In many texts and books about calculus we see     There are functions $f$ for which the anti-derivative cannot be   expressed in terms of standard functions or there are many   integrals that cannot be expressed in terms of standard functions.   What functions are called standard functions and why?

Is there a mathematical reason (or possibly a historical one) that the "elementary" functions are what they are?  As I'm learning calculus, I seem to focus most of my attention on trigonometric, logarithmic, exponential, and $n$th roots, and solving problems that have solutions which are elementary functions.  I've been curious why these functions are called elementary, as opposed to some other functions that turn up rather naturally in mathematics.  What is the reason that these functions take up most of our attention, and is there a reason that some additional functions are not included amongst the elementary functions?  In other words, what property or properties do these functions possess that separates them from non-elementary functions (if there is one)?


Consider $2$ closed sets $A,B$ with $A\cap B=\emptyset$.Note that for $x\in A$,$d(x,B)>0$, because if for some $x\in A,d(x,B)=0$ then $x\in \overline B=B$, which contradicts the disjunction between $A$ and $B$. So, for each  $x\in A$, we can choose $\eta_x$ such that $B(x,\eta_x)\cap B=\emptyset$. Consider $E=\cup_x B(x,\eta_x)$. Similarly construct $F=\cup_yB(y,\eta_y)$. Now, it is clear that $E\cap F=\emptyset$ and $A\subset E$ and $B\subset  F$ and $E,F$ are both open. Is this correct?I just want to make sure whether my approach is correct or how can I proceed through this method.I am not looking for a solution to this problem.

Question: Let $(X, d)$ be a metric space. Let $A$ and $B$ be disjoint subsets of $X$ that are closed in the topology induced by $d$. Prove that there exist disjoint open sets $U$ and $V$ such that $A\subset U$ and $B\subset V$.   Is this proof correct? : By assumption, $A\cap B=\emptyset$, so there is no pair like $(x_A,x_B)$ (i.e., $x_A\in A$ and $x_B\in B$), such that $x_A=x_B$. Because every metric space is Hausdorff, so for every pair $(x_A,x_B)$ there are two disjoint open sets $U_A\ni x_A$ and $V_B\ni x_B$; and thus union of all $U_A$s (which is an open set containing A) are disjoint from union of all $V_B$s (which is an open set containing A).   Thanks a lot for any help.    PS In special case of standard metric topology on $\mathbb{R}$, if $[a,b]$ and $[c,d]$ are disjoint (say $c>b$), intuitively it is apparent that there is a 'space' between $c$ and $b$ so we can have two disjoint open sets, each of them containing $[a,b]$ or $[c,d]$.


In a question from an exam in an undergraduate group theory course, we were asked to prove or disprove that the set of all Torsion elements of a group is necessarily a subgroup.  I knew that the set of Torsion elements is closed under the inverse operation, but was later told that it is not closed under multiplication, therefore disproving the claim. However, I couldn't find any examples of a group $G$ and two elements $a,b$ such that both $a$ and $b$ have a finite order, but $ab$ doesn't. I know that for this to happen $G$ must be an infinite and non-Abelian group, but still couldn't find a valid example.   What are some examples of groups/elements fulfilling the aforementioned property?

Let $G$ be a group and let $a,b$ be two elements of $G$. What can we say about the order of their product $ab$?   says "not much":     There is no general formula relating the order of a product $ab$ to the orders of $a$ and $b$. In fact, it is possible that both $a$ and $b$ have finite order while $ab$ has infinite order, or that both $a$ and $b$ have infinite order while $ab$ has finite order.   On the other hand no examples are provided. $(\mathbb{Z},+), 1$ and $-1$ give an example of elements of infinite order with product of finite order. I can't think of any example of the other kind! So:   What's an example of a group $G$ and two elements $a,b$ both of finite order such that their product has infinite order?     Wikipedia then states:     If $ab = ba$, we can at least say that $\mathrm{ord}(ab)$ divides $\mathrm{lcm}(\mathrm{ord}(a), \mathrm{ord}(b))$   which is easy to prove, but not very effective. So:   What are some similar results about the order of a product, perhaps with some additional hypotheses?


I'm stuck on a question regarding group theory, related to the isomorphism theorems. I am given a group homomorphism $f \colon G_1 \to G_2$, and $N_2$ a normal subgroup of $G_2$. I have proven that the pre-image $N_1 := f^{-1}(N_2)$ is a normal subgroup of $G_1$. Now, if we assume $f$ is surjective, I need to prove that $G_1 / N_1 \cong G_2 / N_2$.  I have already thought of using the first isomorphism theorem, but this has only lead to the conclusion that $G_1 / N_1 \cong G_2$, because $N_1$ is a normal subgroup and thus a kernel, and $f$ is surjective. Other than that, I have thought of using the canonical homomorphism $\varphi \colon G_2 \to G_2/N_2$. I suppose I could show the composition $\varphi \circ f$ is a bijection, but I'm not sure about how to prove this or whether this is the right direction for the proof.

Is the following proof correct, or are certain steps illegal?  Suppose $f:G_1\to G_2$ is a surjective group isomorphism, $N_1\lhd G_1, N_2\lhd G_2$ normal subgroups, with $N_1=f^{-1}(N_2)$. Prove that $(G_1/N_1)\cong (G_2/N_2)$.  Proof:  As $f$ is surjective, we an use the first isomorphism theorem to get $G_1/\ker(f)\cong G_2$, which implies that $$(G_1/\ker f)/(N_1/\ker f)\cong G_2/(N_1/\ker f)$$  Using the first isomorphism theorem we also know that $$N_1/\ker (f)\cong f(N_1)=f(f^{-1}(N_2))=N_2$$  Combining this we can see that $(G_1/\ker f)/(N_1/\ker f)\cong G_2/(N_1/\ker f)\cong G_2/N_2$.  Using the third isomorphism theorem we have that: $$ (G_1/\ker f)/(N_1/\ker f)\cong G_1/N_1$$  And from the last two lines we have $G_1/N_1\cong G_2/N_2$ $\tag*{$\Box$}$


i have server that works on xubuntu. How can i access it from my laptop that runs Ubuntu?

How do I enable Remote Desktop connection on Xubuntu 11.10? I do not find any options such as those present in Ubuntu?


Let $A \in M_n(F)$ be a strictly upper triangular matrix, I’m asked to construct $A$ such that $A^{n-1} \neq 0$. I know that $A^n =0$, and $A^{n-1} = A^{-1}$, and I’m confused because a triangular matrix has an inverse only if it has no zeros on its main diagonal. How can $A$ have an inverse when it is a strictly upper triangular matrix?

I need help with part (c). I could do part (a) and part (b).


I've built a combobox that is dynamically populated depending on the contents of another combobox, and so on. I've decided, although it's a bit terrible, to experiment with iterating through the contents of the source array when populating the target combobox. However, although this results in combobox contents, they are repeated. I've stepped through the code, and the array is only being iterated through once.    private JComboBox regBuildingSelectBox; ...  String[] siteSelectStrings = {"Site", "London", "Long Island"};     JComboBox regSiteSelectBox = new JComboBox(siteSelectStrings);     regSiteSelectBox.addItemListener(new ItemListener() {         public void itemStateChanged(ItemEvent arg0) {             getDropDownVariables gddv = new getDropDownVariables();             for(String s:                    gddv.buildingSelectList                             (regSiteSelectBox.getSelectedItem().toString()))             {                 regBuildingSelectBox.addItem(s);             }         }     });     regSiteSelectBox.setBounds(24, 336, 282, 20);     contentPane.add(regSiteSelectBox);       regBuildingSelectBox = new JComboBox();      regBuildingSelectBox.setBounds(24, 367, 282, 20);     contentPane.add(regBuildingSelectBox);   The code containing the arrays is as follows:  public class getDropDownVariables {      public String[] buildingSelectList(String site)     {         switch (site)         {         case "London":             return new String[]  {"Building", "Harvell",                                  "LYNX Complex", "Caroline", "Salters"};         case "Long Island":             return new String[] {"Building", "Phillips", "Pascal"};         }         return new String[] {"Failed to populate buildings"};     }   And the result:

I'm using a JComboBox with an ItemListener on it. When the value is changed, the itemStateChanged event is called twice. The first call, the ItemEvent is showing the original item selected. On the second time, it is showing the item that has been just selected by the user. Here's some tester code:  public Tester(){      JComboBox box = new JComboBox();     box.addItem("One");     box.addItem("Two");     box.addItem("Three");     box.addItem("Four");      box.addItemListener(new ItemListener(){         public void itemStateChanged(ItemEvent e){             System.out.println(e.getItem());         }     });      JFrame frame = new JFrame();     frame.getContentPane().add(box);     frame.pack();     frame.setVisible(true); }   So when I changed the Combo box once from "One" to "Three" the console shows:  One Three   Is there a way I can tell using the ItemEvent maybe, that it's the second item (ie. the user selected item)? And if someone can explain why it gets called twice, that would be nice too!  Thanks


My 1st level Wizard has a Wisdom of 13 (modifier +1) and proficiency in Wisdom saving throws, but not proficiency in Perception. Does that mean my passive Wisdom (Perception) score equals 10+1 or 10+1+2 (adding my proficiency bonus).

I'm new to D&D. There seems to be a discrepancy between the 5e Starter Set Rulebook and the associated character sheets. The Rulebook says that a passive wisdom (percep) score is "10 + the creature's wisdom modifier, as well as any bonuses."  In the example they have a 1st-level character (with a proficiency bonus of +2) Wisdom of 15 (+2) and a  proficiency in Perception, he or she has a passive Wisdom (Perception) of 14 (10+2+2).  But the Human Fighter Folk hero character has a WIS mod of +1, and a +3 written beside perception, and a passive Wis percep of 13 (not 14?).  The Dwarven Cleric has Wis mod of +3 and a +3 written beside perception, and only a 13 passive wisdom.  I guess this has to do with proficiency in the skill, but I'm confused. Can someone explain these instances and maybe also when proficiency is used, vs when just the modifier or just the skill without proficiency?


When we define trigonometric ratios using a right triangle then it denotes the ratio of its side but what does a trigonometric function of angle greater than 90° denotes in a unit circle ?

The trigonometric ratios of an angle greater than $90^\circ$ are equal to the supplementary angle's ratios.  I'm just clarifying this, but the ratios don't actually exist for angles greater than $90^\circ$ right? (since by definition these ratios are of a right angle triangle). Is it just mathematical custom to assume the ratios of an angle greater than $90^\circ$ to be equivalent to its supplementary angle's ratios? For convenience?


