Wikipedia:Reference desk/Archives/Computing/2012 December 28

= December 28 =

Do you need Internet access to use a QR reader?
I am trying to create a QR code with my Wifi SSID and password in it so that friends can come over and scan my QR code and their phones will automatically connect to my home Wifi. However, after creating the code, I tried it with my Android phone and turned my phone's 4G and Wifi off and used Google Goggles to scan the code. It didn't work because the app said it needs internet access.

My question is, do QR codes have the encoded message embedded in them, or does the QR scanner device need to access the internet to be able to read the code? If the former, then is it just Google Goggle's fault? ie. would this work if I used another QR reader?

Acceptable (talk) 03:06, 28 December 2012 (UTC)
 * It is Google Goggle's fault. The QR code encodes the URL, but the Google Goggles phone application only sends the image to a Google server for decoding. Thus, Google Goggles must be already connected to Internet to decode QR codes. Though you might find an app for Android, that can do the QR code decoding locally in the device without Internet connection. This application claims local decoding capability, and there might be others as well. --hydrox (talk) 04:54, 28 December 2012 (UTC)

C++ standard library list container
Does std::list guarantee that each item that is added to the list will keep the same address until it is deleted? I ask because I need to store references to list-items in separate std::maps, and want to be certain that the list-items stay in place (which rules out std::vector). --NorwegianBluetalk 09:03, 28 December 2012 (UTC)
 * Attempt at clarification: I need to allocate a bunch of objects, and would like them to reside in a container. In addition, I need to create various maps which reference individual objects. To make sure that such references are not invalidated because of additions of new objects to the container, I need to chose a container type which guarantees that existing objects do not move in physical memory when new objects are added. I know that std::vector would be a bad choice, because elements might move when the vector increases in size. Would std::list be a safe choice? --NorwegianBluetalk 16:01, 28 December 2012 (UTC)


 * From my reading of a draft standard (n1905), I think list will be stable. The "capacity" section for std::vector talks explicitly about reallocation on size and how this invalidates references, pointers, and iterators to elements; the comparable section for std::list does not. The only things the standard mentions which invalidates references to members of a std::list are explicitly destructive operations like pop and erase, as you would expect. But neither, to be pedantic (which is all what language and library standards are about) does it explicitly say (that I can find) that references etc. are valid until the item is explicitly destroyed - it would be bonkers if they were invalidated somehow, and the standard very strongly implies that the implementation will be a doubly linked list of items (e.g. list.insert insists that this be a constant time operation, whereas vector.insert does not).  Is that a guarantee? Um, er, hmm, probably... 176.250.45.76 (talk) 16:42, 28 December 2012 (UTC)


 * Thanks! I got hold of a copy of "The C++ Standard Library. A tutorial and a reference" by Nicolai M. Josuttis (1999), which states (p. 167): "Lists don't provide provide operations for capacity or reallocation because neither is needed. Each element has its own memory that stays valid until the element is deleted". Not the standard, of course, but it seems reasonably safe... --NorwegianBluetalk 20:07, 28 December 2012 (UTC)

How do Windows users in the EU obtain a web browser?
European Union v. Microsoft: Windows 7 E, the edition of Windows 7 sold by Microsoft in the European Union, does not include Internet Explorer by default. That means it is difficult to get a web browser for your computer. How do EU users deal with it? Czech is Cyrillized (talk) 14:27, 28 December 2012 (UTC)


 * From memory it had a list that you selected from on install. -- Q Chris (talk) 14:38, 28 December 2012 (UTC)


 * I just set up a brand new Windows 8 Acer laptop for someone, bought in the UK. It came with IE, and I had to manually go to the Chrome and Firefox sites to download them. I never saw a "which browser(s) do you want" screen on this machine (although I have seen it in the past on other machines). 176.250.45.76 (talk) 14:42, 28 December 2012 (UTC)


 * Incidentally, even systems which don't feature IE really still have almost all of it, just without the IE wrapper application. They still ship with Trident (layout engine), which is used by other applications (e.g. steam) to render HTML/CSS content. Any they ship the ancillary libraries (for things like media, http[s], xml, json, svg) too. 176.250.45.76 (talk) 14:52, 28 December 2012 (UTC)


 * Windows 7E was just a shot Microsoft took across the bows of the EU and it never really was sold. For a while Windows 7 shipped with a "ballot" allowing a choice of browser but a regrettable "oversight" let to this getting omitted so again no choice was provided. The case is again going to court to give Microsoft another opportunity for avoidance.Thincat (talk) 15:29, 28 December 2012 (UTC)

What is the most windows 7 like linux distrubution (that also have live cd)? (explained version of this usual question)
What is the most windows 7 like linux distrubution (that also have live cd)??

Yes, I know people post this question alot (and not explain what they really meant) and guys answering it usually post some link with linux is not windows explanation, or just say "why you dont just use windows 7?", so I will explain, my question:

187.115.238.253 (talk) 19:16, 28 December 2012 (UTC)
 * -NO, I am not talking about interface. The distro interface can be anything as long its not super "alien"
 * 1) -This linux distribution will need to be able to be instaled in any computers/notebook/netbook that windows 7 would be able to be installed (PS:no need to work (or work well) with server machines or as OS for Embedded Systems).
 * 2) -Same performance or better.
 * 3) -Almost as easy to use or easier to use.
 * 4) -Able to be used to your average user stuff (excluding gaming obviously as this requeriment would make my entire question useless).


 * Any modern distro you like, plus KDE. ¦ Reisio (talk) 19:26, 28 December 2012 (UTC)


 * Your requirement 2 is probably impossible to satisfy - there will almost certainly be some hardware for which Windows 7 drivers are available but linux drivers aren't. I don't think overall performance or software/hardware compatibility varies that much between recent versions of the most popular distros, and the interface can usually be customised to a great extent.  Maybe look at comparison of Linux distributions? 130.88.99.231 (talk) 17:30, 2 January 2013 (UTC)


 * Certainly correct, but the vital hardware that will not be supported at all will be rare indeed. ¦ Reisio (talk) 00:02, 3 January 2013 (UTC)
 * Thanks, 130.88.99.231 this totally answered my question.

HELP with iphone contacts !!
Hi,I need some help for my deleted iphone contacts.

I got a new iphone, and wanted to get my contacts fom my old iphone.

I synced it with itunes. And to make the back-up for the contacts i used an option to put them in my gmail.

I had used it before with Outlook, so i did not read it carefully , and clicked merge contacts.

It deleted everything in my iphones contacts, and put there only my email contacts.

My contacts were not in my gmail, and i tried backup restore in itunes , but it only gives me my emails.

I have not used i cloud (stupid me), and cant restore them.

If someone knows the solution for the problem, or has experienced this problem before , please help.

Thank you, in advance79.106.109.203 (talk) 19:30, 28 December 2012 (UTC)