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• CodeModel help needed for right-hand singleton.getinstance() assignment.

  - by antarti

  I've been able to generate 99% of what I need with the CodeModel API, but I am stumped here... Using the various "directXX" methods does not add import statements to the generated code, and I can work without the "directXXX" type of methods except for one place in a generated class. Suppose I desire a generated method like: /** * Copies data from this Value-Obj instance, to the returned PERSON instance. * * @return PERSON * */ public PERSON mapVOToPERSON() throws MappingException { Mapper mapper = (com.blah.util.MapperSingleton.getMapperInstance()); return mapper.map(this, PERSON.class); } You can see the right hand of the Mapper assignment in parens. Emitting the entire package+class was the only way I could find to just declare "SomeSingleton.someMethod()" on the right hand side and have the generated code compile. Without the MapperSingleton being added to the object model, there is no import generated... Questions: 1) Is there a way to force an import to be generated? 2) How to declare an expression that gives me the right side of the Mapper assignment within the object model (so that an import of MapperSingleton gets generated. Any help appreciated...

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• Doesn't (didn't) Scala have automatically generated setters?

  - by Malvolio

  Google and my failing memory are both giving me hints that it does, but every attempt is coming up dry. class Y { var y = 0 } var m = new Y() m.y_(3) error: value y_ is not a member of Y Please tell me I am doing something wrong. (Also: please tell me what it is I am doing wrong.) EDIT The thing I am not doing wrong, or at least not the only thing I am doing wrong, is the way I am invoking the setter. The following things also fail, all with the same error message: m.y_ // should be a function valued expression m.y_ = (3) // suggested by Google and by Mchl f(m.y_) // where f takes Int => Unit as an argument f(m.y) // complains that I am passing in Int not a function I am doing this all through SimplyScala, because I'm too lazy and impatient to set up Scala on my tiny home machine. Hope it isn't that... And the winner is ... Fabian, who pointed out that I can't have a space between the _ and the =. I thought out why this should be and then it occurred to me: The name of the setter for y is not y_, it is y_= ! Observe: class Y { var y = 0 } var m = new Y() m.y_=(3) m.y res1: Int = 3 m.y_= error: missing arguments for method y_= in class Y; follow this method with `_` if you want to treat it as a partially applied function m.y_= ^ m.y_=_ res2: (Int) => Unit = def four(f : Int => Unit) = f(4) four(m.y_=) m.y res3: Int = 4 Another successful day on StackExchange.

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• PROLOG - DCG parsing

  - by user2895589

  Hello I am new Prolog and DGC.I want to write a DCG to parse time expressions like 10.20 am or 12 oclock. how can I check 10.20 am is valid expression or not for Olcock I wrote some code. oclock --> digit1,phrase1. digit1 --> [T],{digit1(T)}. digit1(1). digit1(2). digit1(3). digit1(4). digit1(5). digit1(6). digit1(7). digit1(8). digit1(9). digit1(10). digit1(11). digit1(12). phrase1 --> [P],{phrase1(P)}. phrase1(Oclock). i ma checking by query oclock([1,oclock],[]). can someone help me on this.

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• How is the C++ synthesized move constructor affected by volatile and virtual members?

  - by user1827766

  Look at the following code: struct node { node(); //node(const node&); //#1 //node(node&&); //#2 virtual //#3 ~node (); node* volatile //#4 next; }; main() { node m(node()); //#5 node n=node(); //#6 } When compiled with gcc-4.6.1 it produces the following error: g++ -g --std=c++0x -c -o node.o node.cc node.cc: In constructor node::node(node&&): node.cc:3:8: error: expression node::next has side-effects node.cc: In function int main(): node.cc:18:14: note: synthesized method node::node(node&&) first required here As I understand the compiler fails to create default move or copy constructor on line #6, if I uncomment either line #1 or #2 it compiles fine, that is clear. The code compiles fine without c++0x option, so the error is related to default move constructor. However, what in the node class prevents default move constructor to be created? If I comment any of the lines #3 or #4 (i.e. make the destructor non-virtual or make data member non-volatile) it compiles again, so is it the combination of these two makes it not to compile? Another puzzle, line #5 does not cause an compilation error, what is different from line #6? Is it all specific for gcc? or gcc-4.6.1?

