Quite often, when making simple mistakes (like using underscore outside of math mode), LaTeX (or rather tex?) attempts to insert missing math mode delimiters.  e.g. in  \documentclass{standalone} \begin{document} x_2 \end{document}   latex yields:  ./test.tex:3: Missing $ inserted.   And then, instead of telling me that the underscore was not allowed, it spits out multitudes of warnings about missing delimiters etc.  Apparently the original idea was to implement some sort of error-correcting parser. However, at least in my case, this simply does not work and -worse- yields even more confusing error messages.  Is there a way enforce a strict mode that simply bails out on the first error?
In case of a syntax error, pdflatex usually (in \errorstopmode) gets interactive and asks you what to do. I know I can press:   X to terminate S to enter \scrollmode (continue processing without stopping if further syntax errors arise, but stop for other errors) R to enter \nonstopmode (continue processing without stopping if further errors arise) Q to enter \batchmode (continue processing without stopping if further errors arise and suppress further output to the terminal)   Apparently, only the latter three (SRQ) can be provided implicitly by the respecive \...mode commands or the -interaction=...mode command line option. However, what I need is a mode that mimics the implicit pressing of X, that is, to make the pdflatex process terminate after the first error.
How can I combine two render layers? I would like to know which nodes can I combine this two render layers  width?    I've made this with alpha over node and transparent rendering. I want such an image but I don't want to lose the background (Sky texture).    Thanks for helping! :) Finding out which app is using the webcam Yesterday I was working on my laptop. Suddenly I noticed that the indicator light of the webcam was on, despite the fact that I wasn't making a video call or using the webcam in any other way at the moment.  It freaked me out.  It freaked me out that some unknown application on my computer was using my webcam without my permission, and possibly sending that video stream to god knows where on the Internet.  In the end, it turned out to be Skype which was in the process of crashing. (Despite me making no calls at the time.) So that story ended well.  But next time I see the webcam indicator light, I want to be ready. I want to be able to know exactly which app is using the webcam so I could destroy it.  Does anyone know how I can find out which app is using the webcam?  (I'm on Windows XP.) How to calculate the $H_2$ and $H_\infty$ norms of TransferFunctionModels or StateSpaceModels? How can an encryption scheme be indistinguishable with multiple messages but vulnerable to an adaptive chosen-plaintext attack? In order to be indistinguishable with respect to multiple messages, wouldn't the scheme need to be nondeterministic? How would this then possibly be vulnerable to an adaptive CPA? Huge paged pool probably caused by fltMgr.sys , what to do? Inspired exercise Sheet from Indesign I would like to create this sheet which was made it by adobe indesign   Could someone create it with latex ?     Here's my code:  \documentclass[12pt,a4paper,twocolumn]{report} \usepackage[margin=0.5in]{geometry} \usepackage[french]{babel} \usepackage{fontspec} \usepackage{graphicx} \usepackage{amsthm,amssymb,amsfonts,mathtools} \usepackage[utf8]{inputenc} \usepackage{multicol} \usepackage{multirow} \usepackage{amssymb} \usepackage{array} \usepackage{graphicx} \setlength{\columnseprule}{0.5pt} \thispagestyle{empty} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \begin{document} %%%%%%%%%%head%%%%%%%%%%%%%%%%%%%%%%% \twocolumn[    \begin{@twocolumnfalse}  \begin{center}  \fbox{\Large Exercise Sheets} \end{center}     \hrulefill \end{@twocolumnfalse}   ]  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  \fbox{ Exercise $1$:}\\  Compute the following limits \begin{multicols}{2} \begin{enumerate} \item $\lim_{x\to 2}\dfrac{4x^{3}-5x-22}{x^{2}-x-2}$ \item $\lim_{x\to 0^{+}}\dfrac{x-\sqrt{x}}{x+\sqrt{x}}$ \item $\lim_{x\to 1}\dfrac{\sqrt{x+3}+\sqrt{x}-3}{x-1}$ \item $\lim_{x\to 2}\dfrac{x^{2}\sqrt{x+2}-8}{4-x^{2}}$ \end{enumerate} \end{multicols}  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \fbox{ Exercise $2$:}\\ Let $n\in\mathbb{N}^{*}$ \begin{enumerate}     \item calculate : ${\displaystyle \lim_{x\to 0}\dfrac{1-\cos(x)\cos(2x)\ldots+\cos(nx)}{x^2} }$     \item b     \item c     \item d     \item e     \item f \end{enumerate} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \end{document} I am wondering if there exists any formula for the following power series :  $$S = r + r^2 + r^4 + r^8 + r^{16} + r^{32} + ...... + r^{2^k}$$  Is there any way to calculate the sum of above series (if $k$ is given) ? How To Get Command Blocks Talking in Chat Sci-fi film about terraforming Venus, inadvertently killing the native worm-like Venusians I have been searching for the name of a short sci-fi film for decades.  The story is about a team of scientists who figured out a way to terraform Venus by sending algae plants there in a rocket which changes the atmosphere so that humans can live there.  At the end, it works, but the first people that arrive on Venus discover that the algae has killed the native Venusians, a race of worm-like creatures.  The final shot (as I remember it) is of an astronaut finding a half-sphere with writing on it, and he says “it wasn't much, but it showed that they were intelligent…”  I saw it on TV in probably the late seventies or early eighties, possible as an HBO short take that they would show to fill time in between movies.  Does this sound familiar to anyone? What are good books/other readings for elementary set theory? I am looking to expand my knowledge on set theory (which is pretty poor right now -- basic understanding of sets, power sets, and different (infinite) cardinalities). Are there any books that come to your mind that would be useful for an undergrad math student who hasn't taken a set theory course yet?   