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  • C# + Querying XML with LINQ

    - by user336786
    Hello, I'm learning to use LINQ. I have seen some videos online that have really impressed me. In an effort to learn LINQ myself, I decided to try to write a query to the NOAA web service. If you put "http://www.weather.gov/forecasts/xml/sample_products/browser_interface/ndfdBrowserClientByDay.php?zipCodeList=20001&format=24+hourly&startDate=2010-06-10&numDays=5" in your browser's address bar, you will see some XML. I have successfully retrieved that XML in a C# program. I am loading the XML into a LINQable entity by doing the following: string xml = QueryWeatherService(); XDocument weather = XDocument.Parse(xml); I have a class called DailyForecast defined as follows: public class DailyForecast { public float HighTemperature { get; set; } public float LowTemperature { get; set; } public float PrecipitationPossibility { get; set; } public string WeatherSummary { get; set; } } I'm trying write a LINQ query that adheres to the structure of my DailyForecast class. At this time, I've only gotten to this far: var results = from day in response.Descendants("parameters") select day; Not very far I know. Because of the structure of the XML returned, I'm not sure it is possible to solely use a LINQ query. I think the only way to do this is via a loop and traverse the XML. I'm seeking someone to correct me if I'm wrong. Can someone please tell me if I can get results using purely LINQ that adhere to the structure of the DailyForecast class? If so, how? Thank you!

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  • Handling Apache Thrift list/map Return Types in C++

    - by initzero
    First off, I'll say I'm not the most competent C++ programmer, but I'm learning, and enjoying the power of Thrift. I've implemented a Thrift Service with some basic functions that return void, i32, and list. I'm using a Python client controlled by a Django web app to make RPC calls and it works pretty well. The generated code is pretty straight forward, except for list returns: namespace cpp Remote enum N_PROTO { N_TCP, N_UDP, N_ANY } service Rcon { i32 ping() i32 KillFlows() i32 RestartDispatch() i32 PrintActiveFlows() i32 PrintActiveListeners(1:i32 proto) list<string> ListAllFlows() } The generated signatures from Rcon.h: int32_t ping(); int32_t KillFlows(); int32_t RestartDispatch(); int32_t PrintActiveFlows(); int32_t PrintActiveListeners(const int32_t proto); int64_t ListenerBytesReceived(const int32_t id); void ListAllFlows(std::vector<std::string> & _return); As you see, the ListAllFlows() function generated takes a reference to a vector of strings. I guess I expect it to return a vector of strings as laid out in the .thrift description. I'm wondering if I am meant to provide the function a vector of strings to modify and then Thrift will handle returning it to my client despite the function returning void. I can find absolutely no resources or example usages of Thrift list< types in C++. Any guidance would be appreciated.

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  • Javascript Cookie problems IE

    - by blakey87
    Hi guys, been bagging my head over some Javascript, please help, I cant see why it simply wont find my cookie in IE 7 or 8 I am setting the cookie true through another event, but I just want to see IE pick up the cookie which I initially set. Works in firefox too, thanks in advance. var t=setTimeout("doAlert()",8000); var doAlertVar = true; document.cookie = "closed=0;expires=0;path="; function readCookie(name) { var nameEQ = name + "="; var ca = document.cookie; alert(ca); ca = ca.replace(/^\s*|\s*$/g,''); ca = document.cookie.split(';'); for(var i=0;i < ca.length;i++) { var c = ca[i]; while (c.charAt(0)==' ') c = c.substring(1,c.length); if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length); } return null; } function doAlert(){ if(readCookie('closed')==1){ doAlertVar = false; } if(readCookie('closed')==0){ alert("unlicensed demo version\nbuy online at"); } t=setTimeout("doAlert()",5000); }

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  • Why Is Apache Giving 403?

    - by ThinkCL
    I am getting 403 Errors from Apache when I send too many, 12, synchronous HTTP Posts via a desktop app I am building in XCode / Objective-C. The 12 POST requests are just a few kb each and go out instantly one after the other and the Apache Error Log shows... client denied by server configuration: /the-path/the-file.php Apache 2.0 PHP 5 and I have this same setup working fine on my local machine. The error is coming from a VPS with my host, which runs very fast and smooth and has plenty of resources. To debug I threw a sleep(1); function (stalls script execution by 1 second) into the php file and that fixed it. This makes me think that I am breaking some limit for too many requests for a single IP in a certain amount of time. I have googled and combed PHP ini and Apache configs, but I cannot find what that directive/setting might be. I should mention that the although it varies the first 4 or 5 POSTS usually work then it starts returning the 403 error intermittently after that. Just really acting like its bogging down. Any ideas?

