Just now I flagged a comment on  that said nothing other than ~&quot;thank you, that's helpful&quot; and it was deleted immediately.  I did not know this was a feature.  Moreover, I didn't find any documentation on this feature here at meta.SE. Question: I flagged a &quot;thank you&quot; comment as it's &quot;no longer needed&quot; and it was auto-deleted: was there a change I'm unaware of? I'd be particularly interested in understanding precisely how this feature works. This comment was not offensive nor was it spam, just a run-of-the-mill &quot;thank you&quot; comment.  I don't recall this happening for previous &quot;it's no longer needed&quot; flags.  I'm sure it was a single flag that caused this, because it's a 5-month old post. If I knew precisely what was going on, I'd pay a bit more attention to flagging these.
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What are recommended, general strategies to start block-cipher design and/or analysis? Using Perl to change the url homepage for Internet Explorer "Parsing filters unsupported" error during extraction of RAR file I have received an .rar which I wish to unpack as it contains something rather important to me that I need to really have now. However even though I can view the contents of the .rar archive in the Archive Manager, I am unable to extract it due to this error:    The archive should contain two folders within it, each though contain at least 10 audio files as well as a PDF file each (I don't know what the contents exactly should be except for there should be audio files in there, and the content I have described is what I can see from the Archive Manager's view). So the only thing I am left with except the error is one of the folders and one of the audio files, but it says it has 0 bytes in it.  So how exactly do I fix this problem? I am running Ubuntu GNOME 16.04.1 with GNOME 3.20.  Information Update:  In reply to a comment requesting the output from the dpkg -l unrar unrar-free command:  Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name           Version      Architecture Description +++-==============-============-============-================================= un  unrar          &lt;none&gt;       &lt;none&gt;       (no description available) dpkg-query: no packages found matching unrar-free Why does an atom remain uncharged after emission of an alpha particle? When an alpha particle is emitted, two protons and two neutrons leave the nucleus but the electrons remain the same in number. Why does the atom remain uncharged although it appears it should have a net charge of $-2e$? Why does everyone do 9-overlord, not 10-overlord? What is the advantage on saving the money for the overlord when you have 9 drones, and not filling your supply first and then getting the overlord?  In my theory, in the first case you get to wait the saving time with 9 drones, and get to wait almost the same time with 10 drones in the second case. Second case should be better, since 10 drones mine faster than 9? So why does everybody go with the first case?  All this is assuming you go 12 pool or something like that, where you will get more drones after the overlord. 6- and 8-pools are obviously different. I've checked in the home folder but this is all I see. Find the area of the shaded region in the figure below: Find the area of the shaded region in the figure below:    I am completely stuck on how to start off this question. Please help on some guidance on how to start it off. How to adapt the color of a label using pgfplots I created this style that shifts the labels and put them on the bottom of the ybars.  However, I have a problem with the bars that have too short length (for example, see the 8.7 and 5.1 in the example below). I want to check if the values are less than some threshold, or the length of the bar is shorter than the label (number) then change its color.  How can I overlay another label on top of the one in white when the bar is shorter? or maybe change the color of the label to a gradient color? or just overlay the part that is outside of the bar?    \documentclass{standalone}  \usepackage{tikz} \usepackage{pgfplots} \usepackage{pgfplotstable} \usetikzlibrary{calc}  \begin{document} \makeatletter \begin{tikzpicture} \begin{axis}[ ybar, every node near coord/.style={   check for zero/.code={ % If meta=0, make the node a coordinate (which doesn't have text)     \pgfmathfloatifflags{\pgfplotspointmeta}{0}{         \pgfkeys{/tikz/coordinate}     }{}   },   check for zero, color=white, text opacity=1, font=\footnotesize, inner ysep=0.5pt, },% % Bottom nodes  calculate full offset/.code={     \pgfkeys{/pgf/fpu=true,/pgf/fpu/output format=fixed}     \pgfmathsetmacro\testmacro{((\pgfplotspointmeta-\pgfkeysvalueof{/pgfplots/ymin})*10^\pgfplots@data@scale@trafo@EXPONENT@y)*\pgfplots@y@veclength}     \pgfkeys{/pgf/fpu=false} },% nodes near coords bottom/.style={     every node near coord/.append style={         /pgfplots/calculate full offset,         yshift=-\testmacro,         rotate=90, anchor=west,%I need the rotate text here and not in the          %general style, as the ybar redefines the style     } },% ymin=0, nodes near coords={\pgfmathprintnumber[fixed zerofill,precision=1]{\pgfplotspointmeta}}, nodes near coords bottom, ] \pgfplotstableread{ % set real imag mag 1 8.7 2 5.1 3 91.8367  }\mydata \addplot table[x index=0,y