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• OpenGL fast texture drawing with vertex buffer objects. Is this the way to do it?

  - by Matthew Mitchell

  Hello. I am making a 2D game with OpenGL. I would like to speed up my texture drawing by using VBOs. Currently I am using the immediate mode. I am generating my own coordinates when I rotate and scale a texture. I also have the functionality of rounding the corners of a texture, using the polygon primitive to draw those. I was thinking, would it be fastest to make a VBO with vertices for the sides of the texture with no offset included so I can then use glViewport, glScale (Or glTranslate? What is the difference and most suitable here?) and glRotate to move the drawing position for my texture. Then I can use the same VBO with no changes to draw the texture each time. I could only change the VBO when I need to add coordinates for the rounded corners. Is that the best way to do this? What things should I look out for while doing it? Is it really fastest to use GL_TRIANGLES instead of GL_QUADS in modern graphics cards? Thank you for any answer.

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• Using Memcached in Python/Django - questions.

  - by Thomas

  I am starting use Memcached to make my website faster. For constant data in my database I use this: from django.core.cache import cache cache_key = 'regions' regions = cache.get(cache_key) if result is None: """Not Found in Cache""" regions = Regions.objects.all() cache.set(cache_key, regions, 2592000) #(2592000sekund = 30 dni) return regions For seldom changed data I use signals: from django.core.cache import cache from django.db.models import signals def nuke_social_network_cache(self, instance, **kwargs): cache_key = 'networks_for_%s' % (self.instance.user_id,) cache.delete(cache_key) signals.post_save.connect(nuke_social_network_cache, sender=SocialNetworkProfile) signals.post_delete.connect(nuke_social_network_cache, sender=SocialNetworkProfile) Is it correct way? I installed django-memcached-0.1.2, which show me: Memcached Server Stats Server Keys Hits Gets Hit_Rate Traffic_In Traffic_Out Usage Uptime 127.0.0.1 15 220 276 79% 83.1 KB 364.1 KB 18.4 KB 22:21:25 Can sombody explain what columns means? And last question. I have templates where I am getting much records from a few table (relationships). So in my view I get records from one table and in templates show it and related info from others. Generating page last a few seconds for very small table (<100records). Is it some easy way to cache queries from templates? Have I to do some big structure in my view (with all related tables), cache it and send to template?

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• WCF Multiple contracts with duplicate method names

  - by haxelit

  Hello, I have a service with multiple contracts like so. [ServiceContract] public partial interface IBusinessFunctionDAO { [OperationContract] BusinessFunction GetBusinessFunction(Int32 businessFunctionRefID); [OperationContract] IEnumerable<Project> GetProjects(Int32 businessFunctionRefID); } [ServiceContract] public partial interface IBusinessUnitDAO { [OperationContract] BusinessUnit GetBusinessUnit(Int32 businessUnitRefID); [OperationContract] IEnumerable<Project> GetProjects(Int32 businessUnitRefID); } I then explicitly implemented each one of the interfaces like so. public class TrackingTool : IBusinessFunctionDAO, IBusinessUnitDAO { BusinessFunction IBusinessFunctionDAO.GetBusinessFunction(Int32 businessFunctionRefID) { // implementation } IEnumerable<Project> IBusinessFunctionDAO.GetProjects(Int32 businessFunctionRefID) { // implementation } BusinessUnit IBusinessUnitDAO.GetBusinessUnit(Int32 businessUnitRefID) { // implementation } IEnumerable<Project> IBusinessUnitDAO.GetProjects(Int32 businessUnitRefID) { // implementation } } As you can see I have two GetProjects(int) methods, but each one is implemented explicitly so this compiles just fine and is perfectly valid. The problem arises when I actually start this as a service. It gives me an error staying that TrackingTool already contains a definition GetProject. While it is true, it is part of a different service contract. Does WCF not distinguish between service contracts when generating the method names ? Is there a way to get it to distinguish between the service contracts ? My App.Config looks like this <service name="TrackingTool"> <endpoint address="BusinessUnit" contract="IBusinessUnitDAO" /> <endpoint address="BusinessFunction" contract="IBusinessFunctionDAO" /> </service> Any help would be appreciated. Thanks, Raul

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• How do you compare using .NET types in an NHibernate ICriteria query for an ICompositeUserType?

