What are the advantages of building tools/libs from source?
What is the difference between building from source and using an install package?
Why do Windows 10 foreground apps mysteriously launch as background processes? CW complex such that action induces action of group ring on cellular chain complex. Let $X$ be a space that satisfies the hypotheses used to construct a universal cover $\overline{X}$. Let $\pi = \pi_1(X)$ and consider the action of the group $\pi$ on the space $\overline{X}$ given by the isomorphism of $\pi$ with $\text{Aut}(\overline{X})$. Let $A$ be an abelian group and let $\mathbb{Z}[\pi]$ act trivially on $A$, $a \cdot \sigma = a$ for $\sigma \in \pi$ and $a \in A$.  Now, assume that $X$ is a CW complex. How do I see that $\overline{X}$ is a CW complex such that the action of $\pi$ on $\overline{X}$ induces an action of the group ring $\mathbb{Z}[\pi]$ on the cellular chain complex $C_*(\overline{X})$ such that each $C_q(\overline{X})$ is a free $\mathbb{Z}[\pi]$-module and$$C_*(X; A) \cong A \otimes_{\mathbb{Z}[\pi]} C_*(\overline{X})?$$ How to change the snapping increment in different units? I would like to know how to change the increments used for snapping transforms.  This would be useful in a number of situations but my problem now is that when I change the units it does not scale the snapping increments to match.  So when holding down ctrl the cube snaps from here:    To here:    I would like it to snap to the 1 foot grid, or possibly any other amount I find useful.  It would also be nice to be able to change the rotation snap as well. Expectation of truncated normal How to rename objects with python? What is the easiest way to find and replace text in 20 text files in a directory? I have 20 text files with various extensions in a directory.  I want to replace "nnn" with "ooo" in all files.  I could import them into a project in Eclipse or Visual Studio to replace them all but that is overkill and would add other meta files etc.  What is a simple way to do this, I'm thinking: select all files, right click, choose some tool called (e.g. "QuickReplacer") and fill in find and replace, click and done.  Does anyone know of a tool like this? Is a 1st-level spell cast using a 4th-level slot a 1st-level spell, or a 4th-level spell? As the title says: Is a 1st-level spell cast using a 4th-level slot a 1st-level spell, or a 4th-level spell? Given sequence of $L-$Lipschitz functions which converges pointwise, prove uniform convergence Let $f_n:[a.b]\rightarrow \mathbb{R}$ be sequence of $L-$Lipschitz functions, that is: $$\forall x,y\in[a,b]: |f_n(x)-f_n(y)|\leq L|x-y|$$   Suppose $f_n \rightarrow f$ pointwise, prove $f_n \rightrightarrows f$   I have all the parts of the puzzle for the proof, and I'm trying to put them all together, I'm using  in my answer.  I would appreciate is you could correct my proof, and if you have an alternative proof, I would be more then happy to see it.  My proof:   Let $\epsilon&gt;0.$  $f_n$ are uniformly continuous on $[a,b]:$  $\tag{1} \exists \delta&gt;0\ \forall x,y\in[a,b]: |f_n(x)-f_n(y)|&lt;\frac{\epsilon}{3}$  $f$ is also $L-$Lipschitz:  $\tag{2} \forall x,y\in[a,b]:|f(x)-f(y)|&lt;L|x-y|=\frac{\epsilon}{3}$  Let us set a partition of $[a,b]$ such as Stephen Montgomery-Smith suggests:     Pick points $x_1,\dots,x_m \in [a,b]$ which are distance   $\frac{\epsilon}{3}$ from each other.        For each $1 \le i \le m$, find a number $N_i$ so that for all $n \ge  N_i$ we have $|f_n(x_i)-f(x_i)| \le \epsilon/3$.   Let $N = \max_{1 \le i \le m} N_i$      Now given any $x \in [a,b]$, pick $1 \le i \le m$ such that $|x-x_i| &lt;\frac{\epsilon}{3L}:  |f_n(x)-f(x)|&lt;\frac{\epsilon}{3} \tag{3}$   $$\begin{align}|f_n(y)-f(y)| &amp;=|f_n(y)-f_n(x)+f_n(x)-f(x)+f(x)-f(y)| \\ &amp;\leq |f_n(y)-f_n(x)| + |f_n(x)-f(x)|+|f(x)-f(y)| \\ &amp;&lt; \frac{\epsilon}{3} + \frac{\epsilon}{3} + \frac{\epsilon}{3} = \epsilon \\\end{align}$$ Why does my ArrayList contain N copies of the last item added to the list? Are moving objects producing stronger gravity fields? If the strength of gravitational influence exerted by a body is derived from its mass and energy then is it true that a moving object which has some kinetic energy should also produce stronger gravitational pull than a static/slower one?  If that's correct then would it be also possible for an object moving fast enough to produce gravity so strong that it would collapse into a (fast moving) black hole? Lately it's happening to me this:  After completing one or more "First Posts" reviews, I go back to the Review Section main page:   And the post counter shows that there are still posts to review. I click the link to review them, but there is nothing.  Refreshing the page doesn't solve the issue: it shows the wrong number again. Find all n such that $\phi(n) = n/2$ My idea for the solution is something like this:  Since $2 | n$, $n = 2^a p_1^{e1} p_2^{e2} \cdots p_t^{et}$ where $a \geq 1$.  Then, $n/2 = \phi(2^a) \phi(p_1^{e1}) \phi(p_2^{e2}) \cdots \phi(p_t^{et})$.  Looking at the case that $t = 0$,  $n/2 = \phi(2^a) = 2^{a-1}$, and therefore $n = 2^a$.  Otherwise, $n = 2^a \phi(p_1^{e1}) \phi(p_2^{e2}) \cdots \phi(p_t^{et}) = n = 2^a p_1^{e1} p_2^{e2} \cdots p_t^{et}$. Since $\phi(n) &lt; n$, this is a contradiction, and therefore, the only $n$'s that apply are the powers of 2.  Is this right? Also, we were asked to find $n$ such that $\phi(n) = n/3$. How would I go about that one? Geometric interpretation of $\frac {\partial^2} {\partial x \partial y} f(x,y)$ Are there any geometric interpretation for the second partial derivative? i.e.  $$f_{xy} = \frac {\partial^2 f} {\partial x \partial y}$$  In particular, I'm trying to understand the determinant from  for determining whether a critical point is a minima/maxima/saddle points:  $$D(a, b) = f_{xx}(a,b) f_{yy}(a,b) - f_{xy}(a,b)^2$$  I have no trouble understanding $f_{xx}(x,y)$ and $f_{yy}(x,y)$ as the of measure of concavity/convexity of f in the direction of x and y axis. But what does $f_{xy}(x,y)$ means? What do the words 'RELATED' and 'ESTABLISHED' individually signify in RELATED,ESTABLISHED state in iptables? What's the origin of the flattened X that appears when of a small (but powerfull enough) light is reflected in our non-powered TV screen? How to split a string in sql server 2008 using stored procedure and insert the data to table What is wrong with this query? (Unknown error parsing query) Errors and Residuals Is there an easy way to get to www.stackexchange.com from any of the SE sites? One thing I've noticed about the relatively new sitewide layout is that I can't find a quick way to get back to www.stackexchange.com without finding StackExchange in the sites list. As a result, I am typing stackexchange in my toolbar a whole lot more often now. In particular, I tend to enjoy browsing the hot questions list and my own personal feed quite often so visit these pages on a daily basis. Is there an easy link to them that I'm missing?  (On the android app, there is a feed in the menu that I really appreciate, something like that on the desktop would be ideal!) Why is the field inside a conducting shell zero when only external charges are present?