apt-get: How to find link for packages being installed (and skip them)?
Can I see why a package is installed?
What is the difference between currying and partial application? I quite often see on the Internet various complaints that other peoples examples of currying are not currying, but are actually just partial application.  I've not found a decent explanation of what partial application is, or how it differs from currying. There seems to be a general confusion, with equivalent examples being described as currying in some places, and partial application in others.  Could someone provide me with a definition of both terms, and details of how they differ? How to recover a removed file under Linux? By accident, I used rm on a file I didn't want to delete. Is there a way that I can get it back under Linux? copy files over ssh Does Forbidden Island usually need any rule variants for playing with 5+ people? I don't see any reason why Forbidden Island wouldn't be able to handle 5 or maybe even 6 players with some simple variants. Does anyone have any experience with different player numbers with some wisdom to pass on?  It would be slightly harder to gather the required 4 treasure cards at one person, but there would be more people total to trade with. The island would sink faster and it would take longer for a certain critical player to have their turn, even though the navigator and helicopter can move anyone. How can these disadvantages be offset to keep the game strong and sufficiently difficult? Prime factorizations of consecutive numbers, can they both contains powers of greater than or equal to $1000$? I am teaching myself information about groups, but don't really understand how to work through this problem. Here is what I have been thinking so far (please note that I do not need to work through showing any closure): $\mathbb{Z}^*$ denotes the nonzero integers. Prove or disprove: $(\mathbb{Z}^*, \cdot)$ and/or $(\mathbb{Z}^*, \div)$ is a group.  For $(\mathbb{Z}^*, \cdot)$:  Group. Associative Law: Let $a,b,c \in \mathbb{Z}^*$. Then $(a\cdot b)\cdot c=a\cdot (b \cdot c)$, and the associative law holds. Existence of Identity: Let $a \in \mathbb{Z}^*$, then $a \cdot 1 = 1 \cdot a = a$, and the identity holds. Existence of Inverses: Let $a \in \mathbb{Z}^*$. Then the inverse of $a^{-1}=-a$, and the inverse holds. Note that this only works because we are ommitting zero.  Hopefully this looks like I am on the right track. I don't know to what extent I can explain logic vs showing it with mathematical operations, so I would appreciate guidance in this respect.  For $(\mathbb{Z}^*, \div)$: Not a group. Disprove by counterexample.  Yeah, I dunno about this one. I don't think it's true, because we will be introduction rational expressions that won't allow this to hold, but I'm not sure where I can use this information to disprove the statement. Why does increasing the number of features reduce performance? I'm trying to gain an intuition as to why increasing the number of features could reduce performance.  I'm currently using an LDA classifier which performs better bivariately among certain features but worse when looking at more features.  My classification accuracy is performed using a stratified 10-fold xval.    Is there a simple case of when a classifier would work better univariately than bivaraiately to gain a somewhat physical or spatial intuition of what is happening in these higher dimensions? $\mathbb Z[i]/ \langle 1+2i \rangle \cong \mathbb Z_5$ I am trying to prove that $\mathbb Z[i]/ \langle 1+2i \rangle$ is isomorphic to  $\mathbb  Z_5$.   The only thing that came to my mind was trying to apply the first isomorphism theorem using an appropiate function. If I consider the euclidean function $N: Z[i] \setminus \{0 \}  \to  \mathbb N$ defined as $N(a+bi)=a^2+b^2$, then I can express any element $z$ in $\mathbb Z[i]$ as $z=(1+2i)q+r$ with $N(r)=1,2,3,4$ or $r=0$.   If I define $f:\mathbb Z[i] \to \mathbb  Z_5$ as $f(x=(1+2i)q_x+r_x)=\overline{r_x}$, then it is clear that $f(x)=0$ if and only if $x \in  \langle 1+2i \rangle$. The problem with this function is that it doesn't satisfy $f(x+y)=f(x)+f(y)$ and it is not surjective for if $r_x=f(x)=3 (5)$, then if $r_x=a+bi$, we have $a^2+b^2=3$, which is absurd.  I don't know what else to do, any suggestions would be appreciated. Can two particles remain entangled even if one is past the event horizon of a black hole? iMac disk partion FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF and fusion drive unlinked What is the best way to parse html in C#? I'm looking for a library/method to parse an html file with more html specific features than generic xml parsing libraries. Find angle UFO in the picture attached I sent this problem to Presh Talwalkar who suggested me to send it to this site. I tried many things but was not able to find the correct solution.   I made various segments trying to get an equilateral triangle similar to the Russian triangle problem, but no success.  I also tried to flip the triangle UFO over side NO but again no success.   