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  • Type-conditional controls in Haskell

    - by estanford
    I'm going through the 99 Haskell problems to build my proficiency with the language. On problem 7 ("Flatten a nested list structure"), I found myself wanting to define a conditional behavior based on the type of argument passed to a function. That is, since *Main> :t 1 1 :: (Num t) => t *Main> :t [1,2] [1,2] :: (Num t) => [t] *Main> :t [[1],[2]] [[1],[2]] :: (Num t) => [[t]] (i.e. lists nested at different levels have different data types) it seems like I should be able to write a function that can read the type of the argument, and then behave accordingly. My first attempt was along these lines: listflatten l = do if (:t l) /= ((Num t) => [t]) then listflatten (foldl (++) [] l) else id l But when I try to do that, Haskell returns a parse error. Is Haskell flexible enough to allow this sort of type manipulation, do I need to find another way?

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  • best practice for boolean REST results

    - by Andrew Patterson
    I have a resource /system/resource And I wish to ask the system a boolean question about the resource that can't be answered by processing on the client (i.e I can't just GET the resource and look through the actual resource data - it requires some processing on the backend using data not available to the client). eg /system/resource/related/otherresourcename I want this is either return true or false. Does anyone have any best practice examples for this type of interaction? Possibilities that come to my mind: use of HTTP status code, no returned body (smells wrong) return plain text string (True, False, 1, 0) - Not sure what string values are appropriate to use, and furthermore this seems to be ignoring the Accept media type and always returning plain text come up with a boolean object for each of my support media types and return the appropriate type (a JSON document with a single boolean result, an XML document with a single boolean field). However this seems unwieldy. I don't particularly want to get into a long discussion about the true meaning of a RESTful system etc - I have used the word REST in the title because it best expresses the general flavour of system I am designing (even if perhaps I am tending more towards RPC over the web rather than true REST). However, if someone has some thoughts on how a true RESTful system avoids this problem entirely I would be happy to hear them.

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  • How to determine the data type of a CvMat

    - by Chris
    When using the CvMat type, the type of data is crucial to keeping your program running. For example, depending on whether your data is type float or unsigned char, you would choose one of these two commands: cvmGet(mat, row, col); cvGetReal2D(mat, row, col); Is there a universal approach to this? If the wrong data type matrix is passed to these calls, they crash at runtime. This is becoming an issue, since a function I have defined is getting passed several different types of matrices. How do you determine the data type of a matrix so you can always access its data? I tried using the "type()" function as such. CvMat* tmp_ptr = cvCreateMat(t_height,t_width,CV_8U); std::cout << "type = " << tmp_ptr->type() << std::endl; This does not compile, saying "term does not evaluate to a function taking 0 arguments". If I remove the brackets after the word type, I get a type of 1111638032 EDIT minimal application that reproduces this... int main( int argc, char** argv ) { CvMat *tmp2 = cvCreateMat(10,10, CV_32FC1); std::cout << "tmp2 type = " << tmp2->type << " and CV_32FC1 = " << CV_32FC1 << " and " << (tmp2->type == CV_32FC1) << std::endl; } Output: tmp2 type = 1111638021 and CV_32FC1 = 5 and 0

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  • i m trying to return list<object> from webmethod but gives error