index=1,header=false] {\mydata}; \end{axis} \end{tikzpicture} \makeatother \end{document}   * EDIT *  I need to create some special gradient on each label that is below the bar height. For example, I need to adapt something like  to each label that is not showing. However, I cannot find a way to put the macro in the style section of the codes. Or is there any equivalent solution? I need to show the following: $$\lim_{k\rightarrow \infty} \left(1 + \frac{z}{k}\right)^k=e^z$$  For all complex numbers z. I don't know how to start this. Should I use l'Hopitals rule somehow? Calculating peaks in DEM using GRASS How to enable assembly bind failure logging (Fusion) in .NET How do I enable assembly bind failure logging (Fusion) in .NET? Installing Guest Additions causing problems I am trying to install Guest Additions in VirtualBox with Windows XP host and Ubuntu 12.04 guest. I followed the above steps:  Devices-&gt; Insert Guest Additions CD Image. After that I locate the folder /media/VBoxAdditions4.3.4_91027/ and run sudo ./VBoxLinuxAdditions.run   I want to be able to create shared folders and adjust the resolution of the screen. I achieved to do the first issue, but I couldn't do the second one. I didn't get any message, however it is not possible to change the resolution of the screen and I cannot switch to fullscreen. What am I doing wrong?  I found in the instal log the following message: unknown version of the X Window System. I've tried the solution of the proposed link but I got the following message:  Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies: virtualbox-guest-x11 : Depends: xorg-video-abi-11                     Depends: xserver-xorg-core (&gt;= 2:1.10.99.901) E: Unable to correct problems, you have held broken packages.   I tried also to install with the command sudo apt-get install virtualbox-guest-dkms but nothing is changing. During the installation of dkms I got the message: Error! Bad return status for module build on kernel 3.13.0-32-generic(i686). In  answer to the question "why does the moon have the same rotation and revolution periods?", we read:     The mass and speed of rotation of the Earth influence the moon in that some of its rotational energy is actually transferred to the moon. (...) Many of the moons in the solar system have also reached this point of equilibrium. In Jupiter, the moons Amalthea, Thebe, Io, Ganymede, Callista, and Europa, all have identical rotational and revolutionary periods.    My two questions are:   Can we show the mechanics of this quantitatively?  Does the system Earth-Sun experience the same phenomenon, in some measure? Will then the earth slow down its rotation speed until it will show always the same face to the sunlight? In this last case, on which timescale? Do these define metrics on $\mathbb{R}$? What is the name of the problem where lines appear in a photo where there should just be a smooth gradient? An unfair three-sided die. An unfair three-sided die. Side $1$ will be rolled with probability $p_1$ , Side $2$ with probability $p_ 2$ and Side $3$ with probability $p_ 3$ . Find a formula for the probability that the $8^{th}$ $3$ will be rolled on the $10^{th}$ roll.  Attempt:  First 9 rolls there are 7 three's.  $$[\binom{9}{7}(p_3)^7(p_1+p_2)^2]\cdot p_3$$ $$=[84\cdot(p_3)^7(p_1+p_2)^2]\cdot p_3$$  any thoughts of this solution? Multiple vs single field capture for phone number form input Working on a form dealing with phone numbers, I've seen two methods to capture user input .   In past practices example 2 (image below) has proved effective in controlling phone number lengths on forms.   However with responsive in mind it would seem example 1 is considered a more popular pattern on forms. I've researched both patterns with the findings below.     Example 1  Pros   1 input = less taps on mobile device 1 input = less coding   Cons   could be difficult to control phone number format (1-555-555-5555, +22444455555, and etc)   Example 2  Pros   easier to control phone format reduced user error   Cons   3 inputs = more taps on mobile device more inputs = more coding   Both inputs have pros and cons and I'm not such which method would provide the best user experience for responsive environments. Can anyone share some insight or provide a better way to use phone number inputs? Is it possible to change the Environment of a parent process in Python? In Linux When I invoke python from the shell it replicates its environment, and starts the python process. Therefore if I do something like the following:  import os os.environ["FOO"] = "A_Value"   When the python process returns, FOO, assuming it was undefined originally, will still be undefined. Is there a way for the python process (or any child process) to modify the environment of its parent process?  I know you typically solve this problem using something like  source script_name.sh   But this conflicts with other requirements I have. The differences between TeX engines I am confused about what TeX and its offspring (LaTeX, pdfTeX/pdfLaTeX, e-TeX, ConTeXt, LuaTeX, etc.) are.  Some, like LaTeX, seem like add ons to TeX (maybe a change to the eyes and mouth, but not stomach). Others, like pdfTeX, seem like changes to the underlying system (i.e., a change to the stomach).  Is there a good reference that explains the differences and the evolution? I am looking for the stuff above, so I can make non-duplicate proposals on area 51.