My Stored procedure is giving error      "Conversion failed when converting the varchar value to data type int".    What I am trying to do is to use the IN clause, the values inside the IN clause are string here and separated by comma. The stored procedure is -  ALTER PROCEDURE [dbo].[sp_UpdateBulkPageStatus]  @Id Varchar(50), @Status bit AS              BEGIN     UPDATE Page SET Status=@Status WHERE Id in (@id)     END   It given error on running - [dbo].[sp_UpdateBulkPageStatus]  '24,25',1  Now when I am just running the update query with values on it {UPDATE Page SET Status=1 WHERE Id in (24,25)} then it runs perfectly.  What is the problem?

How do I parameterize a query containing an IN clause with a variable number of arguments, like this one?  SELECT * FROM Tags  WHERE Name IN ('ruby','rails','scruffy','rubyonrails') ORDER BY Count DESC   In this query, the number of arguments could be anywhere from 1 to 5.  I would prefer not to use a dedicated stored procedure for this (or XML), but if there is some elegant way specific to , I am open to that.


I was recently referred to  where Jeff refers to creating an FAQ.   Does it exist, and is it accessible from an Android smartphone's Stack Exchange app?

Community FAQ For sites in the Stack Exchange 2.0 network To see a list of commonly used words and phrases, see the . For official guidance from Stack Exchange, visit the . Asking questions                            Answering questions                 Accepting answers        Working with posts  What does it mean when a question or answer is...  ?  ?  ?  ?                                       Comments             Etiquette                         Promotion         Editing and Formatting                                    Tagging                      Reputation, badges, and voting                                         Moderation                                                 Searching and RSS feeds        Accounts, registration and logging in                                     Other                                 ()                                 Site-specific entries Stack Overflow             Meta Stack Exchange       Other     External links           Is your question not part of the FAQ? First look at questions tagged  to see if there is a question not in this index that might have the answer you seek. If you still can't find an answer, then see the following instructions for proposing an FAQ question. How can a question be added to this FAQ?  Ask only the question, stated plainly and simply, in the question body. The answer goes in an answer.  Link back to this index. Paste this at the end of the question:  [Return to FAQ index](/q/7931)   Tag as  and .  When a post seems to have hit a mature state, it will have  added by a moderator.  Flag for a moderator to mark community wiki.  Any FAQ post not yet community wiki should be made into a community wiki.  After the post has the  tag added to it, add a link in the above .


It is understandable that life didn't evolve the capability to sense all wavelengths of light, it simply didn't need it. My question is, why did it evolve the set of wavelengths it has, for example, the human visible range is 390-700nm, so why couldn't it be a different set of wavelengths, like, (say) 300-620nm? Is there a reason for it?

Across the electromagnetic spectrum, 400-700 nm is a narrow spectrum of frequencies and focused in the region of short wavelengths. For example, radio waves cover a large range of frequencies unexploited by the visual system. So what biological reason is there that evolved us to use such a small frequency bandwidth for vision?


2.1-hello     2.2-world     2.3-people     2.10-everywhere  results in this when items are added to a SortedDictionary<String,String>     2.1-hello     2.10-everywhere     2.2-world     2.3-people  What is the best way to get the sort with the behavior decimal/numeric order before the "-" character, with conventional ASCII order/collation after that? Original code was splitting on the "-" and converting the initial parts, which is really not efficient. All ideas appreciated. Thanks.

Anyone have a good resource or provide a sample of a natural order sort in C# for an FileInfo array?  I am implementing the IComparer interface in my sorts.


Is this code valid?  var myfunc1 = function( parameter ) {     parameter = smthg || 0;     //code here }  var myfunc2 = function( parameter ) {     parameter = smthg || 0;     //code here }   In jQuery, developers use single word parameter like e,t,n many times in their library, so I guess it is safe to use the same parameter again and again?

What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?


I want to install some applications but for any installation command it says that this package has no installation candidate. I can't even run sudo apt-get update.   cookie98@cookie98**:~$ sudo apt-get install software-properties-common [sudo] password for cookie98:  Reading package lists... Done Building dependency tree Reading state information... Done Package software-properties-common is not available, but is    referred to by another package. This may mean that the package is missing, has been obsoleted, or is  only available from another source  E: Package 'software-properties-common' has no installation candidate   `

What does the above Error mean? What is an installation candidate?  I was trying to do  sudo apt-get install munin-memcached     and I get this message:  Reading package lists... Done Building dependency tree        Reading state information... Done Package munin-memcached is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package munin-memcached has no installation candidate   I googled for the problem and someone said to do a apt-get upgrade but it still did not solve my problem.


I have a requirement to generate a report which has a column where we need to display whether the product is running on a physical box or a VM. If its running on a VM I need to display its version: something like ESXi 5.1. I am searching for a way to do this from my java code, but haven't been able to find anything yet. Can someone help out please.

I need to detect whether my application is running within a virtualized OS instance or not.  I've found an article with some useful information on the topic. The same article appears in multiple places, I'm unsure of the original source. VMware implements a particular invalid x86 instruction to return information about itself, while VirtualPC uses a magic number and I/O port with an IN instruction.  This is workable, but appears to be undocumented behavior in both cases. I suppose a future release of VMWare or VirtualPC might change the mechanism. Is there a better way? Is there a supported mechanism for either product?  Similarly, is there a way to detect Xen or VirtualBox?  I'm not concerned about cases where the platform is deliberately trying to hide itself. For example, honeypots use virtualization but sometimes obscure the mechanisms that malware would use to detect it. I don't care that my app would think it is not virtualized in these honeypots, I'm just looking for a "best effort" solution.  The application is mostly Java, though I'm expecting to use native code plus JNI for this particular function. Windows XP/Vista support is most important, though the mechanisms described in the referenced article are generic features of x86 and don't rely on any particular OS facility.


I have simple method with AsyncTask, but code suddenly crashed. Any ideas? I got Could not parse malformed JSON:, and now I get NPE at new AsyncTask<String, Void, String>() { My code:  private void getMyPage() {         new AsyncTask<String, Void, String>() {              ProgressDialog dialog = new ProgressDialog(UserProfileActivity.this);              @Override             protected void onPreExecute() {                 super.onPreExecute();                 Create Dialog...             }              @Override             protected String doInBackground(String... params) {                 HashMap<String, String> data = new HashMap<>();                  data.put("token", params[0]);                  LoginLectorUtils apiUtils = new LoginLectorUtils();                 return apiUtils.sendPostRequestWithParams(REQUEST_URL, data);             }              @Override             protected void onPostExecute(String response) {                 super.onPostExecute(response);                 dialog.dismiss();                  if (!response.equalsIgnoreCase("error")) {                     try {                         final JSONObject jsonObject = new JSONObject(response);                          if (jsonObject.getString("error").equals("true")) {                             showDialogConnectionError();                         } else if (jsonObject.getString("error").equalsIgnoreCase("false")) {                             doLoadStuff(                                     jsonObject.getString("name"),                                     jsonObject.getString("phone")                         }                      } catch (Throwable t) {                         Log.e("UserProfileActivity", "Could not parse malformed JSON: \"" + response + "\"");                     }                 } else {                  }             }         }.execute(sharedPrefUtils.getToken());     }

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


I'm trying to figure out how to restore the simple interface names in Ubuntu 16.04. I.e. enp3s0 renamed to eth0.   I have tried to modify the GRUB configuration. I have tried editing /etc/udev/rules.d/10-network.rules, but both methods did nothing for me. Help is greatly appreciated.   /etc/udev/rules.d/10-network.rules: (I hid the mac address names.)  SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="XX:XX:XX:XX:XX:XX″,KERNEL=="enp0s0″, NAME="eth0″ SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="XX:XX:XX:XX:XX:XX″,KERNEL=="wlx02c5c1866772″, NAME="wlan0″  And I changed this line in the GRUB configuration (/etc/default/grub) ...  GRUB_CMDLINE_LINUX=""   to look like this:  GRUB_CMDLINE_LINUX="net.ifnames=1"

A lot of my scripts stopped working after installing Ubuntu 15.10 and I have trouble remembering this new name as I was used to ethx and wlanx for years. Is there a reason for this change? Do I have to get used to this or can I just rename it and go back to good old eth0?  $ ifconfig  enp0s25   Link encap:Ethernet  HWaddr 77:5a:5e:a6:86:d5         inet addr:192.168.31.239  Bcast:192.168.31.255  Mask:255.255.255.0       inet6 addr: fe80::725a:b6ff:fea6:86d7/64 Scope:Link       UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1       RX packets:4833 errors:1332 dropped:0 overruns:0 frame:666       TX packets:5589 errors:0 dropped:0 overruns:0 carrier:0       collisions:0 txqueuelen:1000        RX bytes:3266446 (3.2 MB)  TX bytes:1046654 (1.0 MB)       Interrupt:20 Memory:d3500000-d3520000


code is here:        import re      res = re.match('bbs1','http://bbs1.people.com.cn/userInfo.do?userNick=%E8%85%BE%E9%A3%9E%E4%B8%AD%E5%9B%BD%E9%BE%99')     print(res)   It's print None,but when I change parttern to 'http',it matches; The same parttern in javascript can matched;  var url = 'http://bbs1.people.com.cn/userInfo.do?userNick=%E8%85%BE%E9%A3%9E%E4%B8%AD%E5%9B%BD%E9%BE%99' url.match(/bbs/)

What is the difference between the search() and match() functions in the ?  I've read the  (), but I never seem to remember it.  I keep having to look it up and re-learn it.  I'm hoping that someone will answer it clearly with examples so that (perhaps) it will stick in my head.  Or at least I'll have a better place to return with my question and it will take less time to re-learn it.


The stress of casting wish for creative effects has a 1/3 chance of preventing the caster from ever casting wish again.  (There are plenty of cites all over RPG Exchange.)  Does this preclude using wishes from sources that do not involve the PC casting wish?    Related:  — This question addresses an item that enables the PC "to cast the wish spell from it".     — This question's second bullet point is similar to my question, but is phrased as being able to use items' properties that enable a PC to cast wish.   — This discusses whether an efreeti granting a wish suffers wish stress.  This approaches my question:  Can a PC that cannot cast wish due to the stress have their wish fulfilled by an efreeti or similar?  (This question arose from a dream I had last night:  Dream-me took a ring that I had collected during my adventuring days.  This was not a Ring of Three Wishes, rather a ring like the lamp in "Aladdin's Wonderful Lamp" from Arabian Nights: The host vessel for a djinni that could grant wishes without numerical limit.  I was negotiating with the djinni on the phrasing of a wish that would cancel the contagious aspect of SARS-CoV-2; the djinni told me that if I wished for that, I would never be able to use a wish ever again.  I was willing to pay that price; wouldn't you?)