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• lambda expressions in VB.NET... what am I doing wrong???

  - by Bob

  when I run this C# code, no problems... but when I translate it into VB.NET it compiles but blows due to 'CompareString' member not being allowed in the expression... I feel like I'm missing something key here... private void PrintButton_Click(object sender, EventArgs e) { if (ListsListBox.SelectedIndex > -1) { //Context using (ClientOM.ClientContext ctx = new ClientOM.ClientContext(UrlTextBox.Text)) { //Get selected list string listTitle = ListsListBox.SelectedItem.ToString(); ClientOM.Web site = ctx.Web; ctx.Load(site, s => s.Lists.Where(l => l.Title == listTitle)); ctx.ExecuteQuery(); ClientOM.List list = site.Lists[0]; //Get fields for this list ctx.Load(list, l => l.Fields.Where(f => f.Hidden == false && (f.CanBeDeleted == true || f.InternalName == "Title"))); ctx.ExecuteQuery(); //Get items for the list ClientOM.ListItemCollection listItems = list.GetItems( ClientOM.CamlQuery.CreateAllItemsQuery()); ctx.Load(listItems); ctx.ExecuteQuery(); // DOCUMENT CREATION CODE GOES HERE } MessageBox.Show("Document Created!"); } } but in VB.NET code this errors due to not being allowed 'CompareString' members in the ctx.Load() methods... Private Sub PrintButton_Click(sender As Object, e As EventArgs) If ListsListBox.SelectedIndex > -1 Then 'Context Using ctx As New ClientOM.ClientContext(UrlTextBox.Text) 'Get selected list Dim listTitle As String = ListsListBox.SelectedItem.ToString() Dim site As ClientOM.Web = ctx.Web ctx.Load(site, Function(s) s.Lists.Where(Function(l) l.Title = listTitle)) ctx.ExecuteQuery() Dim list As ClientOM.List = site.Lists(0) 'Get fields for this list ctx.Load(list, Function(l) l.Fields.Where(Function(f) f.Hidden = False AndAlso (f.CanBeDeleted = True OrElse f.InternalName = "Title"))) ctx.ExecuteQuery() 'Get items for the list Dim listItems As ClientOM.ListItemCollection = list.GetItems(ClientOM.CamlQuery.CreateAllItemsQuery()) ctx.Load(listItems) ' DOCUMENT CREATION CODE GOES HERE ctx.ExecuteQuery() End Using MessageBox.Show("Document Created!") End If End Sub

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• How do I define a monadic function to work on a list in J?

  - by Gregory Higley

  Let's say I have the following J expression: # 3 ((|=0:)#]) 1+i.1000 This counts the number of numbers between 1 and 1000 that are evenly divisible by 3. (Now, before anyone points out that there's an easier way to do this, this question is about the syntax of J, and not mathematics.) Let's say I define a monadic function for this, as follows: f =: monad define # y ((|=0:)#]) 1+i.1000 ) This works great with a single argument, e.g., f 4 250 If I pass a list in, I get a length error: f 1 2 3 |length error: f Now, I completely understand why I get the length error. When you substitute the list 1 2 3 for the y argument of the monad, you get: # 1 2 3 ((|=0:)#]) 1+i.1000 If you know anything about J, it's pretty clear why the length error is occurring. So, I don't need an explanation of that. I want to define the function such that when I pass a list, it returns a list, e.g., f 1 2 3 1000 500 333 How can I either (a) redefine this function to take a list and return a list or (b) get the function to work on a list as-is without being redefined, perhaps using some adverb or other technique?

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• Why is T() = T() allowed?