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  • What does the Kernel Virtual Memory of each process contain?

    - by claws
    When say 3 programs (executables) are loaded into memory the layout might look something like this: I've following questions: Is the concept of Virtual Memory limited to user processes? Because, I am wondering where does the Operating System Kernel, Drivers live? How is its memory layout? I know its operating system specific make your choice (windows/linux). They say, on a 32 bit machine in a 4GB address space. Half of it (or more recently 1GB) is occupied by kernel. I can see in this diagram that "Kernel Virtual memory" is occupying 0xc0000000 - 0xffffffff (= 1 GB). Are they talking about this? or is it something else? Just want to confirm. What exactly does the Kernel Virtual Memory of each of these processes contain? What is its layout? When we do IPC we talk about shared memory. I don't see any memory shared between these processes. Where does it live? Resources (files, registries in windows) are global to all processes. So, the resource/file handle table must be in some global space. Which area would that be in? Where can I know more about this kernel side stuff.

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  • The "correct" way of using multilingual support

    - by Felipe Athayde
    I just began working with ASP.NET and I'm trying to bring with me some coding standards I find healthy. Among such standards there is the multilingual support and the use of resources for easily handling future changes. Back when I used to code desktop applications, every text had to be translated, so it was a common practice to have the language files for every languages I would want to offer to the customers. In those files I would map every single text, from button labels to error messages. In ASP.NET, with the help of Visual Studio, I have the resort of using the IDE to generate such Resource Files (from Tools - Generate Local Resource), but then I would have to fill my webpages with labels - at least that is what I've learned from articles and tutorials. However, such approach looks a bit odd and I'm tempted to guess it doesn't smell that good as well. Now to the question: 1) Should I keep every single text in my website as labels and manage its contents in the resource files? It looks/feels odd specially when considering a text with several paragraphs. 2) Whenever I add/remove something, e.g.: a button, to an aspx file I would have to add it to the resource file as well, because generating the resource file again would simply override all my previous changes to it. That doesn't feel like a reusable code at all for me. Any comment suggestion on this one? Perhaps I got it all wrong from tutorials as it doesn't seem like a standardized matter - specially if it required recompiling the entire application whenever some change has to be done.

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  • Using custom detectors with FindBugs Maven plugin

    - by Lóránt Pintér
    I have a nice JAR of some custom FindBugs detectors I'd like to use with the FindBugs Maven plugin. There is a way to do this with the plugin via the <pluginList> configuration parameter, but that only accepts local files, URLs, or resources. The only way I found for doing so is to somehow copy my JAR to a local file (maybe via the Dependency plugin) and then configure the FindBugs plugin something like this: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>findbugs-maven-plugin</artifactId> <version>2.3.1</version> <configuration> <pluginList>${project.build.directory}/my-detectors.jar</pluginList> </configuration> </plugin> But this is not very flexible. Is there a way to use Maven's dependency management features together with FindBugs' plugins? I'd like to use something like this: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>findbugs-maven-plugin</artifactId> <dependencies> <dependency> <groupId>com.lptr.findbugs</groupId> <artifactId>my-detectors</artifactId> <version>1.0</version> </dependency> </dependencies> </plugin> ...but this simply overrides the core FindBugs detectors.