The description of the DnD 5e wish spell states "Finally, there is a 33 percent chance that you are unable to cast wish ever again if you suffer this stress." There are items and situations that grant a "free" wish spell. An example of this is the deck of many things (moon card). Now,   if a player gets such a free wish, is there still a chance that they will not be able to cast wish ever again? if a player already failed the "33% test" in the past, will they be able to use a free wish when it is granted to them?   I know that a DM has, of course, the final say in this, but I am curious to what is common among other DMs. The thing is that 1d3 wishes from a DoMT sounds fun, but it seems a bit disappointing to me if a player gets such a card but is already not allowed to use wish spells anymore (or if the card causes a player to be unable to use wish ever again).


If the rumors are true and gravitational waves have been detected, would we learn any new fundamental physics from them? Or is this simply an important confirmation of a prediction of general relativity that doesn't give us new insight into current unsolved problems?

LIGO has announced the detection of gravitational waves on 11 Feb, 2016. I was wondering why the detection of gravitational waves was so significant?   I know it is another confirmation of general relativity (GR), but I thought we had already confirmed GR beyond much doubt. What extra stuff would finding gravitational waves teach us? Is the detection of gravitational waves significant in and of itself, or is there data which can be extracted from the waves which will be more useful?


My ASP.NET Core 2.1 API app communicates with a third party API so I'm creating an ApiClient with generic CRUD methods in it.  The question is how I should handle a scenario where I got nothing from the API call -- I've seen cases where sometimes APIs return 204 but sometimes, they just return nothing at all with a status 200.  When I try to return null in case my response has nothing in it, I'm getting an error that says I can't do it because T may not be nullable.  Here's my code:  private readonly HttpClient _httpClient  public MyClass(HttpClient httpClient) {    _httpClient = httpClient; }  public Task<T> GetMyData<T>() {    try    {       var response = _httpClient.GetStringAsycn("https://someApiUrl");        // This is where I'm a bit stuck       if(string.IsNullOrEmpty(response))          return null; // <<-- Can't return NULL!        var data = JsonConvert.DeserializeObject<T>(response);       return data;    }    catch(Exception e)    {        throw new Exception(e.Message);    } }

I have a generic method with this (dummy) code (yes I'm aware IList has predicates, but my code is not using IList but some other collection, anyway this is irrelevant for the question...)  static T FindThing<T>(IList collection, int id) where T : IThing, new() {     foreach T thing in collecion     {         if (thing.Id == id)             return thing;     }     return null;  // ERROR: Cannot convert null to type parameter 'T' because it could be a value type. Consider using 'default(T)' instead. }   This gives me a build error      "Cannot convert null to type parameter   'T' because it could be a value type.   Consider using 'default(T)' instead."   Can I avoid this error?


I learnt yesterday that I could pvcreate directly on /dev/sdb instead of /dev/sdb1. I thought that you could only pvcreate on a existing partition. Doing it on a partition adds a level and operations so what are the benefits of creating a partition before doing pvcreate?

I ran into something a couple of weeks ago that I'd never seen before: A filesystem (ext3 I believe) installed to a storage device without a partition. In essence /dev/sdb was the entire filesystem. I know many filesystems can be extended into empty space, so doing this allows extending without dealing with LVM or some other kind of volume manager, but are there any other advantages for setting up storage this way?  The specific case I saw was as the ephemeral data volume for a number crunching server, the boot and root volumes were traditional partitions on a different storage device entirely. -


Using the MutationObserver API, I'm trying to attach events to specific elements when they are loaded into the DOM. Code snippet based on the sample on the :  var targetNode = document.getElementById("myDiv");  // Callback function to execute when mutations are observed var callback = function(mutationsList) {     for(var mutation of mutationsList) {         mutation.addedNodes.forEach(function(currentValue, currentIndex, listObj) {              if (currentValue.querySelectorAll(".questions").length > 0) {                 //we added the questions                 var elements = document.querySelectorAll(".myList, .ofElements");                 //elements is empty here. After the callback fires,                  //I can query again and find the elements                  elements.forEach(function() {                     this.addEventListener("click", function() {alert(this.name + "=" + this.value)});                 });             }         });                 } };  // Create an observer instance linked to the callback function var observer = new MutationObserver(callback);  // Start observing the target node for configured mutations observer.observe(targetNode, { attributes: false, childList: true });   It's matching .questions when it gets added as a child node to the DOM, but at this point it's not able to find the inputs.   Am I misunderstanding how this works? Or is it possible that the code which adds .myList, .ofElements (I cannot modify the source code) is doing something that interferes?

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


I'm using an image for the background, but I only see a blue sky and not the clouds in the bottom of the image near the horizon. It feels like the background image is too close? And in the world tab the preview is just blue. Should I not see the clouds also?  If I create a scen that are 10x10 meter or 100x100 meter or 1000x1000 meter in size, how does Blender set the correct scale or distance between the scene and the background?  I can rotate the background, but can't find any clouds. And I have tested different settings in the Environment Texture node, but all I can see is blue background or very close to the sun. I get this problem often with this type of images, and I don't know what I am doing wrong? Have I missed some kind of settings?  Other types of hdri images, that look spherical, I have no problem with. But this image looks more ordinary. Preciate some help!

I have a large environment texture of space that I'm using as the background of my scene.    However, when I try to use it in my render, I can only see a tiny part of it.    I want to scale down or "zoom out" on the texture, so I can see more of it in the rendered area. I tried to use a Mapping node and scale it that way, but it did nothing (I could rotate, but not scale).  This is my node setup:


may someone show how to compute $\lim_{n \rightarrow \infty} \left(\left(\frac{9}{4} \right)^n+\left(1+\frac{1}{n} \right)^{n^2} \right)^{\frac{1}{n}}$?  According to W|A it's e, but I don't know even how to start...  Please help, thank you.

$\lim_{n\to\infty}((\frac94)^n+(1+\frac1n)^{n^2})^{\frac1n}$  Here's what I did:  $\lim_{n\to\infty}((\frac94)^n+(1+\frac1n)^{n^2})^{\frac1n}\\ =(\lim(\frac94)^n+\lim((1+\frac1n)^{n})^n)^{\frac1n}\\ =(\lim(\frac94)^n+\lim e^n)^{\frac1n}\\$  Any hints on how to continue?  PS: no logs/integration/derivation because we haven't covered it.


There is an HP notebook Pavilion DV6 4gb ram, 15 inch monitor single, HDMI and VGA connections, processor AMD A6. Successfully installed this Ubuntu 19 release. But, after a reset, it keep running monitor display 180 degrees rotated. Then , I use xrandr with NORMAL option, and it works only in my session:  xrandr --output LDVS --rotate normal   After a reboot, in a new session, the monitor appears INVERTED again. By the other hand, after adjusting monitor screen intensity with keypad buttons, after a reboot the screen appears with TOTAL light adjustment, again.  How can I permanently set my config options.?

I used to edit the startup script for the GDM (/etc/gdm/Init/Default) to permanently change my display resolution.   How can I do this with LigthDM in Ubuntu Oneiric?


I don't understand the following question:      And can you tell me where you’re from?   Why is "where you are from" used instead of "where are you from"?

Which of the following is a correct sentence:   Does anyone know where's Linda?  Does anyone know where Linda is?    Does anyone know why and how to use above usage if #2 is correct. Also please let me know this kind of specific structures.


What's the correct or acceptable option to refer to the time or work times from the following options?     1)  "In which hour do you begin / start to work tomorrow"?    (it's not his first day at work, I'm just asking him about the time that he's going to START or to BEGIN tomorrow there.)     2) "In which time are you going to begin / start the university (or   studies) tomorrow.   (As well as example NO.1, it's not his first day at the university, I'm just asking him about the time that he's going to START or to BEGIN tomorrow there.)

Today, when looking up the definitions of the phrasal verb "take sth up", I noticed that one of them was written like this: "to start or begin something such as a job." For the first time I realised that probably "start" and "begin" don't exactly mean the same thing.So the question is what the difference is between the two, and if there are cases when they mean exactly the same thing.


New to this particular community.   My question relates to the word propaedeutic. In particular, I have witnessed the "a" interwoven with "e" to produce propædeutic. I once read that this is an example of a diphthong. Is the æ glyph simply used to denote a difference in pronunciation? Could anyone shed light on the roots of this linguistic practice?   And, if I may, why is propaedeutic, or propedeutic more generally, not recognized as a word when written out in this context?  Any insight?

Typesetting that goes beyond the scope of basic MS Word (e.g. LaTeX, or even modern Word versions with a good OpenType font) often uses ligatures for certain glyph combinations, the most common being   f + f = ﬀ f + i = ﬁ f + l = ﬂ f + f + i = ﬃ f + f + l = ﬄ.   I would assume, however, that there are cases in which a ligature shouldn't be used. Are there any rules or standards telling me when I should use a ligature and when I shouldn't?


What would be the best method for encrypting passwords in a database . In my case I have to encrypt two passwords per user : the user access and your own email account.  The first serious in one direction , comparing the entered password with the one stored in mssql , but the second need it in both directions ( encrypting and decrypting ) because I need it for the user is validated by sending an email through php .  The server I am using has installed PHP Version 5.5.33-1 ~ dotdeb + 7.1  Thank you very much to all.