  - by gabe

  I have an answered StackOverflow question about how to combine to legacy CHAR database date and time fields into one .NET DateTime property in my POCO here (thanks much Berryl!). Now i am trying to get a custom ICritera query to work against that very DateTime property to no avail. here's my query: ICriteria criteria = Session.CreateCriteria<InputFileLog>() .Add(Expression.Gt(MembersOf<InputFileLog>.GetName(x => x.FileCreationDateTime), DateTime.Now.AddDays(-14))) .AddOrder(Order.Desc(Projections.Id())) .CreateCriteria(typeof(InputFile).Name) .Add(Expression.Eq(MembersOf<InputFile>.GetName(x => x.Id), inputFileName)); IList<InputFileLog> list = criteria.List<InputFileLog>(); And here's the query it's generating: SELECT this_.input_file_token as input1_9_2_, this_.file_creation_date as file2_9_2_, this_.file_creation_time as file3_9_2_, this_.approval_ind as approval4_9_2_, this_.file_id as file5_9_2_, this_.process_name as process6_9_2_, this_.process_status as process7_9_2_, this_.input_file_name as input8_9_2_, gonogo3_.input_file_token as input1_6_0_, gonogo3_.go_nogo_ind as go2_6_0_, inputfile1_.input_file_name as input1_3_1_, inputfile1_.src_code as src2_3_1_, inputfile1_.process_cat_code as process3_3_1_ FROM input_file_log this_ left outer join go_nogo gonogo3_ on this_.input_file_token=gonogo3_.input_file_token inner join input_file inputfile1_ on this_.input_file_name=inputfile1_.input_file_name WHERE this_.file_creation_date > :p0 and this_.file_creation_time > :p1 and inputfile1_.input_file_name = :p2 ORDER BY this_.input_file_token desc; :p0 = '20100401', :p1 = '15:15:27', :p2 = 'LMCONV_JR' The query is exactly what i would expect, actually, except it doesn't actually give me what i want (all the rows in the last 2 weeks) because in the DB it's doing a greater than comparison using CHARs instead of DATEs. I have no idea how to get the query to convert the CHAR values into a DATE in the query without doing a CreateSQLQuery(), which I would like to avoid. Anyone know how to do this?

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• Best Functional Approach

  - by dbyrne

  I have some mutable scala code that I am trying to rewrite in a more functional style. It is a fairly intricate piece of code, so I am trying to refactor it in pieces. My first thought was this: def iterate(count:Int,d:MyComplexType) = { //Generate next value n //Process n causing some side effects return iterate(count - 1, n) } This didn't seem functional at all to me, since I still have side effects mixed throughout my code. My second thought was this: def generateStream(d:MyComplexType):Stream[MyComplexType] = { //Generate next value n return Stream.cons(n, generateStream(n)) } for (n <- generateStream(initialValue).take(2000000)) { //process n causing some side effects } This seemed like a better solution to me, because at least I've isolated my functional value-generation code from the mutable value-processing code. However, this is much less memory efficient because I am generating a large list that I don't really need to store. This leaves me with 3 choices: Write a tail-recursive function, bite the bullet and refactor the value-processing code Use a lazy list. This is not a memory sensitive app (although it is performance sensitive) Come up with a new approach. I guess what I really want is a lazily evaluated sequence where I can discard the values after I've processed them. Any suggestions?

