition and formatted the data partition with full format (without /Q option) making sure that all my data is backed up. After that I've created the same folder structure (without files inside) on data partition as it was before formatting.   I then realized that all my photos were NOT backed up :((((  I've tried several tools to recover my data without any success:   Wordershare Photo Recovery Active File Recovery R-Studio PhotoRec from CGSecurity Recuva   There are max 50Mb of new data on that partition, so data overwriting is minimal.  What is the reason why I'm not able to recover my data with data recovery tools: full format or same folder structure?  And... can I get my photos back or they are lost forever?


In the 70s I read this SF book about an alien species destroying earth using asteroids from the astroid belt between Mars and Jupiter. It was done by 2 physicists and was presenting the case that earth should be very cautious about broadcasting itself into Space. That species would be very xenophobic and not tolerate competition from another technologically advanced species. Any help would be appreciated in locating the title of this book.

I don't remember the title/author of a Sci-Fi novel, where the author demonstrated that in case of an encounter with a more advanced alien life form, they would consider most convenient for them to exterminate the human race instead of every other alternative...


Is it safe to remove the downloaded tar once the program is installed (once I run ./configure, make, make install)?

If I'm installing from source, do I need to keep the extracted tarball directory?  So if I download the git tarball. I then do:  tar -xvzf git.tar.gz   This will create a git.x.x. directory, into which I cd, then run ./configure etc. Once I'm done with this process, and git, or whatever is installed, do I need to keep the original git.x.x extracted directory, or is that just used for compiling the program?  I'm somewhat confused by all the directories, and folders used for programs.


In Minecraft, I'm in survival with a wooden pickaxe, and whenever I mine the iron ore I need, it keeps disappearing. Why is this happening? Am I doing something wrong?

I am on Peaceful mode, and I am using a Wooden Pickaxe. Whenever I mine Iron Ore, it just disappears. Am I doing something wrong?


I find that it helps to download source code to see how things work. I did that with MVCForum, and when viewing the source code noticed a using statement as follows:  using MembershipCreateStatus = MVCForum.Domain.DomainModel.MembershipCreateStatus;   The MembershipCreateStatus is an enum and is used in different parts of the code as such.  if (createStatus != MembershipCreateStatus.Success)   Can someone explain why it would be done this way as I have never seen this before. Is it easier to do it this way rather than initialize the class?  *************Update*************  Thanks for the answers, sorry it was a duplicate but if I new about alias I would have search for that not "Using Statements"  I understand the use now.

Where or when would one would use namespace aliasing like  using someOtherName =  System.Timers.Timer;  It seems to me that it would just add more confusion to understanding the language.


Can anyone help me prove that in the most simple way possible?

How  can  i  prove  that :  $$\binom{n}{0}^2+\binom{n}{1}^2+\binom{n}{2}^2+\cdots+\binom{n}{n}^2=\binom{2n}{n}$$  i tried to prove it : by   $$\binom{2n}{n} = \frac{(2n)!}{n!n!} = \frac{2^n (1\cdot3\cdot5\cdots(2n-1))}{n!}$$  but i can’t  take advantage of it.


I am making a bash script but I'm totally new and got lost.  I've made this code  cat * | grep "|*parameter1*|" | grep "|*parameter2*|" | cut -f 8,11,12,15,21,23,34 -d "|" | wc -l   which works just fine, but I need to read the wc -l output into a variable so I can make an average after that with another bash command. Then, print out that average and make it readable to the user.

I have an operation using cut that I would like to assign result to a variable  var4=echo ztemp.xml |cut -f1 -d '.'   I get the error:     ztemp.xml is not a command   The value of var4 never gets assigned; I'm trying to assign it the output of:  echo ztemp.xml | cut -f1 -d '.'   How can I do that?


I'm trying to learn the basics of poker, and I encountered this bit of info:     Sometimes the best texas hold em hand is made by the five shared cards on their own. If they were 10-10-10-10-A and you had 9-9 your hole cards would not play as there is a four-of-a-kind of higher value already showing.   I am unclear about this. What if every player chooses 10-10-10-10 as their hand, since they're shared cards? Who wins?

