I2CDevice::I2CDevice(unsigned int bus, unsigned int device) {     this-&gt;file=-1;     this-&gt;bus = bus;     this-&gt;device = device;     this-&gt;open(); }  int I2CDevice::open(){    string name;    if(this-&gt;bus==0) name = BBB_I2C_0;    else name = BBB_I2C_1;     if((this-&gt;file=::open(name.c_str(), O_RDWR)) &lt; 0){       perror("I2C: failed to open the bus\n");       return 1;    }     if(ioctl(this-&gt;file, I2C_SLAVE, this-&gt;device) &lt; 0){       perror("I2C: Failed to connect to the device\n");       return 1;    }     return 0; }   The above is part of a code doing Linux I2C interface, my question is in the line:  this-&gt;file=::open(name.c_str(), O_RDWR)   I think this is trying to assign a value to the file descriptor this->file using open() function. But why there is a "::" symbol? Why not just "open()".
In C++, what is the purpose of the scope resolution operator when used without a scope? For instance:  ::foo();
I made some scripts on my Raspberry Pi to automate a daily shot at a specific hour.  My DSLR is plugged in through USB. I thought this would keep its battery charged, but no.  Is there really no way automate a DSLR to shoot every 24 hours without having to pick it up, charge/replace its battery, and put in back on the same spot? Why do the :before and :after pseudo-elements require a 'content' property? messenger()->addMessage not working after a $form_state->setResponse In the submitForm of a custom form, I have this:    switch ($form_state-&gt;getValue('suscribe')) {   case 0:     $iStatus = 1;     break;   case 1:     $iStatus = 3;     $sFileName = 'sites/default/files/_private/bulletins/' . $form_state-&gt;getValue('adherent')[1] . ".pdf";     $response = new BinaryFileResponse($sFileName);     $response-&gt;setContentDisposition(       ResponseHeaderBag::DISPOSITION_ATTACHMENT,       'bulletin.pdf'     );     $form_state-&gt;setResponse($response);     break; }  $storage = \Drupal::entityTypeManager()-&gt;getStorage('member'); $id = $form_state-&gt;getValue('adherent')[0]; $entity = $storage-&gt;load($id); $entity-&gt;status = $iStatus; $entity-&gt;save();  \Drupal::messenger()-&gt;addMessage($this-&gt;t('Your wish has been recorded.'));   suscribe is a Yes/No radio button. $form_state-&gt;setResponse($response); triggers the automatic download of a pdf document.    The message (Your wish...) is correctly displayed in case 0. In case 1, the message shows only if I refresh the page (or go to another page). How can I have the message displayed without doing another action after submitting the form in case 1?    By the way, database is correctly updated in both cases. I'm using Drupal 8.6.10. How to pin either a Shortcut or a Batch file to the new Windows 7, 8 and 10 Taskbar and start menu? We are having trouble adding our batch scripts to the Windows 7, 8 or 10 taskbar or start menu.  Our batchfiles take some arguments and just execute other application based on those arguments . To keep it simple, we created some shortcuts for our customers which they just need to click in order to get everything running.  The question here is: How can we pin those shortcuts or batch files to the taskbar or start menu?  (The customers aren't supposed to access the file system and that's why they can only see the taskbar) How to create a circular shaped grid, similar to a manhole cover Can I play against or with Xbox 360 players through my Xbox One? Is it possible to play against and with Xbox 360 players through my Xbox One? Propagate all arguments in a bash shell script Why does the reputation need to be publicly displayed? Prepositional Phrase - confused - at or in I recently flagged a question as "very low quality", just like I've flagged many questions in the past. However, my flag was found to be unhelpful this time. The same thing happened when I recently flagged a post as not an answer.  Are the moderators being more strict when it comes to handling quality related flags? If so, why? Recently I have been working on a mini-game that gives a few players custom spawn eggs. I want the mob to simply have a name and be on a team. I'm attempting to use this command:   /give @p[x=-102,y=48,z=81,distance=..1] shulker_spawn_egg{Team:PurpleTeam,CustomName:"\"Purple Turret\""}   It does give the player a spawn egg, but the resulting shulker spawn does not have a team or a name. Any ideas why this isn't working? Assume there is a public-key encryption scheme $(KeyGen, Enc, Dec)$ with perfect correctness (i.e., for all messages M and valid key-pairs (PK,SK), we have $Dec_{SK}(Enc_{PK}(M))=M$).  Will there always be a function $A$ such that for all messages M and valid public-keys PK, $A_{PK}(Enc_{PK}(M))=M$?  In other words, can a computationally unbounded adversary decrypt the message, having only the public key? Rerender funnel highcharts with new data Simple series convergence/divergence: $\sum_{k=1}^{\infty}\frac{2^{k}k!}{k^{k}}$ How could the Fremen do what they did to the empire in Dune Messiah? How could, and why would, the Fremen's jihad kill 61-Billion people and conquer the known universe?  Their leader Paul was already emperor.  What was left to conquer?  And how could they force this onto Paul when they had no relationship with the Spacing Guild except thru Paul?  If Paul didn't arrange for transportation then how would they get off Arrakis?  And how does a small population of hardened, rugged, but not technologically advanced people do that much conquering in that time?  Also, is there any explanation about how Ix, Tleilex planet and Bene Gesserit planets hold off the wave of jihad? In Windows you have a C-drive. Everything labeled beyond that is with the following letter.   So your second drive is D, your DVD is E and if you put in a USB stick it becomes F and the following drive G. And so on and so forth.  But then, what and where are A and B-drives? Is there a third Holmes sibling? Quitting a job in the US on a work visa, going to Canada and re-entering on a tourist visa (ESTA waiver) I have been working in the USA on an E-3 visa and intend to return home to Australia, but I want to travel around the US before I do so. I am under the impression that after leaving my current company, I will have 10 days to leave the country.   Will I be able to go into Mexico or Canada and re-enter with an ESTA waiver as a tourist? How to flatten a list to return a new list with all the elements? What is the difference between implication symbols: $\rightarrow$ and $\Rightarrow$?