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  • How do I use multiple where clauses in GHCi?

    - by T.R.
    I'm playing around with GHCi for the first time, and I'm having some trouble writing multi-line functions. My code is as follows: Prelude> :{ Prelude| let diffSquares lst = abs $ squareOfSums lst - sumOfSquares lst Prelude| where Prelude| squareOfSums lst = (fst (sumsAndSquares lst))^2 Prelude| sumOfSquares lst = snd (sumsAndSquares lst) Prelude| sumsAndSquares = foldl (\(sms,sqrs) x -> (sms+x,sqrs+x^2)) (0,0) Prelude| :} It gives the following error: <interactive>:1:142: parse error on input `=' Could someone kindly point me in the direction of what I'm missing?

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  • Django: way to test what class a generic relation content_object is?

    - by bitbutter
    In my project I have a class, NewsItem. Instances of NewsItem act like a wrapper. They can be associated with either an ArtWork instance, or an Announcement instance. Here's how the NewsItem model looks: class NewsItem(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') date = models.DateTimeField(default=datetime.datetime.now,) class Meta: ordering = ('-date',) def __unicode__(self): return (self.title()) In a template I'm dealing with a NewsItem instance, and would like to output a certain bunch of html it it's 'wrapping' an Artwork instance, and a different bunch of html if it's wrapping an Announcement instance. Could someone explain how I can write a conditional to test for this? My first naive try looked like this: {% if news_item.content_object.type=='Artwork' %}do this{% else %}do that{% endif %}

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  • How can I send multiple types of objects across Protobuf?

    - by cyclotis04
    I'm implementing a client-server application, and am looking into various ways to serialize and transmit data. I began working with Xml Serializers, which worked rather well, but generate data slowly, and make large objects, especially when they need to be sent over the net. So I started looking into Protobuf, and protobuf-net. My problem lies in the fact that protobuf doesn't sent type information with it. With Xml Serializers, I was able to build a wrapper which would send and receive any various (serializable) object over the same stream, since object serialized into Xml contain the type name of the object. ObjectSocket socket = new ObjectSocket(); socket.AddTypeHandler(typeof(string)); // Tells the socket the types socket.AddTypeHandler(typeof(int)); // of objects we will want socket.AddTypeHandler(typeof(bool)); // to send and receive. socket.AddTypeHandler(typeof(Person)); // When it gets data, it looks for socket.AddTypeHandler(typeof(Address)); // these types in the Xml, then uses // the appropriate serializer. socket.Connect(_host, _port); socket.Send(new Person() { ... }); socket.Send(new Address() { ... }); ... Object o = socket.Read(); Type oType = o.GetType(); if (oType == typeof(Person)) HandlePerson(o as Person); else if (oType == typeof(Address)) HandleAddress(o as Address); ... I've considered a few solutions to this, including creating a master "state" type class, which is the only type of object sent over my socket. This moves away from the functionality I've worked out with Xml Serializers, though, so I'd like to avoid that direction. The second option would be to wrap protobuf objects in some type of wrapper, which defines the type of object. (This wrapper would also include information such as packet ID, and destination.) It seems silly to use protobuf-net to serialize an object, then stick that stream between Xml tags, but I've considered it. Is there an easy way to get this functionality out of protobuf or protobuf-net? I've come up with a third solution, and posted it below, but if you have a better one, please post it too!

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  • HTML: Display:none does this allow multiple ID-Attributes with same name (when "hidden")?

    - by Jan
    Hello, according to the HTML Standards ID-Attributes of any HTML Tag in a webpage have to be unique in the document!? Does this rule also apply to HTML Tags that have been "disabled/hidden" by using: display:none? Example: <html> <body> <div id="one"></div> <div id="one" style="display:none;"></div> </body> </hmtl> Is this valid HTML or not. So the question is do "display:none"= hidden Elements also "count/matter" in regard to the rule only having unique ID-Attributes in a single webpage? Thanks Jan

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  • Can I Always debug multiple instances of a same object that is of type thread with GDB?

    - by yan bellavance
    program runs fine. When I put a breakpoint a segmentation fault is generated. Is it me or GDB? At run time this never happens and if I instantiate only one object then no problems. Im using QtCreator on ubuntu x86_64 karmic koala. UPDATE1: I have made a small program containing a simplified version of that class. You can download it at: example program simply put a breakpoint on the first line of the function called drawChart() and step into to see the segfault happen UPDATE2: This is another small program but it is practically the same as the mandlebrot example and it is still happening. You can diff it with mandlebrot to see the small difference. almost the same as mandlebrot example program

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  • How to modify preorder tree traversal algorithm to handle nodes with multiple parents?

    - by poldo
    I've been searching for a while now and can't seem to find an alternative solution. I need the tree traversal algorithm in such a way that a node can have more than 1 parent, if it's possible (found a great article here: Storing Hierarchical Data in a Database). Are there any algorithms so that, starting from a root node, we can determine the sequence and dependencies of nodes (currently reading topological sorting)?

