T &amp;ref = obj; T *const ptr = &amp;obj;   Is there any difference between these two declarations in C++ in terms of behavior?  I know that first one is called reference (whose members are accessed through dot (.) operator) and second one is called a pointer (whose members are access through arrow (->) operator).   But, if we consider their behavior, they both points to obj and will not be able to point to any object other than the one they are initialized with. We can modify the content of obj using both of them.  If both are same, which one is good for better coding style.
I know references are syntactic sugar, so code is easier to read and write. But what is the difference between a pointer variable and a reference variable?
When I launch certain programs from the command line like eclipse and document viewer in 11.10 it spews a load of information that seems inconsequential.   Also when they are run in the background they sometimes continue to produce output to the terminal which I am currently working on, which is irritating.  I would like them just launch and keep the background stuff in the background. My reasoning is that if you launch these programs through the GUI (eg double clicking on an icon) these messages are never shown to me, so I don't need them in the command line. I wanted to align a set of equations to left. I found on the Internet that you can do it easily with align* environment.   I found it here:   So I did it:  \begin{align*}  f(b)-f(a)=&amp;f((b_1,b_2,\dots,b_k))-f((a_1,a_2,\dots,a_k))=\ &amp;=\sum_{i=1}^{k}[f((a_1,\dots,a_{i-1},b_i,\dots, b_k))-f((a_1,\dots,a_i,b_{i+1},\dots, b_k))  \end{align*}   Unfortunately, I got bunch of red errors saying that there are missing $s. Why? Doesn't that align* environment provide a math environment already? Video editing software options? What video editing software would you recommend on Ubuntu (or Linux in general) and why?  It can be for either beginners or experienced users.  Please only place one piece of software per response and include details to what makes it great! Well, just another idea came up into my mind and i have no idea how to solve it :D Is there infinitely many prime numbers, which are not repunits and their inverse is also prime? (For example, inverse of 31 is 13 which is also prime. i didn't have any other name to describe the function!) P.S:I now know they are called s. Any way to find out what US Customs & Border Protection has in their database on me? I travel from the US to Canada occasionally (about once per year on average) with my family. We are all US citizens and travel with US passports. Every time we re-enter the United States, I am given extra scrutiny.  Most recently, we used an automated check-in procedure at the airport. These are terminals where you scan your passport &amp; fill out a customs declaration online and it prints a receipt which you take to the customs agent. When I got my receipt, it had a big "X" printed on it and we were directed to a line to talk to an agent.  In the past, I've had questions directed at me or my family: "Have you ever been to New York?", "Do you own any firearms?", and once "Where is your daddy?" directed at my then 4 year old son. The agents also seem to examine my photo &amp; my face more closely than the other members of my family.  We get through customs OK, but it gives me a some anxiety. I suspect that there's someone out there with the same name (I have a pretty common name) who is on a "no fly" list or something.  My question is this: is there any way to find out what they're looking for when they scan my passport &amp; see my name? Like a Freedom of Information request or something? I know I could/should ask when I'm in the line, but as I said, it makes me pretty anxious. Is Object constructor called when creating an array in Java? In Java, an array IS AN Object. My question is... is an Object constructor called when new arrays is being created? We would like to use this fact to instrument Object constructor with some extra bytecode which checks length of array being constructed. Would that work? How did the transdimensional Edo god (Edo lord) come to be the overseer of the Edo? TestMethod do not support Web service callouts, test skipped I've been trying to understand $\sigma$-algebras and how it encodes information in context of filtration. While certain parts seem clear and logical, I can't say I get the whole picture.  I'll try to explain the counter-intuition I get with the classical example of : the probability space $\Omega = \{ HH, HT, TH, TT \}$ and a r.v. $X(\omega)$ equal to the number of heads.  