I need to include a header in condition if it is present and if not i need to make the necessary steps for my code to work   I need to do something like...  // check if the header is present(may be .h files) #include"required_header" { block-1 }  //if the header is not present  { block-2 }   If I use like ....  #ifdef required_header #include&lt;required_header&gt; Block-1 #else Block-2   The above case is redirected to Block-2 always because i have included the header file only inside the condition of ifdef and its never included  Hoping for a method to do it.  Thanks in Advance :}  P.S: I have defined the header but assuming i have not done the work of the required header but i want someone else to write that file and I am not sure if he has written it.  Precisely speaking I want the code replacement way in the place of comments in the first given code.
I have a very large codebase (read: thousands of modules) that has code shared across numerous projects that all run on different operating systems with different C++ compilers. Needless to say, maintaining the build process can be quite a chore.   There are several places in the codebase where it would clean up the code substantially if only there were a way to make the pre-processor ignore certain #includes if the file didn't exist in the current folder. Does anyone know a way to achieve that?  Presently, we use an #ifdef around the #include in the shared file, with a second project-specific file that #defines whether or not the #include exists in the project. This works, but it's ugly. People often forget to properly update the definitions when they add or remove files from the project. I've contemplated writing a pre-build tool to keep this file up to date, but if there's a platform-independent way to do this with the preprocessor I'd much rather do it that way instead. Any ideas?
Prove that $a^{2^n}=1 \mod 2^{n+2}$ I would like to prove that  $$a^{2^n}\equiv 1 \pmod {2^{n+2}}$$  I tried induction but could not get it.  Thank you very much! I would like to customize Ubuntu live CD by installing some additional packages. I have followed   but it doesn't seems to work. Can anyone provide clear instructions?   Note: I do not prefer Remastersys, manual way will be appreciated.  Customization  Packages that I want to install:   Thunderbird    Samba    SSH       Changes that I need:   Remove Games menu from the Application menu Firefox shortcut on Desktop Radiance as the default Theme Different default Ubuntu Wallpaper   Configuration file changes   I want the panel to be placed at the bottom I want to paste my Samba configuration file instead of default Samba configuration I have few Firefox shortcuts and folders I would like to show that in Desktop Also it will be nice if you say me how to change the icon sets   Recent Updates   I have customized Ubuntu 10.10 with Firefox shortcuts and few folders on desktops. Everything went smooth. But the installer gets crashes after choosing the timezone. How do i fix this issue? Also setting wallpaper affects the login screen. The wallpaper which i set is displayed on the login screen also. I just want the default one for the login screen. When I try to start Runescape I get an error message that says: CLassNotFoundException and lists Rs2Applet.class. How do I fix this so I can play? Title of short story: God granting immortality to others to find a way to kill himself What's the difference between "cardinal" and "ordinal" as adjectives? Why aren't search engines indexing my content? This is a general, community wiki  question and answer pair intended to address any questions   concerning the reasons a site or specific site contents do not appear   in search engine results.      If your question was closed as a duplicate of this question and you   feel that the information provided here does not provide a sufficient   answer, please open a discussion on .   My site (or specific pages on my site) is not appearing in search engine results.  Why isn't my content indexed and what can I do about it? How do I mount a partition with UFS filesystem (FreeNAS) in Ubuntu 11.10?  I'm a total Ubuntu newbie and just switched from FreeNAS.  There should be ll the info I need I guess, but if anyone would help me get going i'll by glad =) How to convert all shapefiles in folder into KML using ArcPy? I was trying to convert all the shp in a folder into kml.  featureclasses = arcpy.ListFeatureClasses() for fc in featureclasses:  # Set Local Variables   composite = 'COMPOSITE'   pixels = 1024   dpi = 96   clamped = 'CLAMPED_TO_GROUND'   scale = 1   outKML = fc[:-4] + &quot;.kmz&quot;   arcpy.LayerToKML_conversion(fc,outKML, scale, composite,'', pixels, dpi, clamped)   It always says Failed to execute. Parameters are not valid. ERROR 000732: Layer: Dataset ZZZ.shp does not exist or is not supported Failed to execute (LayerToKML). But I can manually do it within ArcMap 10.1 Desktop... How to wrap text around a figure? ^@ spam in tty (but seems to be system-wide) I recently noticed some weird behavior on my GNU/Linux machine. I've been trying to narrow it down but I am unsure where to go next. My setup uses the following:   i3 gdm arch systemd grub2 pulseaudio 4.13.3-1-ARCH   Here is how it manifests iself:   when trying to resize panes in i3 (alt+right click and hold) the action will be randomly canceled (happens on key presses) alt+dragging windows meets a similar fate booting to tty periodically adds ^@s to the login prompt, I'd estimate them to be ~0.5s intervals in