Is the C# Programming Guide right on pretending that arrays implement `IEnumerable`?
Why do C# multidimensional arrays not implement IEnumerable?
Display SharePoint Online in an iframe on different domain We would like to display pages from SharePoint Online in an iframe of a Page hosted somewhere else, e.g. in an Azure Web App:  &lt;iframe src="https://site.sharepoint.com/"&gt;&lt;/iframe&gt;   When we do this (in Chrome for example), we get the following error:     Refused to display " ⏎                      Home.aspx" in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'.   A Page from SharePoint 2013 (on premise) can be displayed in an iframe from a Page hosted on another domain, if the following control is added to the head of the master page:  &lt;WebPartPages:AllowFraming runat="server" /&gt;   However if this control is not added to the master-page, then we also get the above mentioned error.  As far as I know there is no possibility to adjust the master-page in a SharePoint Online Team Site. Is that correct?   In a Publishing Site you are allowed to adjust the master-page, or even add a new one. But I can't find anything similar in Team Sites.  Does anybody know if it is somehow possible to configure domains which do not fall under the "X-FRAME-OPTIONS: SAMEORIGIN"-policy in a SharePoint Online environment? Or if there is another possibility to display SharePoint Online content in an iframe on a different domain. I checked google, checked the Site settings and checked the Office 365 admin center, but didn't find anything. Why isn't my website in Google search results? How can I obtain a Cauchy distribution from two standard normal distributions? I am interested in      Let $X\sim N(0,1), Y \sim N(0,1)$ independently. Show $\frac{X}{X+Y}$   is a Cauchy random variable.   My work:  $f_{X,Y}(x,y)=\frac{1}{2\pi} e^{\frac{-1}{2}(x^2+y^2)}, -\infty&lt;x,y&lt;\infty$ by independence  Let $U=\frac{X}{X+Y},V=X+Y$. (Is there a better $V$ to choose for this bivariate transformation?)  Then, $X=UV, Y=V - UV$. So, $|J|=V$.  $f_{U,V}(u,v)=f_{X,Y}(uv,v-uv)|J|=\frac{v}{2\pi}e^{\frac{-v^2}{2}(2u^2-2u+1)},-\infty&lt;u&lt;\infty$  $f_U(u)=\frac{1}{2\pi}\int_{-\infty}^{\infty}ve^{\frac{-v^2}{2}(2u^2-2u+1)}dv$. Let $y=\frac{v^2}{2}(2u^2-2u+1)$, so $dy=v(1+2u^2-2u)dv$. Then,  $f_U(u)=\frac{1}{2\pi(2u^2-2u+1)}\int_0^{\infty}e^{-y}dy=(\pi[(\frac{u-1/2}{2})^2+1])^{-1}, -\infty&lt;u&lt;\infty$,   which is not exactly a Cauchy distribution. Where did I mess up? More importantly, how would you proceed in solving this problem? Solidify conundrum? I stumbled across a solidify issue, I cannot wrap my head around. I have a simple mesh, consisting of three faces.  When adding a solidify modifier, I expect to get an object with three walls, where every angle is square. However, whatever I try, tweaking the various solidify parameters, what I get is something like the following, with a skewed rim.  Did I hit a bug, or is it a limitation of the solidify modifier? Is there a workaround? What happens if I am afflicted with a condition that worsens on a failed save and choose not to try to save? Do I:   Automatically suffer the effects of the failed save? Keep my current condition? Have no choice and must roll the save regardless?   This came up in a game earlier this afternoon when we decided to just stop saving against the effect that was causing us to fall unconscious. Joining elements of a list in GNU Make Sometimes it’s possible to use either a noun adjunct or the possessive case.     the shop door   the shop’s door   However, in certain phrases it’s not OK to do so.     the ship’s crew (the ship crew is wrong)   The questions are:   How can one find out what to use in such cases as “the shop(’s) door” when a noun adjunct option and the possessive case option are available?  How can one know which option is wrong in order to avoid the construction “ship crew”? Is there a difference in meaning between (a) the shop door (b) the shop’s door? Singular values of the data matrix and eigenvalues of the covariance matrix Associativty of smash product on compact spaces Let $Y,Z$ be compact or $X,Z$ locally compact. Then the canonical bijection    $$ (X \wedge Y) \wedge Z \rightarrow X \wedge (Y \wedge Z) $$    is a homeomoprhism.    I can prove the case when $X,Z$ are locally compact using exponential law. But I don't see how one approaches the case when $Y,Z$ compact. Hints? How to replace text between quotation marks with something from another file? I have the following kind of text: $OU = 'or'; $DINHEIRO_CAIXA = 'Cash balance'; $PAGINA = 'Page'; $DE = 'from'; $ENVIAR = 'Send'; $PRINCIPAL = 'Main';  I've already got all the text within the single quotation marks using cat arquivo | grep -oP &quot;'[^']+'&quot; | tr -d &quot;'&quot; This extracted text was then translated to Portuguese, but now I don't know how to replace the original text between single quotation marks with the translated text, I was looking for something like $OU = 'ou'; $DINHEIRO_CAIXA = 'Dinheiro em caixa'; $PAGINA = 'Pagina'; $DE = 