It is currently said that MD5 is partially unsafe. Taking this into consideration, I'd like to know which mechanism to use for password protection.  This question,   suggests that hashing multiple times may be a good idea, whereas  suggests using salt.  I'm using PHP. I want a safe and fast password encryption system. Hashing a password a million times may be safer, but also slower. How to achieve a good balance between speed and safety? Also, I'd prefer the result to have a constant number of characters.   The hashing mechanism must be available in PHP It must be safe It can use salt (in this case, are all salts equally good? Is there any way to generate good salts?)   Also, should I store two fields in the database (one using MD5 and another one using SHA, for example)? Would it make it safer or unsafer?  In case I wasn't clear enough, I want to know which hashing function(s) to use and how to pick a good salt in order to have a safe and fast password protection mechanism.  Related questions that don't quite cover my question:


I a modeling this little house and then I render it only to see that the door I just modeled is the only thing that shows up.If I create something new that does render anyhow.    I am using renderman and I thought maybe that's the problem but then I tried rendering in blender internal and cycles and the other parts of the house still wont show up.I then changed the display to only rendered objects and except the door everything was invisible, although they do appear in preview rendering both in cycles and blender internal, not in renderman preview rendering cause renderman uses the same files for rendering the actual thing. I also tried to save that file and append everything form the original file to a new instance but that didn't help either.  So,does anyone know how I can get my models to appear in the render ?    I know now this isn't a renderman problem but something in blender itself so i posted it here     any help provided would be appreciated and I apologize for my poor english

I have a model of a building with a sidewalk around it.  Both show up when I switch to rendering mode in both Blender Render and Cycles Render mode.  But:  when I hit F12 for a final proper render, the building shows up -- but the sidewalk doesn't.    I've checked the normals and I thought the normals seemed pointed in the right direction.  I've set the Clipping on the Camera to a high number.  I removed all the materials from the sidewalk and added a new material-- the problem persists.  I've exported the blend as an FBX file and the Sidewalk shows up fine in Unity.  Just in final renders, it doesn't show up.    Here is a blend file: .  I tried to destroy everything unrelated to the issue and label things in a clear way.    Thanks.


I just got a Dell Latitude E6540, but every time I try to turn it off, it restarts automatically. It is running on a 64b Win 7 OS. Can anyone help me please?

Whenever I shut down my computer, or put it in sleep/hybernate, it turns on after two seconds. It doesn't post, it just powers on and then idles. To actually turn it off, I switch off the psu. The problem is now, whenever I switch the psu on and try to boot, it doesn't always turn on. It takes a good amount of flicking the psu switch on and off before the motherboard lights up.  So far I've determined the things its not:    its not caused by the mouse or network waking up the computer. I've been able to go into hybernate for the past year. And all "wake on X" settings in the bios are diabled.  its not a scheduled task waking up the computer at a given hour, it occurs every single time  its not due to an upgrade or new installation, since I haven't done either in a very long time   I'm sure its a hardware issue. So I'd like to know, is my psu dead, or the motherboard? The psu is an Antec Earthwatts 600w, the motherboard is an Asus P5Q-E, both one year old.


I have just installed Ubuntu 20.04.01 LTS on to an old MacBook Pro 7.1, I followed the instruction on installing Ubuntu as the only operating system and all went well with no error but on booting the new installation I get the following errors. Failed to set MoKlistRT: Invalid Parameter Could not create MoKlates has failed: import_mok_state0 failed : Invalid Parameter Continuing boot since secure mode is disabled  System then gives a blank screen and hangs. Any help will be appreciated.

I have a MacBook Pro and only use Ubuntu on it. I just upgraded from 18.04 to 20.04. Now when I start the computer it says: Failed to Set MokListRT: Invalid Parameter Could not create mokListRT: Invalid Parameter Importing MOK states has failed: import_mok_state() failed: Invalid Parameter Continuing boot since secure mode is disabled.  Does anyone know EXACTLY how I can fix this?? Step-by-step process I don't want to mess anything up trying to fix this.


I'll be in Amsterdam end of June for 5 days. I'm from tropical weather and heard spring in Amsterdam is bit cold.   Do I need wear clothing thats suits to cold weather or normal t-shirt and trouser will be fine? Will it be cold in nights? can I wear casual baggy shorts at night?   This question is about what to dress in End of June in Amsterdam.  PS: End of June 2017 was very cold and had some rain with wind. Even though it says end of spring don't forget to put some dress for cold weather.

I am interested in hiking this fall in France and camping along the way. In order to figure what gear I need to pack to camp (particularly for the sleeping bag), I would like to know what temperatures to expect.  I am interested in historical temperatures to figure the usual temperature and I might look at them for other seasons. If that matters, I am thinking about hiking in the Pays Basque (South West of France), the mountainous part.  Where (ideally online and for free) can I find such data? Are there resources that cover Europe, or even the whole world?


Im working on a website and my boss wants me to use CSS variations and I dont know what he is talking about.  Let's say I have 20 different elements using #7d2d39, rather than having:  background-color:#7d2d39 color="#7d2d39"   All over the style sheets he wants me to call it using:  background-color:red1" color="red1"   and somewhere define what "red1" is that way we can globally change one hex color vs. changing it 20 times? It makes sense as I type it, but I dont think this exists.

Possible Duplicate:          We have some "theme colors" that are reused in our CSS sheet.  Is there a way to set a variable and then reuse it?  E.g.  .css OurColor: Blue  H1 {   color:OurColor; }


I got a python error that surprised me this morning. Consider this simple example:  def f(mylist):     m = max(mylist)     max = m   I expected this function to execute without failing, but it throws:  UnboundLocalError: local variable 'max' referenced before assignment  I assumed that since python was an interpreted language, overwriting the built-in max() function wouldn't cause any trouble as long as I didn't try to invoke it again afterwards.  Why does this behavior occur? Does the python interpreter "look ahead" for variable declarations?

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 read that the square of any prime number, excluding 2 and 3, is one greater than a multiple of 24. Is this a conjecture or a theorem? It's hard for me to imagine how such a thing could be proven.

Show that if $n$ is not divisible by $2$ or by $3$, then $n^2-1$ is divisible by $24$.   I thought I would do the following ... As $n$ is not divisible by $2$ and $3$ then $$n=2k+1\;\text{or}\\n=3k+1\;\text{or}\\n=3k+2\;\;\;\;$$for some $n\in\mathbb{N}$. And then make induction over $k$ in each case.$$24\mid (2k+1)^2-1\;\text{or}\\24\mid (3k+1)^2-1\;\text{or}\\24\mid (3k+2)^2-1\;\;\;\;$$This question is in a text of Euclidean Division I'm reviewing, and I wonder if there is a simpler, faster, or direct this way.


I'm trying to work with a (very) large 45gb .txt file that cannot be opened using normal text editors.   Data within each row is separated by a spacing, although there are also spaces within each parameter. For example, 1 row looks somewhat like this:     University of Cambridge CB2 1TQ 0001234567 2011-01-25 12345 11.12345   12.12345 13.12345 14.1234 16.2716)   What I would want to is essentially to clean it up, filter some data, sum up some cells/parameters, append some additional data to each row, and perform clustering analysis (probably with python or C# since I'm starting to pick it up).

I have a very big file 4GB and when I try to read it my computer hangs. So I want to read it piece by piece and after processing each piece store the processed piece into another file and read next piece.  Is there any method to yield these pieces ?  I would love to have a lazy method.


I'm trying to use xelatex with beamer (I know, bad idea!) so that I can use a particular style file that I like. I'm running into some weird math display problems. Here's my MWE:  \documentclass{beamer} \usepackage{unicode-math} \usepackage{xltxtra} \setmathfont{Asana-Math.otf}  \begin{document} \begin{frame} $ a < b \log n $ \end{frame} \end{document}   which yields the following:    So I think that I'll get rid of Asana-Math because maybe it has some font problems. The resulting image I get looks like this:    So either way I'm in a bind. Either basic characters are not recognized or I can't use operators (and this happens with \exp as well).   Is there something obvious that I'm missing ?

I want to typeset math in different font called Antykwa Torunska, which supports maths. Unfortunately, when using it in beamer the math font is switched to the standard math font of beamer. How can I change this behaviour?  Here is a minimal example:  \documentclass{beamer} % Mathekram: \usepackage{amssymb, amstext, amsmath} % Font: \usepackage[math]{anttor} \usepackage[T1]{fontenc}   \begin{document}  \begin{frame}{Testframe}    This is fine: 1234567890, \textit{x}, \textit{p}, \textit{t}\\    This is not fine: $1234567890$, $x$, $p$, $t$ \end{frame}  \end{document}   When I change beamer to article it works fine.


Every time I wish to move to a directory I use very often, I must type this long directory path:  cd /media/prasanth/01D0F888E7BC91801/github projects   or I must use the gui to get into the folder and open the terminal.  Is it possible to assign this long path to a single name and enter it via the terminal like  cd mygitfiles   ?

In the Ubuntu terminal I find myself spending considerable time to switch to a particular directory every time the computer starts up. Is there some way I can make this process easier? Is there some hotkey or some quick directory change that I can use (like speed dial on a phone)?   eg:     cd 1:Changes to saved directory one


It is written in the Goldstein's Classical Mechanics text that  $$\frac{\mathrm d}{\mathrm dt}\left(\frac{\partial {r_i}}{\partial {q_j}}\right) = \frac{\partial {\dot r_i}}{\partial {q_j}}=\sum_k \frac{\partial^2{r_i}}{\partial {q_j}\partial{q_k}}\dot q_k+\frac{\partial^2{r_i}}{\partial {q_j}\partial t},\tag{1.50b}$$ where $$\dot r_i=\frac{\mathrm d}{\mathrm dt}r_i=\sum_k\frac{\partial{}r_i}{\partial{q_k}}\dot q_k+\frac{\partial {r_i}}{\partial t}.\tag{1.46}$$ But it seems to me that there is another term in $\frac{\partial {\dot r_i}} {\partial {q_j}}$ because of product rule which is $$\sum_k \frac{\partial{r_i}}{\partial{q_k}}\frac{\partial{\dot q_k}}{\partial{q_j}},$$ which I think is equal to $$\frac{\partial{r_i}}{\partial{q_j}}\frac{\partial{\dot q_j}}{\partial{q_j}}$$ since $q_j$'s are independent among themselves.   Then how come $$\frac{\mathrm d}{\mathrm dt}\left(\frac{\partial {r_i}}{\partial {q_j}}\right) = \frac{\partial {\dot r_i}}{\partial {q_j}}~?\tag{1.50b}$$ Does $$\frac{\partial{\dot q_j}}{\partial{q_j}} = 0\ ?$$

In the calculus of variations, particularly Lagrangian mechanics, people often say we vary the position and the velocity independently. But velocity is the derivative of position, so how can you treat them as independent variables?


VLC doesnt quit. How do I force quit the application?