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• how to minimize application downtime when updating database and application ORM

  - by yamspog

  We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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• Visual Studio 2008 linker wants all symbols to be resolved, not only used ones

  - by user343011

  We recently upgraded to Visual Studio 2008 from 2005, and I think those error started after that. In our solution, we have a multitude of projects. Many of those are utility projects, or projects containing core functionality used by other projects. The output of those is lib files that are linked to when building the projects generating the final binaries using the "Project dependencies..." option. One of the other projects---Let us call it ResultLib---generates a DLL, and it needs one single function from the core project. This function uses only static function from its own source file, but the project in its entirety uses a lot of low-level Windows functions and also imports a DLL---Let us call it Driver.dll. Our problem is that when building ExtLib, the linker complains about a multitude of unresolved externals, for example all functions exported from Driver.dll, since its lib file is not specified when linking. If we try to fix this by adding all lib files used by other projects that use all of the core project, our resulting ResultLib DLL ends up importing Driver.dll and also exporting all functions defined in it. How do we tell Visual Studio to only try to resolve symbols that are actually used?

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• new Stateful session bean instance without calling lookup

  - by kislo_metal

  Scenario: I have @Singleton UserFactory (@Stateless could be) , its method createSession() generating @Stateful UserSession bean by manual lookup. If I am injecting by DI @EJB - i will get same instance during calling fromFactory() method(as it should be) What I want - is to get new instance of UserSession without preforming lookup. Q1: how could I call new instance of @Stateful session bean? Code: @Singleton @Startup @LocalBean public class UserFactory { @EJB private UserSession session; public UserFactory() { } @Schedule(second = "*/1", minute = "*", hour = "*") public void creatingInstances(){ try { InitialContext ctx = new InitialContext(); UserSession session2 = (UserSession) ctx.lookup("java:global/inferno/lic/UserSession"); System.out.println("in singleton UUID " +session2.getSessionUUID()); } catch (NamingException e) { e.printStackTrace(); } } @Schedule(second = "*/1", minute = "*", hour = "*") public void fromFactory(){ System.out.println("in singleton UUID " +session.getSessionUUID()); } public UserSession creatSession(){ UserSession session2 = null; try { InitialContext ctx = new InitialContext(); session2 = (UserSession) ctx.lookup("java:global/inferno/lic/UserSession"); System.out.println("in singleton UUID " +session2.getSessionUUID()); } catch (NamingException e) { e.printStackTrace(); } return session2; } } As I understand, calling of session.getClass().newInstance(); is not a best idea Q2 : is it true? I am using glassfish v3, ejb 3.1.

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• Using struts 2 with no tags

  - by WannaAsk

  Hi everyone, I wonder if you could guide me on this struts issue - I feel hopeless on this... I am working on migrating our web application to a Struts 2 portlet (I'm using Struts 2.1.8). The thing is, I am forced to avoid struts tags because our application relies on Dijit widgets, which are omitted when using struts tags. So now I should implement the <s:form tag using scriptlets. My question is: how you would suggest I imitate the way struts handles the "action" attribute? Right now it appears I should: Create a regular html form in my jsp. Get/create the ActionConfig object during onsubmit and set on it values which match my desired destination: class+method+result jsp. Execute the action I set in 2. Would you recommend this? If so - is ActionConfig obtained from the session? Can I initiate an action execution from ActionConfig? (Aletrnatively... generating an action url using struts' form.vm file - what do you say?) I would appreciate any help on this - Thanks a lot in advance!!!

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• What's a good way to parameterize "static" content (e.g. CSS) in a Tomcat webapp?

  - by Steven Huwig

  Some of our CSS files contain parameters that can vary based on the deployment location (dev, QA, prod). For example: background: url(#DOJO_PATH#/dijit/themes...) to avoid hardcoding a path to a particular CDN or locally-hosted Dojo installation. These values are textually substituted with the real values by a deployment script, when it copies the contents of the webapp into the Tomcat webapps directory. That way the same deployment archive file (WAR + TAR file containing other configuration) can be deployed to dev, QA, and prod, with the varying parameters provided by environment-specific configuration files. However, I'd like to make the contents of the WAR (including the templatized CSS files) independent of this in-house deployment script. Since we don't really have control over the deployment script, all I can think to do is configure Tomcat with #DOJO_PATH# etc. as environment variables in the application's context.xml, and use Tomcat to insert those parameters into the CSS at runtime. I could make the CSS files into generated JSPs, but it seems a little ugly to me. Moreover, the substitution only needs to be done once per application deployment, so repeatedly dynamically generating the stylesheets using JSP will be rather wasteful. Does anyone have any alternative ideas or tools to use for this? We're committed to Tomcat and to substituting these parameters at deployment or at runtime (that is, not at build time).

