I use enum type but declare it under the use, compile fail.  Then I add a forward declaration, but still compile fail.  I search exists questions about enum forward declaration, found c++ (not C++0x) does not support enum forward declaration.  Can somebody explains why ?   I found similar questions on SO, but nobody explains why.
I'm trying to do something like the following:  enum E;  void Foo(E e);  enum E {A, B, C};   which the compiler rejects.  I've had a quick look on Google and the consensus seems to be "you can't do it", but I can't understand why.  Can anyone explain?  Clarification 2: I'm doing this as I have private methods in a class that take said enum, and I do not want the enum's values exposed - so, for example, I do not want anyone to know that E is defined as  enum E {     FUNCTIONALITY_NORMAL, FUNCTIONALITY_RESTRICTED, FUNCTIONALITY_FOR_PROJECT_X }   as project X is not something I want my users to know about.  So, I wanted to forward declare the enum so I could put the private methods in the header file, declare the enum internally in the cpp, and distribute the built library file and header to people.  As for the compiler - it's GCC.
How to set up Dolphin as default file manager? When will my device get the Android 4.2 update (Jelly Bean)? What may happen after a stack of spells resolves? Within the same phase, once a stack of spells has resolved in its entirety, is priority once again given to a player so that more spells may be cast?  For example:  I attack with a creature. Opponent opts not to block. Now, I want to buff (e.g. +3/+3) my creature multiple times, but I'm afraid of my opponent responding with a burn (e.g. Deal 3 damage) spell at the top of the stack. Can I buff once, ask if opponent wants to respond, then allow the stack to resolve. Then, in the same phase, cast more buff? Heap versus Stack allocation implications (.NET) From an 1 about Heap and Stack, it raised me a question: Why it is important to know where the variables are allocated?  At  someone pointed that the stack is faster. Is this the only implication? Could someone give a code example where a simple allocation location change could solve a problem (eg. performance)?  Note that this question is .NET specific  1 the question is removed from SO. My number is associated with iMessage on other phone, how to remove it? Good day everyone. For only 1 hour (!) I used my relatives iPhone with my sim card and that's it, he keeps receiving all of my iMessages. I tried checking in iTunes all devices associated with my account and his device is not listed. I tried to log in and log out to/from iMessage on his phone with his apple ID, still won't help. How can I stop this nightmare!? When I go to iMessage settings>Send &amp; Receive on his device, there is only my phone number listed, how do I remove it without smashing phone to the wall?! Thanks and have a great day  EDIT. After talking to apple support for some time, they removed my phone number from my friend's iMessage. So I guess if you are facing same problem you have to contact support. How to select lines between two marker patterns which may occur multiple times with awk/sed How to select a good non-stick pan, price point wise? I'm trying to wrap my head around how SQL Server decides to grant certain rights based on a users login privileges.  If a user is part of a group "READ ONLY" which has access to DB1, but they are also a part of a group "SysAdmin" which has full db owner rights to the same DB1, which rights are they given when they log in?  On a similar note. What if they are part of a group but also have a standalone account with other middle of the road privileges? I was going through the fundamental theorem in Number Theory where any non zero integer n can be represented as a product of distinct primes. A related problem with this theorem is to prove that for every such number, there exists a prime $p$ such that $p&lt; \sqrt n$. I was wondering if there is any mathematical proof that no prime $p$ exists for the number $n$ such that $p&gt; \sqrt n$. Show by induction that for all natural numbers n>3  $(1+\frac{1}{n})^n&lt;n$  Let $(1+\frac{1}{n})^n&lt;n$ be true !   We show that $(1+\frac{1}{n+1})^{n+1})&lt;n+1$  $(1+\frac{1}{n})^n(1+\frac{1}{n})&lt;n(1+\frac{1}{n})$   $(1+\frac{1}{n})^{n+1}&lt;n+1$  So now we just need to show that   $(1+\frac{1}{n+1})^{n+1}&lt;(1+\frac{1}{n})^{n+1}$  So here , If I show that :   $(1+\frac{1}{n+1})&lt;(1+\frac{1}{n})$   Does that mean im done with exercise ? Lagrange Multipler KKT condition I am looking at SVM, and reviewing Lagrange multiplier. Let's say with the constraint function $$g(x,y) = x^2 + y^2 -1 &gt; 0, $$ I am maximizing $$f(x,y) = x + y -1 .$$ Intuitively, since the constraint function does not provide a finite constrained region, there is no solution, and $f(x,y)$ can infinitely increase.  However, if I just plainly proceed with Lagrange multiplier calculation,  $$L(x,\lambda) = (x + y -1) +\lambda(x^2 + y^2 -1)$$ I get the solution: $$y,x = -\sqrt{2}/2, \lambda = 1/\sqrt{2}$$ And this still satisfies KKT conditions although the solution is wrong.  $$g(x) =&gt; 0 , \lambda =&gt;      0, \lambda g(x) = 0.