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  • Are function-local typedefs visible inside C++0x lambdas?

    - by GMan - Save the Unicorns
    I've run into a strange problem. The following simplified code reproduces the problem in MSVC 2010 Beta 2: template <typename T> struct dummy { static T foo(void) { return T(); } }; int main(void) { typedef dummy<bool> dummy_type; auto x = [](void){ bool b = dummy_type::foo(); }; // auto x = [](void){ bool b = dummy<bool>::foo(); }; // works } The typedef I created locally in the function doesn't seem to be visible in the lambda. If I replace the typedef with the actual type, it works as expected. Here are some other test cases: // crashes the compiler, credit to Tarydon int main(void) { struct dummy {}; auto x = [](void){ dummy d; }; } // works as expected int main(void) { typedef int integer; auto x = [](void){ integer i = 0; }; } I don't have g++ 4.5 available to test it, right now. Is this some strange rule in C++0x, or just a bug in the compiler? From the results above, I'm leaning towards bug. Though the crash is definitely a bug. For now, I have filed two bug reports. All code snippets above should compile. The error has to do with using the scope resolution on locally defined scopes. (Spotted by dvide.) And the crash bug has to do with... who knows. :) Update According to the bug reports, they have both been fixed for the next release of Visual Studio 2010.

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  • How is a functional programming-based javascript app laid out?

    - by user321521
    I've been working with node.js for awhile on a chat app (I know, very original, but I figured it'd be a good learning project). Underscore.js provides a lot of functional programming concepts which look interesting, so I'd like to understand how a functional program in javascript would be setup. From my understanding of functional programming (which may be wrong), the whole idea is to avoid side effects, which are basically having a function which updates another variable outside of the function so something like var external; function foo() { external = 'bar'; } foo(); would be creating a side effect, correct? So as a general rule, you want to avoid disturbing variables in the global scope. Ok, so how does that work when you're dealing with objects and what not? For example, a lot of times, I'll have a constructor and an init method that initializes the object, like so: var Foo = function(initVars) { this.init(initVars); } Foo.prototype.init = function(initVars) { this.bar1 = initVars['bar1']; this.bar2 = initVars['bar2']; //.... } var myFoo = new Foo({'bar1': '1', 'bar2': '2'}); So my init method is intentionally causing side effects, but what would be a functional way to handle the same sort of situation? Also, if anyone could point me to either a python or javascript source code of a program that tries to be as functional as possible, that would also be much appreciated. I feel like I'm close to "getting it", but I'm just not quite there. Mainly I'm interested in how functional programming works with traditional OOP classes concept (or does away with it for something different if that's the case).

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  • How to remove a specific category on a selected mail in Outlook 2003 with Macro?

    - by szekelya
    Hi, I am trying to transform my Outlook2003 into the closest thing to gmail. I started to use categories, which are pretty similar to labels in gmail. I can assign categories automatically with rules, and I can add categories manually. I have also created "search folders", that show all mails with a given category, if they are not in the Deleted Items or Sent Items folders. This part is almost like the Label views in gmail. Two things are missing basically, which should be done with macros (VBA to be precise) which I'm totally inexperienced with. So hence my questions: -Can someone show me a macro to remove the category "Inbox"? That would act exactly like the Archive button in gmail. In fact I want to assign this macro to a toolbar button and call it Archive. I have a rule that adds the Inbox category to all incoming mail. As I said, I have a search folder displaying all mails categorized as Inbox, and I also have an All Mail search folder, that displays all messages regardless whether they have the Inbox category. Exactly like gmail, just the easy archiving is missing. -Can someone show me a macro that would delete the selected mail/mails and also would remove the Inbox category before deletion? I would replace the default delete button with this macro. (Somewhat less important, as in my search folders I can filter messages that are physically placed in the Deleted Items folder, but it would be more elegant not to have mails categorized as Inbox in the trash. Many thanks in advance, szekelya

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  • Factorial in Prolog and C++