    - by girish
    System.InvalidOperationException: There was an error generating the XML document. --- System.InvalidOperationException: The type WebService.Property.Property_Users was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically. at System.Xml.Serialization.XmlSerializationWriter.WriteTypedPrimitive(String name, String ns, Object o, Boolean xsiType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write1_Object(String n, String ns, Object o, Boolean isNullable, Boolean needType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write8_ArrayOfAnyType(Object o) at Microsoft.Xml.Serialization.GeneratedAssembly.ListOfObjectSerializer.Serialize(Object objectToSerialize, XmlSerializationWriter writer) at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id) --- End of inner exception stack trace --- at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id) at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o, XmlSerializerNamespaces namespaces) at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o) at System.Web.Services.Protocols.XmlReturnWriter.Write(HttpResponse response, Stream outputStream, Object returnValue) at System.Web.Services.Protocols.HttpServerProtocol.WriteReturns(Object[] returnValues, Stream outputStream) at System.Web.Services.Protocols.WebServiceHandler.WriteReturns(Object[] returnValues) at System.Web.Services.Protocols.WebServiceHandler.Invoke() public List<object> GetDataByModuleName(string ModuleName) { List<Property_Users> obj_UserList = new List<Property_Users>(); // performing some operation that add data to obj_UserList List < Object > myList = new List<object>(); return ConvertToObjectList<Property_Users>(obj_UserList); } public List<Object> ConvertToObjectList<N>(List<N> sourceList) { List<Object> result = new List<Object>(); foreach (N item in sourceList) { result.Add(item as Object); } return result; } [WebMethod] public List<object> GetDataByModuleName(string ModuleName) { List<object> obj_list = new List<object>(); obj_list = BAL_GeneralService.GetDataByModuleName(ModuleName); return obj_list; }

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  • Should i use a trigger or Behaviors for this?

    - by Michael
    I have an abstract object called Applicant and two different types of objects that inherit from Applicant called Business and Individual. So I have three classes that look like this: public abstract class Applicant { ... } public class Individual : Applicant { ... } public class Business : Applicant { ... } Now in the DataGrid I want to show all the details of Applicant object. When you choose a row I want to show details of either the business or individual as a internal grid. Something like this <DataGrid> <DataGrid.Columns> <!--Show different columns --> </DataGrid.Columns> <DataGrid.RowDetailsTemplate> <!--Show if Individual --> <DataGrid> <DataGrid.Columns> <DataGridTextColumn Header="First Name" ... /> <DataGridTextColumn Header="Last Name" ... /> </DataGrid.Columns> </DataGrid> <!--Show if business --> <DataGrid> <DataGrid.Columns> <DataGridTextColumn Header="Business Name" ... /> <DataGridTextColumn Header="Tax id" ... /> </DataGrid.Columns> </DataGrid> </DataGrid.RowDetailsTemplate> </DataGrid> Now I'm not sure if I need to use a Triggers or Behaviors to accomplish this? Thanks for everyones help! FYI I'm using Silverlight 4.0 with Prism.

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  • Resolving Circular References for Objects Implementing ISerializable

    - by Chris
    I'm writing my own IFormatter implementation and I cannot think of a way to resolve circular references between two types that both implement ISerializable. Here's the usual pattern: [Serializable] class Foo : ISerializable { private Bar m_bar; public Foo(Bar bar) { m_bar = bar; m_bar.Foo = this; } public Bar Bar { get { return m_bar; } } protected Foo(SerializationInfo info, StreamingContext context) { m_bar = (Bar)info.GetValue("1", typeof(Bar)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_bar); } } [Serializable] class Bar : ISerializable { private Foo m_foo; public Foo Foo { get { return m_foo; } set { m_foo = value; } } public Bar() { } protected Bar(SerializationInfo info, StreamingContext context) { m_foo = (Foo)info.GetValue("1", typeof(Foo)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_foo); } } I then do this: Bar b = new Bar(); Foo f = new Foo(b); bool equal = ReferenceEquals(b, b.Foo.Bar); // true // Serialise and deserialise b equal = ReferenceEquals(b, b.Foo.Bar); If I use an out-of-the-box BinaryFormatter to serialise and deserialise b, the above test for reference-equality returns true as one would expect. But I cannot conceive of a way to achieve this in my custom IFormatter. In a non-ISerializable situation I can simply revisit "pending" object fields using reflection once the target references have been resolved. But for objects implementing ISerializable it is not possible to inject new data using SerializationInfo. Can anyone point me in the right direction?

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  • How to add and relate a node within the parent nodes add form in Drupal.