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• Ruby on Rails user login form in main layout

  - by Jimmy

  Hey guys I have a simple ror application for some demo stuff. I am running into a problem with trying to move my login form from the users controller and just have it displayed in the main navigation so that a user can easily log in from anywhere. The problem is the form doesn't generate the correct action for the html form. Ruby code: <% form_for(url_for(:action => 'login'), :method => 'post') do |f| %> <li><%= f.text_field("username") %></li> <li><%= f.password_field("password") %></li> <li><%= submit_tag("Login")%></li> <% end %> The problem is depending on the controller I am currently in this generates HTML actions like <form action="/home" method="post">...</form> when it should be generating HTML like so <form action="/login" method="post">...</form> I know I could simply do an HTML form here but I want to keep things as easy to maintain as possible. Any help?

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• XML File as Excel file.

  - by FrustratedWithFormsDesigner

  I have a number of reports that I run against my database that need to eventually go to the end-users as Excel spreadsheets. Initially, I was creating text reports, but the steps to convert the text to a spreadsheet were a bit cumbersome. There were too many steps to import text to the spreadsheet, and multi-line text rows were imported as individual rows in Excel (which was incorrect). Currently, I am generating simple XML saving the file with an ".xls" extension. This works better, but there is still the problem of Excel prompting the user with an XML import dialogue every time they open the file, and then having to save a new file if they add notes or change the layout to the file (which they almost certainly will be doing). Sample "xls" file: <?xml version="1.0" standalone="yes"?> <report_rows> <row> <NAME>Test Data</NAME> <COUNT>345</COUNT> </row> <!-- many more row elements... --> </report_rows> Is there any way to add markup to the file to hint to Excel how it should import and handle the file? Ideally, the end user should be able to open and save the file like any othe spreadsheet they create directly from Excel. Is this even possible? UPDATE: We are running Office 2003 here. UPDATE: The XML is generated from a sqlplus script, no option to use C#/.NET here.

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• Can Haskell's monads be thought of as using and returning a hidden state parameter?

  - by AJM

  I don't understand the exact algebra and theory behind Haskell's monads. However, when I think about functional programming in general I get the impression that state would be modelled by taking an initial state and generating a copy of it to represent the next state. This is like when one list is appended to another; neither list gets modified, but a third list is created and returned. Is it therefore valid to think of monadic operations as implicitly taking an initial state object as a parameter and implicitly returning a final state object? These state objects would be hidden so that the programmer doesn't have to worry about them and to control how they gets accessed. So, the programmer would not try to copy the object representing the IO stream as it was ten minutes ago. In other words, if we have this code: main = do putStrLn "Enter your name:" name <- getLine putStrLn ( "Hello " ++ name ) ...is it OK to think of the IO monad and the "do" syntax as representing this style of code? putStrLn :: IOState -> String -> IOState getLine :: IOState -> (IOState, String) main :: IOState -> IOState -- main returns an IOState we can call "state3" main state0 = putStrLn state2 ("Hello " ++ name) where (state2, name) = getLine state1 state1 = putStrLn state0 "Enter your name:"

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• Why won't EF4 generate a method to support my Function Import?

