Try to calculate the following on python shell:  &gt;&gt;&gt; 5.3-2.7 2.5999999999999996 &gt;&gt;&gt; 2.8-2.7 0.09999999999999964 &gt;&gt;&gt; 4.7-2.8 1.9000000000000004 &gt;&gt;&gt; 4.3-2.5 1.7999999999999998 &gt;&gt;&gt;    Why does it happen? How can I prevent this problem from making bugs in my code?
Consider the following code:   0.1 + 0.2 == 0.3  -&gt;  false   0.1 + 0.2         -&gt;  0.30000000000000004   Why do these inaccuracies happen?
Can we have a list of all the Stack Exchange domains somewhere, for firewall purposes? I work behind an really annoying firewall, and I just want the net admin to add all the SE websites to the whitelist. Right now I've lost access to Stack Overflow's authentication, but not Meta's... so I have to come here before I log in there.  It's driving me nuts. Basically I just want to add an exclusion rule for all SE domains; not only the website domains, but also the content domains such as gravatar.com, quantserve.com, the domain that holds static content, etc... How can I vertically align entries in my acronyms' list? I use the Glossaries package to generate it. Here is MWE:  % !TeX program = xelatex % !TeX encoding = utf-8 % !TeX spellcheck = ru_RU  \documentclass[12pt, a4paper]{article}  \usepackage{polyglossia} \setdefaultlanguage{russian} \setmainfont[Ligatures=TeX]{Times New Roman}  \usepackage[xindy={glsnumbers=false}, nonumberlist, nopostdot, nogroupskip]{glossaries} %\setglossarystyle{super} % uncomment for style "super" \makeglossaries  \begin{document}  \newacronym{bam}{ДАП}{Двунаправленная Ассоциативная Память} \newacronym{ai}{ИИ}{Искусственный Интеллект} \newacronym{am}{АП}{Ассоциативная Память} \newacronym{ann}{ИНС}{Искусственная Нейронная Сеть} \newacronym{an}{ИН}{Искусственный Нейрон} \newacronym{it}{ИТ}{Информационные Технологии} \glsaddall  \printglossaries  \end{document}   With the default style I have the following:  As you can see, the long names are not vertically aligned. What I want can be achieved with the    \setglossarystyle{super}   But it this case, short names lose the BOLDness, some small horizontal indent appears and the spacing between lines becomes smaller:  where RED is some extra indent, which I don't need. Thank you for your answers! How should I cite a website URL? Currently the migration path options from SO are:   Meta.SO Serverfault SuperUser Webmasters Programmers   If we are going to be limited to 5 options, shouldn't we periodically re-evaluate which sites are most appropriate?   (10k only) indicate that the top sites for the last 90 days are:   Superuser - 564 - 5% rejected ServerFault - 278 - 10% rejected Tex - 157 - 13% rejected DBA - 144 - 2% rejected Sharepoint - 127 - 1% rejected Programmers - 126 - 26% rejected CodeReview - 100 - 3% rejected Meta.SO - 81 - 18% rejected Wordpress - 75 - 14% rejected Webmasters - 58 - 8% rejected   All these migrations for sites out of the list required a flag and a moderator to process it.  This is just extra work for the mod team!  If we had the top 5 destinations by volume as the 5 options, we would have had a net savings of 160 flags to be processed.  I suspect we will actually see these numbers change quite a bit if it's easier for users to put questions in the appropriate spot without moderator intervention.  Can we have a review of the migration path list based on migration volume?  Think of the flags! Normally while searching using grep, the command I was using was this:  grep -nri "String"   whereas most of my colleagues do this:  grep -nri "String" *   What does the latter do (the * part)? I am running Ubuntu 14.04 from Windows, using virtualbox 5.0. I tried several options to make size of Ubuntu in virtual box larger, but none helped so far.   I am using latest virtual box with latest guest add on installed. sudo apt-get install virtualbox-guest-dkms virtualbox-guest-utils virtualbox-guest-x11 I went to Ubuntu 'software and Updates' and made sure that under 'Additional Drivers' tab, 'using x86 visualization solution...' is active. In virtualbox window, under view->virtual screen 1, all 'resize to' options are disabled.   