$$  I expected that I would have some result that conflicted KKT conditions, but nothing was violated.   Does this mean that Lagrange multiplier under KKT conditions can produce a solution that cannot be solved, without giving any indication of intractability?  If functions are complicated, what's the systematic way to confirm that the optimization with inequality constraint functions is solvable using Lagrange multiplier? Is there any simple method to calculate $\sqrt x$ without using logarithm Suppose that we don't know logarithm, then how we would able to calculate $\sqrt x$, where $x$ is a real number? More generally, is there any algorithm to calculate $\sqrt [ n ]{ x } $ without using logarithm? More simple techniques would be nice.  Here is a simple technique used to approximate square roots by :  For example: $\sqrt {78}\approx 8\frac { 14 }{ 17 } $ , where $8$ is the nearest integer root of $78$, $14 = 78 - 8^2$, $17 = 2 \times 8 + 1$.  if $n=2^k$ we can use the method above.   For example, for $k=2$ Lets calculate $\sqrt [ 4 ]{ 136 } $: $$\sqrt [ 4 ]{ 136 } =\sqrt { \sqrt { 136 }  } \approx \sqrt { 11\frac { 136-{ 11 }^{ 2 } }{ 11\times 2+1 }  } =\sqrt { 11\frac { 15 }{ 23 }  } \\ \sqrt { 11\frac { 15 }{ 23 }  } \approx 3\frac { 11\frac { 15 }{ 23 } -{ 3 }^{ 2 } }{ 3\times 2+1 } =\frac { 544 }{ 161 } =3.38\\$$ The exact result is$$ \sqrt [ 4 ]{ 136 } =3.4149\cdots$$ The method approximates well, but it is working for only $n=2^k$ as I know. The  (or conjecture), suggests that black holes can be entirely described by their mass, angular momentum and charge. All other details of the BH formation are lost.  Is there a simple way of understanding why you would be able to tell the difference between a BH made from protons and one made from electrons, but not between one made from matter rather than anti-matter?  i.e. What is special about charge, and why aren't lepton number, baryon number, strangeness etc, also black hole properties? Adding meta values to permalink I have publications and I want to simply add year and month to the permalink. Currently the year and month of publication is added to the post as a meta value. I've set up publications as a custom post type and created taxonomy for the specific title of the publication. I would like the permalink to be:  publications/publication-title/year-published/month-published/name-of-post  I simply want to add the meta values for the publication year and month to the permalink.   So far, I've been able to pull the year and month published and add it to the url but unfortunately I keep getting a 404 when I try to access posts. I think I'm taking a wrong turn with one of my steps below ...  Any help would be appreciated.  These are the steps I did in the following order:   Since I was adding publication-year and publication-month to the url, I was reading that I had to make WordPress aware of these custom querystring variables. I added the following functions to register these custom variables:  function pubyear_register_rewrite_tag() {       add_rewrite_tag( '%pubyear%', '([0-9]{4})');   }    add_action( 'init', 'pubyear_register_rewrite_tag');  function pubmonth_register_rewrite_tag() {      add_rewrite_tag( '%pubmonth%', '([0-9]{2}');   }    add_action( 'init', 'pubmonth_register_rewrite_tag');    2) Added the year and month to the permalink structure:  add_filter('post_type_link', 'pub_term_permalink', 10, 4);  function pub_term_permalink($permalink, $post, $leavename, $sample) {     if ( false !== strpos( $permalink, '%publication-title%/%pubyear%/%pubmonth%' ) ) {       //get the publication-title      $publicationtype = get_the_terms( $post-&gt;ID, 'publication-type' );       //get the year of the publication      $pubyear = date('Y', get_post_meta($post-&gt;ID, 'pub_date', true));       //get the month of the publication      $pubmonth = date('m', get_post_meta($post-&gt;ID, 'pub_date', true));       $rewritecode = array(          '%publication-type%',          '%pubyear%',          '%pubmonth%',          $leavename? '' : '%postname%',      );       $rewritereplace = array(          array_pop($publicationtype)-&gt;slug,          $pubyear,          $pubmonth,          $post-&gt;post_name      );       $permalink = str_replace($rewritecode, $rewritereplace, $permalink);       }     return $permalink; }   3) Add rewrite rules:  function pub_add_rewrite_rules() {       add_rewrite_rule(  '^([^/]*)/([0-9]{4})/([0-9]{2})/([^/]+)?', 'publications/index.php?pagename=$matches[3]', 'top' );   }    add_action( 'init', 'pub_add_rewrite_rules' );   4) Made sure the custom post type is registered and includes this rewrite array:  'rewrite' =&gt; array     (             'slug' =&gt; 'publications/%publication-type%/%pubyear%/%pubmonth%',     'with_front' =&gt; false          ), How do I programmatically get the field type of a specific field? Let $f_1 , f_2: I\mapsto \mathbb{R}$ bounded functions. Show that $L(f_1)+L(f_2)\leq L(f_1+f_2)$ (Riemann integral) Let $f_1 , f_2: I\mapsto \mathbb{R}$ bounded functions. Show that $L(f_1)+L(f_2)\leq L(f_1+f_2)$ where $L(F)$ is the supremum of the lower sums of the Riemann integral.  