  - by Deane

  I have a stored proc in my database which returns an integer. I added a Function Import to my model. This appears in the EDMX file: <Function Name="GetTotalEntityCount" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo" /> However, no method actually gets generated for this. It should be top level, right? using (MyContext context = new MyContext()) { context.MyMethodShouldBeRightHere(); } Nothing appears in Intellisense, I've gone through the designer.cs file and there's nothing in there, and reflected the DLL...nothing. The code generator is just not generating any code to support this stored proc. I added another table to my database and updated the model, and that came in, so the model will update, it's just specifically ignoring this stored proc. I've tried everything I can think of, and consulted every resource I can find, and as near as I can tell, I'm doing everything right. I'm using EF4, database-first. (I'm pretty sure on the version, anyway. This shows up in the generated file: Runtime Version:4.0.30319.1 )

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• Saving a single entity instead of the entire context - revisited

  - by nite

  I’m looking for a way to have fine grained control over what is saved using Entity Framework, rather than the whole ObjectContext.SaveChanges(). My scenario is pretty straight forward, and I’m quite amazed not catered for in EF – pretty basic in NHibernate and all other data access paradigms I’ve seen. I’m generating a bunch of data (in a WPF UI) and allowing the user to fine tune what is proposed and choose what is actually committed to the database. For the proposed entities I’m: getting a bunch of reference entities (eg languages) via my objectcontext, creating the proposed entities and assigning these reference entities to them (as navigation properties), so by virtue of their relationship to the reference entities they’re implicitly added to the objectconext Trying to create & save individual entites based on the proposed entities. I figure this should be really simple & trivial but everything I’ve tried I’ve hit a brick wall, either I set up another objectcontext & add just the entity I need (it then tries to add the whole graph and fails as it’s on another objectcontext). I’ve tried MergeOptions = NoTracking on my reference entities to try to get the Attach/AddObject not to navigate through these to create a graph, no avail. I've removed the navigation properties from the reference entities. I've tried AcceptAllChanges, that works but pretty useless in practice as I do still want to track & save other entities. In a simple test, I can create 2 of my proposed entities, AddObject the one I want to save and then Detach the one I dont then call SaveChanges, this works but again not great in practice. Following are a few links to some of the nifty ideas which in the end don’t help in the end but illustrate the complexity of EF for something so simple. I’m really looking for a SaveSingle/SaveAtomic method, and think it’s a pretty reasonable & basic ask for any DAL, letalone a cutting edge ORM. http://stackoverflow.com/questions/1301460/saving-a-single-entity-instead-of-the-entire-context www.codeproject.com/KB/architecture/attachobjectgraph.aspx?fid=1534536&df=90&mpp=25&noise=3&sort=Position&view=Quick&select=3071122&fr=1 bernhardelbl.spaces.live.com/blog/cns!DB54AE2C5D84DB78!238.entry

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• How to structure this Symfony web project?

  - by James William

  I am new to Symfony and am not sure how to best structure my web project. The solution must accommodate 3 use cases: Public access to www.mydomain.com for general use Member only access to member.mydomain.com Administrator access to admin.mydomain.com All three virtual hosts point to the Symfony /web directory Questions: Is this 3 separate applications in my Symfony project (e.g. "frontend", "backend" and "admin" or "public", "member", "admin")? Is this a good approach if there is to be some duplicate code (e.g. generating a member list would be common across all 3 applications, but presented differently)? How would I route to the various applications based on the subdomain when a user accesses *.mydomain.com? Where in Symfony should this routing logic be placed? Or, is this one application with modules for each of the above use cases? EDIT: I do not have access to httpd.conf in apache to specify a default page for virtual hosts. I can only specify a directory for each subdomain using the hostin provider's cPanel.