    - by Joshua Green
    I would like to work out a number's factorial. My factorial rule is in a Prolog file and I am connecting it to a C++ code. Can someone tell me what is wrong with my C++ interface please? % factorial.pl factorial( 1, 1 ):- !. factorial( X, Fac ):- X > 1, Y is X - 1, factorial( Y, New_Fac ), Fac is X * New_Fac. // factorial.cpp # headerfiles term_t t1; term_t t2; term_t goal_term; functor_t goal_functor; int main( int argc, char** argv ) { argc = 4; argv[0] = "libpl.dll"; argv[1] = "-G32m"; argv[2] = "-L32m"; argv[3] = "-T32m"; PL_initialise(argc, argv); if ( !PL_initialise(argc, argv) ) PL_halt(1); PlCall( "consult(swi('plwin.rc'))" ); PlCall( "consult('factorial.pl')" ); cout << "Enter your factorial number: "; long n; cin >> n; PL_put_integer( t1, n ); t1 = PL_new_term_ref(); t2 = PL_new_term_ref(); goal_term = PL_new_term_ref(); goal_functor = PL_new_functor( PL_new_atom("factorial"), 2 ); PL_put_atom( t1, t2 ); PL_cons_functor( goal_term, goal_functor, t1, t2 ); PL_halt( PL_toplevel() ? 0 : 1 ); }

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  • RewriteCond and RewriteRule newbie

    - by mybrokengnome
    I'm taking over a website for a client that is running on a custom built CMS (that I didn't write). I don't mess with .htaccess files usually because a lot of the hosting I do is on IIS, or I used WordPress as a CMS and don't have to worry about messing with the .htaccess file. Here's the contents of the file: RewriteEngine on RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ framework.php?%{QUERY_STRING}&resource=$1& [L] I get what it's doing (sending all requests through the framework.php file). The client wants a WordPress blog added to their site. I'm placing it in a /blog/ folder. The problem is that because of the rewrite rules and conditions in the .htaccess file whenever I try to go /blog/ the other CMS freaks out because it doesn't like me trying to go there. My question is how do I write a rule/cond that tells apache to send all requests made to the /blog/ folder to the /blog/ folder, but keep all other requests piped through the framework.php file like it is now? Any help is appreciated, thanks!

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  • c++ use of winmain()

    - by Jack
    Hi, I just started learning programming for windows in c++. I had this crazy image, that win32 programming is based on calling windows functions and sending parameters to and from them. Like, when you want to create window, you call some win32 function that handles windows GUI and say "Hi, please, create me new window, 100 x 100 px, with two buttons", and that GUI function says "Hi, no problem, when something happends, like user clicks one button, I will change this variable xy located in this location". So, I thought that it will be very similiar to console programming. But the very first instruction surprised me. I always thought that every program executes main() function first. So, when I launch app, windows stores some parameters on top of stack and run that application. So I assumed that initializing main() is just a c++ way to tell the compiler where the first instruction should be. But in win32 programming, there is function called winmain() which starts first. So I am little confused. I thought it´s rule that compiler must have main() to start with, that main just defines where ti start, like some start point identifier. So, please, why is there winmain() function instead of main()? When I thought that C++ programming is as logical as assembler, it confuses me once again.

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  • c++ use of winmain()

    - by Jack
    Hi, I just started learning programming for windows in c++. I had this crazy image, that win32 programming is based on calling windows functions and sending parameters to and from them. Like, when you want to create window, you call some win32 function that handles windows GUI and say "Hi, please, create me new window, 100 x 100 px, with two buttons", and that GUI function says "Hi, no problem, when something happends, like user clicks one button, I will change this variable xy located in this location". So, I thought that it will be very similiar to console programming. But the very first instruction surprised me. I always thought that every program executes main() function first. So, when I launch app, windows stores some parameters on top of stack and run that application. So I assumed that initializing main() is just a c++ way to tell the compiler where the first instruction should be. But in win32 programming, there is function called winmain() which starts first. So I am little confused. I thought it´s rule that compiler must have main() to start with, that main just defines where ti start, like some start point identifier. So, please, why is there winmain() function instead of main()? When I thought that C++ programming is as logical as assembler, it confuses me once again.

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  • Division by zero: Undefined Behavior or Implementation Defined in C and/or C++ ?