    - by Espen Christensen
    Hi, I want to accomplish the following scenario in Drupal: You have 2 content-types. Lets say, an application-form for a lisence, and a content-type for persons. Then when you go to add a lisence in the "node/add" submission form in Drupal, i would like to add a relative number of persons that would be related to this lisence, and only this lisence. Say you would like to apply for a lisence, and relate 4 persons to this lisence, then insted of creating the lisence and then create the 4 persons and relate them to the lisence, i would like to do this "inline". So when i add a lisence, there would be a way to add 1 or more persons that would relate to the lisence node. Is this possible, and if so how? I have been looking at the node reference module, and that manages to reference a node to another, but not to add them inline with the other. With the web-development framework Django, there is a way to this with something called "inline-editing", where you get the content-type fields inside another content-type creation form. There you bind them togheter with a ForeignKey. Anybody know of something simular in Drupal, if not, is it another way to achive something simular, that would be as user-friendly?

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  • Date formats in ActiveRecord / Rails 3

    - by cbmeeks
    In my model, I have a departure_date and a return_date. I am using a text_field instead of the date_select so that I can use the JQuery datepicker. My app is based in the US for now but I do hope to get international members. So basically this is what is happening. The user (US) types in a date such as 04/01/2010 (April 1st). Of course, MySQL stores it as a datetime such as 2010-04-01... Anyway, when the user goes to edit the date later on, it shows "01/04/2010" because I am using a strftime("%m/%d/%Y) which doesn't make sense....so it thinks it is January 4th instead of the original April 1st. It's like the only way to accurately store the data is for the user to type in: 2010-04-01 I hope all of this makes sense. What I am really after is a way for the user to type in (or use the datepicker) a date in their native format. So someone in Europe could type in 01/04/2010 for April 1st but someone in the US would type in 04/01/2010. Is there an easy, elegant solution to this? Thanks for any suggestions.

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  • Custom listbox sorting

    - by Arcadian
    I need to sort the data contained within a number of listboxes. The user will be able to select between two different types of sorting using radio boxes, one of which is checked by default on form load. I have created the IF statements needed in order to test whether the checked condition is true for that radio button. but i need some help to create the custom sort algorithms. Each list with contain similar looking data, the only difference in the prefix with which each line starts. For example each line in the first listbox starts with the prefix "G30" and the second listbox will be "G31" and so on. There are 10 listboxes in total (G30-G39 in terms of prefixes). The first search algorithm has to sort the lines by the number order of the first 13 chars. Example: This is how the data looks before sorting G35:45:58:11 JG07 G35:45:20:41 JG01 G35:58:20:21 JG03 G35:66:22:20 JG05 G35:45:85:21 JG02 G35:64:56:11 JG03 G35:76:35:11 JG02 G35:77:97:12 JG03 G35:54:29:11 JG01 G35:55:51:20 JG01 G35:76:24:20 JG06 G35:76:55:11 JG01 and this is how it should look after sorting G35:45:20:41 JG01 G35:45:58:11 JG07 G35:45:85:21 JG02 G35:54:29:11 JG01 G35:55:51:20 JG01 G35:58:20:21 JG03 G35:64:56:11 JG03 G35:66:22:20 JG05 G35:76:24:20 JG06 G35:76:35:11 JG02 G35:76:55:11 JG01 G35:77:97:12 JG03 as you can see, the prefixes are the same. so it is sorted, lowest first, by the next pair integers, then the next pair and the next but not by the value after "JG". the second sort algorithm will ignore the first 13 chars and sort by order of the value after "JG", highest first. any help? theres some rep in it for you :) thanks in advance

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  • Facebook IOS SDK: Error in Publish Story Dialog