Thanks a lot for your suggestions! With arrays, why is it the case that a[5] == 5[a]? Regarding the recalc in question rep increase what happens due to the cap? I cannot see WiFi option in my Ubuntu 15.04. What should I do? Revert asap  lspci -nnk | grep 0280 -A2 output:-  03:00.0 Network controller [0280]: Qualcomm Atheros Device [168c:0042] (rev 30) Subsystem: Foxconn International, Inc. Device [105b:e09a]   rfkill list output:-  0: hci0: Bluetooth Soft blocked: no Hard blocked: no 1: acer-wireless: Wireless LAN Soft blocked: no Hard blocked: no      dmesg | grep ath [    9.545199] ath10k_pci 0000:03:00.0: pci irq msi-x interrupts 8 irq_mode 0 reset_mode 0 [   10.029684] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/cal-pci-0000:03:00.0.bin failed with error -2 [   10.029701] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-5.bin failed with error -2 [   10.029704] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-5.bin': -2 [   10.029711] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-4.bin failed with error -2 [   10.029713] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-4.bin': -2 [   10.029719] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-3.bin failed with error -2 [   10.029721] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-3.bin': -2 [   10.029726] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-2.bin failed with error -2 [   10.029728] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-2.bin': -2 [   10.029733] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware.bin failed with error -2 [   10.029735] ath10k_pci 0000:03:00.0: could not fetch firmware (-2) [   10.029737] ath10k_pci 0000:03:00.0: could not fetch firmware files (-2) [   10.029739] ath10k_pci 0000:03:00.0: could not probe fw (-2) When drawing a line between two nodes in TikZ, you can specify the anchors on the beginning and end nodes in order to control how the line is drawn.  I would like to specify the anchor on the beginning node, and the angle at which the line is drawn, and let TikZ figure out where it will intercept the end node.  The usual use case is when I'm connecting to a "big node" and I would like the lines to be vertical.  I can cheat by placing a coordinate behind the big node, drawing a line to the coordinate instead, and then drawing the big node so that it covers things up.  However this won't work if I need to put an arrow on the end.  I could try to calculate the intercept coordinate on the edge of the big node manually, but that seems against the TikZ spirit.  |- doesn't work in this case.  \documentclass[10pt]{minimal} \usepackage[active,tightpage,pdftex]{preview} \usepackage{tikz}  \begin{document} \begin{preview}  \tikzstyle{RectObject}=[rectangle,fill=white,draw,line width=0.5mm] \tikzstyle{line}=[draw] \tikzstyle{arrow}=[draw, -latex]   \begin{tikzpicture}   %%%%%%%%%%%%%%%%%%%%%%%%   %%  LEFT SIDE   %%%%%%%%%%%%%%%%%%%%%%%%   \draw (1,0) node[RectObject] (Small1A) {A};   \draw (3,0) node[RectObject] (Small1B) {B};   \coordinate (Cheat1A) at (1,2);   \coordinate (Cheat1B) at (3,2);   \path [line] (Small1A.north) -- (Cheat1A);   \path [line] (Small1B.north) -- (Cheat1B);    % need to draw Big Node last to cover up our cheating   \draw (2,2) node[RectObject, inner xsep=1cm] (Big1) {Big Node};    \draw (2,4) node[text width=4cm] (text1) {L: Cheating to control line orientation. Arrows would be hard.};    %%%%%%%%%%%%%%%%%%%%%%%%   %%  RIGHT SIDE   %%%%%%%%%%%%%%%%%%%%%%%%   \draw (7,2) node[RectObject, inner xsep=1cm] (Big2) {Big Node};   \draw (6,0) node[RectObject] (Small2A) {A};   \draw (8,0) node[RectObject] (Small2B) {B};   \path [arrow] (Small2A) -- (Big2);   \path [arrow] (Small2B) -- (Big2);    \draw (7,4) node[text width=4cm] (text2) {R: No cheating. Arrows easy. Can't control line orientation.}; \end{tikzpicture} \end{preview} \end{document}   Here's a side-by-side example of "cheating", which shows what I want to be able to do, and "not cheating", which does not do what I want.    The left side of this example shows what I want to be able to do, except I want to do it without cheating, and I'd like to put arrows on the end of the lines. findstr /v "black"  File1.txt   Above DOS command will display content of 'File1.txt' which are not matching string "black".  How to modify this command , if I need to filter words "black" and "white" ? Evaluating $ \lim_{x \rightarrow 0}\left (\frac{\sin(x)}{x}\right)^\frac{1}{x^2}$ Local server updates for the network I have setup one computer on our network as the file server. Because Internet here in Tanzania is both slow and expensive I would like that one system to download all the updates and then the other 10 computers on the network to get those update files from the server. I'm a bit of a noobie to Ubuntu, but really want to learn how to get this working smoothly so as to help other NGOs and schools here in Tanzania. Brendon Distinct Sylow P subgroups How to find web hosting that meets my requirements? Adding shapefile or feature class as layer in ArcMap using ArcPy I am trying to automate various tasks in ArcGIS Desktop (using ArcMap generally) with Python, and I keep needing a way to add a shapefile to the current map. (And then do stuff to it, but that's another story).  The best I can do so far is to add a layer file to the current map, using the following ("addLayer" is a layer file object):  def AddLayerFromLayerFile(addLayer):  import arcpy  mxd = arcpy.mapping.MapDocument("CURRENT")  df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]  arcpy.mapping.AddLayer(df, addLayer, "AUTO_ARRANGE")  arcpy.RefreshActiveView()  arcpy.RefreshTOC()  del mxd, df, addLayer   However, my raw data is always going be shapefiles, so I need to be able to open them. (Equivalently: convert a shapefile to a layer file without opening it, but I'd prefer not to do that).