Use worksheet name as a variable in a lookup
Is it possible to get the sheetname?
Compute the period of a decimal number a priori Saving image from PHP URL When is JavaScript's eval() not evil? I'm writing some JavaScript code to parse user-entered functions (for spreadsheet-like functionality). Having parsed the formula I could convert it into JavaScript and run eval() on it to yield the result.  However, I've always shied away from using eval() if I can avoid it because it's evil (and, rightly or wrongly, I've always thought it is even more evil in JavaScript, because the code to be evaluated might be changed by the user).  So, when it is OK to use it? How do I check if a string is a number (float)? Can you set custom ringtones for contact groups? In iPhone, you can easily change the default ringtone (Settings → Sounds → Ringtone) and set a custom ringtone for individual people (Contacts → [some person] → Edit → Ringtone).   But can you set a custom tone for a group of contacts? (E.g. "family" or "workmates".)  I think that would be handy—and quite basic functionality, so to speak—but I couldn't find a way to do this through the iPhone UI. Is it possible at all (without jailbreaking)? My textbook explains the proof, which I don't understand:  "Consider two bases $v_1...v_p$ and $w_1...w_q$ of V. Since the vectors $v$ are linearly independent and the vectors $w$ span V..."  How exactly does $w$ span V?   The book then says the same for vectors $v$, that $v$ spans V and hence $p=q$, but I don't really understand how you can assume that given two sets of vectors that are basis, one set must span V. How to identify hardware performance bottleneck in laptop? Is there any tool that helps to determine the weakest link of my current laptop hardware specification? Any online guide to help me choose nice balanced configuration for the new laptop?    I need to find the answers:  a) which component should be invested to increase overall performance the most? CPU? GPU? RAM?  b) which component may decrease overall performance and work as a bottleneck for the specific configuration?    The question is general and regards both to validating the current hardware usage (and its possible bottlenecks) and estimating the performance (and avoiding possible issues) of specs I'm going to choose and buy.    P.S. For the specific laptop I need to replace, the following software will be in use:    Windows antivirus, firewall, dropbox service running in the background mail app + web browser with a dozen or so tabs open from time to time: libreoffice apps, movies, games (both online and installed). Make links posted by users open in a new window Most of the time when I follow a user's link, I just want to see their site, look it over, then return to answer their question (not leave SO completely and not come back). Could we make the links users post open in a new window please?  EDIT: I originally wanted this implemented because it's what some other sites did, but I now definitely prefer SO's way. If I want to open a new tab, I middle-click/control-click (or whatever); if not, I just click. I'm in control of what happens. Would never want to go back now. Using Residue Theorem find $\displaystyle \int_0^{2\pi} \frac{1}{a^2\cos^2 t+b^2 \sin^2 t} dt \;; a,b&gt;0$.   My Try:  So, I am going to use the ellipse $\Gamma = \{a\cos t+i b \sin t: 0\leq t\leq 2\pi\}$.   On $\Gamma$, $z=a\cos t+i b \sin t$, so $|z|^2=z\bar{z}=a^2\cos^2 t+b^2 \sin^2 t$.   Now, $dz=-a\sin t+i b \cos t dt$.   Hence, the integral becomes $\displaystyle \int_\Gamma \frac{dz}{z(iab+(\sin t \cos t)(b^2-a^2))}$. I know that $\displaystyle \int_\Gamma \frac{dz}{z}=2\pi i$. Now, how do I get rid of $\sin t \cos t$ part? I am stuck here. Can somebody please explain how? The set of integers $n$ expressible as $n=x^2+xy+y^2$ Let $S$ be the set of integers $n$, such there exist integers $x,y$ with $$n=x^2+xy+y^2$$   Is the implication $$a,b\in S\implies ab\in S$$ true? If yes, how can I prove it?  I worked out $$n\in S\iff 4n\in S$$ and $$n\in S\iff 3n\in S$$ I tried two approaches. The first is to express $$(a^2+ab+b^2)(c^2+cd+d^2)$$ in the form $$f^2+fg+g^2$$ with polynomials $f,g$ with integer coefficients. I however could not find suitable $f$ and $g$. The second approach is based on $$x^2+xy+y^2=\frac{(2x+y)^2+3y^2}{4}$$ If we have $n=x^2+xy+y^2$ , we have $u^2+3v^2=4n$ for some integers $u,v$ with equal parity. The main problem of this approach is to consider the equal parity. Any ideas ? Get the image URL I want to render an image as a background image via an inline style in twig. I created a field called bg_image and attached it to the standard plain page.  After fiddling around for hours I was able to get the Image URL in node.html.twig  {{ file_url(node.field_bg_image.0.entity.uri.value) }}   but I could not get it to work inside field--field-bg_image.html.twig  Can I get the node from there anyhow, so I can then get the image?  