When do you omit a/an? - "Choose Suspect" I was looking at an Android app, there are two buttons with these names: "Choose Suspect" and "Send Crime Report." After I thought about it, there are bunch of places where 'a/an' are omitted and they look just fine.  So, when is it safe to omit a/an? What's the mental model?  I checked  with similar title - "When do you omit a, an or the?" - which deals with omitting articles after 'of.'
In which situations is it OK to omit articles in short sentences? Recently, in many new online software I often see that developers omit articles in short sentences, especially on action buttons or tooltips.     For instance: "Add new task" (not "Add a new task"), "Create project" (not "Create a project"), but often in the same software I can see "Make a copy". What are situations it can be justified?
I updated a virtual machine running Ubuntu server 15.04 to the just released new stable 15.10.  There were no apparent problems, but after reboot the machine lost its network connection. lspci showed the correct card and lsmod proved that the driver had been loaded.  Hints about editing or removing /etc/udev/rules.d/70-persistent-net.rules did not succeed (still no network, no new file), the famous /lib/udev/write_net_rules did not even exist.  I don't have much clue regarding udev and systemd, so it took me some time to find in /sys/class/net that the network interface name changed. It became ens32, which was renamed from eth0. After I changed /etc/network/interfaces network communication was enabled again.  But - why does this happen at all? And if it happens, shouldn't the interfaces file be updated automatically?  Now that I deleted the virtual network card and created another one, eth0 becomes eno16777728, which is not so, uhm, nice.  Should this behaviour (at least that of the upgrade procedure) be reported as a bug?  Furthermore, is /etc/udev/rules.d/70-persistent-net.rules obsolete now? And (although only partly related) what about /etc/udev/rules.d/70-persistent-cd.rules?)  Edit - additional question (after accepted answer) The dependency of /etc/network/interfaces from the actual interface name bothered me. I tried a new installation of *ubuntu in another virtual machine. To my surprise, /etc/network/interfaces contained a reference to the loopback device only. However, with my original VM this change prevented the network to come up. So what else do I need to change?  Edit Well, from another test I found that a new Ubuntu Server has the network interface card in /etc/network/interfaces, while XUbuntu has not. Maybe it is using network-manager or something else. Proof by induction that $\sum_{i=1}^n \frac{i}{(i+1)!}=1- \frac{1}{(n+1)!}$ Prove via induction that $\sum_{i=1}^n \frac{i}{(i+1)!}=1- \frac{1}{(n+1)!}$ Having a very difficult time with this proof, have done pages of work but I keep ending up with 1/(k+2).  Not sure when to apply the induction hypothesis and how to get the result $1- \frac{1}{(n+2)!}$.  Please help! thanks guys, youre the greatest! Prove that if $g^2=e$ for all $g$ in $G$ then $G$ is Abelian. I recently bought  white LED reading lamp. I like it a lot, but the "white" light produced is significantly blue; I'll guess its  is about 5000K.  I've noticed that, when this is the only source of light, printed text appears slightly fuzzy, and is more difficult to read than with a standard incandescent reading lamp. My guess is that this is  causing color fringing in my eyes, making it harder to read with this new lamp.  Is there a way to make this lamp less blue using some sort of transparent/translucent filter over the lens? This could filter out some of the blue end of the spectrum, or include a  to convert some of the blue to yellow (as  do). The fluorescence idea would be better, as there'd be less light lost. I don't want to go too far, though; a strongly yellow lamp might be worse for reading than this currently blueish lamp. Sum of real numbers that multiply to 1 I've seen a question in my math book with this explanation above it: "If the product of n positive real numbers is 1, then the sum of these numbers must be more than n". I was wondering if this is correct, and if it is, could someone give an explanation or a proof for it? How can we remove the launcher that come with Unity on this new Ubuntu version ? How do I install iTunes on Ubuntu? I've tried different ways to install iTunes, but to no avail. I tried with Wine, but it didn't work. Is it possible to have iTunes on Ubuntu? Show JDBC ResultSet in HTML in JSP page using MVC and DAO pattern What is the pythonic way to avoid default parameters that are empty lists? Sometimes it seems natural to have a default parameter which is an empty list. Yet . If for example, I have a function: def my_func(working_list=[]):     working_list.append(&quot;a&quot;)     print(working_list)  The first time it is called the default will work, but calls after that will update the existing list (with one &quot;a&quot; each call) and print the updated version. So, what is the pythonic way to get the behavior I desire (a fresh list on each call)? What canonical momenta are the "right" ones? I'm doing some classical field theory exercises with the Lagrangian $$\mathscr{L} = -\frac{1}{4}F_{\mu \nu}F^{\mu \nu}$$ where $F_{\mu \nu} = \partial_\mu A_\nu - \partial_\nu A_\mu$. To find the conjugate momenta $\pi^\mu_{\ \ \ \nu} = \partial \mathscr{L} / \partial(\partial_\mu A^\nu)$, I can use two methods.  