    - by SiegeX
    Regarding division by zero, the standards say: C99 6.5.5p5 - The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined. C++03 5.6.4 - The binary / operator yields the quotient, and the binary % operator yields the remainder from the division of the first expression by the second. If the second operand of / or % is zero the behavior is undefined. If we were to take the above paragraphs at face value, the answer is clearly Undefined Behavior for both languages. However, if we look further down in the C99 standard we see the following paragraph which appears to be contradictory(1): C99 7.12p4 - The macro INFINITY expands to a constant expression of type float representing positive or unsigned infinity, if available; Do the standards have some sort of golden rule where Undefined Behavior cannot be superseded by a (potentially) contradictory statement? Barring that, I don't think it's unreasonable to conclude that if your implementation defines the INFINITY macro, division by zero is defined to be such. However, if your implementation does not define such a macro, the behavior is Undefined. I'm curious what the consensus on this matter for each of the two languages. Would the answer change if we are talking about integer division int i = 1 / 0 versus floating point division float i = 1.0 / 0.0 ? Note (1) The C++03 standard talks about the library which includes the INFINITY macro.

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  • Syntax error beyond end of program

    - by a_m0d
    I am experimenting with writing a toy compiler in ocaml. Currently, I am trying to implement the offside rule for my lexer. However, I am having some trouble with the ocaml syntax (the compiler errors are extremely un-informative). The code below (33 lines of it) causes an error on line 34, beyond the end of the source code. I am unsure what is causing this error. open Printf let s = (Stack.create():int Stack.t); let rec check x = ( if Stack.is_empty s then Stack.push x s else if Stack.top s < x then ( Stack.push x s; printf "INDENT\n"; ) else if Stack.top s > x then ( printf "DEDENT\n"; Stack.pop s; check x; ) else printf "MATCHED\n"; ); let main () = ( check 0; check 4; check 6; check 8; check 5; ); let _ = Printexc.print main () Ocaml output: File "lexer.ml", line 34, characters 0-0: Error: Syntax error Can someone help me work out what the error is caused by and help me on my way to fixing it?

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  • Is there a max recommended size on bundling js/css files due to chunking or packet loss?

    - by George Mauer
    So we all have heard that its good to bundle your javascript. Of course it is, but it seems to me that the story is too simple. See if my logic makes sense here. Obviously fewer HTTP requests is fewer round trips and hence better. However - and I don't know much about bare http - aren't http responses sent in chunks? And if a file is larger than one of those chunks doesn't it have to be downloaded as multiple (possibly synchronous?) round trips? As opposed to this, several requests for files just under the chunking size would arrive much quicker since modern web browsers download resources like javascripts in parallel. Even if chunking is not an issue, it seems like there would be some max recommended size just due to likelyhood of packet loss alone since a bundled file must wait till it is entirely downloaded to execute, versus the more lenient native rule that scripts must execute in order. Obviously there's also matters of browser caching and code volatility to consider but can someone confirm this or explain why I'm off base? Does anyone have any numbers to put to it?

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  • Strategies for when to use properties and when to use internal variables on internal classes?

    - by Edward Tanguay
    In almost all of my classes, I have a mixture of properties and internal class variables. I have always chosen one or the other by the rule "property if you need it externally, class variable if not". But there are many other issues which make me rethink this often, e.g.: at some point I want to use an internal variable from outside the class, so I have to refactor it into a property which makes me wonder why I don't just make all my internal variables properties in case I have to access them externally anyway, since most classes are internal classes anyway it aren't exposed on an API so it doesn't really matter if the internal variables are accessible from outside the class or not but then since C# doesn't allow you to instantiate e.g. List<string> property in the definition, then these properties have to be initialized in every possible constructor, so these variables I would rather have internal variables just to keep things cleaner in that they are all initialized in one place C# code reads more cleanly if constructor/method parameters are camel case and you assign them to pascal case properties instead of the ambiguity of seeing "templateIdCode" and having to look around to see if it is a local variable, method parameter or internal class variable, e.g. it is easier when you see "TemplateIdCode = templateIdCode" that this is a parameter being assigned to a class property. This would be an argument for always using only properties on internal classes. e.g.: public class TextFile { private string templateIdCode; private string absoluteTemplatePathAndFileName; private string absoluteOutputDirectory; private List<string> listItems = new List<string>(); public string Content { get; set; } public List<string> ReportItems { get; set; } public TextFile(string templateIdCode) { this.templateIdCode = templateIdCode; ReportItems = new List<string>(); Initialize(); } ... When creating internal (non-API) classes, what are your strategies in deciding if you should create an internal class variable or a property?