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• Abstracting the interpretation of MVC checkboxes values received by the FormsCollection object

  - by Simon_Weaver

  In ASP.NET MVC a checkbox is generated by the HtmlHelper code here: <%= Html.CheckBox("List_" + mailingList.Key, true) %> as this HTML: <input id="List_NEW_PRODUCTS" name="List_NEW_PRODUCTS" type="checkbox" value="true" /> <input name="List_NEW_PRODUCTS" type="hidden" value="false" /> In case you're wondering why is there an extra hidden field? - then read this. Its definitely a solution that makes you first think 'hmmmmm' but then you realize its a pretty elegant one. The problem I have is when I'm trying to parse the data on the backend. Well its not so much of a problem as a concern if anything in future were to change in the framework. If I'm using the built in binding everything is great - its all done for me. But in my case I'm dynamically generating checkboxes with unknown names and no corresponding properties in my model. So i end up having to write code like this : if (forms["List_RETAIL_NOTIFICATION"] == "true,false") { } or this: if (forms.GetValues("List_RETAIL_NOTIFICATION")[0] == "true") { } Both of which i still look at and cringe - especially since theres no guarantee this will always be the return value. I'm wondering if theres a way to access the layer of abstraction used by the model binders - or if I'm stuck with my controller 'knowing' this much about HTTP POST hacks. Yes I'm maybe being a little picky - but perhaps theres a better clever way using the model binders that I can employ to read dynamically created checkbox parameters. In addition i was hoping this this post might help others searcheing for : "true,false". Even though I knew why it does this I just forgot and it took me a little while to realize 'duh'. FYI: I tried another few things, and this is what I found : forms["List_RETAIL_NOTIFICATION"] evaluates to "true,false" forms.GetValues("List_RETAIL_NOTIFICATION")[0] evaluates to "true" (forms.GetValue("List_RETAIL_NOTIFICATION").RawValue as string[])[0] evaluates to "true" forms.GetValues("List_RETAIL_NOTIFICATION").FirstOrDefault() evaluates to "true"

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• Django, url tag in template doesn't work: NoReverseMatch

  - by Lukasz Jocz

  I've encountered a problem with generating reverse url in templates in django. I'm trying to solve it since a few hours and I have no idea what the problem might be. URL reversing works great in models and views: # like this in models.py @models.permalink def get_absolute_url(self): return ('entry', (), { 'entry_id': self.entry.id, }) # or this in views.py return HttpResponseRedirect(reverse('entry',args=(entry_id,))) but when I'm trying to make it in template I get such an error: NoReverseMatch at /entry/1/ Reverse for ''add_comment'' with arguments '(1L,)' and keyword arguments '{}' not found. My file structure looks like this: project/ +-- frontend ¦   +-- models.py ¦   +-- urls.py ¦   +-- views.py +-- settings.py +-- templates ¦   +-- add_comment.html ¦   +-- entry.html +-- utils ¦   +-- with_template.py +-- wsgi.py My urls.py: from project.frontend.views import * from django.conf.urls import patterns, include, url urlpatterns = patterns('project.frontend.views', url(r'^entry/(?P<entry_id>\d+)/', 'entry', name="entry"), (r'^entry_list/', 'entry_list'), Then entry_list.html: {% extends "base.html" %} {% block content %} {% for entry in entries %} {% url 'entry' entry.id %} {% endfor %} {% endblock %} In views.py I have: @with_template def entry(request, entry_id): entry = Entry.objects.get(id=entry_id) entry.comments = entry.get_comments() return locals() where with_template is following decorator(but I don't think this is a case): class TheWrapper(object): def __init__(self, default_template_name): self.default_template_name = default_template_name def __call__(self, func): def decorated_func(request, *args, **kwargs): extra_context = kwargs.pop('extra_context', {}) dictionary = {} ret = func(request, *args, **kwargs) if isinstance(ret, HttpResponse): return ret dictionary.update(ret) dictionary.update(extra_context) return render_to_response(dictionary.get('template_name', self.default_template_name), context_instance=RequestContext(request), dictionary=dictionary) update_wrapper(decorated_func, func) return decorated_func if not callable(arg): return TheWrapper(arg) else: default_template_name = ''.join([ arg.__name__, '.html']) return TheWrapper(default_template_name)(arg) Do you have any idea, what may cause the problem? Great thanks in advance!