I tried to by contradicction $L(f_1)+L(f_2)&gt; L(f_1+f_2)$ and isoleting $L(f_1)&gt; L(f_1+f_2)-L(f_2)$ and usig the definition of sup.  I also tried to use $\sup(A)+\sup(B)=\sup(A+B)$ but it din't work.  Thanks. Selecting features with NULL attributes in QGIS How do I identify which features have NULL attributes in the attribute table of a shapefile?  When i try [field]= 'NULL' it selects the features with value = 0 (see picture) Proving by induction that $\sum\limits_{k=2}^n \frac1{k^2}\le 1$ Update 2014-04-17 04:47 UTC: Stable, with some odds and ends to clean up      The main MSO/MSE sites are stable, but there are plenty of corners left to sweep. For details, see:    Not all of them mind you, just Meta Stack Overflow into Meta Stack Exchange.  I'll have you know, factually, that we really did believe this would take place in six-to-eight weeks when it was , but we've finally got a tentative date established.  If things go according to plan, we'll begin the operation shortly after 8:30 PM EDT on the 16th, completing everything within a few hour window. Ideally, all service disrupting endeavors will be completed within the first hour, which include:   The availability of Meta Stack Overflow The availability of Stack Overflow (more on this shortly) The availability of Chat on Meta Stack Overflow   As you know, we'll be bolting on a standard issue per-site meta on Stack Overflow, while breaking the link between what will have become Meta Stack Exchange and Stack Overflow. There's some irritable innards in that particular region, so we'll be asking folks to expect the unexpected during the maintenance window. Affected sites will be in and out of read-only mode, or quite possibly just down for maintenance while we're doing the actual break.  I'll be posting a system message on both Meta Stack Overflow as well as Stack Overflow itself 24 hours before we begin the actual work.   Did I say tentative in a six-to-eight-something time frame again? Why yes, I did - we're currently running some tests on the dev tier to simulate the split as closely as possible, so that we can better anticipate quirks that we need to address prior to actually doing it.  Once the sites have actually been stood up functionally on the production tier, we're going to get to work on finishing touches. This will include things like site settings (which determine bits of text you see in the question prompts, rep thresholds, etc) and all sorts of other fine tuning.  Once we're done:   Stack Overflow will have a blank, empty child meta site just like every other site The new Meta Stack Exchange will be up and running All rooms on Chat Meta Stack Overflow will be moved to Chat Meta Stack Exchange  I'll send over about 150 - 200 questions from MSE to MSO, most of which will be tag or SO-specific feature related posts that got buried by the network stuff without resolution.   If the tentative date moves, I'll update this post with the new date. However, we do not anticipate this happening any later than Saturday, April 19 - in the case that we see down time we can't mitigate and need to do it on a weekend.  The ground work is basically done, we're finishing up sanity now with a great deal of confidence, and we're pretty certain that we'll hit between those dates, if not directly on the tentative 16th.  Questions? Kvetch? Anonymous confessions? Answer below, and I'll address each in comments. Markov chains, cellular automata, and raster algebra I need to build a probabilistic cellular automaton for simulating land-use changes and am wondering how to implement this in a GIS. I understand that Markov chains are a way of doing this, and IDRISI has some sort of module for Markov chains, but I have no access to IDRISI.  that, with raster data, this can, in theory, be done with any GIS that can do raster algebra. Presumably this means that it can even be done in ArcGIS, and I think I've figured out how to build cellular automata in ModelBuilder (once I know with certainty how to make iteration work there).  Still, I can find next to no practical advice on this. Once I have two datasets, one showing the land use at a certain point in time (time A) and the other at a later time (time B), I imagine doing the following (correct me if I'm wrong):   If there are (for example) 3 types of land use, then there are 9 possible things that can happen to a cell from time A to time B; thus, reclassify each dataset such that each land use is represented by a different number (for example, 9, 11, and 14 at time A and 3, 4, and 5 at time B); Divide one raster by the other, obtaining a raster with 9 possible cell values. Determine the percentage of cells in the new raster that has each of the 9 values (I forgot, how does one do this in ArcGIS?); those will be the probabilities of each type of change (or lack thereof) in land use.   What I cannot figure out, though, is how to apply these probabilities during the next iteration. Finally, I wonder if there is a way of making an external factor (say, proximity to roads) influence the spatial distribution (not the overall likelihood) of change in my model.  Can anyone recommend where to find information on how to do this in ArcGIS?