I need to check the middle part of path appear two times. example:      images hotels AND csv fares   I used bellow regex string to check It. but I couldn't find the way. please help me to continue with this?  ((images|csv|files)([A-Za-z0-9\-]+).*){2}
I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?
Proof that if $p\equiv3\,\left(\mbox{mod 4}\right)$ then $p$ can't be written as a sum of two squares I'd appreciate your help showing that if $p\equiv3\,\left(\mbox{mod 4}\right)$   then p can't be written as a sum of two squares.  Thanks! What is "angle of view" in photography? I read on the :     Focal-length determines the angle-of-view seen through a lens for a   given sensor-size. With a full-frame sensor a lens gives the same   angle-of-view as it would on a 35mm film camera. With a smaller   sensor, the angle-of-view becomes smaller. The crop-factor, also   called FLM, is the ratio representing the difference in equivalent   focal-lengths. So a 150mm on a full-frame DSLR such as the Nikon D700   gives the same angle-of-view as a 100mm on a D7000 since its FLM is   1.5X.      Short focal-lengths show a greater angle-of-view compared to longer   ones. [...]   In layman's terms, what is angle-of-view? Is it the same as focal length? If not, how is it different? How is it used? Why do I need to know about it? I never hear "scissor" or "pant" or "jean". It's always "scissors", "pants", and "jeans", respectively. Are they considered plural? Why do my images look different on my camera than when imported to my laptop? I have been taking some photos with my new camera, and have found that once I import them to my laptop, the colors look washed out, and not as nice and vivid as on the camera LCD display.  It's a Sony HX60, and I am importing them into an HP dm4, running Fedora.  I've read about color profiles, and made sure that the calibration on my monitor was set.  The thing is that the issue arises with just importing them from the camera iteself (using Shotwell) and diplaying them with the standard Image Viewer, it's not even an issue with Gimp or an image editor with a color profile not set.  I am wondering if my camera is using some of color profile that is being lost when imported, or is it that the display on my camera is much better than the one my laptop?  I can then open the image in Gimp, and then use some enhancements to make the image look better, but I just want them to look the same as on my camera.  Any ideas?  Update:  Here is an example image I took:   And here is a photo of the comparison of how the Sony HX60 &amp; the HP dm4 render the output. This photo was taken with a cheap Lumix, but still clearly shows the difference: Where in the world is tikzlibraryhobby.code.tex? I was trying to reproduce Claudio Fiandrino's answer to .  However, I do not have the hobby package by Andrew Stacey in my local distribution.  After reading  and , I looked at the latest  (build on December 7, 2012) but could not located the hobby package in it.  I found  but do not know where each file is supposed to go in my distribution.  How do I add the hobby package? In general, what would be the easy way to get any new TikZ package installed in a Mac?  EDIT:  I have used the drag-and-drop (mac) method as described below.  (1) Drag pml3array.sty file to /Users/Username/Library/texmf/tex/latex folder. (2) Drag hobby.code.tex file to /Users/Username/Library/texmf/tex/generic/pgf/math folder. (3) Drag pgflibraryfpu.code.tex to /Users/Username/Library/texmf/tex/generic/pgf/libraries folder. (4) Drag tikzlibraryhobby.code.tex to /Users/Username/Library/texmf/tex/generic/pgf/frontendlayer/tikz/libraries folder.  I no longer get the hobby cannot be found error message.  But, is this correct? What algorithm for a tic-tac-toe game can I use to determine the "best move" for the AI? What does outputting to /dev/null accomplish in bash scripts? How can I enable multiple users login at a time in remote system? Recently we bought dedicated server with Windows Server 2012 Standard.It's allowing 2 people at a time.So I want to allow more people at a time.  How can I do this? How to skip kernel update? I am running Ubuntu 12.04.1 LTS i686 on VirtulBox. Every time I check the updates, there's a new Linux kernel. If I install the new kernel, I have to install the Virtulbox Guest Additions again and reboot the server. I don't want to do this every week. I know I can manually uncheck the kernel packages from update manager, but is there a way to skip the kernel update automatically? I found an answer here, but it's for Ubuntu 10. Thanks. Lagrangian of Schrodinger field The usual Schrodinger Lagrangian is $$ \tag 1 i(\psi^{*}\partial_{t}\psi ) + \frac{1}{2m} \psi^{*}(\nabla^2)\psi, $$ which gives the correct equations of motion, with conjugate momentum for $\psi^{*}$ vanishing. This Lagrangian density is not real but differs from a real Lagrangian density  $$ \tag 2 \frac{i}{2}(\psi^{*}\partial_{t}\psi -\psi \partial_{t}\psi^{*} ) + \frac{1}{2m} \psi^{*}(\nabla^2)\psi $$ by a total derivative.  My trouble is that these two lagrangian densities lead to different conjugate momenta and hence when setting equal time commutation relations, I am getting different results (a factor of 2 is causing the problem). I can rescale the fields but then my Hamiltonian also changes. Then applying Heisenberg equation of motion, I don't get the operator Schrodinger equation.   