What does the @GLIBC_2.2.5 suffix on symbols do?
Where do object file "Version References" come from?
How would you explain why $e^{i\pi}+1=0$ to a middle school student? Hi I was asked by a friends child who is in middle school why $e^{i\pi}+1=0$. Now I couldn't think of a way to explain it so he would understand. Albert Einstein once said “If you can't explain it simply, you don't understand it well enough” so how would I explain it. What happened to /etc/apt/apt.conf? I was browsing through the apt folder to try my proxy settings and I was unable to find the apt.conf file in Ubuntu 11.04. Is there any alternative file for it?  Adding proxy settings to 99-synaptic in apt.conf.d does not help as it gets overwritten everytime I restart the system. The Chinese government has a really specific list of requirements for visa photos:    I had an old unused photo from last time I applied for a visa or passport, and compared it to the requirements (decided not to use it because it was damaged). It seemed to match most of the requirements, except that it seems that they want a photo which isn't square: The required width is less than the required height.  Assuming most drugstores are still providing square passport photos, the question becomes: Should I cut the photo to match the specified width?   What adds to the confusion is if you look at the  the box for the photo is nearly square, not the oblong shape in the requirements. And I have seen other advice that you need to make sure it fully fits the box.  Any advice about what to do here? Parentheses around more than one paragraph Does English allow one to put parentheses around more than one paragraph? Example:     Paragraph 1.      (Paragraph 2.      Paragraph 3.)      Paragraph 4.   (Of course, this is just a simple example. In reality, it looks more clean since the paragraphs are more than one line long, and are not separated by an empty line.) How many ways can $r$ nonconsecutive integers be chosen from the first $n$ integers? During self-study, I ran across the question of how many ways six numbers can be chosen from the numbers 1 - 49 without replacement, stipulating that no two of the numbers be consecutive.  I can obtain a simple lower bound by saying that, in the worst-case scenario, when you choose a particular number, there are now three numbers that cannot be chosen next.  For example, if I first pick 17, then I can't choose 16, 17, or 18 for the remaining choices.  This gives me the lower bound  $$\frac{49*46*43*40*37*34}{6!} = 6,773,770 \frac{8}{9}$$  This is about 48% of ${}_{49}C_6 =  13,983,816$.  The real answer must be bigger (and an integer).  I haven't found a way to calculate it, though.  The original problem asked to show that the probability of having non-consecutive integers when you choose six is greater than 50%, so if the problem is complicated to count exactly, better approximations that show the answer is above 50% would also be appreciated.   Of course, I can use a computer to do the counting, but I'm interested in learning what methods I'm missing. How do you remove duplicates from a list whilst preserving order? Is there a built-in that removes duplicates from list in Python, whilst preserving order? I know that I can use a set to remove duplicates, but that destroys the original order. I also know that I can roll my own like this:  def uniq(input):   output = []   for x in input:     if x not in output:       output.append(x)   return output   (Thanks to  for that .)  But I'd like to avail myself of a built-in or a more Pythonic idiom if possible.  Related question: How do I upgrade to a newer version of Ubuntu? Currently using Ubuntu 18.04, and my wireless driver is not being detected.  I've included a .  $ dmesg | grep iwl [    6.212724] Loading modules backported from iwlwifi [    6.212724] iwlwifi-stack-public:master:6988:0d8892f2 [    6.224583] iwlwifi 0000:00:14.3: enabling device (0000 -&gt; 0002) [    6.229811] iwlwifi 0000:00:14.3: Direct firmware load for iwl-dbg-cfg.ini failed with error -2 [    6.230540] iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-9000-pu-b0-jf-b0-39.ucode failed with error -2 [    6.230547] iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-9000-pu-b0-jf-b0-38.ucode failed with error -2 [    6.230552] iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-9000-pu-b0-jf-b0-37.ucode failed with error -2 [    6.230557] iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-9000-pu-b0-jf-b0-36.ucode failed with error -2 [    6.230562] iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-9000-pu-b0-jf-b0-35.ucode failed with error -2 [    6.236670] iwlwifi 0000:00:14.3: loaded firmware version 34.0.0 op_mode iwlmvm [    6.248314] iwlwifi 0000:00:14.3: Detected Intel(R) Dual Band Wireless AC 9560, REV=0x318 [    7.264081] iwlwifi 0000:00:14.3: SecBoot CPU1 Status: 0x3, CPU2 Status: 0x2477 [    7.264084] iwlwifi 0000:00:14.3: Failed to start INIT ucode: -110 [    7.276165] iwlwifi 0000:00:14.3: Failed to run INIT ucode: -110   sudo modprobe iwlwifi returns no output. What exactly determines depth of field? There are several questions here about , about , and about . And of course there's the basic . And plenty of  questions. There's related questions like . But there's no be-all-end-all question asking:  What exactly determines depth of field in a photograph?   