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• Vim: change formatting of variables in a script

  - by sixtyfootersdude

  I am using vim to edit a shell script (did not use the right coding standard). I need to change all of my variables from camel-hum-notation startTime to caps-and-underscore-notation START_TIME. I do not want to change the way method names are represented. I was thinking one way to do this would be to write a function and map it to a key. The function could do something like generating this on the command line: s/<word under cursor>/<leave cursor here to type what to replace with> I think that this function could be applyable to other situations which would be handy. Two questions: Question 1: How would I go about creating that function. I have created functions in vim before the biggest thing I am clueless about is how to capture movement. Ie if you press dw in vim it will delete the rest of a word. How do you capture that? Also can you leave an uncompleted command on the vim command line? Question 2: Got a better solution for me? How would you approach this task?

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• "end()" iterator for back inserters?

  - by Thanatos

  For iterators such as those returned from std::back_inserter(), is there something that can be used as an "end" iterator? This seems a little nonsensical at first, but I have an API which is: template<typename InputIterator, typename OutputIterator> void foo( InputIterator input_begin, InputIterator input_end, OutputIterator output_begin, OutputIterator output_end ); foo performs some operation on the input sequence, generating an output sequence. (Who's length is known to foo but may or may not be equal to the input sequence's length.) The taking of the output_end parameter is the odd part: std::copy doesn't do this, for example, and assumes you're not going to pass it garbage. foo does it to provide range checking: if you pass a range too small, it throws an exception, in the name of defensive programming. (Instead of potentially overwriting random bits in memory.) Now, say I want to pass foo a back inserter, specifically one from a std::vector which has no limit outside of memory constraints. I still need a "end" iterator - in this case, something that will never compare equal. (Or, if I had a std::vector but with a restriction on length, perhaps it might sometimes compare equal?) How do I go about doing this? I do have the ability to change foo's API - is it better to not check the range, and instead provide an alternate means to get the required output range? (Which would be needed anyways for raw arrays, but not required for back inserters into a vector.) This would seem less robust, but I'm struggling to make the "robust" (above) work.

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• RMagick transparent_color deprecated? What's the alternative?

  - by user315975

  I'm developing an app that does a fair amount of generating transparent pngs on the fly. These are used as overlays, to show areas of interest in a graphic, so they have to have transparent backgrounds. I am developing in Ruby on Rails, deploying on Heroku. What works fine in development is not working in production. I get this error when I call a drawing routine using RMagick: NotImplementedError (the `transparent_color=' method is not supported by ImageMagick 6.2.4): /usr/local/lib/ruby/gems/1.8/gems/rmagick-1.15.17/lib/RMagick.rb:1691:in `transparent_color=' I'm using RMagick version 2.12.1 on the development machine, but I'm not exactly certain how to discover the version of ImageMagick that it's running, so I'm not sure if this is a case of my local code being behind or ahead. I'm hoping behind, because perhaps then there'll be a replacement for this call. Does anyone know what the fix is here? What's required to generate a transparent background, if not the call I'm using? I can't find this in the documentation: in fact, it was on a third-party site that I found mention of this capability.

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• How can I make hundreds of simultaneously running processes communicate with a database through one

  - by Olfan

  Long speech short: How can I make hundreds of simultaneously running processes communicate with a database through one or few permanent sessions? The whole story: I once built a number crunching engine that handles vast amounts of large data files by forking off one child after another giving each a small number of files to work on. File locking, progress monitoring and result propagation happen in an Oracle database which all (sub-)processes access at various times using an application-specific module which encapsulates DBI. This worked well at first, but now with higher volumes of input data, the number of database sessions (one per child, and they can be very short-lived) constantly being opened and closed is becoming an issue. I now want to centralise database access so that there are only one or few fixed database sessions which handle all database access for all the (sub-)processes. The presence of the database abstraction module should make the changes easy because the function calls in the worker instances can stay the same. My problem is that I cannot think of a suitable way to enhance said module in order to establish communication between all the processes and the database connector(s). I thought of message queueing, but couldn't come up with a way of connecting a large herd of requestors with one or few database connectors in a way so that bidirectional communication is possible (for collecting the query result). An asynchronous approach could help here in that all requests are written to the same queue and the database connector servicing the request will "call back" to submit the result. But my mind fails me in generating an image clear enough so that I can paint into code. Threading instead of forking might have given me an easier start, but this would now require massive changes to the code base that I'm not prepared to do to a live system. The more I think of it, the more the base idea looks like a pre-forked web server to me only that it doesn't serve web pages but database queries. Any ideas on what to dig into, and where? Sample (pseudo) code to inspire me, links to possibly related articles, ready solutions on CPAN maybe?