  - by Rimo

  I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

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• page variable in a repeater

  - by carrot_programmer_3

  Hi I'm having a bit of an issue with a asp.net repeater I'm building a categories carousel with the dynamic categories being output by a repeater. Each item is a LinkButton control that passes an argument of the category id to the onItemClick handler. a page variable is set by this handler to track what the selected category id is.... public String SelectedID { get { object o = this.ViewState["_SelectedID"]; if (o == null) return "-1"; else return (String)o; } set { this.ViewState["_SelectedID"] = value; } } problem is that i cant seem to read this value while iterating through the repeater as follows... <asp:Repeater ID="categoriesCarouselRepeater" runat="server" onitemcommand="categoriesCarouselRepeater_ItemCommand"> <ItemTemplate> <%#Convert.ToInt32(Eval("CategoryID")) == Convert.ToInt32(SelectedID) ? "<div class=\"selectedcategory\">":"<div>"%> <asp:LinkButton ID="LinkButton1" CommandName="select_category" CommandArgument='<%#Eval("CategoryID")%>' runat="server"><img src="<%#Eval("imageSource")%>" alt="category" /><br /> </div> </ItemTemplate> </asp:Repeater> calling <%=SelectedID%> in the item template works but when i try the following expression the value of SelectedID returns empty.. <%#Convert.ToInt32(Eval("CategoryID")) == Convert.ToInt32(SelectedID) ? "match" : "not a match"%> the value is being set as follows... protected void categoriesCarouselRepeater_ItemCommand(object source, RepeaterCommandEventArgs e) { SelectedID = e.CommandArgument); } Any ideas whats wrong here?

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• Dynamic Select boxes page load

  - by Chris

  Hello, I have a dynamic chained select box that I am attempting to show the value of on a page load. In my chained select box, it will default to the first option within the select box on page load, could anyone provide assitance? I stumbled upon this thread, but I can't seem to translate what they are doing with that answer to my language of CF. Dynamic chained drop downs on page refresh Here is the JS script I am using. function dynamicSelect(id1, id2) { // Feature test to see if there is enough W3C DOM support if (document.getElementById && document.getElementsByTagName) { // Obtain references to both select boxes var sel1 = document.getElementById(id1); var sel2 = document.getElementById(id2); // Clone the dynamic select box var clone = sel2.cloneNode(true); // Obtain references to all cloned options var clonedOptions = clone.getElementsByTagName("option"); // Onload init: call a generic function to display the related options in the dynamic select box refreshDynamicSelectOptions(sel1, sel2, clonedOptions); // Onchange of the main select box: call a generic function to display the related options in the dynamic select box sel1.onchange = function() { refreshDynamicSelectOptions(sel1, sel2, clonedOptions); } } } function refreshDynamicSelectOptions(sel1, sel2, clonedOptions) { // Delete all options of the dynamic select box while (sel2.options.length) { sel2.remove(0); } // Create regular expression objects for "select" and the value of the selected option of the main select box as class names var pattern1 = /( |^)(select)( |$)/; var pattern2 = new RegExp("( |^)(" + sel1.options[sel1.selectedIndex].value + ")( |$)"); // Iterate through all cloned options for (var i = 0; i < clonedOptions.length; i++) { // If the classname of a cloned option either equals "select" or equals the value of the selected option of the main select box if (clonedOptions[i].className.match(pattern1) || clonedOptions[i].className.match(pattern2)) { // Clone the option from the hidden option pool and append it to the dynamic select box sel2.appendChild(clonedOptions[i].cloneNode(true)); } } } Thanks so much for any assistance

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• Performance of stored proc when updating columns selectively based on parameters?

  - by kprobst

  I'm trying to figure out if this is relatively well-performing T-SQL (this is SQL Server 2008). I need to create a stored procedure that updates a table. The proc accepts as many parameters as there are columns in the table, and with the exception of the PK column, they all default to NULL. The body of the procedure looks like this: CREATE PROCEDURE proc_repo_update @object_id bigint ,@object_name varchar(50) = NULL ,@object_type char(2) = NULL ,@object_weight int = NULL ,@owner_id int = NULL -- ...etc AS BEGIN update object_repo set object_name = ISNULL(@object_name, object_name) ,object_type = ISNULL(@object_type, object_type) ,object_weight = ISNULL(@object_weight, object_weight) ,owner_id = ISNULL(@owner_id, owner_id) -- ...etc where object_id = @object_id return @@ROWCOUNT END So basically: Update a column only if its corresponding parameter was provided, and leave the rest alone. This works well enough, but as the ISNULL call will return the value of the column if the received parameter was null, will SQL Server optimize this somehow? This might be a performance bottleneck on the application where the table might be updated heavily (insertion will be uncommon so the performance there is not a problem). So I'm trying to figure out what's the best way to do this. Is there a way to condition the column expressions with something like CASE WHEN or something? The table will be indexed up the wazoo as well for read performance. Is this the best approach? My alternative at this point is to create the UPDATE expression in code (e.g. inline SQL) and execute it against the server. This would solve my doubts about performance, but I'd rather leave this in a stored proc if possible.