In Texas Hold'em poker, there are some cases where a particular card, often called kicker, acts as a tiebreaker between players to determine who wins the pot, or if the pot has to be shared.  For some combinations such as three or four of a kind, there is no doubt: the kicker is the 5th card of the chosen combination, and determines the winner.  Example     Alice has 7 and 10   Bob has 7 and K   On the board are 7, 7, 2, 3, 4   In that case, both have a three of a kind. But because Bob has a king and Alice only a 10, he wins.  Most of poker websites explaining the rules clearly mention the role of the kicker applying to three of a kind and double pairs. But much fewer say something about colors, straights and full houses, and I found many contradicting answers. I also asked the question to some used online poker players and they also gave me contradicting answers.  I have tried to search for official tournament rules, but most of them only explain what happens with bad behaviors, bad deals, incorrect or confusing betting, showing cards when you shouldn't, acting when it's not your turn, etc. without mentioning subtleties about combinations at all.  To simplify my question, I will take three examples; I think it's better to start with examples before getting to the general answer if one exists. So, what's happening in the following 3 examples? Could you give a more generalized answer?  Example 1 - Flushes     Alice has 2♣ and 3♣   Bob has 4♣ and 5♣   On the board are 6♣, 8♣, 10♣, 2♥, 5♦   Contradicting answer 1: it's a tie, because the highest card included in the flush is the 10, which everybody chooses to include in their 5 showdown cards. Contradicting answer 2: Bob wins, because he has the greatest private card that is part of the flush  Example 2 - Straight     Alice has 6 and K   Bob has 6 and J   On the board are 4, 5, 7, 8, 10   Contradicting answer 1: it's a tie, because the greatest card in the straight is the 8 for both Alice and Bob Contradicting answer 2: Alice wins, because she owns an extra king, compared to the jack of Bob  Example 3 - Full house     Alice has 3 and 7   Bob has 3 and 6   On the board are 3, 3, 2, 2, 5   Contradicting answer 1: it's a tie, because one is supposed to choose only five cards to make a combination, and a full house is already five cards. There couldn't be any kicker, and thus their showdowns are strictly equals. Contradicting answer 2: Alice wins because of her extra 7, compared to the 6 of Bob  Thank you very much for your answers.  Note: I'm unable to post next to you, so I edit my own post; strange not be able to answer to an answer.  Ok, So if I summarize what you are saying :   In the flush case, Bob wins because at some point, their hand differs. Technically, I can continue comparing the highest private card to decide who wins. I had it correct. In the straight case, if the highest card of the straight is public, then it's technically always a tie, no matter what the players had as second private card (asuming that only one of the two cards was part of the straight). In a full house if both players have the same triplet and the same pair, it's always a tie, no matter what the players had as second private card (assuming again that only one of the two was part of the full house).   Please confirm me that what I summarized is correct.  Thank you for your answer.


Does anybody know how to  save the routes from ArcGIS Network Analyst between set of points as a shapefile in ArcGIS?

I'm using ArcGIS 10.0.  I'd like to be able to specify the location (path) where to create the route layer, for network analysis, when I click on Network Analysis -> New Route. Is that possible?  If it is not, how can I have access to the location where the route layer is created?  I'm using the route layer in a task of a geoprocessing service, and I'd like to give to the task the exact location (absolute path) of the route layer.  Could anybody help?


I can prove the other way around but this is bugging me.

I'm trying to prove that, for a finite set $A$, if the map $f: A\rightarrow A$ is a surjection, then it's an injection.  I've looked at this post:  but the arguments there seem very round-about, proving that injectivity implies surjectivity first.  I think I've seen other proofs, too, but they all sound kind of flimsy.  They tend to go something like "If the function is surjective then no two arguments can go to the same image, since that would require some element of the range not being the image of any element."  While that's true and I see what the argument has in mind, it's no more convincing than the statement of the claim that we're trying to prove!  Without a more rigorous proof, both seem to rely on the intuition that everything has to go to one and only one thing, but we're supposed to be proving that.  But I've been trying to develop a more thorough and direct proof, and haven't been able to.  I've tried induction:     The theorem holds trivially if $|A|=0$.  Suppose the theorem holds up to $n=|X|$, and let $|A|=n+1$ and $f:A\rightarrow A$ be a surjection.  Then let $x\in A$ and $f^{-1}(x)$ be the set of all elements $y\in A$ such that $f(y)=x$...   But at this stage I want to restrict my function, but that has the disadvantage that if $f(y)$ has more than one element in it, when I pluck it out of $A$ as the domain and pluck $x$ out of $A$ as the range, then I may not be dealing with a function mapping from a set to itself and so I don't get to use the inductive hypothesis.  Any other proofs you know about?


