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  • Which design pattern should be used to create an emulator?

    - by Facon
    I have programmed an emulator, but I have some doubts about how to organizate it properly, because, I see that it has some problems about classes connection (CPU <- Machine Board). For example: I/O ports, interruptions, communication between two or more CPU, etc. I need for the emulator to has the best performance and good understanding of the code. PD: Sorry for my bad English. EDITED - Asking for multiple patterns.

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  • Rails Plugins Load Path - I have ActiveRecord Models in a Plugin, How do I load them without Namespa

    - by viatropos
    I have a bunch of models for Oauth services, things like: TwitterToken GoogleToken There are OAuth versions and OpenID versions for some, so I decided to logically organize my gem like so: lib lib/my-auth-gem lib/my-auth-gem/oauth lib/my-auth-gem/oauth/tokens/google_token ... lib/my-auth-gem/openid/tokens/google_token ... I would like to be able to name my models GoogleToken, rather than MyAuthGem::Oauth::Tokens::GoogleToken. How do I do that? This will be for Rails 2.3+ and Rails 3.

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  • Is this a valid pattern for raising events in C#?

    - by Will Vousden
    Update: For the benefit of anyone reading this, since .NET 4, the lock is unnecessary due to changes in synchronization of auto-generated events, so I just use this now: public static void Raise<T>(this EventHandler<T> handler, object sender, T e) where T : EventArgs { if (handler != null) { handlerCopy(sender, e); } } And to raise it: SomeEvent.Raise(this, new FooEventArgs()); Having been reading one of Jon Skeet's articles on multithreading, I've tried to encapsulate the approach he advocates to raising an event in an extension method like so (with a similar generic version): public static void Raise(this EventHandler handler, object @lock, object sender, EventArgs e) { EventHandler handlerCopy; lock (@lock) { handlerCopy = handler; } if (handlerCopy != null) { handlerCopy(sender, e); } } This can then be called like so: protected virtual void OnSomeEvent(EventArgs e) { this.someEvent.Raise(this.eventLock, this, e); } Are there any problems with doing this? Also, I'm a little confused about the necessity of the lock in the first place. As I understand it, the delegate is copied in the example in the article to avoid the possibility of it changing (and becoming null) between the null check and the delegate call. However, I was under the impression that access/assignment of this kind is atomic, so why is the lock necessary? Update: With regards to Mark Simpson's comment below, I threw together a test: static class Program { private static Action foo; private static Action bar; private static Action test; static void Main(string[] args) { foo = () => Console.WriteLine("Foo"); bar = () => Console.WriteLine("Bar"); test += foo; test += bar; test.Test(); Console.ReadKey(true); } public static void Test(this Action action) { action(); test -= foo; Console.WriteLine(); action(); } } This outputs: Foo Bar Foo Bar This illustrates that the delegate parameter to the method (action) does not mirror the argument that was passed into it (test), which is kind of expected, I guess. My question is will this affect the validity of the lock in the context of my Raise extension method? Update: Here is the code I'm now using. It's not quite as elegant as I'd have liked, but it seems to work: public static void Raise<T>(this object sender, ref EventHandler<T> handler, object eventLock, T e) where T : EventArgs { EventHandler<T> copy; lock (eventLock) { copy = handler; } if (copy != null) { copy(sender, e); } }

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  • What OOP pattern to use when only adding new methods, not data?

    - by Jonathon Reinhart
    Hello eveyone... In my app, I have deal with several different "parameters", which derive from IParameter interface, and also ParamBase abstract base class. I currently have two different parameter types, call them FooParameter and BarParameter, which both derive from ParamBase. Obviously, I can treat them both as IParameters when I need to deal with them generically, or detect their specific type when I need to handle their specific functionality. My question lies in specific FooParameters. I currently have a few specific ones with their own classes which derive from FooParameter, we'll call them FP12, FP13, FP14, etc. These all have certain characteristics, which make me treat them differently in the UI. (Most have names associated with the individual bits, or ranges of bits). Note that these specific, derived FP's have no additional data associated with them, only properties (which refer to the same data in different ways) or methods. Now, I'd like to keep all of these parameters in a Dictionary<String, IParameter> for easy generic access. The problem is, if I want to refer to a specific one with the special GUI functions, I can't write: FP12 fp12 = (FP12)paramList["FP12"] because you can't downcast to a derived type (rightfully so). But in my case, I didn't add any data, so the cast would theoretically work. What type of programming model should I be using instead? Thanks!