I'm trying to make a custom launcher in 11.10 for the special force quit launcher we had in 11.04 (you could add it from the list of apps, but now it is nowhere to be found, even in alacarte). So I try using info from  but I have no idea what the actual file or command is for force quit nor where it is in the file system. This question is real specific to force quit itself and is not about asking how to create a launcher. I will create a file called forcequit.desktop and put it in ~/.local/share/applications folder and will then drag it unto the toolbar like it is told elsewhere. The content of the file will look like this: #!/usr/bin/env xdg-open   [Desktop Entry] Version=1.0 Type=Application Terminal=false Exec=sh -c 'notify-send "Click on an application to force-close it, or press Esc to cancel."; xkill' Name=Force Quit Comment=Click on the app to quit with your pointer Icon=gnome-panel-force-quit Categories=System,Accessories;  I suppose it might be a special command that takes an argument, again if you have the info please do tell :) I wrote comments in the file about the info I need. Edit: ok now it works with showing a special X icon and does force quit properly. Now I just need to find out how to get instructions to appear for an end user, just like it does when using from CLI. I'd suppose it displays the launcher's comment on screen somewhere? Any ideas or links ? Or maybe I need to add something to this launcher file ? Last edit: well the solution from the above edit has been found, it is the usage of notify send that does the trick. Like it is now reflected in the code. Enjoy the solution for your desktop (or for end users you support !) Latest edit: all this talk makes me want to go look for notify-send options a little more... and well in a greater scale at all the other commands I can use.....notify-send is part of gnome, is it ? Or is it part of sh? (I doubt it's from sh) Edit to the lastest edit : never mind that. I found an answer to that as well. notify-send is part of the libnotify library package... and notify-send is in the tools folder (I had trouble finding it at first…) and no it isn't specifically part of gnome, but rather another library used by many apps :)


Is it possibe to restart the display driver during a normal desktop session ?   In the driver section of "Computer Management" there is no option.   But possibly there is some tool or command line to do so?

Some times my video card driver (Intel GMA X4500HD) crashes and gets restarted automatically. But more often (almost every time I watch a flash-powered online video for a period of time) it just gets slower and slower and extremely slow until I restart my computer. This looks like a resource leak in the video driver code and I'd like to try restarting it alone without restarting the whole system. How do I restart it (or cause it to crash immediately to be restarted automatically by the OS) manually?


I have recently bought the game and added lots of multiplayer severs that I love. One day I log in and they are all gone; I go onto direct connect and put in the correct IP and it says:  Outdated server, Still on {0}   How do I get my servers back?

Similar to  on the bugs in Minecraft, I would like a complete list of what error codes exist in Minecraft and how they occur, as well as how they can be resolved.


How would I go about making an indicator for the panel on Unity?  I want a button that shows a menu and when you click on the menu items they run commands.    How do I do this?

I'm sure I'm not the only one in this situation: I run Ubuntu 16 on my laptop, and I use that to connect to my workstation in the office.   Now there are a couple things that I have to do every day when I connect to my workstation, such as fixing my bluetooth mouse speed, setting the right resolution for both screens and restoring my wallpaper with nitrogen. For each of these tasks I have a (startup) script which works fine, but when I connect my second screen, the laptop is already booted.  So my question is, next to start-up applications, how could I (i.e.) run nitrogen --restore and scale down the resolution on my laptop (from 2560x1600 to 1440x900) when I connect the second screen?  What I do now is run all seperate scripts again manually, which isn't a big deal, but we don't use Ubuntu to just accept how it is, right? ;)  To clarify; my question isn't too specific for these tasks, but more in a general sense; how could I fire anything from the terminal on specific actions like "input of display detected"?


I recently installed Grive, a third party Google Drive tool for Ubuntu, and in order to sync the folders, you must run the command grive in the Google Drive folder in your home page. Is there a way I can automate a simple command before my system shuts down to ensure I always sync my libraries?  Thanks!

I have a machine running a couple of vagrant VM. The problem I have is that sometimes I forget to shutdown those VM before I shutdown or reboot my machine. Because of that my machine get stuck with this message: waiting for vboxnet0 to become free  I searched about solutions and I found this page :    I tried what they for shutdown, but it doesn't work.  I wrote an sh file for that command:  #!/bin/bash  cd ~/workspace/git/mediaservice vagrant halt   any suggestions?


I'm trying to create a game in python, a game of multiple choice called "Who wants to be a millionaire?" and the problem is I want the program to stop executing the second question once the user failed to answer the first one. print("What is the tallest being in existence?")  input(("If you want to see the choices just press enter. " + name))  print("Is it A, Dinosaur?") print("B, The one and only, Giraffe") print("C,The soul of the ocean Whale") print("or D, None")  print("So what do you believe is the answer ? " + name + " ")  answer_1 = input()  if answer_1 == Q1_answer:     print("Correct! You Have Earned 100,000$ ")     score = +100000 if answer_1 != Q1_answer:     print("Im sorry, You have lost the game.")  print("Which famous inventor was born in 1856?")  print("A Einstein") print("B, Tesla") print("C, Napoleon") print("D, Newton")  answer_2 = input()  if answer_2 == Q2_answer.lower():      print("Correct! It is Tesla Indeed, Your reached  200,000$ ")     score = +100000 else:     print("Sorry, wrong answer. You have lost and earned 0$. ")

I am aware of the die() command in PHP which exits a script early.  How can I do this in Python?


I read about the attributes likely and unlikely of c++20, and i want to ask if there are some reasonable and official data of performance advantages that this new attributes give to the execution. I mean there are examples execution test that give me a measure of how much this feature has impact on performance when the code is executed? I noticed that this attributes are often used in linux kernel development ( in C code ). So my question is: Does not the compiler optimaze the code sufficiently already? There are example or proof of the effective improved performances? Is this true for all kind of machine or some architectures need Likely/Unlikely for a good improvement? EDIT : I'm searching for Graph or data that demostrate the effeciency of this kind of suggestion to the compiler. ( I search online, but i don't find nothing good ) If someone know some paper, or similar can answer this question?

I've been digging through some parts of the Linux kernel, and found calls like this:  if (unlikely(fd < 0)) {     /* Do something */ }   or  if (likely(!err)) {     /* Do something */ }   I've found the definition of them:  #define likely(x)       __builtin_expect((x),1) #define unlikely(x)     __builtin_expect((x),0)   I know that they are for optimization, but how do they work? And how much performance/size decrease can be expected from using them? And is it worth the hassle (and losing the portability probably) at least in bottleneck code (in userspace, of course).


I've been searching for days. When I export and create my fat jar it loads and disappears. It can't find my images.    This is what it all looks like. I used something like this to load them:  File a; a = new File("res/theimage.png");     wood = TextureLoader.getTexture("PNG", new FileInputStream(a));   This works just fine in eclipse but the jar can't find the image. I tried putting the first jar with the fat jar in a folder. It still didn't work so I put all project files in there too. Somehow it couldn't find it still. How do you get your res to be in your lwjgl game. I mainly just want to have a jar file that you click and start easily instead of a zip folder with all the files. I don't know how to do any of this. My game without images works just fine. I rather a visual way of doing this.  Can Images be draw without being textures in LWJGL?

I'm still experimenting with some OpenGL in LWJGL, and as I get to know more and more about OpenGL, I start to do more complicated things like multi texturing, shadowmapping and more. Now, right now I'm using the src folder (src/res) for my resources, and use src/resourcename in my code. When I export it, this won't work on another location as the relative path is ofcourse incorrect. What would be the best way of deploying your game with all the resources in one file? Maybe put the files in the jar?  I would like to hear from a few people how they store and deploy their project with resources, thanks!


I have a input hidden type which specifies the function that needs to be called. How can I do it using Javascript/Jquery  <input type="hidden" name="extrafunction" id="extrafunction" value="edit_data_provider/DataProviderChange1" />   and in Javascript file          var fullfunctionName = $('#extrafunction').val();         var control_name    = fullfunctionName.split('/')[0];         var function_name   = fullfunctionName.split('/')[1];         if(control_name == client_control_name)         {             //The function call which is in function_name var should come here          }

I have the name of a function in JavaScript as a string. How do I convert that into a function pointer so I can call it later?  Depending on the circumstances, I may need to pass various arguments into the method too.  Some of the functions may take the form of namespace.namespace.function(args[...]).


I'm using Lubuntu 18.04 LTS 32 bit and need to know what choices I have, if any. Thanks!

I'm having trouble installing Skype. I have Canonical Partners enabled in Synaptic Package Manager, but skype is not showing in the search. If I try to install via:  sudo apt install skype   I get:   E: Unable to locate package skype   I went to the Skype web site and it offered a .deb file only in 64 bit.


I want to study the convergence of the series of general term $sin(\pi en!)$ In my naive way I see that this limit does not exist at infinity since e is an irrational number but they say it's zero Any explanation to this???? Thanks in advance

I didn't know how to solve this problem.  How to prove $$\sum_{n=0}^{\infty}\sin(e\pi n!)$$ converges?


I am a new user of the Beamer presentation template and would like to display an extensive reference list with numbers to the left of the entries just as the standard bibliography in LaTeX. How can I do so? My bibliography does not fit into a single slide and I think there should be a neat solution for it. Could you provide some suggestions?   EDIT: I have managed to split my bibliography across many slides now I would like to enumerate them just like in LaTeX document class. How can I achieve this?  Thanks

I have several citations in a beamer-based presentation.  Is it possible to split the bibliography across two slides?  I'm using natbib / bibtex.  And I currently just have:  \begin{frame}  \tiny  \bibliographystyle{apalike} \bibliography{Biblio-Database}  \end{frame}   But we're to the point where even tiny won't cut it.  Is there anyway to do this?  I'd really prefer to not create the bibliography by hand because I once had it 'stuck to me' that I omitted an entry in the bibliography (which I'd created by hand)... nothing quite like ending on a clerical omission...


I'm trying to get the fundamental state of an electron in a potential, as in:  $$V(X)=e|x|$$  Where $e$ is a constant. To start with I want to solve it with $e=1$, then where $e$ is big enough that it transforms the potential to something like the delta. And how i solve the problem of having a discontiunity of the derivative in zero?(i mean in the computer)  I have a conceptual problem, If I try to do it with a computer (with a method of matrix diagonalization) the energy is dependent on the big of the $x$ array. Some has a clue to give?  Another thing is that if $e>>1$, it will be like a delta function and inside can't be a bound state with a fundamental energy. Or am I wrong?

As has been , if you take an unbounded potential $V(x)$ (so that all the eigenstates are bound) and you look at the uncertainty product $\Delta x\Delta p$ as a function of the index $n$ of the eigenstate, then for the two usual unbounded potentials (the simple harmonic oscillator and the infinite square well) $\Delta x\Delta p$ grows linearly with $n$.  How does this product behave for other solvable potentials, such as the linear cone potential $V(x)=|x|$?


