In "The C++ Programming Language (4th Edition)" Section 2.3.1, Stroustrup shows 3 different ways to access members of a struct:  void f(Vector v, Vector&amp; rv, Vector* pv) {     int i1 = v.sz;    // access through name     int i2 = rv.sz;   // access through reference     int i4 = pv-&gt;sz;  // access through pointer }    I understand that for the first one, v is passed-by-value, so a copy of the first argument is put on the function's stack and the value of its size sz is stored inside of i1. In the second example, rv is a reference to the struct passed as the second argument. Because it is a reference, we can access the value referred to by rv without a * prefix.   I'm not too sure I understand what's going on with i4, and why someone would pick the third example over the second (or vice-versa).
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?
Why do we use AC for long distance transmission? Why do we use AC (Alternating Current) for long distance transmission of electrical power?  I know that AC is such a current that changes polarity (magnitude and direction) and has fixed poles. How to do the port forwarding from one ip to another ip in same network? I would like do some NAT in iptables. So that, all the packets coming to 192.168.12.87 and port 80 will be forwarded to 192.168.12.77 port 80.  How to do this with iptables?  Or   Any other ways to achieve the same? I'm still a newbie with Linux but I'm trying to learn. I have two USBs, one is 4GB and has the ISO install of Ubuntu (I think it's called live, the one with maximum of 4GB of permanent storage) and got a 64gb usb to make a permanent full install on it. I installed it following  tutorial and everything looks fine (I had to create the EFI partition with the Terminal though) but it just won't boot, the live install boots without problems.   I'm using the school's computers which have the UEFI menu password protected so I can't access that and I won't have a laptop for like 3 weeks (main reason why I'm doing this). I tested it with a friend's laptop disabling the Secure boot but it still wouldn't boot. I also saw that some tutorials don't add the EFI partition so I tried without that one and still won't work. And I know it's not the 64GB usb not booting because I had a live install on it too before and it booted fine.  Please, I have been trying to make it work for two days now, any ideas? I can barely understand this stuff so if you could explain step by step that would be awesome. How to move the center of scaling Hello. I'm a beginner.  In the model shown, when I select all of the top vertices and then scale them to the center, the center of scaling is not the center of the 3d-model.   How do I move the center of scaling? How do I move the manipulator widget where I want it after selecting? Including all the jars in a directory within the Java classpath Use property to show that if $f_n \rightarrow f$ in measure on finite measure set $E$ then $f_n^2 \rightarrow f^2$ in measure on $E$. Consider the following problem:     Let $E$ have finite measure, $\{f_n\} \rightarrow f$ in measure on $E$ and $g$ be a measurable function on $E$ that is finite almost everywhere. Use the fact that $\{f_n \cdot g\} \rightarrow f_n \cdot g$ to prove that $\{f_n^2 \} \rightarrow f^2$ in measure on $E$. Infer from this that if $\{g_n\} \rightarrow g$ in measure on $E$ then $\{f_n \cdot g_n \} \rightarrow f \cdot g$ in measure on $E$.   I'm struggling understand how I can apply the fact that $\{f_n \cdot g\} \rightarrow f_n \cdot g$ in measure to prove that $\{f_n^2 \} \rightarrow f^2$ in measure. I've been able to come up with a proof of the fact that if $\{g_n\} \rightarrow g$ in measure then $\{f_n \cdot g_n \} \rightarrow f \cdot g$ in measure, and this clearly implies the claim that $\{f_n^2 \} \rightarrow f^2$ in measure. Unfortunately my proof doesn't rely on the fact that $\{f_n \cdot g\} \rightarrow f_n \cdot g$ so it doesn't answer the problem since it explicitly asks us to prove it a certain way.  So far my best attempt to utilize the fact is as follows. Let $\eta &gt; 0$ then by triangle inequality and monotonicity of measure  \begin{align*}     \lim_{n\rightarrow \infty}\mu\left\{ \left|f_n^2 - f^2\right| &gt; \eta \right\} &amp;\leq \lim_{n\rightarrow \infty}\mu \left\{\left|f_n - f\right|\cdot \left|f_n\right| + \left|f_n - f\right| \cdot \left|f\right| &gt; \eta \right\} \\     &amp;\leq \lim_{n\rightarrow \infty}\mu\left\{\left|f_n - f\right|\cdot \left|f_n\right| &gt; \eta/2 \right\} + \lim_{n\rightarrow \infty}\mu\left\{\left|f_n - f\right| \cdot \left|f\right| &gt; \eta/2 \right\} \end{align*}  By the fact that $\{f_n \cdot f\} \rightarrow f \cdot f$ in measure \begin{equation*} \lim_{n\rightarrow \infty}\mu\left\{\left|f_n - f\right| \cdot \left|f\right| &gt; \eta/2 \right\} = \mu\left\{\left|f_n \cdot f - f\cdot f\right| &gt; \eta/2 \right\} = 0. \end{equation*} I don't see how to deal with the other limit without first proving the most general statement $\{f_n \cdot g_n \} \rightarrow f \cdot g$ in measure.   Any help or advice is greatly appreciated. "Speed" of Gravity and Speed of Light Some threads here touching speed of gravity made me think about that. This lead to some questions.    