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  • MVC without ORM is not real MVC?

    - by ajsie
    at the moment im integrating ORM (doctrine) into a MVC framework (codeigniter). then it hit me that this was the obvious way of setting up a MVC: the controller calls the models that are representing database tables. look at this picture: MVC + ORM then i wondered, how can a MVC without ORM be real MVC? cause then the models are not real objects, rather aggregations of different functions that perform CRUD, then returning the result to the controller. and there is no need for a state (object properties) i guess so the functions would be all static? correct me if im wrong on this one. i guess a lot of people are using models without ORM. please share your thoughts. how do your models look like?

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  • Oracle/c#: How do i use bind variables with select statements to return multiple records?

    - by twiga
    I have a question regarding Oracle bind variables and select statements. What I would like to achieve is do a select on a number different values for the primary key. I would like to pass these values via an array using bind values. select * from tb_customers where cust_id = :1 int[] cust_id = { 11, 23, 31, 44 , 51 }; I then bind a DataReader to get the values into a table. The problem is that the resulting table only contains a single record (for cust_id=51). Thus it seems that each statement is executed independently (as it should), but I would like the results to be available as a collective (single table). A workaround is to create a temporary table, insert all the values of cust_id and then do a join against tb_customers. The problem with this approach is that I would require temporary tables for every different type of primary key, as I would like to use this against a number of tables (some even have combined primary keys). Is there anything I am missing?

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  • Django: Paginator + raw SQL query

    - by Silver Light
    Hello! I'm using Django Paginator everywhere on my website and even wrote a special template tag, to make it more convenient. But now I got to a state, where I need to make a complex custom raw SQL query, that without a LIMIT will return about 100K records. How can I use Django Pagintor with custom query? Simplified example of my problem: My model: class PersonManager(models.Manager): def complicated_list(self): from django.db import connection #Real query is much more complex cursor.execute("""SELECT * FROM `myapp_person`"""); result_list = [] for row in cursor.fetchall(): result_list.append(row[0]); return result_list class Person(models.Model): name = models.CharField(max_length=255); surname = models.CharField(max_length=255); age = models.IntegerField(); objects = PersonManager(); The way I use pagintation with Django ORM: all_objects = Person.objects.all(); paginator = Paginator(all_objects, 10); try: page = int(request.GET.get('page', '1')) except ValueError: page = 1 try: persons = paginator.page(page) except (EmptyPage, InvalidPage): persons = paginator.page(paginator.num_pages) This way, Django get very smart, and adds LIMIT to a query when executing it. But when I use custom manager: all_objects = Person.objects.complicated_list(); all data is selected, and only then python list is sliced, which is VERY slow. How can I make my custom manager behave similar like built in one?

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  • How should images be stored when multiple sizes are needed?

    - by Josh Curren
    What is the best way to store images? Currently when an image is uploaded I resize it to 3 different sizes (a thumbnail, a normal size, and a large size). I save in a database a description of the image, the format, and use the id number from the database as the image name. Each size image has its own directory. Should I be storing the images in the database? Should I only be storing the larger size and generate the thumbnail as needed? Or any other ideas you have?

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  • Clean way to combine multiple jars? Preferably using ant

    - by Jacob
    I have runtime dependencies on some external jars that I would like to "rejar" into a single jar. These external dependencies are stored in a external_jars directory, and I'd like to be able to not have to list each one out (e.g., to not need to change my build scripts if my dependencies change). Any thoughts? Google gave me a good answer on how to do this if you don't mind listing out each jar you want as a dependency: http://markmail.org/message/zijbwm46maxzzoo5 Roughly, I want something along the lines of the following, which would combine all jars in lib into out.jar (with some sane overwrite rules). jar -combine -out out.jar -in lib/*.jar

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  • Rails - how do you create a user index page like stack overflows with multiple tabs whilst keeping t

    - by adam
    On stackoverflow in the users profile area there are many tabs which all display differing information such as questions asked and graphs. Its the same view though and im wondering hows its best to achieve this in rails whilst keeping the controller skinny and logic in the view to a minimum. def index @user = current_user case params[:tab_selected] when "questions" @data = @user.questions when "answers" @sentences = @user.answers else @sentences = @user.questions end respond_to do |format| format.html # index.html.erb nd end but how do i process this in the index view without a load of if and else statments. And if questions and answers are presented differently whats the best way to go about this.

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  • Django: How to handle imports in a reusable app

    - by facha
    everyone I'm just starting with django. It is not quite clear to me, how should I write an app I could reuse later. In every tutorial I read I see the same piece of code: view.py from project.app.models import MyModel So, if I move my apps to another project, I'll have to modify the "project.app.models" so that it looks like "project2.app.models" for every app I move. Is there a way to avoid that? Thanks in advance.