At times $0$, $1$ and $2$ the available information is represented using $\sigma$-algebras $\mathcal{F}_0=\{\emptyset,\Omega\}$, $\mathcal{F}_1=\{\emptyset, \Omega, \{HH,HT\},\{TH,TT\}\}$ and $\mathcal{F}_2=\{\emptyset, \Omega,\{HH,HT\},\{TH,TT\},\{HH\},\{HT\},\{TH\},\{TT\}\}$.  One can notice that $X(\omega)$ is not measurable with respect to $\mathcal{F}_0$ and $\mathcal{F}_1$, because $X^{-1}((\frac{3}{2}; +\infty))=\{HH\}$. To me it is quite surprising: intuitively $X$ makes perfect sense at all times. In particular it has an expected value at time $0$, which I interpret as that the probability and value of all outcomes $\{\omega\}$ can be computed. How do you think of a non-measurable function?  Here's another way of expressing the same confusion. The most natural choice of $\sigma$-algebra in a finite discrete case is $\mathcal{F}=2^\Omega$, and it is implicitly used in all elementary probability problems. However, this choice of $\mathcal{F}$ does not reflect the fact that some information is known or unknown, conditional probability does. Does it mean that the statement "$\sigma$-algebra is known information" make sense only in conditioning? Why is it convenient then? Understanding Bash's Read-a-File Command Substitution I am trying to understand how exactly Bash treats the following line:  $(&lt; "$FILE")   According to the Bash man page, this is equivalent to:  $(cat "$FILE")   and I can follow the line of reasoning for this second line. Bash performs variable expansion on $FILE, enters command substitution, passes the value of $FILE to cat, cat outputs the contents of $FILE to standard output, command substitution finishes by replacing the entire line with the standard output resulting from the command inside, and Bash attempts to execute it like a simple command.  However, for the first line I mentioned above, I understand it as: Bash performs variable substitution on $FILE, Bash opens $FILE for reading on standard input, somehow standard input is copied to standard output, command substitution finishes, and Bash attempts to execute the resulting standard output.  Can someone please explain to me how the contents of $FILE goes from stdin to stdout? Best way to compare 2 XML documents in Java I'm trying to write an automated test of an application that basically translates a custom message format into an XML message and sends it out the other end.  I've got a good set of input/output message pairs so all I need to do is send the input messages in and listen for the XML message to come out the other end.  When it comes time to compare the actual output to the expected output I'm running into some problems.  My first thought was just to do string comparisons on the expected and actual messages.  This doens't work very well because the example data we have isn't always formatted consistently and there are often times different aliases used for the XML namespace (and sometimes namespaces aren't used at all.)  I know I can parse both strings and then walk through each element and compare them myself and this wouldn't be too difficult to do, but I get the feeling there's a better way or a library I could leverage.   So, boiled down, the question is:  Given two Java Strings which both contain valid XML how would you go about determining if they are semantically equivalent?  Bonus points if you have a way to determine what the differences are. Salesforce Internal Server - What's in a GACK? Background  I have been working with Salesforce Support for several weeks now trying to get them to escalate an internal server error with GACK 2134764861-123797 (1611479512) (1611479512). After a long period of waiting I was told that in order to escalate quickly they needed to reproduce the issue in a controlled way. This was again taking them a considerable amount of time so I created a reduced test case myself () that concisely reproduces the issue with a very small amount of code. I was told that this wasn't a valid reproduction because it caused a different GACK (1291518605-518052 (1659192199) (1659192199)) despite reproducing the exact same user experience.  