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  • slideDown() Makes Everything in Wrapper Shift

    - by Ben
    Hello everyone, I am currently creating a simple menu where there are several names of services and a user can click on one and jQuery will show it's corresponding paragraph describing it below it. My jQuery code is fine and does exactly what I want, however, I have one bug I have yet to iron out. Whenever I click one of these headings and it's description displays, everything in the wrapper for the page shifts to the left about 7 pixels in Firefox, it does the same thing is Google Chrome however I have not measured the amout but I am sure it is irrelevant. Anyways, I am using the slideToggle() command to show the hidden parragraph. I assume this is occuring because when the slideDown occurs it is somehow changing the width of everything and the "margin: 0 auto;" setting for the wrapper rule in my css is compensating for this change. Does anyone have any way I can remedy this problem? I have tried several other fixes I've found around the internet but to no avail. Here is what my code looks like, I put it on jsFiddle to make it easier to view: http://jsfiddle.net/vcH7m/ Feel free to edit it there if you like, or post what needs to be fixed here. Whatever is more convenient. Thank you very much for the help!

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  • URL development and mod_rewrite

    - by iRector
    My site is made-up of the main page, and multiple sub-directories, all under the same domain. My URLS are currently like .................| Ideal clean version: mysite.com mysite.com/?content=content1 ......................| mysite.com/content1/ mysite.com/?content=content2&page=4 ........| mysite.com/content2/4/ mysite.com/?content=content3 ......................| mysite.com/content3/ mysite.com/?content=content4 ......................| mysite.com/content4/ mysite.com/?content=article&id=34 ............| mysite.com/article/34/ Then the sub-directories are essentially the same: mysite.com/subdir, mysite.com/subdir2, mysite.com/subdir3, etc mysite.com/subdir/?content=content1 ...................| mysite.com/subdir/content1/ mysite.com/subdir/?content=content2&page=4 .....| mysite.com/subdir/content2/4/ mysite.com/subdir/?content=content3 ...................| mysite.com/subdir/content3/ mysite.com/subdir/?content=content4 ...................| mysite.com/subdir/content4/ mysite.com/subdir/?content=article&id=34 .........| mysite.com/subdir/article/34/ I've used mod_rewrite briefly, but I'm not sure how to approach these multiple variables. Also, how would I differentiate between the actually subfolders, and the content variable. As so to prevent 'subdir' or 'subdir2' from being plugged in as the content variable for the root site. I've played around with plenty of code snippets, but I've wiped my .htaccess slate clean, and approach you all in an attempt to help me repopulate it. Your input would thoroughly be appreciated. Note: The only time the page query string will be needed is when 'content' == 'content2' ?content=content2&page=4 **Same rule is shared by the article/id relationship, all other 'content' values are expected to be dynamic.

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  • Find all CSS rules that apply to an element

    - by Carl Byström
    Many tools/APIs provide ways of selecting elements of specific classes or IDs. There's also possible to inspect the raw stylesheets loaded by the browser. However, for browsers to render an element, they'll compile all CSS rules (possibly from different stylesheet files) and apply it to the element. This is what you see with Firebug or the WebKit Inspector - the full CSS inheritance tree for an element. How can I reproduce this feature in pure JavaScript without requiring additional browser plugins? Perhaps an example can provide some clarification for what I'm looking for: <style type="text/css"> p { color :red; } #description { font-size: 20px; } </style> <p id="description">Lorem ipsum</p> Here the p#description element have two CSS rules applied: a red color and a font size of 20 px. I would like to find the source from where these computed CSS rules originate from (color comes the p rule and so on).

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  • How to emulate mod_rewrite in PHP

    - by Tyler Crompton
    I have a few URLs that I want to map to certain files via PHP. Currently, I am just using mod_rewrite in Apache. However, my application is getting too large for the rewriting to be done with regular expressions. So I created a file router.php that does the rewriting. I understand to do a redirect I could just send the Location: header. However, I don't always want to do a redirect. For example, I may want /api/item/ to map to the file /herp/derp.php relative to the document root. I need to preserve the HTTP method as well. "No problem," I thought. I made my .htaccess have the following snippet. RewriteEngine On RewriteRule ^api/item/$ /cgi-bin/router.php [L] And my router.php file looks as follows: <?php $uri = parse_url($_SERVER['REQUEST_URI']); $query = isset($uri['query']) ? $uri['query'] ? array(); // some code that modifies the query require_once "{$_SERVER['DOCUMENT_ROOT']}/herp/derp.php?" . http_build_query($query); ?> However, this doesn't work, because the OS is looking for a file named derp.php?some=query. How can I simulate a rewrite rule such as RewriteRule ^api/item/$ /herp/derp/ [L] in PHP. In other words, how do I tell the server to process a different URL than requested and preserve the query and HTTP method without causing a redirect? Note: Using variables set in router.php is less than desirable and is bad structure since it's only supposed to be responsible for handling URLs. I am open to using a light-weight third party solution.

