If you care, setter (plural: setters) and getter (plural: getters) are parts of a computer programms that get (or retrieve) and set (or store) values in memory.  But why do you write that words, that are, anyway, rather artificial (do they have uses in other contexts?) with double t?  You don't do it with other words such as producer, consumer. Even words that finish in consonant (reader) or in t (eater) are just added the r or er suffix.  Please clarify this non important issue to me.
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'?
How to calculate the correct focal length needed for a subject of a given size and distance? I need to purchase my first ever lens. So far I've only used lenses that were built into a camera. This specific lens is for the BlackMagic Deign Pocket Cinema Camera (a video only camera, but one that uses photography lenses). I would prefer this to be a prime lens.  I have tried to find the exact way to calculate the focal length of the lens I need but I have not been able to find a good resource to make this simple enough for my limited optics knowledge. Can you please explain a simple way to calculate the focal length of a lens given the following inputs as an example:    I would prefer a simplified mathematical explanation so that I may use it to make similar determinations in the future using a "" method.  I have . Using that method, I came up with:  Required lens focal length = 7.02mm sensor height x (77in / 36in) = 15mm   Is that correct? What is the difference between 'su -' , 'sudo bash' and 'sudo sh'? I would like to know what is the difference between    su - sudo bash sudo sh   I cannot login as root while doing su - because I do not have the root password - I mean I have my user password with which I can sudo "command"  but this password does not work for su - I can log in as root with sudo bash with my user password and I can login while doing sudo sh but then I get a command prompt in this form # Weight Painting Won't Get Rid of Weird Protrusions Any class of a nonempty $X$ generates a base for a topology on $X$. Theorem Any class $\mathcal{A}$ of subsets of a nonempty set $X$ is the subbase for a unique topology $\tau$ on $X$. That is to say, the finite intersections of members of $\mathcal{A}$ form a base for the topology $\tau$ on $X$. Example Consider $X=\{a,b,c,d\}$ Let $\mathcal{A}=\{\{a,b\},\{b,c\},\{d\}\}$ The finite intersection of members of $\mathcal{A}$ give us: $$\mathcal{B}=\{\{a,b\},\{b,c\},\{d\},\{b\},\varnothing,X\}$$  How is it true that $X \in \mathcal{B}$ ? By definition of subbase, the finite intersection of members of $\mathcal{A}$ are the members of some base $\mathcal{B}$. But for $a_i \in \mathcal{A}, \displaystyle\bigcap a_i \neq X$ for any finite intersection of $a_i$'s. Look: $\{a,b\}\cap\{b,c\}\cap \{d\} \neq \{a,b,c,d\}$ nor do any other intersection of elements of $\mathcal{B}$ result in $X$. Anybody know what's going on here? Why is $X \in \mathcal{B}$? How do I install and manage GNOME Shell extensions? How do I install GNOME Shell extensions?  Is it possible to update, remove and manage the extensions? How do I get transparency to work with the Principled BSDF shader? How do I get the Cycles Principled BSDF shader to support a base color image such as a 32bit png with alpha or a tga with an alpha channel, and get the transparency to work. I don't see anywhere on the Principled BSDF shader that handles transparency.  Without success, I have tried:   Properties Editor>Render tab>Film rollout>Transparent Properties Editor>Material tab>Settings rollout>Viewport Alpha (changing to other than Opaque). Adding a Transparent BSDF and Diffuse BSDF after the base color image node and using a Mix Shader to combine them. Dynamic loading of python modules Baking lots of bread - keeping a yeast starter How do I change my profile picture, or avatar? Where does the image come from? How do I change my profile picture, or avatar? How do I change my profile picture on all SE sites at once? How can I use different avatars on different SE sites? How do avatars work? How do the SE sites know when I changed my Gravatar? Why do SE sites show a different Gravatar identicon than other sites where I use the same email address? How can I use a Gravatar image after logging in to facebook.stackoverflow.com? I changed my picture but am still seeing the old one    See also: Is there a software utility to adjust screen gamma/brightness/contrast? I use to work at night and it is eye-hurting to watch at lightbulb-bright screens (I've got two - laptop's built-in panel and an external 18-inch CRT) in a dark environment. So I adjust my screens to be darker.  Can I do this a software way instead of pressing monitors' buttons that many times every time? Every time I install a new Linux kernel, it gets left in the grub_config, making the boot menu longer each time.    I know I can manually search through the installed packages and remove them.  Does Ubuntu provide any easier way to clean them up or keep them from showing in the boot list? When is Gauss' law not applicable? What's the difference between X = X++; vs X++;? Have you ever tried this before?  static void Main(string[] args) {     int x = 10;     x = x++;     Console.WriteLine(x); }   Output: 10.  but for   static void Main(string[] args) {     int x = 10;     x++;     Console.WriteLine(x); }   Output: 11.  