Is it just a property of the lens? Can lenses be designed to give more depth of field for the same aperture and focal length? Does it change with camera sensor size? Does it change with print size? How do those last two relate? dpkg error: "trying to overwrite file, which is also in..." In the tense of present perfect, Are 'recent past' and 'hot news' the same? How to Screen Sharing / VNC to an iMac without waking the display? I have an iMac mid 2011 at home. When I was not home, I may need to access my mac with Screen Sharing. However the iMac display will turn itself on when I connect via Screen Sharing. The problem is I don't want to scare my family at home (with the elders and kids) as the iMac "turn itself on suddenly".   This is a problem specific for iMac. On MacBooks (Pro, Air, whatever) I can set the brightness to the lowest setting so the screen is black (i.e. the LED light is off). However on an iMac you cannot turn off the LED backlit by setting brightness. The display is still bright and everything is clearly visible even on lowest brightness setting.  Therefore these solution are not working as the display will turn on as soon as you move your mouse or hit any key on the keyboard via Screen Sharing.   Sleep Display (by Ctrl+Shift+Eject) Using the code listed on    Question: Is the a way to keep the iMac display off entirely while you accessing it with Screen Sharing? Upgrade to the specific php 7.1/7.2 from php 7.0 in Ubuntu 16.04 How can I upgrade to php 7.1 from php 7.0 in ubuntu 16.04 ?  If I do a php -v I get this message:  PHP 7.0.8-0ubuntu0.16.04.3 (cli) ( NTS ) Copyright (c) 1997-2016 The PHP Group Zend Engine v3.0.0, Copyright (c) 1998-2016 Zend Technologies     with Zend OPcache v7.0.8-0ubuntu0.16.04.3, Copyright (c) 1999-2016, by Zend Technologies I bought a Mac (13", early 2011) almost 5 years ago. When I first got it, it was running under OS X 10.7 and it was pretty fast. I've being upgrading it ever since and it's now running under Mac OS X 10.11.  I guess it didn't totally survive the upgrades because, today, there's a lot of bugs, freezes, lags, "spinning beach ball" appearing,... for example, when I write something on a normal program/editor, the cursor freezes for a few seconds, then catches up to what I'm writting.  As you can guess, that's really annoying! I've been thinkning about upgrading the hardware but I don't know what to do: should I change the RAM to 8 GB - 1 333 MHz (currently my computer has 4 GB - 1 333 MHz)? Or should I upgrade to an SSD (which is pretty expensive and difficult to install)?  Thank you very much. Langage to declare a circuit board Finding the missing digits of $23!$ It is given $23!=2585201xy38884976640000$. Now it is required to find the value of $x$ and $y$. I know I could find it by using divisibility rules and solving simultaneous equations. Is there any other way to solve it (without computing it by a calculator)? This question is just out of curiosity. Why LastModifiedbyid in Trigger.new gives old value I have noticed the strange behaviour of salesforce due to which even my code broke down in production.  I was trying to stop the user from updating some field..I used before udpate trigger and code like Trigger.new[i].LastModifiedbyId..  Ideally it should give the current user in Trigger.new[i].LastModifiedbyId in  but it gives oldrecordLastModifiedbyId..  Although userinfo.getuserid resolves the problem later.  Any idea about this behaviour of salesforce. Long names cut off in questions and answers The Unhandled Exception's name is cut off in this  and in the answer too. The last 'n' looks like an 'r'.  Using Firefox 3.6.6.  Examples: Programmatical Setting of 'Store Relative Pathways' for multiple MXDs ArcGIS 10.1 I am looking to move large number of mxds to a different location on the same drive. Many mxds haven't got 'Store relative pathways' option checked therefore this operation will result in broken links to data. I've only started using ArcGIS 10.1 and it is now possible to programmatically update relative pathways for all mxds by using arcPy and setting relativePaths to be "True". I had a go at writing Python script which (in theory) loops through a top folder and searches for all mxds and then updates "Store relative pathways" setting to be on. When I run this script in PyScripter, it fails to complete, I get the following error:  "exceptions.NameError: name 'mxd' is not defined  Can anyone help ?!? Thanks in advance, Magda      import arcpy, os  folderPath = r"C:\My Folder Path\...\...\..."  for filename in os.listdir(folderPath):     fullpath = os.path.join(folderPath, filename)     if os.path.isfile(fullpath):         basename, extension = os.path.splitext(fullpath)         if extension.lower() == ".mxd":             mxd = arcpy.mapping.MapDocument(fullpath)             mxd.relativePaths = 'True'         mxd.save() del mxd Which answer is correct?       Tony _______to have children until his little daughter was born. After   she won his heart, he decided he wanted a big family.       A. didn't want.   B. hadn't wanted.   This is a multiple choice question from the Understanding and Using English Grammar Workbook 3rd edition by Betty Azar. To me, both answers are correct as I cannot see the diffrence. Please show me the wrong option to delete.