I am currently writing my cover letter for an application.  In the opening sentence I want to put emphasis on the most important fact about my profile: That I am a statistician and that this is my passion. I am applying in the area of financial statistics. I thought about using the classical "I am writing to apply", but instead somehow a punchline, something like:  Statistics and solving quantitatitve problems is my passion. I studied .....   I am not sure about this sentence, first is this a good idea? Second is the "is" correct? Or is an "are" necessary?

Can anyone tell me if I should use inspire or inspires in this phrase?     An extraordinary leader whose vision, values, integrity and boundless curiosity inspires all who follow in his footsteps.


I defined a .py file in this format:  foo.py  def foo1(): pass def foo2(): pass def foo3(): pass   I import it from another file:  main.py  from foo import *  # or import foo   Is it possible list all functions name, e.g. ["foo1", "foo2", "foo3"]?    Thanks for your help, I made a class for what I want, pls comment if you have suggestion  class GetFuncViaStr(object):     def __init__(self):         d = {}         import foo         for y in [getattr(foo, x) for x in dir(foo)]:             if callable(y):                d[y.__name__] = y     def __getattr__(self, val) :         if not val in self.d :            raise NotImplementedError         else:            return d[val]

I have a Python module installed on my system and I'd like to be able to see what functions/classes/methods are available in it. I want to call the help function on each one. In Ruby I can do something like ClassName.methods to get a list of all the methods available on that class. Is there something similar in Python? eg. something like: from somemodule import foo print(foo.methods)  # or whatever is the correct method to call


If I get this:  No command 'pdf' found, but there are 16 similar ones pdf: command not found   How do I see the 16 similar commands?

When you write the command name wrong, bash often does this:  septi@norbert:~$ good No command 'good' found, did you mean:  Command 'gold' from package 'binutils' (main)  Command 'gmod' from package 'gmod' (universe)  Command 'goo' from package 'goo' (universe)  Command 'god' from package 'god' (universe)  Command 'geod' from package 'proj-bin' (universe)  Command 'gord' from package 'scotch' (universe) good: command not found   Or sometimes it does this:  septi@norbert:~$ nftp No command 'nftp' found, but there are 23 similar ones nftp: command not found   Is there any way to ask bash to show these 23 similar commands for me? And, is there a way to show similar commands, including those that aren't yet installed, instead of running the application, ftp for example?


I've just installed Lubuntu 17.10 on my laptop and removed Windows 7. But I can't find my former hard disks (D:\, E:). When I tried Lubuntu without installing ( and deleting the previous os ) I could use my hard disks. But they have disappeared. What can I do?

I have a Toshiba satellite A-200 laptop with a Vista OS on it with 4 NTFS partitions  (C:) Vista  (D:) Entertainment  (E:) Work  (F:) Sources   and I wanted to start using Ubuntu instead. So I tried it first from the live CD and everything was OK and all the partitions were shown and working and so I decided to install Ubuntu to replace Vista on the (C:) drive. After I did that I can no longer find my folders and files on the (D:), (E:), (F:) partitions and the only file system that is shown is one 198 GB although my HDD is 320 GB.  I can't access the lost data on the remaining 120 GB which I hope is still there and not totally lost  I am now working from the live CD but I am unable to install testdisk. Can I recover the Vista partitions by the product recovery CD to get my laptop back to the factory settings? Can I recover the NTFS partitions using a recovery program for Windows or will that make the problem worse?   I need these data badly as I don't have a backup for them.


I deleted the synctex file by mistake and I'd like to know if there's a way to recover it. I want to be able to Ctrl-click in the preview and jump to the corresponding place in the LaTeX source.  I'm using TeXworks. Recompiling the source won't work.

I have this weird issue with forward and inverse searches. I am using WinEdt + Sumatra combination. The forward and inverse search works perfectly on certain some .tex files, but fails on some others.  Currently, I am working on a .tex file and the inverse search always points to the end of a section. Where ever I double click in a particular section of the pdf, the inverse search points to the end of that section in the .tex file.  Moreover, when I try to perform forward search (Shift+F8) from the .tex file, the section in the pdf file doesn't get highlighted.  There are other .tex files where both the searches work perfectly. What could be the issue with this .tex file?


Black screen after upgrade from 19.04 to 19.10 How do I fix this?  Sony Vaio computer  This is an udate, but the problem is not yet solved. I tried the suggested fix (temporary/permenant) with "nomodset" and updated the grub file,but it did nothing. My screen does not go black. It first is purple, then light grey,then the video driver Nvidia shows, and the background comes up on the screen for about 10 seconds. This is where the icons and connections normally show up, but now they do not, and it goes blank back to light grey like the rest is not loading. However,there are only 2 icons, Netflix and Pandora,which cannot run because there's no Wi-Fi etc.  Any suggestions?

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


I'd like to save a document as PDF without any loss in picture quality, with sensible file size.     PNG images were imported to the Microsoft Word document. The advantage of PNG format is lossless compression which makes it suitable for schematics or blueprints (as it doesn't damage lines and edges). I don't know how Word stores it internally, but it works. These images are still pixel-to-pixel equal to original (not distorted). The filesize of DOCX is similar to PNG which was imported into. That's what I'd like to achieve with PDF.  I've tried PDF Creator with option Format >> PDF >> Compression >> Color and greyscale >> ZIP. It works. Image quality is ok, but the PDF file size is way too big. It can be tens of times bigger (e.g., 100 MB) than the original DOCX or PNG.   How can I force PDF to store graphics internally as PNG or other efficient format that ensures good file size?

I will admit I am a total noob when it comes to this. I have a Word 2010 file that has images and when I do either Save As PDF or print using a PDFCreator, I always get images with jagged diagonal lines and generally of worse quality. I tried it with JPEG as well as PNG, I tried it with Word 2010 and OpenOffice. No luck.  I even turned image compression off in Word 2010...still compressed it.  What am I doing wrong? Surely, there is a way to keep some quality when it comes to images?


I have mounted a Veracrypt file partition just to find out that one of the two VirtualBox machines on that volume is inaccessible. When I look into the volume I can see that this machine folder is empty - no .vdi file. However I did not delete it. What's strange is that the partition seems almost full but only the second virtual machine .vdi file is there (second machine has 7GB, whole partition has 28GB). The Trash folder is also empty. I've tried data recovery software but none I've tried supports network drives so they refuse to open the mounted volume. The only one that opened it was R-Studio, but it did not find the second machine's .vdi. When trying to restore volume header (which I did not back up nor do I have recovery DVD) VeraCrypt claims I entered wrong password. Anyone knows how to resurrect the machine?

I have mounted a Veracrypt volume just to find out that one of the two VBox machines on that volume is inaccessible. When I look into the volume I can see that this machine folder is empty - no .vdi file. However I did not delete it. What's strange is that the space used is as big as it would be with the .vdi file. The Trash folder is also empty. I've tried data recovery software but none I've tried supports network drives so they refuse to open the mounted volume. Anyone knows how to resurrect the .vdi file? After re-mounting the volume the file is missing still.


From August 2015 through August 2016 I was on a Nuclear/Radiation Physics based work placement in a scientific research institute, between my second and third years of my university Maths degree. I am now back at university, half way through my third year.  About half way through my work placement (which I thoroughly enjoyed), my supervisor suggested that the work I was doing could be considered publishable. Being an undergraduate this was (and is) obviously a very exciting prospect. It turned out that we did decide to write a paper, and my supervisor said to be that I would get to be the first author. I don't understand much, but I'm under the impression that's something to be excited about too.  I finished with all the analysis and wrote a draft of the paper. It was then time for me to leave my placement and my (now ex-)supervisor are still in correspondence, whilst he finalizes the paper. There have been various (unrelated) issues which have held him back from spending time on it - but he suspects (as it stands) that he will possibly finish it and submit it to a journal by the end of February. He's basically completely reformatting a lot of the paper, and probably rewriting a whole bunch of it, because being an undergraduate I have no idea how to write a paper. Of course this means that if I do turn out to be first author, my supervisor has probably been very generous.  Long story short - if things go well and the paper is accepted in whichever journal, is this a big deal or nothing to be so bothered about? I ask basically to figure out where this ranks in terms of putting it on a C.V. (or something). Is this something to simply add on as an achievement, or something to really highlight?   I understand my question is really rather ambiguous. Essentially I'm really not sure what to expect under the circumstances that the paper is published - if anything.

In my field (theoretical computer science), authors of any paper are always listed alphabetically; our papers .  (Well... hardly ever.)  In most other disciplines, at least within science and engineering, the ordering of authors is a signal about their relative contributions to the paper, with the first author indicating the most significant contributor.  Hiring and promotion committees do give extra weight to "first-author papers" (and sometimes have to be reminded that not all areas have them).  As an outsider, I find this practice confusing.  What does first authorship actually mean in your discipline? I understand vaguely that the first author is supposed to be the one who "", but what counts as "work" in this comparison?  Does "most" mean "more than all the other coauthors together" or just "more than any other coauthor"?  What happens when the comparison is unclear?   How often is "did the most work" the actual truth, versus a cover story for a more complex political decision?  I realize that the precise answer is different for every paper.  I'm looking for general guidelines for how an outsider (like me) should interpret first authorship in your field.  Pointers to guidelines from journals or professional societies would be especially helpful.  Please give only one answer per discipline.


I have a backup from SQL Server 2016. I want to restore it in my pc but I am getting this error.     The database was backed up on a server running version 13.00.1400.   That version is incompatible with this server, which is running   version 11.00.5343.   I have searched in Google and have try to upload some patches but it's still the same.How can I fix it.

When trying to restore a backup to a SQL Server Express 2008 database I got the following error:  Restore failed for Server '...\SQLEXPRESS'.  (Microsoft.SqlServer.SmoExtended) System.Data.SqlClient.SqlError: The database was backed up on a server running version 10.50.1600.  That version is incompatible with this server, which is running version 10.00.2531.  Either restore the database on a server that supports the backup, or use a backup  that is compatible with this server. (Microsoft.SqlServer.Smo)   Is there a way to get a backup which is compatible with the older (in my case 10.00.2531) version from the newer (in my case 10.50.1600) version of SQL Server Express?