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• Progressbar behaves strangely

  - by wanderameise

  I just created an application in C# that uses a thread which polls the UART for a receive event. If data is received an event is triggered in my main thread (GUI) and a progress bar is controlled via PerformStep() method (of course, I previously set the Max value accordingly). PerformStep is invoked using the following expression to handle cross threading this.Invoke((Action)delegate{progressBar2.PerformStep();}) When running this application the progressbar never hits its final value. It stops at 80%. When debugging and stopping at the line mentioned above, everything works fine using single steps. I have no idea what is going one! Start read thread on main thread: pThreadWrite = new Thread(new ThreadStart(ReadThread)); pThreadWrite.Start(); Read Thread: private void ReadThread() { while(1) { if (ReceiveEvent) { FlashProgressBar(); } } } Event that is triggered in main thread: private void FlashProgressBar() { this.Invoke((Action)delegate { progressBar2.PerformStep();}); } (It's a simplified representation of my code) It seems as if the internal progress is faster than the visual one.

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• Spring annotation-based container configuration context:include & exclude filters

  - by lisak

  Hey, first off I point to the similar question. I spent more than an hour to set this up, but PathMatchingResourcePatternResolver still scans everything. I have one common.xml (that is imported from specific.xml) and a specific.xml bean definition file. The context is loaded from specific.xml. In common.xml there is this element: <context:component-scan base-package="cz.instance.transl"> <context:exclude-filter type="aspectj" expression="cz.instance.transl.model..* &amp;&amp; cz.instance.transl.service..* &amp;&amp; cz.instance.transl.hooks..*"/> </context:component-scan> Where classes in packages like cz.instance.transl.service.* should not be subject of scanning, but everything else in here cz.instance.transl.* should be scanned through. But PathMatchingResourcePatternResolver marks everything as matching resources. It is the same with regex. BTW: in xml style configuration, one can have many components that share a common.xml beans via "import resource" when loading context. How this is done when Annotation-based container configuration is used ?

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• How to remove words based on a word count

  - by Chris

  Here is what I'm trying to accomplish. I have an object coming back from the database with a string description. This description can be up to 1000 characters long, but we only want to display a short view of this. So I coded up the following, but I'm having trouble in actually removing the number of words after the regular expression finds the total count of words. Does anyone have good way of dispalying the words which are less than the Regex.Matches? Thanks! if (!string.IsNullOrEmpty(myObject.Description)) { string original = myObject.Description; MatchCollection wordColl = Regex.Matches(original, @"[\S]+"); if (wordColl.Count < 70) // 70 words? { uxDescriptionDisplay.Text = string.Format("<p>{0}</p>", myObject.Description); } else { string shortendText = original.Remove(200); // 200 characters? uxDescriptionDisplay.Text = string.Format("<p>{0}</p>", shortendText); } }

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• capture text, including tags from string, and then reorder tags with text

  - by Brian

  I have the following text: abcdef<CONVERSION>abcabcabcabc<2007-01-12><name1><2007-01-12>abcabcabcabc<name2><2007-01-11>abcabcabcabc<name3><2007-02-12>abcabcabcabc<name4>abcabcabcabc<2007-03-12><name5><date>abcabcabcabc<name6> I need to use regular expressions in order to clean the above text: The basic extraction rule is: <2007-01-12>abcabcabcabc<name2> I have no problem extracting this pattern. My issue is that within th text I have malformed sequences: If the text doesn't start with a date, and end with a name my extraction fails. For example, the text above may have several mal formed sequences, such as: abcabcabcabc<2007-01-12><name1> Should be: <2007-01-12>abcabcabcabc<name1> Is it possible to have a regular expression that would clean the above, prior to extracting my consistent pattern. In short, i need to find all mal formed patterns, and then take the date tag and put it in front of it, as provided in the example above. Thanks.