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  • I'm trying to make a php Curl call to formstack api, but I get nothing

    - by Oskar Calvo
    This is one of my first curls code, so it can have mistakes I'm trying to be able to make calls to form/:id/submissions https://www.formstack.com/developers/api/resources/submission#form/:id/submission_GET If I load: https://www.formstack.com/api/v2/form/1311091/submission.json?oauth_token=44eedc50d015b95164897f5e408670f0&min_time=2012-09-01%2000:01:01&max_time=2012-10-27%2000:01:01 If works great. If I try this code: <?php $host = 'https://www.formstack.com/api/v2/'; // TODO this should manage dinamics values or build an action in every method. $action = 'form/1311091/submission.json'; $url = $host . $action; // TODO this values will arrive like an array with values $postData['oauth_token']= '44eedc50d015b95164897f5e408670f0'; $postData['min_time'] ='2012-09-01 00:01:01'; $postData['max_time'] ='2012-10-27 00:01:01'; // TODO make a method with this action function getElements($postData) { $elements = array(); foreach ($postData as $name=>$value) { $elements[] = "{$name}=".urlencode($value); } } $curl = curl_init(); curl_setopt($curl, CURLOPT_URL, $url); curl_setopt($curl, CURLOPT_HTTPGET, true); curl_setopt($curl, CURLOPT_POSTFIELDS, $elements); $result = curl_exec($curl) ; curl_close($curl); var_dump($result); ?>

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  • Better language or checking tool?

    - by rwallace
    This is primarily aimed at programmers who use unmanaged languages like C and C++ in preference to managed languages, forgoing some forms of error checking to obtain benefits like the ability to work in extremely resource constrained systems or the last increment of performance, though I would also be interested in answers from those who use managed languages. Which of the following would be of most value? A language that would optionally compile to CLR byte code or to machine code via C, and would provide things like optional array bounds checking, more support for memory management in environments where you can't use garbage collection, and faster compile times than typical C++ projects. (Think e.g. Ada or Eiffel with Python syntax.) A tool that would take existing C code and perform static analysis to look for things like potential null pointer dereferences and array overflows. (Think e.g. an open source equivalent to Coverity.) Something else I haven't thought of. Or put another way, when you're using C family languages, is the top of your wish list more expressiveness, better error checking or something else? The reason I'm asking is that I have a design and prototype parser for #1, and an outline design for #2, and I'm wondering which would be the better use of resources to work on after my current project is up and running; but I think the answers may be useful for other tools programmers also. (As usual with questions of this nature, if the answer you would give is already there, please upvote it.)

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  • Why do I have to specify pure virtual functions in the declaration of a derived class in Visual C++?

    - by neuviemeporte
    Given the base class A and the derived class B: class A { public: virtual void f() = 0; }; class B : public A { public: void g(); }; void B::g() { cout << "Yay!"; } void B::f() { cout << "Argh!"; } I get errors saying that f() is not declared in B while trying do define void B::f(). Do I have to declare f() explicitly in B? I think that if the interface changes I shouldn't have to correct the declarations in every single class deriving from it. Is there no way for B to get all the virtual functions' declarations from A automatically? EDIT: I found an article that says the inheritance of pure virtual functions is dependent on the compiler: http://www.objectmentor.com/resources/articles/abcpvf.pdf I'm using VC++2008, wonder if there's an option for this.

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  • Bing search API and Azure

    - by Gapton
    I am trying to programatically perform a search on Microsoft Bing search engine. Here is my understanding: There was a Bing Search API 2.0 , which will be replaced soon (1st Aug 2012) The new API is known as Windows Azure Marketplace. You use different URL for the two. In the old API (Bing Search API 2.0), you specify a key (Application ID) in the URL, and such key will be used to authenticate the request. As long as you have the key as a parameter in the URL, you can obtain the results. In the new API (Windows Azure Marketplace), you do NOT include the key (Account Key) in the URL. Instead, you put in a query URL, then the server will ask for your credentials. When using a browser, there will be a pop-up asking for a/c name and password. Instruction was to leave the account name blank and insert your key in the password field. Okay, I have done all that and I can see a JSON-formatted results of my search on my browser page. How do I do this programmatically in PHP? I tried searching for the documentation and sample code from Microsoft MSDN library, but I was either searching in the wrong place, or there are extremely limited resources in there. Would anyone be able to tell me how do you do the "enter the key in the password field in the pop-up" part in PHP please? Thanks alot in advance.