tty I can see those being passed to vim when I open the command bar (:) using a pager like less in tty mode and searching with / will result in  (?) being spammed htop's search (/) is instantly canceled by the periodic keypress  holding a key and trying to have it be repeated (such as holding space) will stop the other occurrences from happening (e.g. only one or two happen) any tooltip (such as chrome tooltips) get instantly closed because of key presses   Here is what I have tried:   tried switching DE temporarily (gnome, cinnamon, xfce) tried killing programs one by one until I was left with a tty session and essentially systemd services + pulseaudio tried booting on an arch livecd - problem does not manifest  overriding grub2 with init=/bin/bash drops me into a shell where the problem does not manifest I have tried pressing all keys to verify it wasn't a hardware problem, however previous steps point to it not being hardware I have made a diff of dmesg, from the init=/bin/bash and the regular boot - the main difference seems to be systemd being started in the regular boot Made a diff of lsmod from init=/bin/bash and regular boot, tried to rmmod modules that seemed related   My system is up to date, I'm not quite sure what other steps I can do to track this down. Any other debugging tips? $\sin \frac{1}{x}$ is not uniformly continuous on $[1, \infty]$ While studying the problem of determining the orbit of a binary star system, my astronomy notes say: "the projection of an ellipse onto a plane is still an ellipse (except the special case in which it's a segment)". How could I prove this?  EDIT: As suggested i'm adding what I know about ellipses. I know the basics of ellipses in the plane, the equation of an ellipse in a plane in cartesia coordinates, the equation of an ellipse in polar coordinates, the fact that ellipses can be obtained by the intersection of planes with a cone. In my geometry course we defined ellipses as the the points of the plane such that the ratio between the distance from a point and a line is constant and less than 1. I also know that the sum of the distances of the points of the ellipse from the foci is constant. Can you please clarify if it's acceptable to use these terms interchangebly and if not point out to significant differences between these titles. It seems to me that it may be something with scale of an organization (perhaps, small/medium businesses have managing directors, and large corporations have chief executive officers) but I'm not sure. I do understand that a person may bear one or another of these titles formally, but what about real differences? No command 'bla' found, did you mean:? So, when a command is not found, by what means is the "did you mean:" list populated? What program finds these alternate commands?  What is the meaning of: "(main), (universe)..."? Can I change which program finds these? What's the correct usage of "hopefully"? $VAR vs ${VAR} and to quote or not to quote Can Xdebug be triggered by Drush commands? I'm running into an issue with my Features modules and installation profile when installing the site with drush si. There are a number of probably related issues in the Features issue queue, but none with good solutions. The interesting part (mentioned in some of the issues) is that it works fine when installing the site through the browser, but fails when installing with drush si.  I have an idea of what's wrong, but need to confirm it. The only way I can think of confirming it is to step through the code with a debugger (Xdebug is what I have set up). So, is it possible to trigger Xdebug from a command run with Drush? Specifically, can I get Xdebug to kick in when I run drush si? Evaluate $\int_0^1 \frac{\log \left( 1+x^{2+\sqrt{3}}\right)}{1+x}\mathrm dx$ I am trying to find a closed form for  $$\int_0^1 \frac{\log \left( 1+x^{2+\sqrt{3}}\right)}{1+x}\mathrm dx = 0.094561677526995723016 \cdots$$  It seems that the answer is $$\frac{\pi^2}{12}\left( 1-\sqrt{3}\right)+\log(2) \log \left(1+\sqrt{3} \right)$$  Mathematica is unable to give a closed form for the indefinite integral.  How can we prove this result? Please help me.  EDIT  Apart from this result, the following equalities are also known to exist: $$\begin{align*} \int_0^1 \frac{\log \left( 1+x^{4+\sqrt{15}}\right)}{1+x}\mathrm dx &amp;=\frac{\pi^2}{12} \left( 2-\sqrt{15}\right)+\log \left( \frac{1+\sqrt{5}}{2}\right)\log \left(2+\sqrt{3} \right) \\ &amp;\quad +\log(2)\log\left( \sqrt{3}+\sqrt{5}\right) \\ \int_0^1 \frac{\log \left( 1+x^{6+\sqrt{35}}\right)}{1+x}\mathrm dx &amp;= \frac{\pi^2}{12} \left( 3-\sqrt{35}\right)+\log \left(\frac{1+\sqrt{5}}{2} \right)\log \left(8+3\sqrt{7} \right) \\ &amp;\quad +\log(2) \log \left( \sqrt{5}+\sqrt{7}\right) \end{align*}$$  Please take a look . Invalid signature for Kali Linux repositories : "The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository" How to make sense out of the $\epsilon-\delta$ definition of a limit? The informal intuition for the limit of a function is this:     What is the value of the function $f$ as $x$ gets infinitely close to $c$?   How on earth does this monster  $$ \lim_{x \to c} f(x) = L  \iff  (\forall \varepsilon &gt; 0)(\exists \ \delta &gt; 0) (\forall x \in D)(0 &lt; |x - c | &lt; \delta \ \Rightarrow \ |f(x) - L| &lt; \varepsilon)$$ capture our intuition?  I want the answer to explain and motivate every bit of this formal statement. Remember: I am able to parse the statement, I just don't see how it captures our informal intuition.