The usage of "an"
When should I use "a" vs "an"?
How do I install Netbeans? I used NetBeans for Java development on Windows and remember finding it in the Ubuntu Software Center on Natty, but now it's gone. Is there a PPA I can use or will it be re-added to the official repos? $f:\mathbb R \to \mathbb R$ be a continuous such that $f(f(f(x)))=x,\forall x \in \mathbb R$ , is $f(x)=x , \forall x \in \mathbb R$? Let $f:\mathbb R \to \mathbb R$ be a continuous function such that $f(f(f(x)))=x,\forall x \in \mathbb R$ , then is it true that $f(x)=x , \forall x \in \mathbb R$ ? I can see that $f$ is bijective , hence strictly monotone . But I cannot progress further . Please help. Thanks in advance I have Sanguinare Vampiris. I don't really want to become a vampire. How can I cure myself? Can a polymorphed creature use class features that don't require speech or hand gestures? The Polymorph spell states (in part):     The target’s game statistics, including mental ability scores, are   replaced by the statistics of the chosen beast. It retains its   alignment and personality.      The creature is limited in actions it can perform by the nature of its   new form, and it can’t speak, cast spells, or take any other action   that requires hands, or speech.   So, can a polymorphed Paladin use their Divine Smite class feature?  It expends a spell slot, but it is not a spell, and as far as we can tell does not require hands or speech.  We know (based on the 10th level Transmutation Wizard feature) that a wizard is supposed to be able to polymorph herself, and we can assume that she is also supposed to be able to maintain concentration needed to stay in the new form (otherwise it would be a pretty useless ability).  This is (as far as I can tell) not something any of the beasts eligible as polymorph targets can normally do.  So it is clear that the polymorphed creature maintains some abilities from her old form.  The question is which ones.    The Druid's Wild Shape ability explicitly says you can use class features, while Polymorph does not, suggesting that you can't use class features while polymorphed.  However, Wild Shape also explicitly says that you can continue to concentrate on a spell (see below, emphasis mine), and Polymorph does not, yet we believe that a polymorphed creature can continue to concentrate on the polymorph spell.  So the fact that Wild Shape explicitly allows something and Polymorph is not explicit about it does not necessarily mean that the polymorphed creature cannot do those things.  From Wild Shape rules:     You can't cast spells, and your ability to speak or take any action   that requires hands is limited to the capabilities of your beast form.   Transforming doesn't break your concentration on a spell you've   already cast, however, or prevent you from taking actions that are   part of a spell, such as call lightning, that you've already cast.   So, since Polymorph is silent on the question of whether or not class abilities can be used, and states only that the polymorphed creature cannot perform actions that require hands or speech, how can we best determine whether (RAI) polymorphed creatures maintain any of their old abilities beyond spell concentration? Encode/Decode URLs in C++ Does anyone know of any good C++ code that does this? For $f$ in dual space, there exists $x$ with norm 1 and $f(x)=\|f\|$ if space is reflexive (and nontrivial) Let $X\ne\{0\}$ be a reflexive space and let $f\in X^*$, where $X^*$ is the dual of $X$. I want to know: in general, does there exist an $x\in X$ with $\|x\|=1$, and $f(x)=\|f\|$, where $\|f\|$ is defined as $\sup\{|f(x)|:x\in X,\|x\|=1\}$?  I know this is true for $\mathbb{R}^n$ with the norm from the standard inner product, but I'm wondering if it is true in general. Minimum value of $\left(a+\frac{1}{b}\right)^2+\left(b+\frac{1}{c}\right)^2+\left(c+\frac{1}{a}\right)^2$ Given $a,b,c \in \mathbb{R^+}$ such that $a+b+c=12$   Find Minimum value of $$S=\left(a+\frac{1}{b}\right)^2+\left(b+\frac{1}{c}\right)^2+\left(c+\frac{1}{a}\right)^2$$  My Try: By Cauchy Schwarz Inequality we have  $$\left(a+\frac{1}{b}\right)+\left(b+\frac{1}{c}\right)+\left(c+\frac{1}{a}\right)\le \sqrt{3}\sqrt{S}$$  $\implies$  $$\sqrt{3S} \ge 12+\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$$  Now by $AM \ge HM $ inequality we have  $$\frac{a+b+c}{3} \ge \frac{3}{\frac{1}{a}+\frac{1}{b}+\frac{1}{c}}$$ $\implies$  $$\frac{1}{a}+\frac{1}{b}+\frac{1}{c} \ge \frac{3}{4}$$  hence  $$\sqrt{3S} \ge 12+\frac{3}{4}=\frac{51}{4}$$  hence  $$3S \ge \frac{2601}{16}$$  so $$S \ge \frac{867}{16}$$  is this approach correct and any better approach please share. Just looking for the difference between   2&gt;&amp;- 2&gt;/dev/null |&amp; &amp;&gt;/dev/null &gt;/dev/null 2&gt;&amp;1   and their portability with non-Bourne shells like tcsh, mksh, etc. What are PATH and other environment variables, and how can I set or use them? Questions about    setting environment variables the PATH   are very common here, and in most cases the answers are very similar to each other. In the future it would be nice to have a good Q/A for this.  