Is ∅ equivalent to {∅}?
Is $\emptyset \in \emptyset$ or $\emptyset \subseteq \emptyset$?
How do I generate the upper triangular indices from a list? Is there a way to check if a file is checked out by another user? I am going trhough a list file by file and would like to avoid the "file is opened by another user" error. Something like this would be nice:  Guid id = new Guid(slideLibrary); // ID of Slide-Library. List list = ctx.Web.Lists.GetById(id); ListItemCollection items = list.GetItems(CamlQuery.CreateAllItemsQuery()); ctx.Load(items); // Loading all the fields System.Security.SecureString pwd = new System.Security.SecureString(); foreach (char c in "pwd".ToCharArray()) pwd.AppendChar(c);  ctx.Credentials = new SharePointOnlineCredentials(login, pwd); ctx.ExecuteQuery();  // Iterating through all the entries. foreach (var item in items) {     String currentID = item["ID"].ToString(); // Getting the ID of the current item.      if (!item.IsCheckedOut()) // This is the part I am looking for.     {        // Do stuff     }     else     {        Console.WriteLine("Item is blocked, skipping it.")     } }   I have yet not been able to find something fitting. Dynamic Server Name in SQL Statements (from clause) Why do close votes expire? I nominated  to be closed as a dup. I see that two other people upvoted my comment, so they might have voted to close it as well. Now, we didn't gather enough votes, and all close votes expired ... and I can't re-vote to close. What is the motivation behind expiring close votes ... especially for close-as-duplicate? Update: Please take into consideration:  Beta Stack Exchange sites have a smaller community, and fewer people with voting privileges Closing as a duplicate is &quot;usually the right thing&quot; IMHO - much less controversial than closing as off topic. After a vote is reset, the original users can't vote again. On a small site, this makes it even harder to get a consensus of five votes. So all wizards get an invitation to Hogwarts at 11... How do they know whom to invite?  If a wizard is Muggle-born, then nobody would know about their existence.  Or do they register some weird magical stuff being done by them before 11? Installing "firmware-b43-installer" offline How can I install firmware-b43-installer driver if I can't connect to internet by wire? Shapefile projections not matching up in QGIS? To start off with, I'm very new to QGIS. I'm attempting to place a shapefile with locations for 3 substations on a map of Peniche, Portugal. The locations for the substations are given in latitude and longitude coordinates.   When I start off by importing the substation shapefile, I make sure that both the layer CRS and project CRS are set to EPSG:32629, which gives each substation point the correct coordinates, however the scale is at 1:1, which is not correct. As soon as I then add a raster map of the region or a shapefile of Portugal using the same CRS the position of the substations also becomes incorrect.   I'm sure there's a simple solution I'm not getting, but I've been trying for a while and have had no success. Here's a dropbox link to the files Why are all of my appliances becoming energized when ground wire is excluded? Find the first occurrence/starting index of the sub-array in C# Can a union be initialized in the declaration? Difference between block size and cluster size Different dependencies for different build profiles Is it possible to have a different set of dependencies in a maven pom.xml file for different profiles?  e.g.  mvn -P debug mvn -P release   I'd like to pick up a different dependency jar file in one profile that has the same class names and different implementations of the same interfaces. This girl that I'm friends with and have actually seen in person before, keeps posting [on social media] that she "loves when the transfer goes through" and gets $2000-$6000 for free quite often. She said you can make up to $6500 a day. She is not very smart and barely spells correctly. She keeps saying that all she is doing is "transfers" and that's it. So many of my friends are feeding into this crap. So I asked her what it is. She basically said "it's legit" and asked me for my bank username and password so she could see how much money to deposit into my account. I said no way and left it at that. She also said she is not stealing or doing anything illegal. She is getting her friends free money and I think they're naive. What is she actually doing? Is it illegal? I am sure she is incapable of doing crazy money wiring to different countries.   Thank you everyone for answering my question. I am not stupid, I did not give her my information. I knew she was up to something illegal, so thank you for giving me some input on what exactly she is doing. I submitted an anonymous tip to my local sheriff's department. I'm hoping they see it and pursue it, or forward it to the right authorities I.e the FBI or something. Is there a command where I can teleport myself to a specific kind of block? I can't find my house and I have specific kind of blocks in it like beacons, enchantment tables, furnaces, stuff like that. I didn't put a bed and I never viewed the coordinates. How to get from Heathrow Airport to King's Cross, London? My wife and I will be arriving in London via Heathrow Airport (LHR) and are staying at a hotel near King's Cross station. So, we were wondering what the best (which means fastest but also easiest when carrying two large pieces of luggage and two carry-ons) way to get from LHR to King's Cross?  I gather that, with only one changeover, we can take the Tube. However, in the interest of other passengers, we thought it would be best to take a taxi, or maybe a bus?  Thoughts? What is the best way to remove accents (normalize) in a Python unicode string? I have a Unicode string in Python, and I would like to remove all the accents (diacritics). I found on the web an elegant way to do this (in Java):  convert the Unicode string to its long normalized form (with a separate character for letters and diacritics) remove all the characters whose Unicode type is &quot;diacritic&quot;.  Do I need to install a library such as pyICU or is this possible with just the Python standard library?  And what about python 3? Important note: I would like to avoid code with an explicit mapping from accented characters to their non-accented counterpart. PHP - Get rid of notation Facebook: Ways to preserve image quality of uploaded images? After uploading an image, Facebook converts it to a new image.  Their conversion process introduces artifacts and mottling to the magenta-ish parts of the image.  Original image:   Facebook's conversion:   Are there ways to preserve the original quality of this image and have the image appearance on Facebook reflect more of the original quality? Can a multi-core processor run multiple processes at the same time? I understand that a multi-core processor can run multiple threads of the same process at the same time using its different cores. Can it also run multiple processes at the same time(each core running a different process)? The left-nav is great - I like it, users who don't can disable it. Perfect world. Now it's stickied it's always there too, which is really useful.  When I'm navigating in areas not directly linked to in the left nav and have scrolled down, I often want to re-use the other navigation. This means scrolling up. Which is fine, of course it's how websites work.  However, if the left-nav had a "Top" link which took the user to the very top of the page it would be great for getting back to specific contextual menus and things that are not linked to in the left-nav.  For example, if I'm viewing questions on a specific tag and I've scrolled down, I sometimes want to get back up to the top to remove a tag, or change from "Latest" to "Featured" etc. Although clicking the "Questions" link in the left-nav takes me back to the top, it removes the tag(s) I was searching with.  There are other use cases where this would be useful, like long questions and answers (Etc). So I think a "Top" link in the left nav would be very useful.    I think this is different to the  as it doesn't mention the left-nav, and my question is suggesting this idea because we have a good place to put it and it'll be a useful addition to the left-nav.