None of these options helped. This is frustrating. Any comments or help? Can the problem be I am using 64 bit system? Does this problem occurs in earlier/later versions? If not, please suggest a 'good' version of Ubuntu for virtualbox. This is a general, community wiki question regarding duplicate content.  If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on .     What does Google consider to be duplicate content? Will the way I am presenting my content result in a duplicate content penalty? How can I avoid having my site's content treated as duplicate content? How to find and delete files older than specific days in unix? I've been looking for the name of a sci-fi romance book about space travel but haven't been successful so far. I came across it a few years ago, read the plot on its back cover but didn't read the book. It is about two spacecraft pilots, a man and a woman, who travelled at light speed (or maybe FTL, I can't remember) in separate ships. Every time they return to Earth, centuries have passed on Earth because of time dilation. They meet each other for a few times on Earth in different eras, but don't know when, if ever, they will meet again. I don't know how it ends.   If anyone knows which book I'm talking about, could you please tell me the name? Thanks a lot! How to show ascii art at the top of the terminal when it's opened? As you can see on this screenshot of 's Guake he has a startup message of ASCII art when he opens it, and that's what I'd like to do, can someone help me? I have a directory on my Windows 7 machine that has hundreds if not thousands of sub-directories.  Some of them have files, some do not.  I want to delete all the empty directories.  Looking at the del and rmdir DOS command, it does not look like you can recursively do this without deleting all the files.  Is there a way to do this from the command line? Probability of Various Combinations of Weather There's a 10% chance it will rain today. There's a 15% chance it will snow today.   What percentage chance is it that it will:   Both rain and snow (it can both rain and snow at the same time)? Neither rain nor snow? -   Raining and snowing are independent of each other.  EDIT: (ADDED)   Rain or snow but not both? Probability of selecting an even natural number from the set $\Bbb N$. I confirmed on  thread that there are as many as even natural numbers as there are natural numbers.   Question : Suppose I have selected a number $n \in \mathbb N$; what is the probability that $n$ is even?  My Thought : $\text{Probability} = \dfrac{\text{n(E)}}{\text{n(S)}}$ Here $\text{n(S)}$ is the set of all natural numbers i.e. $\mathbb N$, and $\text{n(E)}$ is set of all even natural numbers. Since it is proved that number of elements is the set $\mathbb N$ is exactly the same as the number of elements in the set of natural numbers (it’s very easy to put the set of natural numbers, $\Bbb N=\{0,1,2,3,\dots\}$, into one-to-one correspondence with the set $\text{E}=\{0,2,4,6,\dots\}$ of even natural numbers; the map $\Bbb N\to \text{E}:n\mapsto 2n$ is clearly a bijection.) ; Thus, Probability $= \boxed 1$ I know this is definitely wrong.Probability must be $0.5$. But where am I wrong? Can anyone explain ? Thanks! An operator on the other side of the Schrödinger equation A form of the  is  $$     \left[-\frac{\hbar^2}{2m} \nabla^2 + V(\vec{r}, t)\right]\Psi = i\hbar \frac{\partial}{\partial t} \Psi $$  The bracketed term is of course the Hamiltonian, and the whole equation can hence be written as  $$     \hat{H}\Psi = i\hbar \frac{\partial}{\partial t} \Psi $$  My question is, is there a existing/named operator represented by $i\hbar \frac{\partial}{\partial t}$? That is, can we further rewrite the equation as  $$     \hat{H}\Psi = \hat{\Theta}\Psi $$  For some predefined operator $\hat{\Theta} = i\hbar \frac{\partial}{\partial t}$? Let $a,b,c\in\mathbb{R}$ such that $\sqrt{a^2+b^2}=1&lt;c$.  Find $I:=\int_{0}^{2\pi} \frac{1}{a\cos(t)+b\sin(t)+c}dt$.  