Estimate error of the steepest descent method
Why does the classical path give the dominant contribution in the path integral?
Placing a single algorithm in two columns Evaluating and proving $\lim\limits_{x\to\infty}\frac{\sin x}x$ Compare nullable types in Linq to Sql I have a Category entity which has a Nullable ParentId field. When the method below is executing and the categoryId is null, the result seems null however there are categories which has null ParentId value.  What is the problem in here, what am I missing?  public IEnumerable&lt;ICategory&gt; GetSubCategories(long? categoryId) {     var subCategories = this.Repository.Categories.Where(c =&gt; c.ParentId == categoryId)         .ToList().Cast&lt;ICategory&gt;();      return subCategories; }   By the way, when I change the condition to (c.ParentId == null),  result seems normal. How to draw a fish? I would like to draw an image like the following.     This is what I've done so far (I used tikz, but any other package is welcome):  \documentclass{article} \usepackage{tikz}  \begin{document}     \begin{tikzpicture}         \draw[fill=blue] (.5,0) rectangle (4,2);         \draw[fill=red] (1,1) to[bend left=50] (3,1) to[bend left=50] (1,1);         \draw[fill=red] (3,1) -- (3.5,1.5) -- (3.3,1) -- (3.5,.5) -- cycle;         \draw[fill=white] (1.6,1.1) circle (.15cm);          \draw[fill=blue] (1.55,1.1) circle (.05cm);              \end{tikzpicture} \end{document}     Edit: April 2nd, Time for explanation  In Italy (but I also think in other countries), a practical joke done on April 1st is called "pesce d'Aprile" (= April's fish, that is an ) and is often related to fishes.  The usual one is to stick a drawing of a fish on someone's back without he/she realizes it.  Some years ago a colleague of mine stuck some "pesci d'Aprile" with written below "sono disponibile" (= I'm easy) on the rear of all the cars in our company car parking. Some other colleagues didn't realize it, and they had gone around with that drawing for days.  Another funny example happened in Milan . Someone put on the windshield of a lot of cars a false fine for illegal parking. On the fine sheet was written "per il pagamento rivolgersi agli uffici comunali di via Gadio, 2" (= for payment, please contact the municipal offices in via Gadio, 2), the address of the Civic Aquarium.  Hence, this question was simply a way to put    P.S. = Since I earned a lot of reputation points with this trick question, I decided to give them back to the Community awarding a bounty to the two answers posted on April, 1st.  Moreover, I accepted Robert's one since he guessed without spoiling, and I thank the other two answerers.  To the downvoters: you're probably technically right, but:   there's already too much sadness in the world, let's laugh now and then! humor is part of the LaTeX philosophy, Prof. Knuth himself docet if only serious questions are accepted, why did they create a fun tag? Is it possible to build a single mysql query (without variables) to remove all records from the table, except latest N (sorted by id desc)?  Something like this, only it doesn't work :)  delete from table order by id ASC limit ((select count(*) from table ) - N)   Thanks. for loop wget directory creation error As a Ubuntu beginner. I am trying to download links from multiple text files with wget2 in batch. The -P &quot;$f&quot; creates directory name with .txt suffix. Is it possible to ignore .txt for -P &quot;$f&quot;. Any modification suggestions. for f in *.txt;do wget2 -i &quot;$f&quot; -P &quot;$f&quot;;done Quote environment with reference at the end right Is there a way to make comments in the node editor? I'd like to have a node like the Frame node but one that can have lots of text, not just a header. I've looked and it looks like there isn't any such capability so far, so I was wondering how easy it would be for someone to create a custom Comment node as an add-on or script (I don't know the differences between the two). I myself would love to leave detailed comments in complex node trees so that I can figure out what I was doing/what to do when I come back to them months later. This has happened to me many times in the last 5 years: an upgrade broke my system. Each time I end up with this situation, I have to reinstall the whole system, which is really annoying.  Is there any way to roll back the most recent upgrade to be able to have a functional system without reinstalling? If not, which is the best way to suggest this as a top priority idea?   