I have git repos stored in different directories which have long paths /opt/too/long/path/to/type/every/time/git-repo and it's kind of difficult to remember plus to cd to the directory every time is a pain and tedious. (I know TAB helps but that gets tedious too.) So, my life would be much easier if I could store the pwd somewhere and later do something like cd thatgitrepo.

cd - can move to the last visited directory. Can we visit more history other than the last one?


I want to change an A record of my root domain www.domain.com to CNAME dyndns.org.  But the cpanel gives me the following error:  already has a SOA record. You may not mix CNAME records with other records for the same name.   Can you please explain what this means? And how do I fix it?

This is a  about CNAMEs at the apices (or roots) of zones   It's relatively common knowledge that CNAME records at the apex of a domain are a taboo practice.  Example: example.com. IN CNAME ithurts.example.net.  In a best case scenario nameserver software might refuse to load the configuration, and in the worst case it might accept this configuration and invalidate the configuration for example.com.  Recently I had a webhosting company pass instructions to a business unit that we needed to CNAME the apex of our domain to a new record. Knowing that this would be a suicide config when fed to BIND, I advised them that we would not be able to comply and that this was bunk advice in general. The webhosting company took the stance that it is not outright forbidden by standard defining RFCs and that their software supports it. If we could not CNAME the apex, their advice was to have no apex record at all and they would not provide a redirecting webserver. ...What?  Most of us know that  insists that A CNAME record is not allowed to coexist with any other data., but let's be honest with ourselves here, that RFC is only Informational. The closest I know to verbiage that forbids the practice is from :     If a CNAME RR is present at a node, no other data should be   present; this ensures that the data for a canonical name and its aliases   cannot be different.   Unfortunately I've been in the industry long enough to know that "should not" is not the same as "must not", and that's enough rope for most software designers to hang themselves with. Knowing that anything short of a concise link to a slam dunk would be a waste of my time, I ended up letting the company get away with a scolding for recommending configurations that could break commonly used software without proper disclosure.  This brings us to the Q&A. For once I'd like us to get really technical about the insanity of apex CNAMEs, and not skirt around the issue like we usually do when someone posts on the subject.  is off limits, as are any other Informational RFC applicable here that I didn't think of. Let's shut this baby down.


I'm reading my first ever novel in English (French is my mother tongue): Tales of Horror by H.P Lovecraft. Surprisingly, reading this book is fine for me, however there's a sentence construction I don't fully understand.  This is when Lovecraft is starting a sentence with For. He's using this style so often that I arrived at a point I really want to understand this way of writing. Random examples: From The Shunned House:  For on my ears rang the reverberations of that shocking scream, while my nostrils revolted at the stench which filled the place.  From Herbert West - Reanimator:  For that visitor was neither Italien nor policeman.  Could you please explain to me the purpose of adding For at the beginning of sentences like in these examples? Does this way of constructing a sentence has a particular name? I'm a bit confused by this style so I want to know more about it. Thanks for your answers

As I understand it, 'for' is a coordinating conjunction. Learning German as a second language has taught me specifics about reforming sentences, but it is an awful lot less common in English. If I were to rearrange the sentence: "I ate lunch, for I was hungry," so that 'for' was the first word of the sentence, by my reckoning I should end up with "For that I was hungry, I ate lunch." Does this new sentence have any grammatical errors? I inserted the word 'that' after 'for', because without it the sentence didn't sound right. Should I have? Is there a rule for that? Thank you in advance, an aspiring author.  Additional Information:  I am not having problems with the sentence, this is a general question to increase my knowledge of the manipulations of coordinating conjuntions.