    - by lividsquirrel
    I've successfully set up the "DemoApp" project from the Facebook IOS SDK to use my "OKC ThunderCast" Facebook application. I have also configured another "Tester" application from scratch to successfully use the Facebook SDK and publish stories to my news feed. However, in my production application, I always get this result when calling the "dialog" method. The full description of the error message is "Error on line 52 at column 17: Opening and ending tag mismatch: div line 0 and body" Here's a detailed walkthrough of all of my code to make sure nothing is missed. 1) A UIViewController calls the "authorize" method NSArray *fbPerms = [NSArray arrayWithObjects:@"read_stream", @"offline_access", nil]; [[FacebookSingleton sharedInstance].facebook authorize:fbPerms delegate:self]; Note: The FacebookSingleton is a class I wrote that always returns a single instance of the "Facebook" class. I am using it successfully in other applications. 2) Safari is opened and the user is successfully authenticated and authorized 3) The application is called back and the "handleOpenUrl" method is called, which calls the "fbDidLogin" method of the UIViewController - (BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url { Facebook *fb = [FacebookSingleton sharedInstance].facebook; return [fb handleOpenURL:url]; } 4) The same UIViewController handles the "fbDidLogin" event, and calls the "dialog" method - (void)fbDidLogin { [[FacebookSingleton sharedInstance].facebook dialog:@"feed" andDelegate:self]; } I also have the necessary "URL Schemes" and "URL Types" entries in the .plist file. To my eyes, I am using exactly the same code in the "DemoApp", "Tester", and production applications. But while the DemoApp and Tester work, I always see this HTML error in the feed dialog in my production application. Has anyone seen a similar issue? Could it be related to the Facebook "Bundle ID" setting in the Facebook application settings? Is there some build or .plist setting that is different? I have invested a great deal of time into troubleshooting with no success in several weeks. Thanks in advance...

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  • What data structure to use / data persistence

    - by Dave
    I have an app where I need one table of information with the following fields: field 1 - int or char field 2 - string (max 10 char) field 3 - string (max 20 char) field 4 - float I need the program to filter on field 1 based upon a segmented control and select a field 2 from a picker. From this data I need to look up field 4 to use in a calculation. Total records will be about 200. I never see it go above 400 - 500. I am going to use a singleton which I am able to do, I just need help with the structure for this with data persistence. What type of data structure should I use for this and should I use NSNumber, NSString, etc. or old data types like float, Char, etc. I thought about a struct put into an array but there is probably a better way. This is new to me so any help or reference to examples would be great. I also thought about a plist or dictionary but it looks like it is just a lookup and a field which obviously won't work. Core data looked like overkill to me. Also, with any recommendation how should I get initial data into it? I want the user to be able to edit and add to the database. Sorry for the old terms, you can see what generation I am from... Thanks in advance!!!!

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  • emacs: x-popup-menu max size constraints?

    - by Cheeso
    I'm working on an intellisense or code-completion capability for C#. So far, so good. Right now I have basic completion working. There are 2 ways to request completion. The first cycles through all the potential matches. The second presents a popup menu of the matches. It works for types: And also for local variables: I'm confronting two problems with x-popup-menu: the popup menu can expand to consume all available screen space, when the number of choices is large. Literally it can obscure the entire screen. The silly thing is, it's scrollable. First it expands to consume all available space, then it also becomes scrollable. Is there a way I can limit the maximum size of x-popup-menu? To specify the position of the popup menu, I pass in a position, and x-popup-menu uses that as the *middle*, not the left, of the top line of the menu. Why middle? who knows. What this means is, if I specify (40 . 60) for the location of the menu, and the menu happens to be 100 pixels wide, the menu will extend beyond the left border of the emacs window. You can see this in the 2nd image above. If I knew how wide the popup would be before specifying the position, I could compensate. But I don't. Is there a workaround? Is there a way to get x-popup-menu to take its position as the LEFT rather than the middle.

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  • Password Protect for fun

    - by WaZ
    Hi there, I am working on a blog for my friend. I want to gift him the blog on his birthday. Just for some fun I want to restrict access to the blog. e.g. The website. www.myfriend.com opens with a splash screen. The screen has his picture and a question regarding him. these questions can be. If you know me.... What is my nickname? Whats my fav. sport? etc etc This restriction should not be based on the default user management offered by Wordpress and should involve a simple answer to a question which is randomly generated from list of questions once the visior gives a correct answer the page redirects to the blog please note even if the user types www.myfriend.com/blog they should be able to see it. this restriction is not a restriction in true sense but just involves some user interaction. Its just for fun but adds a bit of spice. Much appreciated. Thanks.