My Question  What makes up a GACK? Is there any information that I can take from their structure that can give me clues on which errors are related without access to the full back-end tools that Salesforce Support uses? It is not infrequent that without premier support it takes me upwards of two weeks to escalate platform bugs and I am hoping that I can somehow use the information from the GACK to reduce this time. Proving the sum of two independent Cauchy Random Variables is Cauchy Is there any method to show that the sum of two independent Cauchy random variables is Cauchy? I know that it can be derived using Characteristic Functions, but the point is, I have not yet learnt Characteristic Functions. I do not know anything about Complex Analysis, Residue Theorem, etc.   I would want to prove the statement only using Real Calculus. Feel free to use Double Integrals if you please.   On searching, I found . However, I was wondering if I could get some help directly on the convolution formula:  $$f_Z(z)=\int_{-\infty}^\infty f_X(x)f_Y(z-x)\,dx=\int_{-\infty}^\infty\frac{1}{\pi^2}.\frac{1}{1+x^2}.\frac{1}{1+(z-x)^2}dx\tag{1}$$  Here I have supposed that $X,Y$ are Independent Standard Cauchy. But I think the general formula can be derived easily after some substitutions. I need some help on how to proceed from $(1)$.  EDIT: Just as what the hint in the hyperlink said, I got the answer using that hint. However, I am not quite sure that the hint is algebraically correct. Maybe there has been some typing mistake in the book. Can't login with Google on recently released iPhones and iPads I just switched from an iPhone 7 to an iPhone XR (both are on latest iOS version available).  When I try to login into the Stack Exchange app with my Google account it says:     Request failed   Could not perform this request with your account. Please try logging   back in. If this persist, let us know on meta.   this happens consistently.  I have 2FA enabled on my Google account if it matters.  Is this a known bug? What's wrong with this argument that $[0,1]$ is countable? How to install XAMPP? Meaning of $\int\mathop{}\!\mathrm{d}^4x$ What the following formula mean?  $$\int\mathop{}\!\mathrm{d}^4x$$  I know that this $\int f(x)\mathop{}\!\mathrm{d}x$ is the integral of the function $f$ over the $x$ variable, but the following $\int\mathop{}\!\mathrm{d}^4x$ leave empty the argument and also have the $\mathrm{d}$ elevated to the fourth power. What that mean?  Update.  In the Einstein-Hilbert action we have (note that I have understand that the other parts of the integral are relevant only after your answers, thus sorry.):  $$S=\frac{c^4}{16\pi G}\int\mathop{}\!\mathrm{d}^4x \, \ R \sqrt{-g}$$ Usage of "second/third/fourth ... last" In German there is a pattern for counting items from the end of a list. The last item is "das letzte", the one before is "das vorletzte", the one before that is "das vorvorletzte" and for each other item there's just another "vor" added.  While searching for an English translation for the German word "vorvorvorletzte" I came across   and  but none of them showed any usage pattern. Furthermore I didn't find any indication of which variant ("to", "from", no preposition) is used most nor to what area of the world those translations apply.  So I am still wondering: When there are items 1, 2, 3, 4 and 5, how can/will item 2 be called?   third from last? fourth from last? anteantepenultimate? fourth-last? fourth to last? the last but three item? the last but four item?   Is this a question of dialect/local use? What happens if I beat Ganon in Zelda: Breath of the Wild? I'm close to maxing out my character and I want to beat Ganon solely for the TRUE ending, but I'm too scared of losing some of my personal favorites from the Guardian Spear++ to fighting those damned Guardians (it was so fun).  So, after beating Ganon    Do monsters disappear? - Including the corrupted Guardians, but also the blood moons, I don't want to just face off against the Yiga Clan... Am I gonna run out of resources? - As a survival game Zelda BOTW has some emphasis on the survival genre but to me it is a survival-esque action-adventure game. Are special weapons still available when you max out? - Like the Savage Lynel Spears or Swords) I'm trying to show that the group $U(Z_{54})$ is cyclic.  To start, I found the divisors of 54 = {1, 2, 3, 6, 9, 18, 27, 54}  Then I started to find the elements using the powers of a.  Where $U(Z_{54})= &lt;a&gt;$  Therefore, $&lt;a^{54/1}&gt;$={ e }  $ &lt;a^{54/2}&gt;$= { e, $ a^{36}$ }  and such, where the last would be &lt; $a^{54/54}$> = { e }  The things I would like to know is, how does this process show that it's cyclic? Is it because the first divisor (1) and the last divisor (54) is equal to e? Therefore creating a cycle?  Also, what would the &lt; a > to the powers finding the elements process be called?  Thank you!