I tried to find like triangles, but not enough.  Could you please give me a hint?   Thanks, R. de Souza Is the Nintendo Switch region locked? Many Nintendo devices often come with , which means if you purchase a device in one country, you won't be able to play games from another (generally).  Is the Nintendo Switch also region locked like many of its predecessors such as the Wii U and Wii? How to justify $\phi(n) \ge \sqrt{n}$ If $\phi(n)$ is the Euler-totient function, how can I show that $\phi(n) \ge \sqrt{n}$? How to reinstall Windows 10 on new hard disk I've been using Windows 10 for a couple of month now (joined the Insider Preview).  Now my hard drive started ticking so I've bought a new SSD and I want to move the windows installation to the new hard drive, which has been connected to the computer (unpartitioned). I don't mind and I even prefer reinstalling it over again.   Since I have the free version of Windows 10 pro, can I still reinstall it anew? Does the windows 10 installation offer disk management and partition like the older Windows installations used to? How should I reinstall Winodws 10 x64 the easiest but still remain on free mode? Is it possible to upgrade the graphics card in modern laptops? As there's no definitive answer to this, and I would prefer not to be too specific about particular models, what are the things that determine whether this is possible or not?   What expansion slots would the laptop require to do this? How can you find out if a motherboard/chipset supports upgrades?  Is heat an issue? Could it void the warranty? How is battery life affected? Does a shortcode with a single attribute have to use an array? I want to build a shortcode that takes a single attribute.  Everything online is telling me to make it using an array:  // Add Shortcode function bg_comparison_points_shortcode( $atts ) {     // Attributes     $atts = shortcode_atts(         array(             'custom_field' =&gt; '',         ),         $atts,         'comparison_points'     );     return bg_calculate_points($custom_field); } add_shortcode( 'comparison_points', 'bg_comparison_points_shortcode' );   But in my mind something like this would be much simpler  // Add Shortcode function bg_comparison_points_shortcode( $custom_field ) {     return bg_calculate_points($custom_field); } add_shortcode( 'comparison_points', 'bg_comparison_points_shortcode' );   Is there a problem doing this simpler version? How to draw line through group plots in pgfplots? This issue has been driving me crazy for the past 10-20h. I have a group plot (pgfplots) where I have 2 plots one under another. I'd like to draw a vertical line (e.g. a helpline at x=150e-6) that would go through all of them.  When drawing inside the axis or rather nextgroupplot environment I can use something like this: \draw[thin] (axis cs:150e-6,\pgfkeysvalueof{/pgfplots/ymin}) -- (axis cs:150e-6,\pgfkeysvalueof{/pgfplots/ymax}); but this allows me to draw only on one of the subplots. If I go outside the axis environment I am able to draw on the entire {tikzpicture}, but I can't use the axis reference.  \begin{figure*}[h] \centering \begin{tikzpicture}  \begin{groupplot}[       group style = {group size=1 by 2, x descriptions at=edge bottom, vertical sep=0.2cm},       ytick={0, 1.8},       ymin=0,       ymax=3,       xmin=0,       xmax=550e-6,       change x base=true,       x SI prefix=micro]  \nextgroupplot \addplot table [x index = {0}, y index = {1}, col sep=comma] {plots/plot1reduced.csv};  \nextgroupplot[x unit=s] \addplot table [x index = {0}, y index = {3}, col sep=comma] {plots/plot1reduced.csv};  \draw[thin] (axis cs:150e-6,\pgfkeysvalueof{/pgfplots/ymin}) -- (axis cs:150e-6,\pgfkeysvalueof{/pgfplots/ymax});  \end{groupplot} \end{tikzpicture} \caption{Case 1} \label{fig:case1plot} \end{figure*} Proving that the Hopf map $S^3 \to S^2$ is a submersion I need to show that the Hopf map $H : S^3 \to S^2$ is a submersion. There are many ways to define it, but for now I've gone with the restriction of the function $F : \mathbb{R}^4 \to \mathbb{R}^3$ mapping $$(x,y,u,v)\mapsto (2(xu+yv), 2(xv-yu), x^2+y^2-u^2-v^2).$$ It wasn't too bad to show that $F$ is a submersion, but is there a way to go from here to show that $H$ is a submersion? I can write down $H$ as the composition $$S^3 \overset{\iota}{\hookrightarrow} \mathbb{R}^4 \overset{F}{\to} \mathbb{R}^3 \overset{\pi}{\to} S^2,$$ and define $\pi(p) = p/\lVert p\rVert$, but I don't really know where to go after computing the Jacobian of $\pi$, and I don't know if this will even work for my purposes (I don't see how to argue that the composition of the corresponding differentials here isn't rank $1$ — I know $d\iota$ has trivial kernel but things seem to break down once I get to $d\pi$). I'm really just trying to avoid having to compute the Jacobian of $H$ with respect to the stereographic projections and show that that beast of a thing is full rank. Am I on the right track, or is there a better way? NRPE unable to read output, but why?