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• Random number generation in MVC applications

  - by SlimShaggy

  What is the correct way of generating random numbers in an ASP.NET MVC application if I need exactly one number per request? According to MSDN, in order to get randomness of sufficient quality, it is necessary to generate multiple numbers using a single System.Random object, created once. Since a new instance of a controller class is created for each request in MVC, I cannot use a private field initialized in the controller's constructor for the Random object. So in what part of the MVC app should I create and store the Random object? Currently I store it in a static field of the controller class and lazily initialize it in the action method that uses it: public class HomeController : Controller { ... private static Random random; ... public ActionResult Download() { ... if (random == null) random = new Random(); ... } } Since the "random" field can be accessed by multiple instances of the controller class, is it possible for its value to become corrupted if two instances attempt to initialize it simultaneously? And one more question: I know that the lifetime of statics is the lifetime of the application, but in case of an MVC app what is it? Is it from IIS startup till IIS shutdown?

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• Is this XML file correct for RSS feeding?

  - by Hermet

  Hi guys I am generating a XML-RSS type file from PHP. The output for example is like this <?xml version="1.0" encoding="iso-8859-1"?> <rss version="2.0"> <channel> <title>Mi web mola</title> <link>http://www.dominio.com/blog.php</link> <language>es-ES</language> <description>Mallas y eso</description> <generator>Autor</generator> <item> <title>Articulo de prueba</title> <link>http://www.midominio.com/2342</link> <pubDate>14/06/2010</pubDate> <description><![CDATA[Descripcion de prueba bla bla bla]]></description> <content:encoded><![CDATA[Contenido prueba]]></content:encoded> </item> </channel> </rss> ... and all I can see in the Firefox preview is the title and the description of the blog, not the items, but in the source it appears correctly, so I've thought it must be a parse error or something like that.. What could be wrong? Again, excuse me for my bad english, and thank you very much.

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• 2D Histogram in R: Converting from Count to Frequency within a Column

  - by Jac

  Would appreciate help with generating a 2D histogram of frequencies, where frequencies are calculated within a column. My main issue: converting from counts to column based frequency. Here's my starting code: # expected packages library(ggplot2) library(plyr) # generate example data corresponding to expected data input x_data = sample(101:200,10000, replace = TRUE) y_data = sample(1:100,10000, replace = TRUE) my_set = data.frame(x_data,y_data) # define x and y interval cut points x_seq = seq(100,200,10) y_seq = seq(0,100,10) # label samples as belonging within x and y intervals my_set$x_interval = cut(my_set$x_data,x_seq) my_set$y_interval = cut(my_set$y_data,y_seq) # determine count for each x,y block xy_df = ddply(my_set, c("x_interval","y_interval"),"nrow") # still need to convert for use with dplyr # convert from count to frequency based on formula: freq = count/sum(count in given x interval) ################ TRYING TO FIGURE OUT ################# # plot results fig_count <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = nrow)) # count fig_freq <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = freq)) # frequency I would appreciate any help in how to calculate the frequency within a column. Thanks! jac EDIT: I think the solution will require the following steps 1) Calculate and store overall counts for each x-interval factor 2) Divide the individual bin count by its corresponding x-interval factor count to obtain frequency. Not sure how to carry this out though. .

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