'de'; $ENVIAR = 'enviar'; $PRINCIPAL = 'Principal';  I've tried using grep -F to replace the file itself, but it failed miserably because the pattern didn't match since I don't have the quotation marks on the new file, is there a way to do this? How to prove that $\mathbb{Q}$ ( the rationals) is a countable set I want to prove that $\mathbb{Q}$ is countable. So basically, I could find a bijection from $\mathbb{Q}$ to $\mathbb{N}$. But I have also recently proved that $\mathbb{Z}$ is countable, so is it equivalent to find a bijection from $\mathbb{Q}$ to $\mathbb{Z}$? I'm working on this problem already, the domain and co-domain are the set of Rational Numbers. we see that setting $x = 1$ and $y = n$, we obtain $f(n + 1) = f(n) + 1$  But I'm trying to prove that $f(n) = n + 1$ for all $n$, the case when $n = 1, 2$ is obviously true, how do I approach this via induction? What temperature can you attain with a solar furnace? why can't `_` be exported to the environment of bash? In bash, why can't _ be exported to the environment of the shell?  $ export _ $ export | grep _= $   output nothing. Or do I miss something?   How can I export _ into the environment?  See also . Thanks. PHP Session data not being saved I have one of those "I swear I didn't touch the server" situations. I honestly didn't touch any of the php scripts. The problem I am having is that php data is not being saved across different pages or page refreshes. I know a new session is being created correctly because I can set a session variable (e.g. $_SESSION['foo'] = "foo" and print it back out on the same page just fine. But when I try to use that same variable on another page it is not set! Is there any php functions or information I can use on my hosts server to see what is going on?  Here is an example script that does not work on my hosts' server as of right now:  &lt;?php session_start(); if(isset($_SESSION['views']))     $_SESSION['views'] = $_SESSION['views']+ 1; else     $_SESSION['views'] = 1;  echo "views = ". $_SESSION['views']; echo '&lt;p&gt;&lt;a href="page1.php"&gt;Refresh&lt;/a&gt;&lt;/p&gt;'; ?&gt;   The 'views' variable never gets incremented after doing a page refresh. I'm thinking this is a  problem on their side, but I wanted to make sure I'm not a complete idiot first.  Here is the phpinfo() for my hosts' server (PHP Version 4.4.7): For some of the apps I've developed (then proceeded to forget about), I've been writing plain SQL, primarily for MySQL.  Though I have used ORMs in python like , I didn't stick with them for long.  Usually it was either the documentation or complexity (from my point of view) holding me back.  I see it like this: use an ORM for portability, plain SQL if it's just going to be using one type of database. I'm really looking for advice on when to use an ORM or SQL when developing an app that needs database support.  Thinking about it, it would be far better to just use a lightweight wrapper to handle database inconsistencies vs. using an ORM. When something gets wet, it usually appears darker. This can be observed with soil, sand, cloth, paper, concrete, bricks...  What is the reason for this? How does water soaking into the material change its optical properties? Unable to install Cisco Packet Tracer 7.3 on Ubuntu 20.04 I am trying to install Packet Tracer 7.3 (latest version) on Ubuntu 20.04 but do not succeed to so so because of two dependencies which are not installable ("libdouble-conversion1" and "qt-at-spi").  However I successfully installed the previous version (7.2.2) which was available in an Ubuntu installer format (.run file) but I nothing happens when I run it from my gnome desktop.  I am quite a newbie in Linux so I appologies if answers are obvious...  Thanks in advance ;-)  Denis Let $a&gt;0$ and $f: \mathbb R \rightarrow \mathbb R$ with a property $\forall x,y \in \mathbb R;$ such that $0\;&lt;\;y\;-\;x\;&lt;\;a$ $$f(x)\;&lt;f(y).$$ Prove if the statements are true or false:  $1)$ $f$ must be injective.  $2)$ $f$ must be surjective.  I tried to use a quarter of a circle with radius $r=a$ or a right-angled triangle and translate it. When I moved it, I saw new values of $f$. I concluded the maximum value in the previous interval can't appear again in another interval when the distance between one point in the first interval and one point in the second is less than $a$. I also considered using an absolute value function, but I haven't done anything. I think, but I haven't proven it, that the function must be bijective. What are all of the connected subsets of $\mathbb{Q}$? The answer are the singletons of $\mathbb{Q}$. I can show that the open intervals of $\mathbb{Q}$ are disconnected by choosing some irrational in the open set and using it to form a separation. But strangely enough, I am having a hard time seeing why the subset $\{p,q \}$ of $\mathbb{Q}$ is disconnected. If say $p &lt; q$ and we choose some irrational $p &lt; x &lt;q$, the separation of $\{p,q \}$ would, I think, be given by $ \{p\}$ and $\{q\}$. But these aren't open in $\mathbb{Q}$ ...?