So the question is: What are environment variables, like the executable PATH, and how can I change and use them on major operating systems?  A good answer would include a simple explanation of what environment variables and especially PATH mean to the OS, as well as simple guidelines on how to set and read them accordingly. the method getApplicationContext() is undefined Is there any way to find out if a file is a directory?  I have the file name in a variable. In Perl I can do this:  if(-d $var) { print "it's a directory\n" } In my native language, we can say:     I have dog   Because I don't want to say a dog (one dog, how many dogs) or the dog (that dog, the listener don't care which dog).  p.s. after 3 years later, I have to say, why I ask this question, is I still cannot grasp how to use the right 'article word'. sometimes, a noun will use an article, sometimes, a noun could not(or omit) the article word before it. there aren't a formula for this. So, I have to remember all the time! I feel so frustrate What is the Mediator in this Feynman Diagram $q\bar{q} \rightarrow gg$? Let's consider the t-channel version of the process $q\bar{q} \rightarrow gg$. What is the mediator in this case, a $q$ or a $\bar{q}$? Naively, I would have thought a $q$ (as to have one fermion line), but I am not $100 \%$ sure. raw_input in python without pressing enter Binary search (bisection) in Python Is there a library function that performs binary search on a list/tuple and return the position of the item if found and 'False' (-1, None, etc.) if not?  I found the functions bisect_left/right in the , but they still return a position even if the item is not in the list. That's perfectly fine for their intended usage, but I just want to know if an item is in the list or not (don't want to insert anything).  I thought of using bisect_left and then checking if the item at that position is equal to what I'm searching, but that seems cumbersome (and I also need to do bounds checking if the number can be larger than the largest number in my list). If there is a nicer method I'd like to know about it.  Edit To clarify what I need this for: I'm aware that a dictionary would be very well suited for this, but I'm trying to keep the memory consumption as low as possible. My intended usage would be a sort of double-way look-up table. I have in the table a list of values and I need to be able to access the values based on their index. And also I want to be able to find the index of a particular value or None if the value is not in the list.  Using a dictionary for this would be the fastest way, but would (approximately) double the memory requirements.  I was asking this question thinking that I may have overlooked something in the Python libraries. It seems I'll have to write my own code, as Moe suggested. Can a full version of Ubuntu be Installed on a USB Drive? Will an iOS reinstall make a jailbroken iOS device "unjailbroken" and “supported by Apple” again? Will an    Work on any jailbroken-iPhone and Make a jailbroken-iPhone "unjailbroken"? Make a jailbroken-iPhone "supported by Apple"?   Similarly, does such an iOS reinstall reset the iPhone (jailbroken or not) back to a "clean, factory default" state?  My near-term purpose: I have an iPhone 4S running iOS 5.1 I'd like to jailbreak to at least install better Google Voice integration like . I've just recently started playing D&amp;D 4e through the Red Box, and I am confused about how to fill in the power cards.  So, take Nimbus of Holy Shielding for instance. I understand the Target and Hit components as well as the effect, but my question is about the Attack component. It reads:     Attack: Wisdom vs Will.   Does the mean whatever my Wisdom score is, without the modifier, is compared to the Will score of the enemy? Would I then not even have to roll a d20 to see if it works? Proof that Pi is constant (the same for all circles), without using limits Turn off buffering in pipe I have a script which calls two commands:  long_running_command | print_progress   The long_running_command prints progress but I'm unhappy with it. I'm using print_progress to make it nicer (namely, I print the progress in a single line).  The problem: Connection a pipe to stdout also activates a 4K buffer, so the nice print program gets nothing ... nothing ... nothing ... a whole lot ... :)  How can I disable the 4K buffer for the long_running_command (no, I do not have the source)?