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  • Why don't file type filters work properly with nsIFilePicker on Mac OSX?

    - by Eric Strom
    I am running a chrome app in firefox (started with -app) with the following code to open a filepicker: var nsIFilePicker = Components.interfaces.nsIFilePicker; var fp = Components.classes["@mozilla.org/filepicker;1"] .createInstance(nsIFilePicker); fp.init(window, "Select Files", nsIFilePicker.modeOpenMultiple); fp.appendFilter("video", "*.mov; *.mpg; *.mpeg; *.avi; *.flv; *.m4v; *.mp4"); fp.appendFilter("all", "*.*"); var res = fp.show(); if (res == nsIFilePicker.returnCancel) return; var files = fp.files; var paths = []; while (files.hasMoreElements()) { var arg = files.getNext().QueryInterface( Components.interfaces.nsILocalFile ).path; paths.push(arg); } Everything seems to work fine on Windows, and the file picker itself works on OSX, but the dropdown menu to select between file types only displays in Windows. The first filter (video in this case) is in effect, but the dropdown to select the other type never shows. Is there something extra that is needed to get this working on OSX? I have tried the latest firefox (3.6) and an older one (3.0.13) and both don't show the file type dropdown on OSX.

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  • Too many false positives when using FxCop.

    - by mark
    Dear ladies and sirs. We are using FxCop and it generates too many false positives to our liking. For instance, if a private method is invoked using reflection, then this method is reported as potentially unused - understandable and we suppress this warning explicitly using the SuppressMessage attribute. However, FxCop reports the same warning for the methods invoked from that method, which we already suppressed warnings about. This is stupid and generates too much noise. There are also false reports on member variables used in these methods. Also, there are problems with generic types (I even saw something about it in MS connect). Anyway, I am wondering if anyone knows whether Microsoft is going to upgrade FxCop, because it seems to be stuck in version 1.36 for a long time. BTW, I we do not use StyleCop, because it is way too picky and we just do not have the time to examine all the zillion messages in order to suppress them all. Besides, the StyleCop report seem to augment, rather than replace FxCop. Maybe anyone can suggest a good alternative to FxCop? We are using VS2008 pro. Thanks.

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  • Virtual properties duplicated during serialization when XmlElement attribute used

    - by Laramie
    The Goal: XML serialize an object that contains a list of objects of that and its derived types. The resulting XML should not use the xsi:type attribute to describe the type, to wit the names of the serialized XML elements would be an assigned name specific to the derived type, not always that of the base class, which is the default behavior. The Attempt: After exploring IXmlSerializable and IXmlSerializable with eerie XmlSchemaProvider methods and voodoo reflection to return specialized schemas and an XmlQualifiedName over the course of days, I found I was able to use the simple [XmlElement] attribute to accomplish the goal... almost. The Problem: Overridden properties appear twice when serializing. The exception reads "The XML element 'overriddenProperty' from namespace '' is already present in the current scope. Use XML attributes to specify another XML name or namespace for the element." I attempted using a *Specified property (see code), but it didn't work. Sample Code: Class Declaration using System; using System.Collections.Generic; using System.Xml.Serialization; [XmlInclude(typeof(DerivedClass))] public class BaseClass { public BaseClass() { } [XmlAttribute("virt")] public virtual string Virtual { get; set; } [XmlIgnore] public bool VirtualSpecified { get { return (this is BaseClass); } set { } } [XmlElement(ElementName = "B", Type = typeof(BaseClass), IsNullable = false)] [XmlElement(ElementName = "D", Type = typeof(DerivedClass), IsNullable = false)] public List<BaseClass> Children { get; set; } } public class DerivedClass : BaseClass { public DerivedClass() { } [XmlAttribute("virt")] public override string Virtual { get { return "always return spackle"; } set { } } } Driver: BaseClass baseClass = new BaseClass() { Children = new List<BaseClass>() }; BaseClass baseClass2 = new BaseClass(){}; DerivedClass derivedClass1 = new DerivedClass() { Children = new List<BaseClass>() }; DerivedClass derivedClass2 = new DerivedClass() { Children = new List<BaseClass>() }; baseClass.Children.Add(derivedClass1); baseClass.Children.Add(derivedClass2); derivedClass1.Children.Add(baseClass2); I've been wrestling with this on and off for weeks and can't find the answer anywhere.

