javascript sum with parseFloat giving wronge value
Is floating point math broken?
Optional argument after splat argument File changed listener in Java I'd like to be notified when a file has been changed in the file system. I have found nothing but a thread that polls the lastModified File property and clearly this solution is not optimal. My friend recently received a new digital drawing tablet (Wacom Intuos Pro). Among other features, there is a hole that resembles a charm hole found on mobile phones:    Other parts of the package (e.g. pen) do not have such holes, so it isn't possible to attach them using a band. What is the purpose of this hole? Is it just for attaching various charms and such? In a  a doubt was voiced about my answer, which claims GCM to requires $2^{128}$ for a successful forgery. The doubt was that the square root needs to be taken meaning the security would be $2^{64}$.  So of course I immediately checked the relevant security theorem ():  $$\mathbf{Adv}^{\text{auth}}_{\operatorname{GCM}[\operatorname{Perm}(n),\tau]}(\mathcal A)\leq \frac{0.5(\sigma+q+q'+1)^2}{2^n}+\frac{q'(\ell_A+1)}{2^\tau}$$  with $\sigma$ being the total plaintext size in blocks, $q$ being the total number of encryption queries, $q'$ being the total number of decryption queries, $n$ being the size in bits of the underlying permutation, $\ell_A$ being maximum authenticated input length in blocks and $\tau$ being the tag size in bits.  Now clearly from this we can see that performing $2^{n/2}=2^{64}$ queries yields a strong enough advantage for a break.  Now my question is: When talking about "n-bits of security" or "needs $2^n$ operations to break", do we usually talk about "online" security, ie queries to an oracle can be done and cost $1$ or "offline" security where no oracles are available or do we need to make this decision depending on the situation?  TL;DR: Does GCM offer 64 or 128 bit security? Why don't sandwich toasters have an on/off switch? The absolute majority of electrical appliances have an On/Off switch. However, the absolute majority of sandwich toasters do not - you just plug them into the socket and unplug them when you're done. At least, that's the case for all household sandwich toasters I've ever seen. I'm referring to this device, not the vertical toaster (where the lever doubles as a switch):    It looks like some models do have a switch, but apparently these are just the larger/industrial types, not the common variety.  Why is that? Find the general solution of $y'= a^{x + y}$ where y is the function Possible Duplicate:          Sounds like a silly question, but bear with me..  If you go into Peet's Coffee and access the wifi, you're taken to a web page that requires a 4-digit code you get with a purchase.   If you do the same at Starbucks you're taken to a page and asked to OK the terms of service.   I want to build something similar for a local independent coffee shop, something that requires the user to write a little about themselves before they can access the Internet.  I'm not sure which way to go -- looking for wifi routers that run an internal web server, or finding one that lets you direct users to an external website for authentication, somehow redirecting back to the access point once successful.   Has anyone done anything like this and can share their experience? How to prove this binomial identity $\sum_{r=0}^n {r {n \choose r}} = n2^{n-1}$? I am trying to prove this binomial identity $\sum_{r=0}^n {r {n \choose r}} = n2^{n-1}$ but am not able to think something except induction,which is of-course not necessary (I think) here, so I am inquisitive to prove this in a more general way.  The left side of an identity occurs while solving another problem (concerning binomial theorem) so I am more interested in deriving the right side from the left side, else I have to remember it now onward.  EDIT: I am more interested in an algebraic proof rather than combinatorial argument or something involving calculus (however I liked  and  solution), hence I am removing the combinatorics tag. Why does a 'sudo -i' login shell break a here-doc command string argument? In the sequence of five commands below, all depend on single-quotes to hand off possible variable substitution to the called bash shell rather than the calling shell. The calling user is xx, but the called shell will be run as user yy. The first command substitutes $HOME with the calling shell's value because the called shell is not a login shell. The second command substitutes the value of $HOME loaded by a login shell, so it is the value belonging to user yy. The third command does not rely on a $HOME value and creates a file in the guessed home directory of user yy.  