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• Project Naming Convention Feedback Please

  - by Sam Striano

  I am creating a ASP.NET MVC 3 application using Entity Framework 4. I am using the Repository/Service Pattern and was looking for feedback. I currently have the following: MVC Application (GTG.dll) GTG GTG.Controllers GTG.ViewModels Business POCO's (GTG.Business.dll) This contains all business objects (Customer, Order, Invoice, etc...) EF Model/Repositories (GTG.Data.dll) GTG.Business (GTG.Context.tt) I used the Entity POCO Generator Templates. GTG.Data.Repositories Service Layer (GTG.Data.Services.dll) GTG.Data.Services - Contains all of the service objects, one per aggregate root. The following is a little sample code: Controller Namespace Controllers Public Class HomeController Inherits System.Web.Mvc.Controller Function Index() As ActionResult Return View(New Models.HomeViewModel) End Function End Class End Namespace Model Namespace Models Public Class HomeViewModel Private _Service As CustomerService Public Property Customers As List(Of Customer) Public Sub New() _Service = New CustomerService _Customers = _Service.GetCustomersByBusinessName("Striano") End Sub End Class End Namespace Service Public Class CustomerService Private _Repository As ICustomerRepository Public Sub New() _Repository = New CustomerRepository End Sub Function GetCustomerByID(ByVal ID As Integer) As Customer Return _Repository.GetByID(ID) End Function Function GetCustomersByBusinessName(ByVal Name As String) As List(Of Customer) Return _Repository.Query(Function(x) x.CompanyName.StartsWith(Name)).ToList End Function End Class Repository Namespace Data.Repositories Public Class CustomerRepository Implements ICustomerRepository Public Sub Add(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Add End Sub Public Sub Delete(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Delete End Sub Public Function GetByID(ByVal ID As Integer) As Business.Customer Implements IRepository(Of Business.Customer).GetByID Using db As New GTGContainer Return db.Customers.FirstOrDefault(Function(x) x.ID = ID) End Using End Function Public Function Query(ByVal Predicate As System.Linq.Expressions.Expression(Of System.Func(Of Business.Customer, Boolean))) As System.Linq.IQueryable(Of Business.Customer) Implements IRepository(Of Business.Customer).Query Using db As New GTGContainer Return db.Customers.Where(Predicate) End Using End Function Public Sub Save(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Save End Sub End Class End Namespace

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• Problem Binding to a Brush Property in WPF

  - by Krisc

  Working in WPF, writing a custom user control. I am trying to change the background property of the Border element when I change the value of a property of the class. Right now I am working on simply binding it to a DP, though if there is a better way I am open to suggestions. Here is the XAML for the UserControl <UserControl x:Class="MyProject.MyControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:js="clr-namespace:MyProject" mc:Ignorable="d" x:Name="MyControlRootLayout" Background="Transparent" d:DesignHeight="300" d:DesignWidth="300" Cursor="Hand"> <Border x:Name="RootBorder" Background="{Binding Path=CoreBackground, ElementName=MyControlRootLayout}" > </Border> </UserControl> And the code... public partial class MyControl : UserControl { public static DependencyProperty IsSelectedProperty = DependencyProperty.Register("IsSelected", typeof(bool), typeof(MyControl)); public static DependencyProperty CoreBackgroundProperty = DependencyProperty.Register("CoreBackground", typeof(Brush), typeof(MyControl)); public MyControl() { CoreBackground = new SolidColorBrush(Color.FromArgb(0, 255, 245, 104)); InitializeComponent(); Margin = new Thickness(5); } public Brush CoreBackground { get { return (Brush)GetValue(CoreBackgroundProperty); } set { SetValue(CoreBackgroundProperty, value); } } public bool IsSelected { get { return (bool)GetValue(IsSelectedProperty); } private set { SetValue(IsSelectedProperty, value); } } } Instead, the background comes out as transparent.