How can I implement a button that copies the text displayed on to clipboard with a simple method? I'm having a mental block.

                     www.testexample.com

                     <button className="iconHolder">                                          <FiCopy />                     Copy                     </button>

What is the best way to copy text to the clipboard (multi-browser)? I have tried: function copyToClipboard(text) {     if (window.clipboardData) { // Internet Explorer         window.clipboardData.setData("Text", text);     } else {         unsafeWindow.netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");         const clipboardHelper = Components.classes["@mozilla.org/widget/clipboardhelper;1"].getService(Components.interfaces.nsIClipboardHelper);         clipboardHelper.copyString(text);     } }  But in Internet Explorer it gives a syntax error. In Firefox, it says unsafeWindow is not defined. A nice trick without using :


I was wondering while studying for my complex analysis finals, on chapter on orientation, is it possible to find some holomorphic function on the unit closed disk which sends the unit circle with the counterclockwise orientation into the unit circle with clockwise orientation?  It seems like an interesting question to ponder about, but I cannot think of any as of now, I was wondering if anyone could give me an example of a function which could do this?

Still quite unsure about the chapter on orientation. For instance the Mobius map indeed preserves orientation, and I can show this rigorously, however I am still having difficulty understanding what it means for a holomorphic function $f$ to preserve orientation over some region in the complex plane. Which is why I asked a question regarding this $2$ days ago, but did not receive an answer.   The problem I am still thinking about is, I cannot show or provide a counter argument for why there does or does not exist some holomorphic function $f$ on a $\{z:|z|\le1\}$ such that it sends the unit circle with the counter- clockwise orientation into the unit circle with the clockwise orientation?  From the comment from this question asked earlier, one did suggest the use of the Argument principle which states that:     Argument Principle: If $f$ is meromorphic on a simply connected region $D$ and $\Gamma$ is a simply closed curve in $D$ not passing through the roots $z_j$ nor the poles $p_k$ of $f,$ then $$\frac{1}{2\pi i}\oint_{\Gamma}\frac{f'(z)}{f(z)}dz=n-m$$   Where $n$ is the number of roots of $f$(including multiplicities) in $\Gamma$ and $m$ is the number of poles of $f$ (including multiplicities) inside $\Gamma.$     I am really curious to find out why we can apply this to try and provide an explanation for my problem. I would appreciate some help because I am quite confused with orientation at the moment, and I think this problem is good in the sense it will help me understand some important notions on holomorphic functions which send or does not send certain orientation on a region to a different orientation of the same region.   I would really appreciate some rigorous argument for this problem. Much help will be appreciated.


I have an ASUS K53E (Intel i5 CPU, 4GB DDR3 RAM, 500GB HD) notebook computer that I bought new in 2012. I run Windows 7 Home Premium on it, and have (had?) Ubuntu 12 on it too. When I downloaded Ubuntu initially, it placed a purple dual-boot startup program on the computer that asks me to choose either Windows or Ubuntu.  The startup program says, "Ubuntu, with Linux 3.2.0-54 generic pae".  It all worked fine until the other day. While updating Ubuntu (to v. 14, I believe), it hiccuped and the download stopped before completion. I can no longer enter Ubuntu, although the dual-boot startup program still allows me to select and use Windows. I tried the "Ubuntu, with Linux 3.2.0-54 geneic pae (recovery mode)". However, every time I try to start Ubuntu, only text appears. The last line always says: "ountall: Disconnected from Plymouth".  What should I do?  1st choice: How can I fix and update Ubuntu?  -- or --  2nd choice: How can I delete Ubuntu completely (and the dual-boot startup program)?  I'd rather keep an up-to-date version of Ubuntu on the laptop, as I am thinking of ditching Windows altogether, but I do want to keep Windows running for the time being.

After Ubuntu boots, the tty1   Ctrl+Alt+F1 shows this:     Thegatorade-PC login: mountall: disconnected from Plymouth    mountall: Event failed   This happened after partitioning with gparted and happens every time I use Ubuntu.


I have two type of array.  First type    $arr = [1,2,3];   Second type  $arr = [[1,2,3],[4,5,6],[7,8,9]];   How to check that my array is single or multi array.  I am using below code which is always giving me as Multi Array   if(is_array($arr)){       echo "Multi Array";   } else{       echo "SingleArray";   }

What is the most efficient way to check if an array is a flat array of primitive values or if it is a multidimensional array? Is there any way to do this without actually looping through an array and running is_array() on each of its elements?


asks to enumerate the problems with overdifferencing in time series, and so far that post has focused on one specific problem: the removal of process memory in a manner that could hurt forecasts. Fractional differencing is referenced as a solution.  There are some comments about why (or when) a first difference would remove memory. Certainly if the process was a true random walk, no memory would be lost by differencing.  What is the mechanism behind "memory loss" from taking a difference? When does it occur, and why does it occur?

seems to be a well known and renowned machine learning expert in the field of finance. I am very far from his level, as have not yet finished my PhD in economics, and only have an applied level statistical knowledge. I have encountered a much . I can not say I completely understand all the mathematical parts. But there are some claims in the paper, which seem to completely contradict things, which I have learned on statistics and economics thus far, or at least seem to be illogical for me. For a specific example, the paper under the section Pitfall #4 and Solution #4 suggests, that by differencing time series to make them stationary for classical statistical models (ARIMA etc.) removes the memory of the series and thus makes them lose the predictive power:     The conclusion is that, for decades, most empirical studies have   worked with series where memory has been unnecessarily wiped-out. The   reason this is a dangerous practice is that fitting a memory-less   series will likely lead to a spurious pattern, a false discovery.   Incidentally, this over-differentiation of time series may explain why   the Efficient Markets Hypothesis is still so prevalent among academic   circles: Without memory, series will not be predictive, and   researchers may draw the false conclusion that markets are   unpredictable.   In economics there really is a simplified theoretical model on equity returns, which posits, that it is a memory-less white noise, and the prices (the integrated returns) follow a random walk. But from an empirical perspective, as far as I understand the memory-less attribute of returns pertains only to the individual data points themselves, not the series as a whole. A differentiated series still should have a "collective" memory put together, and it has almost the same information as the integrated version, only lacks a constant value. So it should have the same predictive power as well, should it not? Or it is me, who has a lack of understanding?


I have the following problem.  I already solved it but I am not happy with my solution.  I hope for a more slick solution and maybe somebody can help with it.  Is there a way to solve this problem with just the stars/bars method?  Compute the number of ways to permute all letters from $D,D,D,O,O,O,G,G,G$ such that no two $D$ are adjacent and no two $G$ are adjacent.  My attempt. For $k=2,3$, let $\Delta_k$ denote the set of permutations s.t. only $k$ of $D$ are adjacent, and let $\Gamma_k$ denote the set of permutations s.t. only $k$ of $G$ are adjacent.  Let $U$ be the set of all permutations without any conditions. Then $$|U|=\frac{(3+3+3)!}{3!3!3!}=1680.$$  We have $$|\Delta_3|=\frac{(1+3+3)!}{1!3!3!}=140$$ (as $\Delta_3$ is the set of permutations of $DDD,O,O,O,G,G,G$), and $$|\Delta_2|+2|\Delta_3|=\frac{(1+1+3+3)!}{1!1!3!3!}=1120$$ since this number counts the permutations of $DD,D,O,O,O,G,G,G$.  Therefore $$|\Delta_2|=1120-2(140)=840.$$  Similarly $|\Gamma_3|=140$ and $|\Gamma_2|=840$. We want to find $|\Delta_i\cap\Gamma_j|$.  Since $\Delta_3\cap\Gamma_3$ is the set of permutations of $DDD,O,O,O,GGG$, $$|\Delta_3\cap\Gamma_3|=\frac{(1+3+1)!}{1!3!1!}=20.$$  Since $|\Delta_2\cap\Gamma_3|+2|\Delta_3\cap\Gamma_3|$ counts the permutations of $DD,D,O,O,O,GGG$, we have $$|\Delta_2\cap\Gamma_3|+2|\Delta_3\cap\Gamma_3|=\frac{(1+1+3+1)!}{1!1!3!1!}=120$$ so $$|\Delta_2\cap\Gamma_3|=120-2(20)=80.$$  Similarly $|\Delta_3\cap\Gamma_2|=80$. We now want to find $|\Delta_2\cap\Gamma_2|$.  Since $|\Delta_2\cap\Gamma_2|+2|\Delta_3\cap\Gamma_2|+2|\Delta_2\cap\Gamma_3|+4|\Delta_2\cap\Gamma_3|$ counts the number of permutations of $DD,D,O,O,O,GG,G$, we get $$|\Delta_2\cap\Gamma_2|+2|\Delta_3\cap\Gamma_2|+2|\Delta_2\cap\Gamma_3|+4|\Delta_2\cap\Gamma_3|=\frac{(1+1+3+1+1)!}{1!1!3!1!1!}=840.$$  Hence $$|\Delta_2\cap\Gamma_2|=840-2(80)-2(80)-4(20)=440.$$ By inclusion-exclusion principle we have $$|\Delta_2\cup\Delta_3\cup\Gamma_2\cup\Gamma_3|=\sum_{k=2}^3|\Delta_k|+\sum_{k=2}^3|\Gamma_k|-\sum_{i=2}^3\sum_{j=2}^3|\Delta_i\cap \Gamma_j|.$$  Therefore $$|\Delta_2\cup\Delta_3\cup\Gamma_2\cup\Gamma_3|=2(840)+2(140)-(440+80+80+20)=1340.$$  The question asks for the size of $U\setminus(\Delta_2\cup\Delta_3\cup\Gamma_2\cup\Gamma_3)$, which is $$|U|-|\Delta_2\cup\Delta_3\cup\Gamma_2\cup\Gamma_3|=1680-1340=340.$$

Q: How many arrangements of a,a,a,b,b,b,c,c,c are there such that  $\hspace{5mm}$ (i). no three consecutive letters are the same?  $\hspace{5mm}$ (ii). no two consecutive letters are the same?  A:(i). 1314. ${\hspace{5mm}}$ (ii). 174.  I thought of using the General Principle of Inclusion and Exclusion along with letting $p_i$ denote a property that.. , and doing so, I will evaluate $E(0)$, which gives us the number of arrangements without any of the properties.   How do I go about doing that? I am trying to use the method stated above in solving this question, but I am unable to generalize the properties $p_i$.