I have a homework question:   Let $f(z) = 1 + z + 2z^2 + 3z^3 + 5z^4 + 8z^5 + 13z^6 + ...$.   (a): Show that $f(z) = \frac{1}{1-z-z^2}$ for all z in the disk  $\{z: |z| < R\}$ for some number R.   (b): Find the value of R in part (a).  My professor gave us a hint: show that $f$ satisfies the equation $f(z) = 1 + zf(z)+ z^2f(z)$.  I know that the series is something like $\sum_{n=0}^{\infty} c_n z^n$ where $c_n$ is the nth Fibonacci number, but I don't know how to approach showing equivalence.  I don't think that I understand how his hint helps us. I feel like it should be my jumping off point for this problem, but I don't see how it helps me at all.

I'd really like your help with this following problem: Let ${a_n}$ be a Fibonacci series $a_1=a_0=1$ and $a_{n+2}=a_n+a_{n+1}$ for every $n \geq 0$.  Let $f(x)=\sum_{0}^{\infty}a_nx^n$, I need to find the radius of convergence and to prove that in the range of this radius $f(x)= \frac{1}{1-x-x^2}$.  we know that the convergence radius $R=\lim_{n\to \infty} |\frac {a_n}{a_{n+1}}| $, How can I apply it in this case? Any direction to prove that $f(x)$ is as requested?  Thanks alot!


I'm trying to write a password validator application using python tkinter. If the inserted password contains at least 2 numbers, at least 2 special characters and a length of at least 7, the password is considered Strong, else Weak. If I enter a weak password the program will work, but if I enter a strong password I face this error: Exception in Tkinter callback Traceback (most recent call last):   File "/usr/lib/python3.8/tkinter/__init__.py", line 1883, in __call__     return self.func(*args)   File "/home/liana/projects/python/modification/modify.py", line 15, in submit     charcheck += 1 UnboundLocalError: local variable 'charcheck' referenced before assignment  I don't know why. Here's my code: import tkinter as tk   numcheck = 0 charcheck = 0  root=tk.Tk()   root.geometry("600x400")   passw_var=tk.StringVar()   def submit():      password=passw_var.get()         passw_var.set("")     for i in range(len(password)):         if(password[i]=='!' or password[i]=='@' or password[i]=='#' or password[i]=='$' or password[i]=='&' or password[i]=='%' or password[i]=='*'):             charcheck += 1          elif (ord(password[i])>=48 and ord(password[i])<=57):             numcheck += 1       if (len(password)>=7 and charcheck>=2 and numcheck>=2):         result_label = tk.Label(root, text='STRONG', font=('calibre',10, 'bold')).grid(row=3, column=2)      else:         result_label = tk.Label(root, text='WEAK', font=('calibre',10, 'bold')).grid(row=3, column=2)         passw_label = tk.Label(root, text = 'Enter Your password: ', font = ('calibre',10,'bold'))      passw_entry=tk.Entry(root, textvariable = passw_var, font = ('calibre',10,'normal'), show = '*')      sub_btn=tk.Button(root,text = 'Submit',                    command = submit)      passw_label.grid(row=1,column=0)  passw_entry.grid(row=1,column=1)  sub_btn.grid(row=2,column=1)      root.mainloop()   I'd like to know where I'm making a mistake. Thank you

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


I am trying to call a function in a derived class with the same name existing in the base class. The function simply prints class elements. For example:  class A                             // Base Class {                                     public:                                string a;      int b;       A(){};                         //Default Constructor                               A(string x,int y):a(x),b(y){}  //Parametrized Constructor      ~A(){};                        //Destructor      void printInfo()      {         cout << a << endl;         cout << b << endl;      };      };  class B:public A                    // Derived Class {                                     public:                                string c;        B(){};                         //Default Constructor                               B(string z):c(z){}             //Parametrized Constructor      ~B(){};                        //Destructor      void printInfo()      {         cout << a << endl;         //I am trying to call printInfo of A inside this function      };  };   So that in the output, when I create an object of B (let's say B example;) and try to use printInfo() member function of class B (Ex: example.printInfo();), I would print first c and then a and b. Also it will not be limited with 2 classes, but more than 5 classes having a common printInfo() member function. How do I achieve this ?

How do I call the parent function from a derived class using C++? For example, I have a class called parent, and a class called child which is derived from parent. Within  each class there is a print function.  In the definition of the child's print function I would like to make a call to the parents print function.  How would I go about doing this?