Correctly parsing an XML file in C#
How does one parse XML files?
Sending a message to nil in Objective-C As a Java developer who is reading Apple's Objective-C 2.0 documentation: I wonder what "sending a message to nil" means - let alone how it is actually useful.  Taking an excerpt from the documentation:     There are several patterns in Cocoa   that take advantage of this fact. The   value returned from a message to nil   may also be valid:         If the method returns an object, any pointer type, any integer scalar   of size less than or equal to   sizeof(void*), a float, a double, a   long double, or a long long, then a   message sent to nil returns 0.   If the method returns a struct, as defined by the Mac OS X ABI Function   Call Guide to be returned in   registers, then a message sent to nil   returns 0.0 for every field in the   data structure. Other struct data   types will not be filled with zeros.   If the method returns anything other than the aforementioned value   types the return value of a message   sent to nil is undefined.      Has Java rendered my brain incapable of grokking the explanation above?  Or is there something that I am missing that would make this as clear as glass?  I do get the idea of messages/receivers in Objective-C, I am simply confused about a receiver that happens to be nil. Posts flagged for attention but there are none The comment with the Flagged Posts that seems to be new as of today states there are posts with flags awaiting my attention but the counter shows zero and when I go into flagged posts there is nothing waiting for me. I'm going down my huge backlog of unplayed Steam games and I'm thinking the best way to tackle the list is to go through the shortest games first and then concentrate on the 20+ hour ones. I'm wondering if there's a website or something else that has an estimated amount of gameplay time for games.   Is there anything like that? The characteristic and minimal polynomial of a companion matrix of a monic polynomial $f \in \mathbb F\left[x\right]$ in $1$ variable $x$ over a field $\mathbb F$ plays an important role in understanding the structure of finite dimensional $\mathbb F[x]$-modules.  It is an important fact that the characteristic polynomial and the minimal polynomial of $C(f)$ are both equal to $f$. This can be seen quite easily by induction on the degree of $f$.  Does anyone know a different proof of this fact? I would love to see a graph theoretic proof or a non inductive algebraic proof, but I would be happy with anything that makes it seem like more than a coincidence! What to do when you discover a mistake in the archived copy of your PhD thesis? I've just defended my PhD in mathematics and started a postdoc. While working  on an improvement of one of the results of my thesis, I realized that there are several minor mistakes and a big bug in a proof that invalids a minor result in the thesis (about 3-4 pages out of 110). Unfortunately neither I nor my advisor or referees figured it out the mistake. Though the result is minor, it is announced in the introduction and the manuscript is on-line on an ArXiv-like server, so that I could publish a new version but not cancel the one on-line.   What is the best thing to do? Upload an errata? Upload a "revised" version of the thesis?  Publish a "revised version" of the thesis on my web-page?  Can this damage my future career, making me look not "reliable" as a researcher? I'm trying to access an XML file within a jar file, from a separate jar that's running as a desktop application.  I can get the URL to the file I need, but when I pass that to a FileReader (as a String) I get a FileNotFoundException saying "The file name, directory name, or volume label syntax is incorrect."  As a point of reference, I have no trouble reading image resources from the same jar, passing the URL to an ImageIcon constructor.  This seems to indicate that the method I'm using to get the URL is correct.  URL url = getClass().getResource("/xxx/xxx/xxx/services.xml"); ServicesLoader jsl = new ServicesLoader( url.toString() );   Inside the ServicesLoader class I have   XMLReader xr = XMLReaderFactory.createXMLReader(); xr.setContentHandler( this ); xr.setErrorHandler( this ); xr.parse( new InputSource( new FileReader( filename )));   What's wrong with using this technique to read the XML file? SQL - Query to get server's IP address All html canvas shapes are given the color of the last object added Remove the Yoast SEO Post Metabox Yoasts SEO plugin adds a metabox to the post edit screen. I'm trying to remove this for users who aren't editors or above.  I've tried putting a remove_meta_box call in on admin_init, trying to remove the action on $wpseo_metabox but to no avail.  How do I remove this metabox without requiring user intervention (the user should never know the metabox existed, so clicking on screen options is not an option ) Semigroups and solutions of equation I used the OzTeX implementation of TeX, also I used to typeset my docs in plain TeX, not LaTeX for me, so I had no problem to insert an image using the OzTeX, now I'm back to TeX docs, am using the TeXWorks frontend, but I can't insert an .eps image file, it seems the \includegraphics macro its only for LaTeX, so I can't use it, any idea on how to insert an image when using plain TeX? Show rigorously that the sum of integrals of $f$ and of its inverse is $bf(b)-af(a)$ Suppose $f$ is a continuous, strictly increasing function defined on a closed interval $[a,b]$ such that $f^{-1}$ is the inverse function of $f$. Prove that,   $$\int_{a}^bf(x)dx+\int_{f(a)}^{f(b)}f^{-1}(x)dx=bf(b)-af(a)$$   A high school student or a Calculus first year student will simply, possibly, apply change of variable technique, then integration by parts and he/she will arrive at the answer without giving much thought into the process. A smarter student would probably compare the integrals with areas and conclude that the equality is immediate.  