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  • How can I capture a multiline pattern using a regular expressions in java?

    - by lampShade
    I have a text file that I need to parse using regular expressions. The text that I need to capture is in multiline groups like this: truck zDoug Doug's house (123) 456-7890 [email protected] 30 61234.56 8/10/2003 vehicle eRob Rob's house (987) 654-3210 [email protected] For this example I need to capture truck followed by the next seven lines.In other words, in this "block" I have 8 groups. This is what I've tried but it will not capture the next line: (truck)\n(\w). NOTE: I'm using the program RegExr to test my regex before I port it to Java.

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  • How might I wrap the FindXFile-style APIs to the STL-style Iterator Pattern in C++?

    - by BillyONeal
    Hello everyone :) I'm working on wrapping up the ugly innards of the FindFirstFile/FindNextFile loop (though my question applies to other similar APIs, such as RegEnumKeyEx or RegEnumValue, etc.) inside iterators that work in a manner similar to the Standard Template Library's istream_iterators. I have two problems here. The first is with the termination condition of most "foreach" style loops. STL style iterators typically use operator!= inside the exit condition of the for, i.e. std::vector<int> test; for(std::vector<int>::iterator it = test.begin(); it != test.end(); it++) { //Do stuff } My problem is I'm unsure how to implement operator!= with such a directory enumeration, because I do not know when the enumeration is complete until I've actually finished with it. I have sort of a hack together solution in place now that enumerates the entire directory at once, where each iterator simply tracks a reference counted vector, but this seems like a kludge which can be done a better way. The second problem I have is that there are multiple pieces of data returned by the FindXFile APIs. For that reason, there's no obvious way to overload operator* as required for iterator semantics. When I overload that item, do I return the file name? The size? The modified date? How might I convey the multiple pieces of data to which such an iterator must refer to later in an ideomatic way? I've tried ripping off the C# style MoveNext design but I'm concerned about not following the standard idioms here. class SomeIterator { public: bool next(); //Advances the iterator and returns true if successful, false if the iterator is at the end. std::wstring fileName() const; //other kinds of data.... }; EDIT: And the caller would look like: SomeIterator x = ??; //Construct somehow while(x.next()) { //Do stuff } Thanks! Billy3

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  • c++ Design pattern for CoW, inherited classes, and variable shared data?

    - by krunk
    I've designed a copy-on-write base class. The class holds the default set of data needed by all children in a shared data model/CoW model. The derived classes also have data that only pertains to them, but should be CoW between other instances of that derived class. I'm looking for a clean way to implement this. If I had a base class FooInterface with shared data FooDataPrivate and a derived object FooDerived. I could create a FooDerivedDataPrivate. The underlying data structure would not effect the exposed getters/setters API, so it's not about how a user interfaces with the objects. I'm just wondering if this is a typical MO for such cases or if there's a better/cleaner way? What peeks my interest, is I see the potential of inheritance between the the private data classes. E.g. FooDerivedDataPrivate : public FooDataPrivate, but I'm not seeing a way to take advantage of that polymorphism in my derived classes. class FooDataPrivate { public: Ref ref; // atomic reference counting object int a; int b; int c; }; class FooInterface { public: // constructors and such // .... // methods are implemented to be copy on write. void setA(int val); void setB(int val); void setC(int val); // copy constructors, destructors, etc. all CoW friendly private: FooDataPrivate *data; }; class FooDerived : public FooInterface { public: FooDerived() : FooInterface() {} private: // need more shared data for FooDerived // this is the ???, how is this best done cleanly? };

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  • How can I get my setup.py to use a relative path to my files?