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  • Ruby on Rails: How do you do HTTP auth over multiple controllers?

    - by DerNalia
    So, Here are the relevant routes map.namespace "admin" do |admin| admin.root :controller => :site_prefs, :action => :index admin.resources :site_prefs admin.resources :link_pages admin.resources :menu_bars admin.resources :services admin.resources :users end And I have this for one controller: before_filter :authenticate protected def authenticate authenticate_or_request_with_http_basic do |username, password| username == "1234" && password == "1234" end end How do I set up my admin controllers to authenticate no matter what page within any of those controllers is navigated to, yet only have it authenticate once among all the admin controllers, and have the code all in one spot. Right now, the only I can think of to authenticate is to copy the auth code into each controller, and I hate having duplicate code... so.... yeah

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  • Multiple Actions (Forms) on one Page - How not to lose master data, after editing detail data?

    - by nWorx
    Hello all, I've got a form where users can edit members of a group. So they have the possibilty to add members or remove existing members. So the Url goes like ".../Group/Edit/4" Where 4 is the id of the group. the view looks like this <% using (Html.BeginForm("AddUser", "Group")) %> <%{%> <label for="newUser">User</label> <%=Html.TextBox("username")%> <input type="submit" value="Add"/> </div> <%}%> <% using (Html.BeginForm("RemoveUser", "Group")) %> <%{%> <div class="inputItem"> <label for="groupMember">Bestehende Mitglieder</label> <%= Html.ListBox("groupMember", from g in Model.GetMembers() select new SelectListItem(){Text = g}) %> <input type="submit" value="Remove" /> </div> <%}%> The problem is that after adding or removing one user i lose the id of the group. What is the best solution for solving this kind of problem? Should I use hidden fields to save the group id? Thanks in advance.

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  • Why does multiple sessions started on the same page gets the same session id?

    - by Calmarius
    I tryed the following: <?php session_name('user'); session_start(); // sets an 'user' cookie with session id. // This session stores the user's login data. // Its an ordinary session. $USERSESSION=$_SESSION; // saving this session $userSessId=session_id(); session_write_close(); //closing this session session_name('chatroom'); session_start(); // set a 'chatroom' cookie but contains the same session id and points to the same data :( . // This session would be used to store the chat text. This session would be // shared between all users joined in this chat room by setting the same session id for all members. // by calling session_regenerate_id would make a diffent session id for every user and it won't be a chat room anymore. ?> So I want to do a chat like thing with sessions. On the client side it would be done with ajax that polls this php page in every 5-10 seconds. Sessions may be cached in the server's memory so it can be accessible fast. I can store the chat in the database but my service runs on a free webhost which is limited, only 4 mysql connections allowed at a time which is almost nothing. I try to touch my database as least times as possible.

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  • Android/Eclipse: Creating multiple builds with different com identifiers.

    - by Dave
    Hi, I have an app that requires two builds - one is a demo app, the other uses the same codebase but uses a flag to introduce different functionality. The identifier must be different each time (e.g. com.siteA.appA and com.siteB.appB). However it doesn't appear to be trivial to use the refactor functionality in Eclipse to change the com identifier - all references change apart from the "import com.siteA.appA.R" reference. Is there a way to create different builds with different com identifiers/app name within Eclipse? Thanks

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  • how do i check if multiple folders exist if so delete them on button click?

    - by NightsEVil
    hi i have a few folders created by my application and id like that when they click a button named "clean up" that it would check to see if any of the predetermined folders exist, if they do then delete them, this is what i have tried so far whats wrong with it? string tempFolder = Environment.GerFolderPath(Environment.SpecialFolder.ApplicationData); if (Directory.Exists(tempFolder + "//" + "temp1")) if (Directory.Exists(tempFolder + "//" + "temp2")) if (Directory.Exists(tempFolder + "//" + "temp3")) if (Directory.Exists(tempFolder + "//" + "temp4")) { System.IO.Directory.Delete(tempFolder + "\\" + "temp1", true); System.IO.Directory.Delete(tempFolder + "\\" + "temp2", true); System.IO.Directory.Delete(tempFolder + "\\" + "temp3", true); System.IO.Directory.Delete(tempFolder + "\\" + "temp4", true); } else { MessageBox.Show("No Cleanup Needed"); } so whats wrong? i tested it and it seemed to with 2 folder but not 4 or more

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  • How do you stop echo of multiple values with 'foreach' in PHP?

    - by Aaron EA
    How do you when using custom fields in Wordpress echo just the first value using foreach? Currently the code is: <?php for(get_field('venue_event') as $post_object): ?> <a href="<?php echo get_permalink($post_object); ?>"><?php echo get_the_title($post_object) ?></a> <?php endforeach; ?> This takes the field from the wordpress page (the field is a link to another page), creates a link to that page using get_permalink but when I want to echo the page title it does it, but then it also echos all other values that are not needed.

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