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  • What is a simple way to add a timer to a method

    - by John
    The following is in C#. I'm trying to do something very simple (I think). I have a method that loads an XML document XDocument doc = XDocument.Load(uri); , but I don't want to tie up pc resources if there are issues (connectivity, document size, etc.). So I'd like to be able to add a timeout variable that will cut the method off after a given number of seconds. I'm a newbie when it comes to asynchronous programming and find it confusing that there are so many examples written so many different ways . . . and none of them appear simple. I'd like a simple solution, if possible. Here's my thoughts so far on possible solution paths: 1) A method that wraps the existing load public XDocument LoadXDocument(string uri, int timeout){ //code } 2) A wrapper, but as an extension method XDocument doc = XDocument.LoadWithTimeout(string uri, int timeout); 3) A generic extension method. Object obj = SomeStaticClass.LoadWithTimeout(??? method, int timeout); 3), on its face seems really nice, because it would mean being able to generically add timeouts to many different method calls and not specifically tied to one type of object, but I suspect that it is either i)impossible or ii) very difficult. Please assist. Thanks.

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  • Populating PDF Fields using FDFACX

    - by NWilliams
    I was recently asked to preform some updates to an existing PDF document. The changes required were completed using Adobe Designer (the only tool I have available to me). These changes included alignment, and new text. Note that there were fillable form fields on the forms, and they were left untouched. The saved version of the form was then put into our ASP.NET application, which pre-populates the form fields were applicable (things like name, address etc... things we have in our database). For some reason, the new form does not populate. I've confirmed that the form fields have the correct names, that the actual file (the pdf) that is being pre-populated has the same permissions as others that are working. There are no errors thrown, and no difference in a step through with a working form and a non-working form. This is a legacy project and I have no real experience with the PDF populator they are using ... FDFACX .NET? And can't find a lot of info on it online. Any ideas?

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  • How can I take advantage of IObservable/IObserver to get rid of my "god object"?

    - by Will
    In a system I'm currently working on, I have many components which are defined as interfaces and base classes. Each part of the system has some specific points where they interact with other parts of the system. For example, the data readying component readies some data which eventually needs to go to the data processing portion, the communications component needs to query different components for their status for relaying to the outside, etc. Currently, I glue these parts of the system together using a "god object", or an object with intimate knowledge of different parts of the system. It registers with events over here and shuttles the results to methods over there, creates a callback method here and returns the result of that method over there, and passes many requests through a multi-threaded queue for processing because it "knows" certain actions have to run on STA threads, etc. While its convenient, it concerns me that this one type knows so much about how everybody else in the system is designed. I'd much prefer a more generic hub that can be given instances which can expose events or methods or callbacks or that can consume these. I've been seeing more about the IObservable/IObserver features of the reactive framework and that are being rolled into .NET 4.0 (I believe). Can I leverage this pattern to help replace my "god object"? How should I go about doing this? Are there any resources for using this pattern for this specific purpose?

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  • Qt/C++ Error handling

    - by ShiGon
    I've been doing a lot of research about handling errors with Qt/C++ and I'm still as lost as when I started. Maybe I'm looking for an easy way out (like other languages provide). One, in particular, provides for an unhandled exception which I use religiously. When the program encounters a problem, it throws the unhandled exception so that I can create my own error report. That report gets sent from my customers machine to a server online which I then read later. The problem that I'm having with C++ is that any error handling that's done has to be thought of BEFORE hand (think try/catch or massive conditionals). In my experience, problems in code are not thought of before hand else there wouldn't be a problem to begin with. Writing a cross-platform application without a cross-platform error handling/reporting/trace mechanism is a little scary to me. My question is: Is there any kind of Qt or C++ Specific "catch-all" error trapping mechanism that I can use in my application so that, if something does go wrong I can, at least, write a report before it crashes?

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  • Visual C++ 2010, rvalue reference bug?

    - by Sergey Shandar
    Is it a bug in Visual C++ 2010 or right behaviour? template<class T> T f(T const &r) { return r; } template<class T> T f(T &&r) { static_assert(false, "no way"); return r; } int main() { int y = 4; f(y); } I thought, the function f(T &&) should never be called but it's called with T = int &. The output: main.cpp(10): error C2338: no way main.cpp(17) : see reference to function template instantiation 'T f<int&>(T)' being compiled with [ T=int & ] Update 1 Do you know any C++x0 compiler as a reference? I've tried comeau online test-drive but could not compile r-value reference. Update 2 Workaround (using SFINAE): #include <boost/utility/enable_if.hpp> #include <boost/type_traits/is_reference.hpp> template<class T> T f(T &r) { return r; } template<class T> typename ::boost::disable_if< ::boost::is_reference<T>, T>::type f(T &&r) { static_assert(false, "no way"); return r; } int main() { int y = 4; f(y); // f(5); // generates "no way" error, as expected. }