    - by Chris B.
    I'm trying to build a Python distribution with distutils. Unfortunately, my directory structure looks like this: /code /mypackage __init__.py file1.py file2.py /subpackage __init__.py /build setup.py Here's my setup.py file: from distutils.core import setup setup( name = 'MyPackage', description = 'This is my package', packages = ['mypackage', 'mypackage.subpackage'], package_dir = { 'mypackage' : '../mypackage' }, version = '1', url = 'http://www.mypackage.org/', author = 'Me', author_email = '[email protected]', ) When I run python setup.py sdist it correctly generates the manifest file, but doesn't include my source files in the distribution. Apparently, it creates a directory to contain the source files (i.e. mypackage1) then copies each of the source files to mypackage1/../mypackage which puts them outside of the distribution. How can I correct this, without forcing my directory structure to conform to what distutils expects?

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  • Which type of design pattern should be used to create an emulator?

    - by Facon
    I have programmed an emulator, but I have some doubts about how to organizate it properly, because, I see that it has some problems about classes connection (CPU <- Machine Board). For example: I/O ports, interruptions, communication between two or more CPU, etc. I need for the emulator to has the best performance and good understanding of the code. PD: Sorry for my bad English. EDITED: Asking for multiple patterns.

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  • Where should I store user config data? Specificaly the path to the data file?

    - by jamone
    I have an app using a SQLite db, and I need the ability for the user to move the data file and point the app to where it moved to. I used the Entity Framework to create the model, and by default it puts the connection string in the App.Config file. From what I've read if I make changes to the connection string there then they won't take effect until the app is restarted. That seems a bit clunky for my use. I see how I can init my model and pass in a custom string but I'm unsure what the best practice is in where to store basic user prefrences such as this? Ini, Registry, somewhere else? I don't want the user to have to "Open" the file each time, just when it relocates and then the app will try to auto open from then on.

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  • Is There a Good Pattern for Creating a Unique Id based on a Type?

    - by Michael Kelley
    I have a template that creates a unique identifier for each type it is instanced. Here's a streamlined version of the template: template <typename T> class arType { static const arType Id; // this will be unique for every instantiation of arType<>. } // Address of Id is used for identification. #define PA_TYPE_TAG(T) (&arType<T >::Id) This works when you have an executable made purely of static libraries. Unfortunately we're moving to an executable made up of dlls. Each dlls could potentially have its own copy of Id for a type. One obvious solution is to explicitly instantiate all instances of arType. Unfortunately this is cumbersome, and I'd like to ask if anyone can propose a better solution?

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  • How Do I Remove The First 4 Characters From A String If It Matches A Pattern In Ruby

    - by James
    I have the following string: "h3. My Title Goes Here" I basically want to remove the first 4 characters from the string so that I just get back: "My Title Goes Here". The thing is I am iterating over an array of strings and not all have the h3. part in front so I can't just ditch the first 4 characters blindly. I have checked the docs and the closest think I could find was chomp, but that only works for the end of a string. Right now I am doing this: "h3. My Title Goes Here".reverse.chomp(" .3h").reverse This gives me my desired output, but there has to be a better way right? I mean I don't want to reverse a string twice for no reason. I am new to programming so I might have missed something obvious, but I didn't see the opposite of chomp anywhere in the docs. Is there another method that will work? Thanks!

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  • Is there an easier way to do Classic ASP "relative path"?

