constant pointer vs pointer on a constant value
What is the difference between char * const and const char *?
Troubleshooting "program does not contain a static 'Main' method" when it clearly does...? Where should I copy-paste-install software to? I'm installing IntelliJ, and the readme tells me to choose an installation folder. Where is a good, standard place to put installed programs? Is there a simple way to convert C++ enum to string? Show that $3p^2=q^2$ implies $3|p$ and $3|q$ This is a problem from "" (specifically, exercise set 2 #9), which is one of my math texts. Please note that this isn't homework, but I would still appreciate hints rather than a complete answer.  The problem reads as follows:     If 3p2 = q2, where $p,q \in \mathbb{Z}$, show that 3 is a common divisor of p and q.   I am able to show that 3 divides q, simply by rearranging for p2 and showing that  $$p^2 \in \mathbb{Z} \Rightarrow q^2/3 \in \mathbb{Z} \Rightarrow 3|q$$  However, I'm not sure how to show that 3 divides p.    Edit:  Moron left a comment below in which I was prompted to apply the solution to this question as a proof of $\sqrt{3}$'s irrationality. Here's what I came up with...  [incorrect solution...]  ...is this correct?  Edit:  The correct solution is provided in the comments below by Bill Dubuque. Just don't show UI for actions that can't be actioned Recently I just deleted one of my answer in stackoverflow where there was one comment. After deleting the answer it also show for sometime that we all know but in the comment it still allow us to up to make it useful but as I clicked it it just showed me the message:  If we are not allowed to do then what was the meaning? Why don't it just be removed or make it disable if the answer is deleted. Just don't show UI for actions that can't be actioned What is the difference between below variables assignments?   var=23 var =23 var= 23 var = 23   Is there any difference in space around the assignment operator? Run VirtualBox in background, without a window? This is my last homework problem and I've been looking at it for a while. I cannot nail down what is wrong with this proof even though its obvious it is wrong based on its conclusion. Here it is:     Find the flaw in the following bogus proof by strong induction that   for all $n \in \Bbb N$, $7n = 0$.      Let $P(n)$ denote the statement that $7n = 0$.      Base case: Show $P(0)$ holds.      Since $7 \cdot 0 = 0$, $P(0)$ holds.      Inductive step: Assume $7·j = 0$ for all natural numbers $j$ where $0 \le j \le k$ (induction hypothesis). Show $P(k + 1)$: $7(k + 1) = 0$.      Write $k + 1 = i + j$, where $i$ and $j$ are natural numbers less than $k + 1$.  Then, using the induction hypothesis, we get $7(k + 1) = 7(i + j) = 7i + 7j = 0 + 0 = 0$. So $P(k + 1)$ holds.      Therefore by strong induction, $P(n)$ holds for all $n \in \Bbb N$.   So the base case is true and I would be surprised if that's where the issue is.  The inductive step is likely where the flaw is. I don't see anything wrong with the strong induction declaration and hypothesis though and the math adds up! I feel like its so obvious that I'm just jumping over it in my head. I would like to convert tab to spaces in gVim. I added the following line to my _vimrc:  set tabstop=2   It works to stop at two spaces but it still looks like one tab key is inserted (I tried to use the h key to count spaces afterwards).  I'm not sure what should I do to make gVim convert tabs to spaces? For an irrational number $\alpha$, prove that the set $\{a+b\alpha: a,b\in \mathbb{Z}\}$ is dense in $\mathbb R$ I am not able to prove that this set is dense in $\mathbb{R}$. Will be pleased if you help in a easiest way. $A=\{a+b\alpha: a,b\in \mathbb{Z}\}$ where $\alpha$ is a fixed irrational number. call function declared below Is it possible to call a function which is declared below in bash?  Example  if [ "$input" = "yes" ]; then     YES_FUNCTION elif [ "$input" = "no" ]; then     NO_FUNCTION else     exit 0; fi  YES_FUNCTION() {   .....   ..... }  NO_FUNCTION() {   .....   ..... } Can I be admitted to graduate school in a different field from my degree?  Specific cases include:   If I've taken plenty of advanced courses in field X in the process of completing a degree in another field, can I apply to graduate school in X? What if I haven't taken many courses in X, but I have acquired a good grasp of X through self-study or working in a related field? What if I've never studied X, but I have done very well in an unrelated field?  Could I be admitted to graduate school in X on the basis of general intellectual promise, and then make up the missing background after enrollment?   Note that this question is an attempt to provide a comprehensive answer, to avoid the need for a profusion of field-specific questions on this topic (see the associated ). Please feel free to edit the question or answer to improve them. Could someone explain to me what the collision of two photons would look like? Will they behave like,   Electromagnetic waves: they will interfere with each other and keep their wave nature Particles: they will bounce like classical balls   I assume that energy of that system is too small to make creation of pairs possible. Interpretation of the rating of a real transformer The rating of a real transformer is 15 kVA , 2300/230-V then can we say that the primary rms is 2300 V or can we say that the secondary rms is 230 V or both.  To clarify further, suppose to solve for certain characteristics of this transformer like primary current and secondary current i use the equivalent circuit equation of the transformer referred to the primary side as:  Vp = aVs + Req*Ip + jXeq*Ip  Then what should i use for Vp or Vs in the above equation looking at the rating of the transformer.  In the above equation looking at the rating data given above is Vp= 2300 or Vs = 230 ?As mentioned earlier the transformer is mentioned to be real. How can I distinguish between words which have the -ing in a sentence that are nouns, verbs, or adjectives?    For example sometimes -ing come with word to give us a noun, and sometimes a verb or an adjective.       That interesting snake.   That crawling snake.   That barking dog keeps everyone awake.     Is there any rule to determine whether a word with -ing is a noun, verb, or adjective? Eigenvectors of real symmetric matrices are orthogonal Crookshanks is Hermione's familiar in PoA, GoF, and OOTP. I cannot recall mention of Crookshanks following OOTP, though. What happened to Crookshanks? Does canon refer to Crookshanks in either HBP or DH? How to make a circular array using offset object as center? We know that the there is an Object Offset option for Array modifier, but when trying to make a circular array with that offset object as the center of the array circle, it always doesn't behave quite like what's expected. So how to make a nice and controllable circular array?  P.S.: There is an old  about moving the object's origin. I wonder if there is any way to do this without changing the location of the origin. :) Create WiFi hotspot on ubuntu Although many questions have already been asked regarding WiFi hotspot, I didn't get any of the solutions working for me.  I connect to the Internet using a 3G Dongle of Huawei 3772 (Vodafone). The connection type is Mobile Broadband connection. I have to share this Internet connection with my other devices like mobile phones and laptops.  How can I create a WiFi hotspot connection for this connection.  I am using Ubuntu 12.04 LTS.  I would like to note that I have already tried some help links from Ubuntu but, they are so confusing that I could not understand them. How to add a loopback interface? I want to add two more loopback interfaces.  I used the following command:  ifconfig lo: 127.0.0.2 netmask 255.0.0.0 up   and type in ifconfig, i can see the loopback address was added.  But if i want to add one more interface... (for example 127.0.0.3) the previous interface (127.0.0.2) was overwritten.  Also when i look in /etc/network/interfaces i see no entry.  How can i add multiple loopback interfaces permanently?