Command used:  sudo gedit /var/www/html/testphp.php Failed to register: Timeout was reached

I have ubuntu 12.04 running in a virtual machine on virtual box.  Its existence is mainly as a 'toy' to play about with Ubuntu, so for this reason I wanted the GUI (is that what 'Dash' is in ubuntu 12.04?  Anyway...)  One thing I am currently using this machine for is a LAMP server.     I use 'gedit' to edit my files, but because I haven't correctly set permissions yet I just open it with sudo in terminal.  Just now, to try to simplify this process I created a shell script on the desktop with a very simple job - sudo gedit  I can't help thinking there must be an even more obvious way to open gedit as root from the GUI than this.  So is there?  Edit:  I just 'improved' my script by replacing sudo with gksudo.  Now I don't have to have a terminal window open while gedit is open.   So I guess this is quite convenient for now :)   It would be good, for the sake of knowledge, to know if this is anything close to how the more seasoned ubuntu users would do this type of thing.


How to prove there are no sets $x,y$ such that $x\in y$ and $y\in x$ according to axioms of $\mathsf{ZFC}$?

From axiom of regularity, how can I prove following statement? $$x \notin y \lor y \notin x$$  I’ve been reading about ZF theory.  So far, I understood the axiom of regularity as follows:  $$\forall x (x \neq \phi \Rightarrow  \exists z. z \in x \land z \cap x = \phi)$$  From this, (and with other axioms in ZF), I should be able to derive the first statement, but have not managed to do so.  Question:   How can I derive the statement within ZF?


I am currently following . The recommended solution implements the ordered solution i.e. if you have A, B then combinations are A, B, AB.  Nevertheless, I would like to include any possible ordering of elements i.e. A, B, BA, AB. Is there any way to do that in Python?  Thank you.

I have a list with 15 numbers in, and I need to write some code that produces all 32,768 combinations of those numbers.   I've found  (by Googling) that apparently does what I'm looking for, but I found the code fairly opaque and am wary of using it. Plus I have a feeling there must be a more elegant solution.  The only thing that occurs to me would be to just loop through the decimal integers 1–32768 and convert those to binary, and use the binary representation as a filter to pick out the appropriate numbers.   Does anyone know of a better way? Using map(), maybe?


I'm writing a realively normal document. I just adjusted it to print it double sided. Now a few pages have weird placement of text and images. Notice that the text should be directly under the section header and the image directly below it.   The source for the page:  \subsection{Cartridge} The newly designed cartridge is half the height of proof of concept's cartridge while holding the same amount of plastic tube. The force needed to pull the plastic out of the cartridge is the same, as described in chapter \ref{subsec:des2_cart}. The difference between size is shown in figure \ref{fig:cartimprove}. The cartridge does not damage the plastic bag. The cartridge is found to be easy to replace thanks to the sliding the mechanism, although it is advised to test this mechanism with other test subjects. It should, however, be noted that there is quite some space needed between to cartridge and the sealer mechanism to get the cartridge out. This space is needed because the opening between the seal beams is too small for the cartridge to pass through. So to get the cartridge out you will need to tilt it quite a bit. Figure \ref{fig:carttilt} visualizes this.\\  \begin{figure}[H]     \begin{center}         \includegraphics[width=0.8\textwidth]{img/cartimprove.PNG}         \caption{Size reduction of new cartridge}         \label{fig:cartimprove}     \end{center} \end{figure}   and my preamble:  \documentclass[12pt, twoside, openright, titlepage]{article} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \renewcommand{\familydefault}{\sfdefault}   \usepackage[margin=2cm, twoside]{geometry} \usepackage{amsfonts, amsmath, amssymb} \usepackage[none]{hyphenat} \usepackage{fancyhdr} \pagestyle{fancy} \usepackage{float}  \usepackage{multicol}  \usepackage{siunitx}  \usepackage{pdfpages} \usepackage{pdflscape}  % References % \usepackage{hyperref} \usepackage[ backend=biber, citestyle=numeric, sorting=none, hyperref=true ]{biblatex} \addbibresource{ref.bib}  % Images %  \usepackage{graphicx} \usepackage{caption} \usepackage{subcaption} \usepackage{wrapfig}  % pro and cons lists* \newcommand*\MyPitem{% \item[\textbf{\color{green}\scalebox{1}{+}}]} \newcommand*\MyCitem{% \item[\textbf{\color{red}\scalebox{1.1}{-}}]}  % Page layout%  \fancyhead{} \fancyfoot{} \fancyhead[RO, LE]{\slshape title} \fancyhead[LO, RE]{\slshape name} \fancyfoot[LE, RO]{\thepage} \renewcommand{\footrulewidth}{0pt}  \parindent 0ex \usepackage{tikz,amsmath, amssymb,bm,color} \usetikzlibrary{calc,patterns,decorations.pathmorphing,decorations.markings,shapes,arrows} % needed for BB \usetikzlibrary{calc}  \begin{document} \includepdf[fitpaper=false, pages=-, noautoscale=true]{inc/frontpage.pdf}  \cleardoublepage

I'm writing a latex document which contains a table. This table is doesn't fit the actual page so it's placed in the next page.  The problem is that vertical spaces are added automatically in the previous page in order to fill the page and I want to avoid that from happening.  I use H in order to add the table figure.


I was absolutely happy and also surprised, when I could see that after reaching 200 reputation points, I got +100 reputation for every sub-account. It's a very kind decision.  It also means that if someone reaches 200 reputation, you trust him so strongly that you clear most of the beginner's limits for them.   However, is 200 reputation enough for you to trust someone that strongly? Isn't it a bit few?

The number of upvotes for a question is a flawed measure of question quality, one particular issue is that the amount of exposure a question gets matters a lot. Questions that were linked in the hot questions list tend to get an enormous amount of votes, much more than any questions gets organically on the site itself.  The kind of question that tend to get to the top spot of the hot questions list tend to be simpler, less technical questions with an appeal to a broader audience. The hot questions list distorts the voting even beyond the mere effect the increased views have. It exposes the question to users that might be interested in reading about that topic, but are not active users on the site and wouldn't have seen and voted on the post otherwise.  I think this distortion of voting is harmful, as the result might not be representative of the community of that specific site. For example, while I might enjoy reading some answers on Security.SE, I'm by far not qualified to actually evaluate them. If I voted there, my votes would not provide any actual value as I can only judge the answers in a very superficial way. Another example would be Skeptics where the community requires answers to cite references supporting their claim. This works very well and the community also votes that way, but the moment a question hits the hot questions list, voting becomes unreliable and answer not meeting our standard are upvoted anyway.  I think that this interaction between the hot questions feature and the low barrier to voting on sites where one didn't earn any reputation at all leads to a distortion of voting and dilutes the usefulness of post scores.   My proposal would be to not count the association bonus for the voting privilege. This means that in order to vote a user would have to get at least one upvote on an answer, two upvotes on a question or five accepted suggested edits. I think that this barrier is low enough to barely inconvenience anyone with a serious interest in the site, and significant enough to prevent drive-by voting by non-experts from the greater SE network.


In the last scene of Return of the Jedi, Princess Leia tells Luke that she remembers their mother, and she says, "She was so beautiful and kind but always sad". This statement looks like she have spent good enough time to observe her behaviour.  But in Revenge of the Sith, we see that their mother dies while giving birth to both of them.   So how did Princess Leia remembered anything about her mother?

In Return of the Jedi, Luke asks Leia if she has any memories of her real mother.     Luke: Leia, do you remember your mother, your real mother?      Leia: Just a little bit. She died when I was very young.      Luke: What do you remember?      Leia: Just images really, feelings.      Luke: Tell me.      Leia: She was, very beautiful, kind, but sad. Why are you asking me this?      Luke: I have no memory of my mother. I never knew her.   How is this possible? In Episode III, Padme dies soon after giving birth to Luke and Leia. Would this be considered a plot-hole?


Is there a way to this simple equation? I'm getting as a product result : 858.2999999999999682365192655  the simple equation is this:  from decimal import Decimal   x = Decimal(57220) * Decimal(0.03)  y = x / Decimal(2)  print(y)   The expected answer should be 858.30 Also tried this but it rounds this off to 858.00     x = Decimal(57220) * Decimal(0.03)   y = x / Decimal(2)   z = round(y, 2)   print(z)   I'm really sorry I'm just a beginner here in python  BTW I'm using 3.6 version of python  Edited : I'm sorry it should be 57220 :(

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


The following series converges when $|x| < 1$:  \begin{align*}    \sum\limits_{n=1}^\infty n x^n \\ \end{align*}  Show that it converges to:  \begin{align*}      \frac{x}{(1-x)^2} \\ \end{align*}

How can I evaluate $$\sum_{n=1}^\infty\frac{2n}{3^{n+1}}$$? I know the answer thanks to , but I'm more concerned with how I can derive that answer. It cites tests to prove that it is convergent, but my class has never learned these before. So I feel that there must be a simpler method.  In general, how can I evaluate $$\sum_{n=0}^\infty (n+1)x^n?$$


Let $G$ be a group. Let $t$ be the no. of subgroups of $G$ which are not normal. Prove that $t\neq 1$.  My Work:  Case 1: $G$ is abelian. Then all subgroups are normal. Hence, $t=0$  Case 2: $G$ is non abelian. Assume $t=1$. Then there is a subgroup $H$ which is not normal in $G$. Then if there is another subgroup $K$ such that $K\neq H,G,\{0\}$ then $K\triangleleft G$. Then I was going to get a contradiction using 2nd isomorphism theorem. But how can I prove the existence of such $K$? I am stuck now. Can anyone please help me?

Let $G$ be a group. Let $n$ be the number of subgroups of $G$ that are not normal. Prove that $n\not=1$.     When $G$ is Abelian, then this is trivial since $n=0$. For the non-Abelian group $G$, I have to show that $n\geq 2$. But I don't see how to go on. Any hint?


I am writing a paper with ieeeconf style. Now I added an lstlisting but the numbering is slighty off the normal text-region. You can see it here:    Can someone help me to fix this?  Code:

I'm trying to add sample code to my document. It seems that the listing is left aligned with the margin, and the numbers go outside it. How should I align the number, instead of the code? Here is my latex code:  \documentclass[a4paper,10pt]{article} \usepackage[utf8x]{inputenc} \usepackage{listings}  %opening \title{} \author{}  \begin{document} Some dummy text. Some dummy text. Some dummy text. Some dummy text. \begin{figure} \begin{minipage}[b]{0.4\linewidth} \begin{lstlisting}[language=C, %frame=single, basicstyle=\footnotesize\ttfamily, numbers=left,stepnumber=1, morekeywords={assert} ] void test(int x, int y){   if(x > 5){     x++;     if (x < 3)        x--;     else        y = x;   }   assert (x < 10 ); } \end{lstlisting} \caption{A simple example} \end{minipage}  %another minipage goes here  \end{figure}  \end{document}   Thank you.