Is it possible to work with the real Lagrangian density and somehow get the correct commutation relations? I would have expected two Lagrangians differing by total derivative terms to give identical commutation relations (since canonical transformations preserve them). But perhaps I am making some very simple error. Unless all conjugate momenta are equivalent for two Lagrangians differing by total derivatives, how does one choose the correct one?   I guess the same thing happens for other first order systems like Dirac Lagrangian also. I've tried to render my scene but there's an object that won't show up. I've checked the camera, I've checked the visibility, it isn't hidden and it's showing in the viewport. I feel like I've opened every setting and have achieved nothing. I’m trying to render a book with a cover, flipping pages and stacks of pages. I have no idea how to fix the fact that the book cover doesn’t render. If I create a plane and select both the book cover and the plane and join them with Ctrl+J, the render contains a book cover but it doesn’t turn as it’s rigged to do so because it’s now linked to the plane and loses all the animated properties. As soon as I unjoin them the book cover stops rendering and everything appears as you see it there, a book with binding, pages, but no cover. For the life of me I cannot figure out what’s going on. There's a link to the file here: How can I get back to Blender's default theme? Even though I am relatively new to Blender I am recording a tutorial for a Blender exporter. I have been advised that I should use the Default colour scheme (for the UI). I have no idea which one that is. Can anyone tell me? A function that is continuous at the origin but not differentiable there Show that $f(x,y)=\dfrac{xy^2}{x^2+y^2}$ (with $(x,y)\not=(0,0)$ and $f(0,0)=0$) is continuous but not differentiable at $(0,0)$.  I tried to show continuity with an $\epsilon -\delta$ argument but I don't know how to factorize the expression so that I can have something useful.   For differentiability I think I should show that the partials are not continuous at $(0,0)$. But finding the partials is also painful. I've been reading about a lot of different types of philosophies, religions, ways of thinking etc. I was wondering what are the most recently created philosophical ways of looking at the universe? Where can one find out about new cutting edge ideas?  Example: Before we had Marxism, Communism, Zen, Christianity etc. Now X,Y, and Z have been created building on and evolving the ideas of A,B,C.   Everything I read about are ideas that were created a long time ago. What is new and updated? I was wondering how to list all the hardware info in my computer?   Both terminal and GUI solutions please. Is there a single utility to monitor most hardware's working status? Just like some software in Windows?   Thanks and regards! Sum of binomial coefficients with index divisible by 4 I am trying to obtain a closed form expression for  $\sum {n \choose 4k}$  I am trying to use the binomial expansion of $(1 + i)^n$ and $(1 - i)^n$. $$(1 + i)^n + (1 - i)^n = 2\left(\sum {n \choose 4k} -\sum {n \choose 4k + 2}\right)$$ Stuck at this now. I can't come up with a way to simplify the second term on RHS. Any help would be appreciated. A way for "new users" to ask about their post specifically We currently require that new users have 5+ reputation to participate in meta support discussions (bugs, feedback, governance, etc). This is primarily because the use case for meta is not intrinsically obvious, so we require a modicum of "experience" with the site before jumping into it.   But that blocks new users with legitimate questions about their own posts.  Setting aside any arguments about new-users-are-evil-and-suck-the-life-out-of-our-community, I would like to propose a very specific path for new users to ask about their own question provisionally.  Instead of blocking a new user with this message:     You must have at least 5 reputation on &lt;site> to ask a question on meta.   We can change this to:     You must have at least 5 reputation on &lt;site> to post on meta, but you may ask a question about your own post specifically.      Link to your post: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;      ask about this post   cancel    The system will check whether the linked question provided belongs to the author. . The user can then proceed with the post provided they leave the template (below) intact:     Title &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;      &nbsp;         &lt;!--Do not remove-->   &lt;!--Note: Questions not about your post will be deleted-->      I have a question about the post:       &lt;!-- Your question below: -->   &nbsp;     Not only is this a great and gentle introduction to the proper use of meta, but it stands to help new users just when they need it most (learning to use the community).   Of course this doesn't 100% guarantee that someone won't get it wrong on occasion. But this is an awful lot of in-your-face guidance without simply telling people "read our FAQ" (which they never do). And if a user manages to step over all that guidance and still manages to misuse meta, I have no compunction about summarily removing a question they should never have posted.   But this just-in-time learning is a very effective way of learning a new site in a gentle and thoughtful way. If this is abused more often than not, it is easy to disable. But it's better than assuming clueless newbie every time. Vertical line for the the right margin in Notepad++ Play Framework (2.1.3) doesn't run any tests Split Data Based on Year in a Visual force Page PDF