Why does the fourth command fail? The intention is that it writes the same file, but relying on the $HOME variable belonging to user yy to ensure it actually does end up in her home directory. I don't understand why a login shell breaks the behaviour of a here-doc command passed in as a static single-quoted string. The failure of the fifth command verifies that this problem is not about variable substitution.  xx@host ~ $ sudo -u yy bash -c 'echo HOME=$HOME' HOME=/home/xx xx@host ~ $ sudo -iu yy bash -c 'echo HOME=$HOME' HOME=/home/yy xx@host ~ $ sudo -u yy bash -c 'cat &gt; /home/yy/test.sh &lt;&lt; "EOF" &gt; script-content &gt; EOF &gt; ' xx@host ~ $ sudo -iu yy bash -c 'cat &gt; $HOME/test.sh &lt;&lt; "EOF" &gt; script-content &gt; EOF &gt; ' bash: warning: here-document at line 0 delimited by end-of-file (wanted `EOFscript-contentEOF') xx@host ~ $ sudo -iu yy bash -c 'cat &gt; /home/yy/test.sh &lt;&lt; "EOF" &gt; script-content &gt; EOF &gt; ' bash: warning: here-document at line 0 delimited by end-of-file (wanted `EOFscript-contentEOF')   These commands were issued on a Linux Mint 18.3 Cinnamon 64-bit system, which is based on Ubuntu 16.04 (Xenial Xerus).  Update: The here-doc aspect is just clouding the issue. Here's a simplification of the problem:  $ sudo bash -c 'echo 1 &gt; echo 2' 1 2 $ sudo -i bash -c 'echo 1 &gt; echo 2' 1echo 2   Why does the first of those two commands preserve the linebreak and the second does not? sudo is common to both commands, yet seems to be escaping/filtering/interpolating differently depending on nothing but the "-i" option. Is an expanding map on a compact metric space continuous? I got inspired by this question  to think about the following problem: Suppose you have a compact metric space $(X,d)$ and an expanding map $T:X\rightarrow X$, i.e. $d(Tx,Ty)\geq d(x,y)$ for every $x,y\in X$. Is the map $T$ then continuous? Without assuming continuity we already know that $T^n(X)$ must be dense in $X$ for any $n\geq 1$, since given $z\in X$ the orbit of $z$ must accumulate upon $z$. But showing continuity has escaped me so far. If there are counter-examples using the Axiom of Choice that also interests me. Describing groups with given presentation? $\langle x,y\ |\ xy=yx,x^5=y^3\rangle$ and $\langle x,y\ |\ xy=yx,x^4=y^2\rangle$. I'm trying to describe the groups with presentations $\langle x,y\ |\ xy=yx,x^5=y^3\rangle$ and $\langle x,y\ |\ xy=yx,x^4=y^2\rangle$. I have some problems getting a good picture of what they look like...   For the first one, $xy=yx$ allows us to say that any element in the group can be written as $x^iy^j$ for some $i,j$. More precisely, using $x^5=y^3$, we can always reduce $j$ to $0,1$ or $2$, whereas $i$ could have any value. So I was thinking about $\mathbb{Z} \times C_3$. But the other way around (reducing $i$ this time) it's also $C_5 \times \mathbb{Z}$. But then I should be able to prove that both descriptions are equivalent, which I can't do...  For the second, I proceed similarly and get to the same kind of problem...  Could you tell me where I'm going wrong?  Thank you very much in advance! Centering in the \align* environment How to clone a Windows 10 dell onto an SSD I've recently bought a Dell Inspiron 3650, and would like to clone the disk onto a samsung SSD I have bought for it, in order to speed up boot times etc.  Samsung provide a clone tool called "Samsung data migration", which I've had success with in the past for cloning a system from a HDD to SSD.  Having tried it on the dell, the disk is not bootable, Leaving me with an error that no bootable media can be found. I've tried using a recovery usb to fix any boot system errors, but this fails with an error.  Booting into windows on the old HDD, the system recognises the disks have the same ID and disables the SSD, so it looks like the clone was successful.  I've tried disabling secure boot in the bios and then doing the clone, but this doesn't make a difference.  What else should I try? The system has Windows 10 home installed and is brand new, straight out of the box. Auto mount a disk drive in ubuntu 14.04 LTS (Bookmark directory not found) What is the possessive of "you guys"? in -> inner  out -> outer / (outter?)  What is the history or set of rules behind why 'inner' doubles the 'n' but 'outer' doesn't double the 't'? Why are Harry's GoF dreams in the third-person? How can I disable cloud-init? I have a fully-configured instance and an image from that for an autoscaling group. When autoscaling new instances from this image, it calls cloud-init. cloud-init changes the hostname and breaks fstab.  I want to prevent cloud-init from starting on instance launch. Alien invasion movie, giant robot aliens with long legs capturing people Coloring lines inside textarea