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  • apache proxy module gives 403 forbidden error

    - by naiquevin
    I am trying to use the apache's proxy module for working with xmpp on ubuntu desktop. For this i did the following things - 1) enabled mod_proxy by creating a symlink of proxy.conf, proxy.load and proxy_http.load from /etc/apache2/mods-available/ in the mods-enabled directory. 2) Added the following lines to the vhost <Proxy http://mydomain.com/httpbind> Order allow,deny Allow from all </Proxy> ProxyPass /httpbind http://mydomain.com:7070/http-bind/ ProxyPassReverse /httpbind http://mydomain.com:7070/http-bind/ I am new to using the proxy module but what i can make from the above lines is that requests to http://mydomain.com/httpbind will be forwarded to http://mydomain.com:7070/http-bind/. Kindly correct if wrong. 3) added rule Allow from .mydomain.com in /mods-available/proxy.conf Now i try to access http://mydomain.com/httpbind and it shows 403 Forbidden error.. What am i missing here ? Please help. thanks Edit : The problem got solved when i changed the following code in mods_available/proxy.conf <Proxy *> AddDefaultCharset off Order deny,allow Deny from all Allow from mydomain.com </Proxy> to <Proxy *> AddDefaultCharset off Order deny,allow #Deny from all Allow from all </Proxy> Didnt get what was wrong with the initial code though

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  • How should rules for Aggregate Roots be enforced?

    - by MylesRip
    While searching the web, I came across a list of rules from Eric Evans' book that should be enforced for aggregates: The root Entity has global identity and is ultimately responsible for checking invariants Root Entities have global identity. Entities inside the boundary have local identity, unique only within the Aggregate. Nothing outside the Aggregate boundary can hold a reference to anything inside, except to the root Entity. The root Entity can hand references to the internal Entities to other objects, but they can only use them transiently (within a single method or block). Only Aggregate Roots can be obtained directly with database queries. Everything else must be done through traversal. Objects within the Aggregate can hold references to other Aggregate roots. A delete operation must remove everything within the Aggregate boundary all at once When a change to any object within the Aggregate boundary is committed, all invariants of the whole Aggregate must be satisfied. This all seems fine in theory, but I don't see how these rules would be enforced in the real world. Take rule 3 for example. Once the root entity has given an exteral object a reference to an internal entity, what's to keep that external object from holding on to the reference beyond the single method or block? (If the enforcement of this is platform-specific, I would be interested in knowing how this would be enforced within a C#/.NET/NHibernate environment.)

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  • Chrome targeted CSS

    - by Chris
    I have some CSS code that hides the cursor on a web page (it is a client facing static screen with no interaction). The code I use to do this is below: *, html { cursor: url('/web/resources/graphics/blank.cur'), pointer; } Blank.cur is a totally blank cursor file. This code works perfectly well in all browsers when I host the web files on my local server but when I upload to a Windows CE webserver (our production unit) the cursor represents itself as a black box. Odd. After some testing it seems that chrome only has a problem with totally blank cursor files when served from WinCE web server, so I created a blank cursor with one pixel as white, specifically for chrome. How do I then target this CSS rule to chrome specifically? i.e. *, html { cursor: url('/web/resources/graphics/blank.cur'), pointer; } <!--[if CHROME]> *, html { cursor: url('/web/resources/graphics/blankChrome.cur'), pointer; } <![endif]-->

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  • C when to allocate and free memory - before function call, after function call...etc