However, I am an undergrad student of Analysis and I would want to solve the problem "carefully". That is, I wouldn't want to forget my definitions, and the conditions of each technique. For example, while applying change of variables technique, I cannot apply it blindly; I must be prudent enough to realize that the criterion to apply it includes continuous differentiability of a function. Simply with $f$ continuous, I cannot apply change of variables technique.  Is there any method to solve this problem rigorously? One may apply the techniques of integration (by parts, change of variables, etc.) only after proper justification.  The reason I am not adding any work of mine is simply that I could not proceed even one line since I am not given $f$ is differentiable. However, this seems to hold for non-differentiable functions also.  I would really want some help. Pictorial proofs and/or area arguments are invalid. 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. I have installed QGIS3 from the AUR package, as well as all optional dependencies:   However, when launching, I receive the following error:  Couldn't load plugin 'processing'   ModuleNotFoundError: No module named 'osgeo'  Traceback (most recent call last):   File "/usr/share/qgis/python/qgis/utils.py", line 311, in loadPlugin     __import__(packageName)   File "/usr/share/qgis/python/qgis/utils.py", line 664, in _import     mod = _builtin_import(name, globals, locals, fromlist, level)   File "/usr/share/qgis/python/plugins/processing/__init__.py", line 28, in      from processing.tools.dataobjects import *          # NOQA   File "/usr/share/qgis/python/qgis/utils.py", line 664, in _import     mod = _builtin_import(name, globals, locals, fromlist, level)   File "/usr/share/qgis/python/plugins/processing/tools/dataobjects.py", line 51, in      from processing.algs.gdal.GdalUtils import GdalUtils   File "/usr/share/qgis/python/qgis/utils.py", line 664, in _import     mod = _builtin_import(name, globals, locals, fromlist, level)   File "/usr/share/qgis/python/plugins/processing/algs/gdal/GdalUtils.py", line 35, in      from osgeo import gdal   File "/usr/share/qgis/python/qgis/utils.py", line 664, in _import     mod = _builtin_import(name, globals, locals, fromlist, level) ModuleNotFoundError: No module named 'osgeo'   Python version: 3.6.4 (default, Jan  5 2018, 02:35:40) [GCC 7.2.1 20171224]  QGIS version: 3.0.0-Girona Girona, exported   Python Path: /usr/share/qgis/python /home/thiago/.local/share/QGIS/QGIS3/profiles/default/python /home/thiago/.local/share/QGIS/QGIS3/profiles/default/python/plugins /usr/share/qgis/python/plugins /usr/lib/python36.zip /usr/lib/python3.6 /usr/lib/python3.6/lib-dynload /usr/lib/python3.6/site-packages /home/thiago/.local/share/QGIS/QGIS3/profiles/default/python   It seems to be a path issue, but I am not sure how to solve it. Pacman shows gdal and python-gdal both as installed. Why should I use a private variable in a property accessor? How to Self-Study Mathematical Methods? Edit:  Ok, user  made comment that truly helps narrow the focus of my question. Basically, I'm asking for a self-study course of Mathematical Methods.  Thanks to his recommendation I identified a book that is very close to the answer:  Mathematical Methods in the Physical Sciences by Mary L. Boas  Supposedly, the book covers most of the Math a person needs to learn in order to understand the simulations I presented.  Does this book suit my needs?    Hello,  I have always been interested on the idea to study Math at an Undergraduate level to be able to implement simulations like the followings:  Finite Difference Simulation of the Wave Equation    Heat Equation in Two Dimensions    Besides my precollege experience in Math, I have only been able to do very simple simulations due to my lack of knowledge of Advanced Math. Every time I ask about the inner workings of the simulations I get redirected to papers that look like foreign language to me and, unfortunately, I depend on easy-to-read tutorials to understand them, and while I have found   I'm more interested in reaching the solution myself.  I checked some of the questions related to book recommendations for self-study and while they are very helpful I'm interested in learning by example (There is a book called: "Accelerated C++ Practical Programming by Example" that fits very well my study habits)  Thanks in advance. When using sudo to allow edits to files, I regularly get 'permission denied'.  For example, my mouse is jittery and sluggish, so I want to disable polling:  sudo echo "options drm_kms_helper poll=N"&gt;/etc/modprobe.d/local.conf   I'm prompted for a password, and then get:  bash: /etc/modprobe.d/local.conf: Permission denied   So I tried to do a temporary change to disable polling by using:  sudo echo N&gt; /sys/module/drm_kms_helper/parameters/poll   Yet again the system responded with:  bash: /sys/module/drm_kms_helper/parameters/poll: Permission denied   Any ideas? When you're driving and you open 1 car window, say the front one, there comes a horrible noise, but when you open another window just the slightest bit, this noise goes away (I'm sure most people know what I'm talking about then I mention this 'noise').   Why does this noise occur? Why does it go away when another window is slightly opened?   (Not sure about the tag). How to find the sum of all the numbers that can be formed using the digits 2,3,3,4,4,4.. What should be the way of doing this type of problem?? Please guide What does protection from [quality] do? Example 1) Let's say I have some random creature with protection from white, and my opponent plays , a white card with the effect "Destroy all creatures." Can my creature with protection from white be destroyed by a white card that isn't actually targeting it specifically?  Example 2) I was playing a match with a friend where I had  on the field against his 3 zombies. Is he able to declare his zombies as blockers even though Elite Inquisitor has "protection" from zombies?  If he can declare them as blockers, does protection mean that no damage is dealt by the zombies to  Elite Inquisitor?