How can I get the image URL to use as inline style? I thought maybe I can pass a variable from field--field-bg_image.html.twig to image.html.twig and then just render  {{ uri }}   instead of  &lt;img{{ attributes.addClass(classes) }} /&gt;   but I could not get it to pass the variable there unless I use includes  {% include 'image.html.twig' with {'image': image, 'isFromField': isFromField} %}   (isFromField is true, when it comes from the field--field-bg_image.html.twig) But that didn't work either. The Image was never rendered that way.  Would be very glad if you can help - my php knowledge is very basic. Thanks How to check if jQuery.ajax() request header Status is "304 Not Modified"? Find all rings $R$ satisfying $\mathbb Z \subset R \subset \mathbb Z[\frac {1}{2}]$ Find all rings $R$ satisfying $\mathbb Z \subset R \subset \mathbb Z[\frac {1}{2}]$.   Solution: Let $f \in R$. Then $f= \frac {m}{2^n}$ for some integers $m,n$.  Since $2^{n-1} \in R$, hence $\frac {m}{2} \in R$. Hence one gets that $ \frac {1}{2} \in R$, so $R=\mathbb Z[\frac {1}{2}]$, so there is no ring $R$ satisfying given conditions.     What are the other possible solutions of this problem?    P.S: You can give a solution using any theorem from commutative algebra also. In my opinion the accepted answer should permanently stick as only the original question submitter has the ability to accept. iMac with 8GB RAM -- memory always almost full I have a 27'' iMac (Late 2012, OS X 10.9.2) with 8GB RAM. The usage of memory is always above 7GB, even though I don't think I am running that much stuff. This leads to the occasional hanging of a program and occasional feeling of the computer being lagged.  The heaviest thing I am running is a Parallels virtualization of a defunct Windows laptop (for my Windows-only programs; work-related). Then I mostly surf with Chrome (10-20 tabs, some with youtube videos). Of course I have other things opened, like Mail, Evernote and a few more. But I don't think a 8GB RAM computer should be overwhelmed by that. I could be wrong.  I am willing to provide an export of processes from the Activity Monitor. I tried looking into it, of course, and I am running A LOT of small processes (unknown to me) -- system stuff I presume. I am a long-time PC user and I know my way around process management in PCs, but not on Mac.  What do you think? Do I just need more RAM or it doesn't feel like it?  Regards, How to partition harddisk for Ubuntu 18.04 I want to partition my hard disk, but I don't have any other software running(like dual booted).  And I do not know how to do it. Can you send the instructions? Checking for null before event dispatching... thread safe? Something that confuses me, but has never caused any problems... the recommended way to dispatch an event is as follows:  public event EventHandler SomeEvent; ... {     ....     if(SomeEvent!=null)SomeEvent(); }   In a multi-threaded environment, how does this code guarantee that another thread will not alter the invocation list of SomeEvent between the check for null and the invocation of the event? As per c99 standard, size of long long should be minimum 64 bits. How is this implemented in a 32 bit machine (eg. addition or multiplication of 2 long longs). Also, What is the equivalent of long long in C++. Although many have attempted to explain the difference among \mathrm, \textrm, \textnormal and \text (and others?), I found them misleading.  See for example the LaTeX's Wiki \mathrm explanation   Why is it wrong? Let's try all of them within an article and a beamer and you'll see the difference and, therefore, error.  equation.tex  \begin{eqnarray*}   \int_1^9\! \cos{x} \,\mathrm{d}x &amp; &amp; \textrm{this is textrm}\   \sum_1^9 y                       &amp; &amp; \textsf{this is textsf}\   \prod_1^9 z                      &amp; &amp; \textnormal{this is textnormal}\   \bigcup_1^9 w                    &amp; &amp; \text{and this is just text} \end{eqnarray*}   article.tex  \documentclass{article} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb}  \begin{document}   \input {equation} \end{document}     And until here everything looks fine...  beamer.tex  \documentclass{beamer} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb}  \begin{document}   \begin{frame}     \input{equation}   \end{frame} \end{document}     And here we can clearly see that \mathrm does not behave as expected, i.e. does not provide a function aspect to the d. Does anyone know what am I supposed to use here instead? Just \text?? o.O  Moreover, I cannot see any difference between \textnormal and \text.  Finally, \textrm looks useless.. Why doesn't backpropagation work when you initialize all the weight the same value (say 0.5), but works fine when given random numbers?   Shouldn't the algorithm calculate the error and work from there, despite the fact that the weights are initially the same?