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• How to read pair in freemarker

  - by Lukasz Rys

  Ok i'm having little trouble with reading pair. So I'm creating my pair private Pair<Integer, Integer> count(somethink) { int c1 = 2; int c2 = 4; return new Pair<Integer, Integer>(c1, c2); } And 'sending' it to ftl via java mv.addObject("counted", count(somethink)); I won't write everythink how it sends because I dont think it really matters with my issue. So i'm recieving it in "ftl". Then i was trying to 'read' it <#list counted?keys as key> <a href="#offerOrderTab"><@spring.message "someMsg"/>(${key}/${counted[key]})</a> </#list> After then i'm getting error Expecting a string, date or number here, Expression x is instead a freemarker.ext.beans.SimpleMethodModel As i suppose you dont iterate pairs (or I'm wrong?) i know its pair that contains only one key and one value but still i have to do send it that way and I thought its goin be to similar to iterating through map, in java i would use pair.first() and pair.second() but it doesn't work in ftl (ye i know it shouldnt work). I also tried to cast it to String by using ?string but it didnt work too

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• C# Linq Select Problem in Method Chain.

  - by Gnought

  Note that the _src inherit IQueryable<U> and V inherit new(); I wrote the following statement, there is no syntax error. IQueryable<V> a = from s in _src where (s.Right - 1 == s.Left) select new V(); But if i re-wrote it as follows, the Visual Studio editor complains an error in the "Select" IQueryable<V> d = _src.Where(s => s.Right - 1 == s.Left).Select(s=> new V()); The Error is: The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly. Candidates are: System.Collections.Generic.IEnumerable<V> Select<U,V>(this System.Collections.Generic.IEnumerable<U>, System.Func<U,V>) (in class Enumerable) System.Linq.IQueryable<V> Select<U,V>(this System.Linq.IQueryable<U>, System.Linq.Expressions.Expression<System.Func<U,V>>) (in class Queryable) Could anyone explain this phenomenon, and what the solution is to fix the error?

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• NSRegularExpression for stripping HTML Tag

  - by Prazi

  I am developing a ebook reader app. I have the .ePUB file for the entire ebook where in each topic of the ebook is a html file. I want to implement the search functionality in the app. I am using NSRegularExpression class for searching. Please consider the following html code: <temp> I am temp in tempo with temptation </temp> Say for example in the above html code I just want to search for the word temp. Now in above code temp is appearing 5 times - <temp> </temp> temp tempo temptation. I am looking for a regular expression where I can only extract the whole word "temp". I don't want to consider the word temp in the html tags <temp> </temp>. I also don't want the word tempo and temptation to be considered. Thanks in advance

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• Mono Develop 2.4.1 + linq error.

  - by Nev_Rahd

  I just started to learn Mono Develop Installed Mono Develop 2.4.1 and trial version of Mono Touch. my Code: using System; using System.Xml.Linq; using System.Collections.Generic; namespace RSSReader { public static class RSSRepository { public static IList<FeedItem> GetFeeds(string url) { XDocument rssFeed = XDocument.Load(url); Console.Write(rssFeed.ToString()); var feeds = new List<FeedItem>(); try { var query = from item in rssFeed.Descendants("item") select new FeedItem { Title = item.Element("title").Value, Published = DateTime.Parse(item.Element("pubDate").Value), Url = item.Element("link").Value }; feeds = query.ToList(); } catch (Exception ex){ Console.WriteLine(ex.Message); } return feeds; } } } This is throwing an error: An implementation of 'select' query expression pattern could not be found. Are you missing 'System.linq' using directive or 'System.Core.dll' assembly reference? I got both references to System.Xml.Linq and System.Core What am i missing ?

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• Determining presence of prototype with correct return type

  - by R..

  Here's a random problem in C black magic I just came up with: Write a function that returns 1 if malloc has been prototyped to return a pointer type and 0 if malloc has a return type of int (either implicitly or due to wrong prototype), without invoking any implementation-defined or undefined behavior. I believe it's solvable, but I haven't worked out the solution. Note that calling the function cannot be necessary and in fact is not possible since calling a function with the incorrect prototype is undefined behavior. I have some ideas for ingredients but I think it makes for a better puzzle (and possibly more diverse ideas) if I leave them out for now. I don't need the solution for any immediate use, but it could be handy in configure scripts and such. Update: A better example of the usefulness (with strdup instead of malloc): #undef strdup #define strdup(x) (strdup_has_proto ? strdup((x)) : my_strdup((x))) i.e. being able to implement X_has_proto as an expression at the source level could be a portable way to use functions which a system might or might not have, and fall back on a local replacement, without needing any separate configure step.