    - by Keith P
    I am working with my first straight C project, and it has been a while since I worked on C++ for that matter. So the whole memory management is a bit fuzzy. I have a function that I created that will validate some input. In the simple sample below, it just ignores spaces: int validate_input(const char *input_line, char* out_value){ int ret_val = 0; /*false*/ int length = strlen(input_line); cout << "length = " << length << "\n"; out_value =(char*) malloc(sizeof(char) * length + 1); if (0 != length){ int number_found = 0; for (int x = 0; x < length; x++){ if (input_line[x] != ' '){ /*ignore space*/ /*get the character*/ out_value[number_found] = input_line[x]; number_found++; /*increment counter*/ } } out_value[number_found + 1] = '\0'; ret_val = 1; } return ret_val; } Instead of allocating memory inside the function for out_value, should I do it before I call the function and always expect the caller to allocate memory before passing into the function? As a rule of thumb, should any memory allocated inside of a function be always freed before the function returns?

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  • No idea how to solve SICP exercise 1.11

    - by Javier Badia
    This is not homework. Exercise 1.11: A function f is defined by the rule that f(n) = n if n<3 and f(n) = f(n - 1) + 2f(n - 2) + 3f(n - 3) if n 3. Write a procedure that computes f by means of a recursive process. Write a procedure that computes f by means of an iterative process. Implementing it recursively is simple enough. But I couldn't figure out how to do it iteratively. I tried comparing with the Fibonacci example given, but I didn't know how to use it as an analogy. So I gave up (shame on me) and Googled for an explanation, and I found this: (define (f n) (if (< n 3) n (f-iter 2 1 0 n))) (define (f-iter a b c count) (if (< count 3) a (f-iter (+ a (* 2 b) (* 3 c)) a b (- count 1)))) After reading it, I understand the code and how it works. But what I don't understand is the process needed to get from the recursive defintion of the function to this. I don't get how the code formed in someone's head. Could you explain the thought process needed to arrive at the solution?

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  • mod_rewrite to redirect URL with query string

    - by meeble
    I've searched all over stackoverflow, but none of the answers seem to be working for this situation. I have a lot of working mod_rewrite rules already in my httpd.conf file. I just recently found that Google had indexed one of my non-rewritten URLs with a query string in it: http://domain.com/?state=arizona I would like to use mod_rewrite to do a 301 redirect to this URL: http://domain.com/arizona The issue is that later on in my rewrite rules, that 2nd URL is being rewritten to pass query variables on to WordPress. It ends up getting rewritten to: http://domain.com/index.php?state=arizona Which is the proper functionality. Everything I have tried so far has either not worked at all or put me in an endless rewrite loop. This is what I have right now, which is getting stuck in a loop: RewriteCond %{QUERY_STRING} state=arizona [NC] RewriteRule .* http://domain.com/arizona [R=301,L] #older rewrite rule that passes query string based on URL: RewriteRule ^([A-Za-z-]+)$ index.php?state=$1 [L] which gives me an endless rewrite loop and takes me to this URL: http://domain.com/arizona?state=arizona I then tried this: RewriteRule .* http://domain.com/arizona? [R=301,L] which got rid of the query string in the URL, but still creates a loop.

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  • What is the performance impact of CSS's universal selector?

    - by Bungle
    I'm trying to find some simple client-side performance tweaks in a page that receives millions of monthly pageviews. One concern that I have is the use of the CSS universal selector (*). As an example, consider a very simple HTML document like the following: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>Example</title> <style type="text/css"> * { margin: 0; padding: 0; } </head> <body> <h1>This is a heading</h1> <p>This is a paragraph of text.</p> </body> </html> The universal selector will apply the above declaration to the body, h1 and p elements, since those are the only ones in the document. In general, would I see better performance from a rule such as: body, h1, p { margin: 0; padding: 0; } Or would this have exactly the same net effect? Essentially, what I'm asking is if these rules are effectively equivalent in this case, or if the universal selector has to perform more unnecessary work that I may not be aware of. I realize that the performance impact in this example may be very small, but I'm hoping to learn something that may lead to more significant performance improvements in real-world situations. Thanks for any help!

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  • routes as explained in RoR tutorial 2nd Ed?