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  • CQRS without using others patterns

    - by John Smith
    I would like to explain CQRS to my team of developers. I just can't figure out how to explain it in the simplest way so they can implement the pattern rapidly without any others frameworks. I've read a lot of resources including video and articles but I don't find how to implement CQRS without using others patterns like a service Bus, event sourcing pattern, domain driven design. I know the purpose of these pattern but for the first step, I don't want them to think CQRS and theses patterns must be tied together. My first idea is to say that CQRS is about separating the read part and the write part. The read part is composed only of the UI project, and DAL project. Then the write part is composed of a typical multilayer architecture: UI/BLL/DAL. Then, does CQRS say we must also have two datastore ? What about the notion of commands which reveal the user's intention, is it also something part of CQRS or DDD ? Basically, how to implement CQRS without using others patterns. I concede it's also not that clear in my mind because I've used to work with NCQRS/DDD/Event Sourcing/ServiceBus in my personal project. Thanks

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  • Memory optimization while downloading

    - by lboregard
    hello all i have the following piece of code, that im looking forward to optimize, since i'm consuming gobs of memory this routine is heavily used first optimization would be to move the stringbuilder construction out of the download routine and make it a field of the class, then i would clear it inside the routine can you please suggest any other optimization or point me in the direction of some resources that could help me with this (web articles, books, etc). i'm thinking about replacing the stringbuilder by a fixed (much larger) size buffer ... or perhaps create a larger sized stringbuilder thanks in advance. StreamWriter _writer; StreamReader _reader; public string Download(string msgId) { _writer.WriteLine("BODY <" + msgId + ">"); string response = _reader.ReadLine(); if (!response.StartsWith("222")) return null; bool done = false; StringBuilder body = new StringBuilder(256* 1024); do { response = _reader.ReadLine(); if (OnProgress != null) OnProgress(response.Length); if (response == ".") { done = true; } else { if (response.StartsWith("..")) response = response.Remove(0, 1); body.Append(response); body.Append("\r\n"); } } while (!done); return body.ToString(); }

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  • How can I get git to work with a remote server?

    - by Adrienne
    I am the CM person for a small company that just started using Git. We have two Git repositories currently hosted on a Windows box that is our all-purpose Windows server. But, we just set up a dedicated server for our CM software on an Ubuntu Linux server named "Callisto". So I created a test Git repository on Callisto. I gave its directory all of the proper permissions recursively. I had the sysadmin create a login for me on Callisto, and I created a key to use for logging in via SSH. I set up my key to use a passphrase; I don't know if that could be contributing to my problems? Anyway, I know my SSH login works because I tested it through puTTY. But, even after hours of trials and head scratching, I can't get my Windows Git bash (mSysGit) to talk to Callisto for the purposes of pushing or pulling Callisto's git repository files. I keep getting "Fatal error. The remote end hung up unexpectedly." And I've even gotten the error that Git doesn't recognize the test repository on Callisto as a git repository. I read online that the "Fatal error...hung up unexpectedly" is usually a problem with the server connection or permissions. So what am I missing or overlooking here? And why doesn't a pull using the git:// protocol work, since that only uses read-only access? Group and public permissions for the git repository's directory on Callisto are set to read and execute, but not write. If anyone could help, I would be so grateful. Thank you.

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  • CRM 2011 - Set/Retrieve work hours programmatically