    - by Alex.Piechowski
    Right now, I'm having trouble. First of all I have a page, let's call it "http://blah.com/login". That obviously goes strait to "index.asp" A line of Main.asp: <!--#include file="resource/menu.asp"--> Page top includes all of what I need for my menu... so: Part of resource/menu.htm: <div id="colortab" class="ddcolortabs"> <ul> <li><a href="main.asp" title="Main" rel="dropmain"><span>Main</span></a></li> ... </ul> </div> <!--Main drop down menu --> <div id="dropmain" class="dropmenudiv_a"> <a href="main/announcements.asp">Announcements</a> <a href="main/contacts.asp">Contact Information</a> <a href="main/MeetingPlans.asp">Meeting Plan</a> <a href="main/photos.asp">Photo Gallery</a> <a href="main/events.asp">Upcoming Events</a> </div> Let's say I click on the "announcements" (http://blah.com/login/main/announcements.asp) link... Now I'm at the announcements page! But wait, I include the same menu file. Guess what happens: I get sent to "http://blah.com/login/main/main/announcements.asp Which doesn't exist... My solution: Make a menu_sub.asp include for any subpages. But wait a second... this WORKS, but it gets REALLY REALLY messy... What can I do to use just one main "menu.asp" instead of "menu_sub.asp"? using "/main/announcements.asp" WON'T be an option because this is a web application that will be on different directories per server. Any ideas? PLEASE

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  • How can I refactor this to work without breaking the pattern horribly?

    - by SnOrfus
    I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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  • What's the best practice or design pattern for user registration ?

    - by Space Cracker
    We have a big portal that needs user registration to allow them use its services. It's already done in .NET and SOL Server 2005. we are in the phase now of discovering all the problems of the current registration system to build a new robust flexible one that can be extended easily and can be more usable for all services. Could any help me find best practices and design patterns to help me rebuild this using good architectural practices?

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  • How to handle building and parsing HTTP URL's / URI's / paths in Perl

    - by Robert S. Barnes
    I have a wget like script which downloads a page and then retrieves all the files linked in img tags on that page. Given the URL of the original page and the the link extracted from the img tag in that page I need to build the URL for the image file I want to retrieve. Currently I use a function I wrote: sub build_url { my ( $base, $path ) = @_; # if the path is absolute just prepend the domain to it if ($path =~ /^\//) { ($base) = $base =~ /^(?:http:\/\/)?(\w+(?:\.\w+)+)/; return "$base$path"; } my @base = split '/', $base; my @path = split '/', $path; # remove a trailing filename pop @base if $base =~ /[[:alnum:]]+\/[\w\d]+\.[\w]+$/; # check for relative paths my $relcount = $path =~ /(\.\.\/)/g; while ( $relcount-- ) { pop @base; shift @path; } return join '/', @base, @path; } The thing is, I'm surely not the first person solving this problem, and in fact it's such a general problem that I assume there must be some better, more standard way of dealing with it, using either a core module or something from CPAN - although via a core module is preferable. I was thinking about File::Spec but wasn't sure if it has all the functionality I would need.

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  • Is there a recommended logging path/folder for ASP.NEt applications?

    - by the-locster
    Currently we use log4net and create a new folder (usually below C:) with write and create access rights for the worker process user. Is there perhaps a standard windows folder we should or could be using such as LOCALAPPDATA? I'm guessing that LOCALAPPDATA is a bad choice in the general case because IIS users tend to be non-interactive users and thus I don't think they have the usual user folder structrues available.

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  • JPA: what is the proper pattern for iterating over large result sets?

    - by Caffeine Coma
    Let's say I have a table with millions of rows. Using JPA, what's the proper way to iterate over a query against that table, such that I don't have all an in-memory List with millions of objects? I suspect that the following will blow up if the table is large: List<Model> models = entityManager().createQuery("from Model m", Model.class).getResultList(); for (Model model : models) { // do something with model } Is pagination (looping and manually updating setFirstResult()/setMaxResult()) really the best solution?

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  • File.Exists("SDF File Path") returns a FALSE when run through Unit tests even though it exists in th

    - by shiva-hv
    I am writing Unit tests for a Windows Project. The Executable project on the Client Side of this Windows Project has a code File.Exists("LanguageLookups.sdf") which is used to check and return a Bool if the sdf file exists in the Execution Directory or not. But when i execute the same piece of Code through a Unit test; The code File.Exists("LanguageLookups.sdf") returns a FALSE. Its not able to find this SDF File. Can anybody help me on this?

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