    - by 7stud
    The author, Michael Hartl, says: Here the rule: get "static_pages/home" maps requests for the URI /static_pages/home to the home action in the StaticPages controller. How? The type of request is given, the url is given, but where is the mapping to a controller and action? My tests all pass, though. I also tried deleting all the actions in the StaticPagesController, which just looks like this: class StaticPagesController < ApplicationController def home end def about end def help end def contact end end ...and my tests still pass, which is puzzling. The 2nd edition of the book(online) is really frustrating. Specifically, the section about making changes to the Guardfile is impossible to follow. For instance, if I instruct you to edit this file: blah blah blah dog dog dog beetle beetle beetle jump jump jump and make these changes: blah blah blah . . . go go go . . . jump jump jump ...would you have any idea where the line 'go go go' should be in the code? And the hint for exercise 3.5-1 is flat out wrong. If the author would put up a comment section at the end of every chapter, the rails community could self-edit the book.

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  • How to generate a monotone MART ROC in R?

    - by user1521587
    I am using R and applying MART (Alg. for multiple additive regression trees) on a training set to build prediction models. When I look at the ROC curve, it is not monotone. I would be grateful if someone can help me with how I should fix this. I am guessing the issue is that initially, MART generates n trees and if these trees are not the same for all the models I am building, the results will not be comparable. Here are the steps I take: 1) Fix the false-negative cost, c_fn. Let cost = c(0, 1, c_fn, 0). 2) use the following line to build the mart model: mart(x, y, lx, martmode='class', niter=2000, cost.mtx=cost) where x is the matrix of training set variables, y is the observation matrix, lx is the matrix which specifies which of the variables in x is numerical, which one categorical. 3) I predict the test set observations using the mart model found in step 2 using this line: y_pred = martpred(x_test, probs=T) 4) I compute the false-positive and false-negative errors as follows: t = 1/(1+c_fn) %threshold based on Bayes optimal rule where c_fp=1 and c_fn. p_0 = length(which(y_test==1))/dim(y_test)[1] p_01 = sum(1*(y_pred[,2]t & y_test==0))/dim(y_test)[1] p_11 = sum(1*(y_pred[,2]t & y_test==1))/dim(y_test)[1] p_fp = p_01/(1-p_0) p_tp = p_11/p_0 5) repeat step 1-4 for a new false-negative cost.

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  • Invalid quantifer error using Regular Expression (UK Telephone numbers)

    - by Matt
    HI all, as per the title I am getting the error "Invalid Quantifier" Trying to match this reg ex:- ^(((+44\s?\d{4}|(?0\d{4})?)\s?\d{3}\s?\d{3})|((+44\s?\d{3}|(?0\d{3})?)\s?\d{3}\s?\d{4})|((+44\s?\d{2}|(?0\d{2})?)\s?\d{4}\s?\d{4}))(\s?#(\d{4}|\d{3}))?$ Infact ive tried a few UK telephone number regex's from the regex librairy but im getting the same error all the time. If anyone can help id be much appreciative! Just for info, im using the jQuery form validation librairy, and here is my code: - $(document).ready(function(){ //Set Fields to be validated $("#EventForm").validate(); $( "#StartDate" ).datepicker(); $( "#EndDate" ).datepicker(); //Add Postcode Regex Method to Validator Function $.validator.addMethod( "postcode", function(value, element, regexp) { var check = false; var re = new RegExp(regexp); return this.optional(element) || re.test(value); }, "Please enter a valid postcode." ); //Add UK Telephone number Regex Method to Validator Function $.validator.addMethod( "telephone", function(value, element, regexp) { var check = false; var re = new RegExp(regexp); return this.optional(element) || re.test(value); }, "Please enter a valid UK telephone number in the format - 01856 666666." ); //Add Postcode Regular Expression Rule to Postcode Field $("#EventPostcode").rules("add", { postcode: "^([a-zA-Z]){1}([0-9][0-9]|[0-9]|[a-zA-Z][0-9][a-zA-Z]|[a-zA-Z][0-9][0-9]|[a-zA-Z][0-9]){1}([ ])([0-9][a-zA-z][a-zA-z]){1}$"}); $("#EventTelephoneNo").rules("add", { telephone: "^(((\+44\s?\d{4}|\(?0\d{4}\)?)\s?\d{3}\s?\d{3})|((\+44\s?\d{3}|\(?0\d{3}\)?)\s?\d{3}\s?\d{4})|((\+44\s?\d{2}|\(?0\d{2}\)?)\s?\d{4}\s?\d{4}))(\s?\#(\d{4}|\d{3}))?$"}); }); Many thanks

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