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• in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

  - by Steve

  Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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• How to evaluate json member using variable ?

  - by Miftah

  Hi i've got a problem evaluating json. My goal is to insert json member value to a function variable, take a look at this function func_load_session(svar){ var id = ''; $.getJSON('data/session.php?load='+svar, function(json){ eval('id = json.'+svar); }); return id; } this code i load session from php file that i've store beforehand. i store that session variable using dynamic var. <?php /* * format ?var=[nama_var]&val=[nilai_nama_var] */ $var = $_GET['var']; $val = $_GET['val']; $load = $_GET['load']; session_start(); if($var){ $_SESSION["$var"] = $val; echo "Store SESSION[\"$var\"] = '".$_SESSION["$var"]."'"; }else if($load){ echo $_SESSION["$load"]; } ?> using firebug, i get expected response but i also received error uncaught exception: Syntax error, unrecognized expression: ) pointing at this eval('id = json.'+svar); i wonder how to solve this

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• SQL aggregate query question

  - by Phil

  Hi, Can anyone help me with a SQL query in Apache Derby SQL to get a "simple" count. Given a table ABC that looks like this... id a b c 1 1 1 1 2 1 1 2 3 2 1 3 4 2 1 1 ** 5 2 1 2 ** ** 6 2 2 1 ** 7 3 1 2 8 3 1 3 9 3 1 1 How can I write a query to get a count of how may distinct values of 'a' have both (b=1 and c=2) AND (b=2 and c=1) to get the correct result of 1. (the two rows marked match the criteria and both have a value of a=2, there is only 1 distinct value of a in this table that match the criteria) The tricky bit is that (b=1 and c=2) AND (b=2 and c=1) are obviously mutually exclusive when applied to a single row. .. so how do I apply that expression across multiple rows of distinct values for a? These queries are wrong but to illustrate what I'm trying to do... "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 AND b=2 AND c=1 ..." .. (0) no go as mutually exclusive "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 OR b=2 AND c=1 ..." .. (3) gets me the wrong result. SELECT COUNT(a) (CASE WHEN b=1 AND c=10 THEN 1 END) FROM ABC WHERE b=2 AND c=1 .. (0) no go as mutually exclusive Cheers, Phil.

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• Coding the R-ight way - avoiding the for loop

  - by mropa

  I am going through one of my .R files and by cleaning it up a little bit I am trying to get more familiar with writing the code the r-ight way. As a beginner, one of my favorite starting points is to get rid of the for() loops and try to transform the expression into a functional programming form. So here is the scenario: I am assembling a bunch of data.frames into a list for later usage. dataList <- list (dataA, dataB, dataC, dataD, dataE ) Now I like to take a look at each data.frame's column names and substitute certain character strings. Eg I like to substitute each "foo" and "bar" with "baz". At the moment I am getting the job done with a for() loop which looks a bit awkward. colnames(dataList[[1]]) [1] "foo" "code" "lp15" "bar" "lh15" colnames(dataList[[2]]) [1] "a" "code" "lp50" "ls50" "foo" matchVec <- c("foo", "bar") for (i in seq(dataList)) { for (j in seq(matchVec)) { colnames (dataList[[i]])[grep(pattern=matchVec[j], x=colnames (dataList[[i]]))] <- c("baz") } } Since I am working here with a list I thought about the lapply function. My attempts handling the job with the lapply function all seem to look alright but only at first sight. If I write f <- function(i, xList) { gsub(pattern=c("foo"), replacement=c("baz"), x=colnames(xList[[i]])) } lapply(seq(dataList), f, xList=dataList) the last line prints out almost what I am looking for. However, if i take another look at the actual names of the data.frames in dataList: lapply (dataList, colnames) I see that no changes have been made to the initial character strings. So how can I rewrite the for() loop and transform it into a functional programming form? And how do I substitute both strings, "foo" and "bar", in an efficient way? Since the gsub() function takes as its pattern argument only a character vector of length one.

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