    - by Philip Rich
    I am attempting to retrieve a resources work hours to perform some logic I require. I understand that the CRM scheduling engine is a little clunky around such things, but I assumed that I would be able to find out how the working hours were stored in the DB eventually... So a resource has associated calendars and those calendars have associated calendar rules and inner calendars etc. It is possible to look at the start/end and frequency of aforementioned calendar rules and query their codes to work out whether a resource is 'working' during a given period. However, I have not been able to find the actual working hours, the 9-5 shall we say in any field in the DB. I even tried some SQL profiling while I was creating a new schedule for a resource via the UI, but the results don't show any work hours passing to SQL. For those with the patience the intercepted SQL statement is below:- EXEC Sp_executesql N'update [CalendarRuleBase] set [ModifiedBy]=@ModifiedBy0, [EffectiveIntervalEnd]=@EffectiveIntervalEnd0, [Description]=@Description0, [ModifiedOn]=@ModifiedOn0, [GroupDesignator]=@GroupDesignator0, [IsSelected]=@IsSelected0, [InnerCalendarId]=@InnerCalendarId0, [TimeZoneCode]=@TimeZoneCode0, [CalendarId]=@CalendarId0, [IsVaried]=@IsVaried0, [Rank]=@Rank0, [ModifiedOnBehalfBy]=NULL, [Duration]=@Duration0, [StartTime]=@StartTime0, [Pattern]=@Pattern0 where ([CalendarRuleId] = @CalendarRuleId0)', N'@ModifiedBy0 uniqueidentifier,@EffectiveIntervalEnd0 datetime,@Description0 ntext,@ModifiedOn0 datetime,@GroupDesignator0 ntext,@IsSelected0 bit,@InnerCalendarId0 uniqueidentifier,@TimeZoneCode0 int,@CalendarId0 uniqueidentifier,@IsVaried0 bit,@Rank0 int,@Duration0 int,@StartTime0 datetime,@Pattern0 ntext,@CalendarRuleId0 uniqueidentifier', @ModifiedBy0='EB04662A-5B38-E111-9889-00155D79A113', @EffectiveIntervalEnd0='2012-01-13 00:00:00', @Description0=N'Weekly Single Rule', @ModifiedOn0='2012-03-12 16:02:08', @GroupDesignator0=N'FC5769FC-4DE9-445d-8F4E-6E9869E60857', @IsSelected0=1, @InnerCalendarId0='3C806E79-7A49-4E8D-B97E-5ED26700EB14', @TimeZoneCode0=85, @CalendarId0='E48B1ABF-329F-425F-85DA-3FFCBB77F885', @IsVaried0=0, @Rank0=2, @Duration0=1440, @StartTime0='2000-01-01 00:00:00', @Pattern0=N'FREQ=WEEKLY;INTERVAL=1;BYDAY=SU,MO,TU,WE,TH,FR,SA', @CalendarRuleId0='0A00DFCF-7D0A-4EE3-91B3-DADFCC33781D' The key parts in the statement are the setting of the pattern:- @Pattern0=N'FREQ=WEEKLY;INTERVAL=1;BYDAY=SU,MO,TU,WE,TH,FR,SA' However, as mentioned, no indication of the work hours set. Am I thinking about this incorrectly or is CRM doing something interesting around these work hours? Any thoughts greatly appreciated, thanks.

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  • C++ union data-structure, easy acccess of bits within a DWORD

    - by TK
    Im running through a set of DirectX tutorials online and I have the following structure: struct CUSTOMVERTEX { FLOAT x, y, z, rhw; // from the D3DFVF_XYZRHW flag DWORD color; // from the D3DFVF_DIFFUSE flag } My basic understanding of directX leads me to thing tha color is made up of 8-bit alpha, red, green and blue channels. I am attempting to get east access to these channels. Rather than write the following code numerous times (within the CUSTOMVERTEX structure): public: int red() { return (color & 0x00FF0000) >> 16; } I could write a more elegant somution with a combination of a union and a structure e.g. struct CUSTOMVERTEX { FLOAT x, y, z, rhw; // from the D3DFVF_XYZRHW flag #pragma pack(2) union { DWORD color; // from the D3DFVF_DIFFUSE flag struct { char a; char r; char g; char b; }; }; } However this does not appear to function as expected, the values in r, g, & b almost appear the reverse of whats in color e.g. if color is 0x12345678 a = 0x78, r = 0x56. Is this an endieness issue? Also what other problems could I be expecting from this solution? e.g. overflow from the color members? I guess what Im asking is ... is there a better way to do this?!

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  • Scalability 101: How can I design a scalable web application using PHP?