The speed of gravity was not measured until today (at least there are no undebated papers to that effect). It seems common knowledge/belief among physicists that the speed of gravity is the same as the speed of light.    And this is my question: Is that speed of light = speed of gravity a result of GR or is that fed into the theory? Or is there some evidence from other sources than GR for this? Does the same speed imply some deep-lying relation between gravity and electromagnetism? Give us better search-by-score syntax how to calculate $$\int_0^\infty \frac{x^{3}}{e^{x}-1} \; dx$$   Be $q:= e^{z}-1 , p:= z^{3}$ , then $e^{z} = 1 $ if $z= 2\pi n i $, so the residue at 0 is : $$\frac{p(z_{0})}{q&#39;(z_{0})} = 2\pi i n ^{3}$$  problem is that this is not symmetric, so how does one find the definite integral? How can I safely create a nested directory in Python? What is the most elegant way to check if the directory a file is going to be written to exists, and if not, create the directory using Python? Here is what I tried:  import os  file_path = "/my/directory/filename.txt" directory = os.path.dirname(file_path)  try:     os.stat(directory) except:     os.mkdir(directory)         f = file(filename)   Somehow, I missed os.path.exists (thanks kanja, Blair, and Douglas). This is what I have now:  def ensure_dir(file_path):     directory = os.path.dirname(file_path)     if not os.path.exists(directory):         os.makedirs(directory)   Is there a flag for "open", that makes this happen automatically? A concise definition of a frame of reference in Newtonian mechanics? I've read  on frame of reference and also followed all of the references cited in the text (Salençon, Brillouin, Norton, etc) but I'm struggling to find any concise definition in all of that.   I would like a concise definition for a frame of reference in the context of Newtonian mechanics. This definition should not involve any additional qualifiers such as inertial and must be mature enough as to differentiate a frame of reference and a coordinate system. Is there one such definition? Is it possible to dynamically set Views' pager settings? Say for instance, you have a view that displays when viewing a certain node type, but you want the pager settings to be different for each individual node. I was thinking of making a CCK field like "pager setting" and then give it an integer option of x-y. But I don't know if it's possible to somehow dynamically plug that field into the Views' settings. Or is there another way to do this maybe? Traditional statistical tests, like the two sample t-test, focus on trying to eliminate the hypothesis that there is no difference between a function of two independent samples. Then, we choose a confidence level and say that if the difference of means is beyond the 95% level, we can reject the null hypothesis. If not, we "can't reject the null hypothesis". This seems to imply that we can't accept it either. Does it mean we're not sure if the null hypothesis is true?   Now, I want to design a test where my hypothesis is that a function of two samples is the same (which is the opposite of traditional statistics tests where the hypothesis is that the two samples are different). So, my null hypothesis becomes that the two samples are different. How should I design such a test? Will it be as simple as saying that if the p-value is lesser than 5% we can accept the hypothesis that there is no significant difference? Deleting comments under posts in the mod queue should be easier Ever since mods gained the ability to undelete comments, deleting them has become easier as the confirmation dialog was removed.  However, this is not the case in the mod queue &mdash; I still get a confirmation dialog for each comment I want to delete in the queue under a custom-flagged post (single-comment flags can be deleted just fine). And since this is the place from where I delete comments the most, it can be annoying.  In addition, the "purge comments" button, when invoked from the queue, refreshes it, so I have to scroll back down, remember which post I just purged, and mark the flag as helpful. Usually not a big issue but if there are multiple "obsolete comments" flags, then it can get confusing.  Could the workflow for comment thread moderation from within the queue be improved? Ideally, make comment deletion work like everywhere else on the site, and make the purge button AJAX-based like the comment deletes. How do I remove macOS completely from my MacBook Air 2015 and install Windows 10 only after?  I have tried formatting my drive to GPT and tried booting a Windows Installation USB however I'm stuck at the installer not being able to find any drives. error: Unable to find vcvarsall.bat Differences between hosting options for SharePoint apps Throughout the Star Wars saga, no matter the era, no matter who's broadcasting, blue holograms are exceedingly common.       Additionally, Snoke's hologram occasionally flashes blue.    However, multi- and full-color holograms do exist.      If these more advanced holograms exist, why aren't they more commonly used? And what exactly makes the holograms blue in the first place? Why is my USB drive showing corrupted data when plugged as an internal SATA drive? Was or is? Confusion