First method: directly apply this to $\mathscr{L}$. We get a a factor of $2$ since there are two $F$'s, and another factor of $2$ since each $F$ contains two $\partial_\mu A_\nu$ terms, giving $$\pi^\mu_{\ \ \ \nu} = -F^\mu_{\ \ \ \nu}.$$  Second method: get $\mathscr{L}$ in terms of $A$ by expanding and integrating by parts, yielding $$\mathscr{L} = \frac{1}{2}(\partial_\mu A^\mu)^2 - \frac{1}{2}(\partial_\mu A^\nu)^2.$$ Differentiating this gets factors of $2$ and gives $$\pi^\mu_{\ \ \ \nu} = \partial_\rho A^\rho \delta^\mu_\nu - \partial^\mu A_\nu.$$  These two answers are different! (They do give the same equations of motion, at least.) I guess that means doing the integration by parts changed the canonical momenta.  Is this something I should be worried about? In particular, I have another exercise that wants me to show that one of the canonical momenta vanishes -- this isn't true for the ones I get from the second method! Plus, my stress-energy tensor is changed too. When a problem asks for "the" canonical momenta, am I forbidden from integrating by parts? Pass values from parent to child component on click lightning I have this below code where i am trying to first search an account name and on hit button it displays the result set.  On the button click i am also loading an child component which is displaying the id of the record.  I need the child component should get displayed once i click on the record.  How can i achieve this -   Parent Component -   &lt;aura:component controller="SimpleAccountController"&gt;     &lt;aura:attribute name="account" type="account[]"/&gt;     &lt;ui:outputText aura:id="outName" value="" class="text"/&gt;     &lt;ui:inputText aura:id="name" label="Enter Name:" placeholder="Your Name" /&gt;     &lt;ui:button aura:id="button" buttonTitle="Click to see what you put into the field" class="button" label="Click me" press="{!c.getInput}"/&gt;     &lt;aura:iteration var="acc" items="{!v.account}"&gt;             &lt;a onclick="{!c.accountselected}" data-recId="{!acc.Id}"&gt;         &lt;p&gt;{!acc.Name} : {!acc.Type} : {!acc.Industry} : {!acc.Rating}&lt;/p&gt;             &lt;/a&gt;         &lt;c:HelloWorkdChildCmp selectedaccount="{!acc.Id}" /&gt;     &lt;/aura:iteration&gt; &lt;/aura:component&gt;   COntroller -   ({     getInput : function(cmp, evt) {         var myName = cmp.find("name").get("v.value");         var myText = cmp.find("outName");         var greet = "Hi, " + myName;         myText.set("v.value", greet);         var action = cmp.get("c.seaAcc");         action.setParams({ "s" : myName });         action.setCallback(this, function(response) {             var state = response.getState();             if (state === "SUCCESS") {                 cmp.set("v.account", response.getReturnValue());                 //alert("From server: " + response.getReturnValue());             }         });         $A.enqueueAction(action);     },      accountselected : function(cmp, evt) {        console.log(evt.currentTarget.getAttribute("data-recId")) ;     }  })   Child component -   &lt;aura:component &gt;     &lt;aura:attribute name="selectedaccount" type="String"/&gt;     &lt;div&gt;Id: {!v.selectedaccount}&lt;/div&gt; &lt;/aura:component&gt; I basically need to highlight a particular word in a block of text. For example, pretend I wanted to highlight the word &quot;dolor&quot; in this text: &lt;p&gt;     Lorem ipsum dolor sit amet, consectetuer adipiscing elit. &lt;/p&gt; &lt;p&gt;     Quisque bibendum sem ut lacus. Integer dolor ullamcorper libero.     Aliquam rhoncus eros at augue. Suspendisse vitae mauris. &lt;/p&gt;  How do I convert the above to something like this: &lt;p&gt;     Lorem ipsum &lt;span class=&quot;myClass&quot;&gt;dolor&lt;/span&gt; sit amet, consectetuer adipiscing elit. &lt;/p&gt; &lt;p&gt;     Quisque bibendum sem ut lacus. Integer &lt;span class=&quot;myClass&quot;&gt;dolor&lt;/span&gt; ullamcorper     libero. Aliquam rhoncus eros at augue. Suspendisse vitae mauris. &lt;/p&gt;  Is this possible with jQuery? Edit: As  , this is quite possible without jQuery - but I was hoping there might be a special method of jQuery which would let you do selectors on the text itself. I'm already using jQuery heavily on this site, so keeping everything wrapped up in jQuery would make things perhaps a bit more tidy. The no. of all possible matrices of order $3\times 3$ with each entry $0$ and $1$ and $ -1$. The product of all the elements of a finite abelian group I'm trying to prove the following statements.  