    - by Legend
    I am building a web-application and have a couple of quick questions. From what I learnt, one should not worry about scalability when initially building the app and should only start worrying when the traffic increases. However, this being my first web-application, I am not quite sure if I should take an approach where I design things in an ad-hoc manner and later "fix" them. I have been reading stories about how people start off with an app that gets millions of users in a week or two. Not that I will face the same situation but I can't help but wonder, how do these people do it? Currently, I bought a shared hosting account on Lunarpages and that got me started in building and testing the application. However, I am interested in learning how to build the same application in a scalable-manner using the cloud, for instance, Amazon's EC2. From my understanding, I can see a couple of components: There is a load balancer that first receives requests and then decides where to route each request This request is then handled by a server replica that then processes the request and updates (if required) the database and sends back the response to the client If a similar request comes in, then a caching mechanism like memcached kicks into picture and returns objects from the cache A blackbox that handles database replication Specifically, I am trying to do the following: Setting up a load balancer (my homework revealed that HAProxy is one such load balancer) Setting up replication so that databases can be synchronized Using memcached Configuring Apache to work with multiple web servers Partitioning application to use Amazon EC2 and Amazon S3 (my application is something that will need great deal of storage) Finally, how can I avoid burning myself when using Amazon services? Because this is just a learning phase, I can probably do with 2-3 servers with a simple load balancer and replication but until I want to avoid paying loads of money accidentally. I am able to find resources on individual topics but am unable to find something that starts off from the big picture. Can someone please help me get started?

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  • Help! I'm a Haskell Newbie

    - by Darknight
    I've only just dipped my toe in the world of Haskell as part of my journey of programming enlightenment (moving on from, procedural to OOP to concurrent to now functional). I've been trying an online Haskell Evaluator. However I'm now stuck on a problem: Create a simple function that gives the total sum of an array of numbers. In a procedural language this for me is easy enough (using recursion) (c#) : private int sum(ArrayList x, int i) { if (!(x.Count < i + 1)) { int t = 0; t = x.Item(i); t = sum(x, i + 1) + t; return t; } } All very fine however my failed attempt at Haskell was thus: let sum x = x+sum in map sum [1..10] this resulted in the following error (from that above mentioned website): Occurs check: cannot construct the infinite type: a = a -> t Please bear in mind I've only used Haskell for the last 30 minutes! I'm not looking simply for an answer but a more explanation of it. Thanks in advanced.

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  • Is there a way to specify a per-host deploy_to path with Capistrano?

    - by Chad Johnson
    I have searched and searched and asked a question already and have not received a clear answer. I have the following deploy script (snippet): set :application, "testapplication" set :repository, "ssh://domain.com//srv/hg/#{application}" set :scm, :mercurial set :deploy_to, "/srv/www/#{application}" role :web, "domain1.com", "domain2.com" role :app, "domain1.com", "domain2.com" role :db, "domain1.com", :primary => true, :norelease => true role :db, "domain2.com", :norelease => true As you see, I have set deploy_to to a specific path. And, I also have specified multiple web servers. However, each web server should have a different deployment path. I want to be able to run "cap deploy" and deploy to all hosts in one shot. I am NOT trying to deploy to staging and then to production. This is all production. My question is: how exactly do I specify a path per server? I have read the "Roles" documentation for Capistrano, and this is unclear. Can someone please post a deploy file example? I have read the documentation, and it is unclear how to do this. Does anyone know? Am I crazy? Am I thinking of this wrong or something? No answers anywhere online. Nowhere. Nothing. Please, someone help.

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  • How to update to jersey 2.X on an app using jersey 1.1X?

    - by Maxrunner
    i recently faced a problem with the handling of exceptions using jersey. In this case it was that the exceptions thrown from Exception mapper are not re thrown to the underlaying container, i searched and found that this has been fixed in the 2.0 version. But i'm using jersey 1.10 and the 2.X dependencies are all different and its also maven based. Since this project is not using maven, how do i use the more recent version?In the 2.X versions there are no jackson json jars for example. So i'm having some doubts in how to upgrade. Here's my web.xml config entry for jerse <servlet> <servlet-name>Jersey REST Service</servlet-name> <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class> <init-param> <param-name>com.sun.jersey.config.property.packages</param-name> <param-value>com.mobile.rest.resources</param-value> </init-param> <init-param> <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name> <param-value>true</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>Jersey REST Service</servlet-name> <url-pattern>/rest/*</url-pattern> </servlet-mapping> regards,

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