Could anyone explain why this? What is the biggest display of power through the Force in Star Wars? Biblatex 3.3 name formatting I would like to create a custom format for citing authors' names in the text, let's call it "newformat". One option I can think of is creating a new bibmacro for names where the parameters are changed to my liking, such as   \documentclass{article}    \usepackage{filecontents}   \usepackage[backend=biber]{biblatex}[2016/01/01] %the latest version of biblatex?   % biber is version 2.4; the latest?  \begin{filecontents}{\jobname.bib} @misc{Doe12,   author = {Doe, John},   year = {2012},   title = {A macro for formatting names}, } \end{filecontents}  \addbibresource{\jobname.bib} \nocite{*}  \newbibmacro{name:newformat}{\printnames{authors}} \DeclareNameFormat{newformat}{%   \usebibmacro{name:newformat}{\textbf{#1}}{\textbf{#3}}{#5}{#7}%   \usebibmacro{name:andothers}% }  \begin{document}    \section*{Testing the format here}    I am citing   \citename{Doe12}[newformat]{author}    \printbibliography % to make sure that the .bib file is properly formated.  \end{document}   Here, I just used \textbf for the sake of the example, but I ultimately want to use other functions, say upper case or palindrome!  However, I get this weird error message:  ! Illegal parameter number in definition of \blx@defformat@d. &lt;to be read again&gt;                     3 l.20   \usebibmacro{name:last}{#1}{#3                                      }{#5}{#7}%   which seems to indicate that the second option {#3} is not expected. I am a bit at a lost here; I checked the biblatex package and \usebibmacro{name:last} must be given 4 parameters, isn't it? Please advise. I'm trying to get my head around mutable vs immutable objects. Using mutable objects gets a lot of bad press (e.g. returning an array of strings from a method) but I'm having trouble understanding what the negative impacts are of this. What are the best practices around using mutable objects? Should you avoid them whenever possible? Uniform integrability of a backward submartingale Let $\{\mathcal{F}_n\}_n$ be a decreasing sequence of sub-$\sigma$-fields of $\mathcal{F}$($\mathcal{F}_{n+1}\subset\mathcal{F}_n$) and let $\{X_n\}_n$ be a backward submartingale($E[|X_n|]&lt;\infty$, $X_n$ is $\mathcal{F}_n$ measurable and $E[X_n|\mathcal{F}_{n+1}]\geq X_{n+1}$).  If we know $l=\lim_{n\rightarrow\infty}E[X_n]&gt;-\infty$, how to prove that $\{X_n\}_n$ is uniformly integrable? Many thanks!  I have an idea, it is enough to show:    $\sup_nE[|X_n|]&lt;\infty$;  $\forall\epsilon&gt;0$, $\exists\delta&gt;0$ s.t. $\forall A\in\mathcal{F}$ such that $\mathbb{P}(A)&lt;\delta$, we have $\sup_nE[1_{A}|X_n|]&lt;\epsilon$.    For $|X_n|=2X_n^+-X_n$, we have  $$E[|X_n|]=2E[X_n^+]-E[X_n]\leq 2E[X_0^+]-l\leq 2E[|X_0|]-l$$  which implies $\sup_nE[|X_n|]&lt;\infty$.  Secondly, $\forall A\in\mathcal{F}$, we can suppose without loss of generality that $A\in\mathcal{F}_0$.  $$E[1_{A}|X_n|]=2E[[1_{A}X_n^+]-E[[1_{A}X_n]$$  Does someone have an idea for this term? Thanks a lot..... My linear algebra professor proved that      Diagonalizable matrices with complex values are dense in set of $n \times n$ complex matrices.   He defined a metric (I believe) that was somehow related to the usual metric on $\mathbb{R}^{n^2}$.  Then somehow proved that diagonalizable matrices were dense because for any matrix $A$ if $\det(A - \lambda I) = 0$ on an open subset, then $\det(A - \lambda I)$ was the zero polynomial.  I Googled around a bit and found some stuff talking about the Zariski topology, and I am not sure this is what I want. Most of what I have found on this topology is much more general than what he was doing.  Does anyone know any resources that would explain how to go about proving this statement?  Edit: I found out how to prove this the way my professor did.  We define the norm of a matrix by $$ |A| = \max\{|Ax| : |x| = 1 \}.$$ Now we have a distance $d(A, B) &lt; \epsilon$. You can prove that if $(A - B)_{ij} &lt; \epsilon/n$, then $|A - B| &lt; \epsilon$.  Let $p(x)$ be the characteristic polynomial of $A$, an $n \times n$ matrix.  $$p(x) = \prod_1^n (x - x_i) = x^n + (-1)\sigma_1 x^{n - 1} + \cdots + (-1)^n\sigma_n$$ where $\sigma_1, \ldots, \sigma_n$ are the elementary symmetric polynomials of $x_1, \ldots, x_n$ which are the eigenvalues.  The discriminant of the characteristic polynomial is a symmetric polynomial, therefore it can be written in terms of the elementary symmetric polynomials, which in turn can be written in terms of the entries of the matrix.  But since the discriminant is a polynomial, it only has finitely many roots. Therefore for $\epsilon &gt; 0$, by changing the entries of the matrix less than $\epsilon / n$ we can find a new matrix $B$ such that $|B - A| &lt; \epsilon$ and the discriminant is not zero.   The discriminant being not zero means $B$ has distinct eigenvalues, thus has a basis of eigenvectors. Therefore, it is diagonalizable.  Thus the set of diagonalizable matrices is dense in the set of matrices with respect to that metric. How to evaluate $ \lim \limits_{n\to \infty} \sum \limits_ {k=1}^n \frac{k^n}{n^n}$? I can show that the following limit exists but I am having difficulties to find it. It is $$\lim_{n\to \infty} \sum_{k=1}^n \frac{k^n}{n^n}$$ Can someone please help me? How does ServerName and ServerAlias work?