I read this idea was described in brainstorm.ubuntu.com, but it feels it is dead... and the forums are full of examples of upgrades breaking things, that's why I feel something needs to be done about this topic. Thanks! Do class spells take up spell slots? So I'm fairly new and ended up being the Cleric in my also fairly new group. I haven't played a caster before and the book says that at level 1 I have Bless and Cure Wounds. Do I need to assign these to a spell slot or do I have them inherently (not to be confused with a cantrip; I know I'd have to use a slot to cast them)? Process descendants How to prevent alt-f1 from selecting Dash I'm trying out  with gnuplot to generate the data.  This works by having pgfplots write some stuff to an external file, run gnuplot on the file, and then use the generated data to plot the graph.  The problem I'm having is that I get different behaviour under xelatex as pdflatex or lualatex.  In xelatex, the data file is littered with ^^I whereas in the other two formats these are tabs.  It appears that the code ^^I is getting stored as a macro which then gets written out to the file, so possibly there's something funny going on with the ^^I syntax: xelatex is reading it literally.  Indeed, when I do \show\pgfplots@TAB (the macro in question) then for pdflatex and lualatex then I get a literal tab whereas for xelatex I get ^^I.  So how do I get a tab in xelatex?  And why isn't \gdef\pgfplots@TAB{^^I} working?  (The previous line in the code, by the way, is \catcode`\^^I=12 - I don't know if that has anything to do with it.) A matrix and its transpose have the same set of eigenvalues/other version: $A$ and $A^T$ have the same spectrum I am using Microsoft Visual C++ on Windows and Qt Creator on Ubuntu. I can't change permissions on my flash drive (FAT32), even as root.  How can I change permissions on a FAT32 flash-drive? I want to start a modal operator by clicking a button in a panel in the properties region. It should then stop when I click somewhere in the 3D viewport. I want to execute some code when I start and finish the operator (see the code below). I tried modifiyng the modal operator template with an execute method to start the modal operator. But the now the context.space_data.type is always &quot;PROPERTIES&quot; because that's where the panel is located, I guess. Is this a bad way of doing what I want? class MY_OPERATOR_OT_click_on_3dview(bpy.types.Operator):          bl_idname = &quot;mesh.click_on_3dview&quot;     bl_label = &quot;Click on 3D&quot;      def modal(self, context, event):                  if context.space_data.type != 'VIEW_3D':             return {'PASS_THROUGH'}                  if event.type in {'MIDDLEMOUSE', 'WHEELUPMOUSE', 'WHEELDOWNMOUSE'}:             # allow navigation             return {'PASS_THROUGH'}         elif event.type == 'LEFTMOUSE':             # DO ALL THE POST-SELECT STUFF             return {'FINISHED'}         elif event.type in {'RIGHTMOUSE', 'ESC'}:             return {'CANCELLED'}          return {'RUNNING_MODAL'}      def execute(self, context):         # DO ALL THE SETUP STUFF           context.window_manager.modal_handler_add(self)              return {'RUNNING_MODAL'}            def cancel(self, context):         print(&quot;CANCEL???&quot;) What does NOEXEC flag mean when mounting directories on RHEL? I am trying to understand the NOEXEC flag when mounting.  I am having an execution issue within the /tmp directory on someone elses machine that I cannot access atm where the /tmp directory is mounted onto a different drive than '/' and NOEXEC is present.  I wanted to try and recreate this scenario on my machine, but I do not have a second hard drive.  I tried doing the following command:  mount --bind /test1 /test2   I then removed the bind flag and added NOEXEC in /etc/fstab.  Then, I created a file in /test2 called test.sh where it just echos 'hello world'.  I try and run it and it said 'permission denied'.  I then ran chmod 777 test.sh and was able to execute the file just fine.  I thought that the NOEXEC flag should not allow me to execute anything?  Is mount --bind /test1 /test2 not the same as mounting from a completely different physical drive? As in /test1 and /test2 are on different drives? resolv.conf not working properly with Ethernet in Ubuntu I have a Lenovo X200 laptop on which I am running Ubuntu 9.10. Recently, (I assume after some updating, but I really don't know) my ethernet port stopped working under Linux. A more tech/linux-savvy friend of mine was able to temporarily fix the problem by manually editing the resolv.conf file with the DNS servers he found through his connection. However, after rebooting, the problem came back and now I am looking for a more permanent solution. Regex match entire words only File upload with Javascript without user intervention