So, I set $z=e^{it}$ and then $dz=ie^{it}dt$ and so $\frac{dz}{iz}=dt$. Therefore,  $\begin{align*} I &amp; =\frac{1}{i}\int_{|z|=1} \frac{dz/z}{a\cdot\frac{z+z^{-1}}{2}+b\cdot\frac{z-z^{-1}}{2i}+c} \newline &amp;=\frac{2}{i}\int_{|z|=1} \frac{dz}{a\cdot(z^2+1)-ib\cdot(z^2-1)+2cz} \newline &amp;=\frac{2}{i}\int_{|z|=1} \frac{dz}{(a-ib)z^2+2cz+a+ib}\newline &amp;= \frac{2}{i}\int_{|z|=1} \frac{dz}{(z-z_+)(z-z_-)}\end{align*}$  Where $z_{\pm}=\frac{-2c\ \pm\ \sqrt{4c^2-4(a+ib)(a-ib)}}{2(a-ib)}=\frac{-c\ \pm\ \sqrt{c^2-(a^2+b^2)}}{(a-ib)}=\frac{-c\ \pm\ \sqrt{c^2-1}}{(a-ib)}$.  Therefore, if we define $f(z)=\frac{1}{z-z_-}$, we get that $f$ is analytic in $\{z:|z|\leq 1\}$ since  $$|z_-|=\Bigg|\frac{-c-\sqrt{c^2-1}}{a-ib}\Bigg|=\bigg|c+\sqrt{c^2-1}\bigg|&gt;|c|&gt;1$$  Finally from Cauchy's Integral Formula:  $$I=\frac{2}{i}\cdot 2\pi i\cdot f(z_+)=4\pi \frac{1}{z_+-z_-}=\frac{2\pi(a-ib)}{\sqrt{c^2-1}}$$ Which is not always real... So my question is what is the problem.  Moreover, sometimes it is correct, e.g. $a=1,b=0,c=2$ gives the correct answer $\frac{2\pi}{\sqrt{3}}$. I used to do a full factory wipe then flashed a stock firmware with Odin, that helped me get back to having access to my mobile network then I flashed to Resurrection Remix 5.5.3 and lost access to my mobile network (Emergency Calls Only) I checked my IMEI and it appears to be valid. I didn't backup my /efs I didn't do anything to it. What seems to be the solution? I have a Samsung Galaxy S3 (I-9300) Is linear algebra more “fully understood” than other maths disciplines? In , it was discussed how LA is a foundation to other branches of mathematics, be they pure or applied. One answer argued that linear problems are fully understood, and hence a natural target to reduce pretty much anything to.   Now, it's evident enough that such a linearisation, if possible, tends to make hard things easier. Find a Hilbert space hidden in your domain, obtain an orthonormal basis, and bam, any point/state can be described as a mere sequence of numbers, any mapping boils down to a matrix; we have some good theorems for existence of inverses / eigenvectors/exponential objects / etc..  So, LA sure is convenient.  OTOH, it seems unlikely that any nontrivial mathematical system could ever be said to be thoroughly understood. Can't we always find new questions within any such framework that haven't been answered yet? I'm not firm enough with G&ouml;del's incompleteness theorems to judge whether they are relevant here. The first incompleteness theorem says that discrete disciplines like number theory can't be both complete and consistent. Surely this is all the more true for e.g. topology.  Is LA for some reason exempt from such arguments, or does it for some other reason deserve to be called the best understood branch of mathematics? `testl` eax against eax? I am trying to understand some assembly.  The assembly as follows, I am interested in the testl line:  000319df  8b4508        movl   0x08(%ebp), %eax   000319e2  8b4004        movl   0x04(%eax), %eax   000319e5  85c0          testl  %eax, %eax   000319e7  7407          je     0x000319f0     I am trying to understand that point of testl between %eax and %eax? I think the specifics of what this code isn't important, I am just trying to understand the test with itself - wouldn't the value always be true? How can I prove $\sup(A+B)=\sup A+\sup B$ if $A+B=\{a+b\mid a\in A, b\in B\}$ If $A,B$ non empty, upper bounded sets and $A+B=\{a+b\mid a\in A, b\in B\}$, how can I prove that $\sup(A+B)=\sup A+\sup B$? LCM. What am I missing? Problem statement:  Let $S$ be the set of all positive integers $n$ such that $n^2$ is a multiple of both $24$ and $108$. Which of the following integers are divisors of every integer $n$ in $S$? The choices are: $12, 24, 36, 72$. The solution is $12$ and $36$. My solution was $S = \{36, 36* 6^3, 36*6^5, ...\}$  I can't figure out this problem. I started by finding the $\text{lcm}(24,108)$ and solved for $n$. I got some of the numbers in the set $S$, but not all of them, and I don't see what I'm missing. Update: added the choices and what my results