Let $G$ be a finite abelian group $G = \{a_{1}, a_{2}, ..., a_{n}\}$.   If there is no element $x \neq e$ in $G$ such that $x = x^{-1}$, then $a_{1}a_{2} \cdot \cdot \cdot a_{n} = e$.   Since the only element in $G$ that is an inverse of itself is the identity element $e$, for every other element $k$, it must have an inverse $a_{k}^{-1} = a_{j}$ where $k \neq j$. Thus $a_{1}a_{1}^{-1}a_{2}a_{2}^{-1} \cdot \cdot \cdot a_{n}a_{n}^{-1} = e$.   If there is exactly one $x \neq e$ in $G$ such that $x = x^{-1}$, then $a_{1}a_{2} \cdot \cdot \cdot a_{n} = x$.   This is stating that $x$ is not the identity element but is its own inverse. Then every other element $p$ must also have an inverse $a_{p}^{-1} = a_{w}$ where $p \neq w$. Similarly to the first question, a rearrangement can be done: $a_{1}a_{1}^{-1}a_{2}a_{2}^{-1} \cdot \cdot \cdot xx^{-1} \cdot \cdot \cdot  a_{n}a_{n}^{-1} = xx^{-1} = e$. And this is where I am stuck since I proved another statement.    Any comments would be appreciated for both problems. How can I rotate about an arbitrary point in 3D (instead of the origin)? I have some models that I want to rotate using quaternions in the normal manner, except instead of rotation about the origin, I want it to be offset slightly. I know that you don't say, in 3d space, that you rotate about a point; you say you rotate about an axis. So I'm visualizing it as rotating about a vector whose tail is positioned not at the local origin.  All affine transformations in my rendering / physics engine are stored using SQT (scale, quaternion, translation; an idea borrowed from the book Game Engine Architecture.) So I build a matrix each frame from these components and pass it to the vertex shader. In this system, translation is applied, then scale, then rotation.  In one specific case, I need to translate an object in world space, scale it, and rotate it about a vertex not centered at the object's local origin.  Question: Given the constraints of my current system described above, how can I achieve a local rotation centered about a point other than the origin? Automatic upvote to anyone who can describe how to do this using only matrices as well :) Django set default form values I have a Model as follows:  class TankJournal(models.Model):     user = models.ForeignKey(User)     tank = models.ForeignKey(TankProfile)     ts = models.IntegerField(max_length=15)     title = models.CharField(max_length=50)     body = models.TextField()   I also have a model form for the above model as follows:  class JournalForm(ModelForm):     tank = forms.IntegerField(widget=forms.HiddenInput())       class Meta:         model = TankJournal         exclude = ('user','ts')   I want to know how to set the default value for that tank hidden field. Here is my function to show/save the form so far:  def addJournal(request, id=0):     if not request.user.is_authenticated():         return HttpResponseRedirect('/')      # checking if they own the tank     from django.contrib.auth.models import User     user = User.objects.get(pk=request.session['id'])      if request.method == 'POST':         form = JournalForm(request.POST)         if form.is_valid():             obj = form.save(commit=False)              # setting the user and ts             from time import time             obj.ts = int(time())             obj.user = user              obj.tank = TankProfile.objects.get(pk=form.cleaned_data['tank_id'])              # saving the test             obj.save()      else:         form = JournalForm()      try:         tank = TankProfile.objects.get(user=user, id=id)     except TankProfile.DoesNotExist:         return HttpResponseRedirect('/error/') Use of "Proper" as a postpositive adjective I have an inkling that the following word usage is grammatically-correct; however, it is immensely difficult to search for confirmation, as all I receive for queries like &quot;Proper as an adjective&quot; are reams of results on &quot;Proper adjectives&quot;. The word itself I am using as a postpositive adjective, similar in form to the phrase &quot;time immemorial&quot;.  The shelter remains in name only; the shelter proper is in another town. Work in theory remained, although operations proper had mostly been outsourced.  Can anyone advise? Can Mystique create objects? Let $A,B \in \mathbb{M}_n (\mathbb{C})$. If $A^2B + BA^2 = 2ABA$ then exist $k \in \mathbb{N}$ where $(AB-BA)^k = 0$.  I tried solve with minimal polynomial, but I did not have much effect. In the following figure prove that: $AK||BC$ In arbitrary triangle $ABC$, let $G$ be centroid and $AH$ be a height.We extend $HG$ beyond $G$ to intersect circumcircle at $K$.Prove that $AK||BC$       I connected midpoint of $BC$ to $K$ and $A$ to show $MA=MK$ but failed...