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  • 406 Not Acceptable error when using Jquery $.post in Firefox but not in Safari or Chrome

    - by jlfenaux
    I'm using Jquery (1.3.2) $.post command to trigger an ajax call to a rails server. The code works great on Safari and on Google Chrome (mac), but when I tried it on Firefox (3.5.7), I got a weird '406 Not Acceptable' error. When I look at the headers, it Firefox indicated that it accepted only ' text/javascript' responses. And the response Content-Type was 'text/html; charset=utf-8'. In Chrome the accepted types were 'application/json, text/javascript, /, text/javascript' and the response Content-Type was 'application/json; charset=utf-8'. I tried to force the content type in rails to 'text/javascript' format.json do render :json => @races.to_json, :content_type => 'text/javascript' end The content type is indeed changed in Chrome, but not in Firefox where it remains 'text/html'. Here is the code I used to trigger the ajax call. $.post( "/locator", params, function(data){...}, "json" ); Is there something I can do to make this work in Firefox? Thanks

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  • How do I show information to users belonging to different groups (web) in modx

    - by Gaurav Sharma
    Hello Everyone, I have created a website using modx evolution v1.0.2. The website that I have developed has 12 different types of users (categorized in groups). Each user will be shown a different price depending on the group to which he belongs. Till now I have been able to fetch the group name of current logged in user (created a snippet for that), but how can I achieve the above mentioned functionality so that each user should be able to see only the price that I have coded according to his group. For example: If a user is associated with the 'ocassional' group then he should be shown the price as , say, 50 bucks and if a user is associated with the 'regular' group then he should be shown the price as, say, 40 bucks I can easily do this by coding a single snippet for every product's variant, but there are a lot of variants (more than 100 and growing). I have created a resource(page) for every product and it's variant. Every variant has a price. It is this price that I want to be shown according to the logged in user group membership. I hope I am able to explain my query clearly. Please help me do this functionality. Thanks

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  • Can protobuf-net serialize this combination of interface and generic collection?

    - by tsupe
    I am trying to serialize a ItemTransaction and protobuf-net (r282) is having a problem. ItemTransaction : IEnumerable<KeyValuePair<Type, IItemCollection>></code> and ItemCollection is like this: FooCollection : ItemCollection<Foo> ItemCollection<T> : BindingList<T>, IItemCollection IItemCollection : IList<Item> where T is a derived type of Item. ItemCollection also has a property of type IItemCollection. I am serializing like this: IItemCollection itemCol = someService.Blah(...); ... SerializeWithLengthPrefix<IItemCollection>(stream, itemCol, PrefixStyle.Base128); My eventual goal is to serialize ItemTransaction, but am snagged with IItemCollection. Item and it's derived types can be [de]serialized with no issues, see [1], but deserializing an IItemCollection fails (serializing works). ItemCollection has a ItemExpression property and when deserializing protobuf can't create an abstract class. This makes sense to me, but I'm not sure how to get through it. ItemExpression<T> : ItemExpression, IItemExpression ItemExpression : Expression ItemExpression is abstract as is Expression How do I get this to work properly? Also, I am concerned that ItemTransaction will fail since the IItemCollections are going to be differing and unknown at compile time (an ItemTransaction will have FooCollection, BarCollection, FlimCollection, FlamCollection, etc). What am I missing (Marc) ? [1] http://stackoverflow.com/questions/2276104/protobuf-net-deserializing-across-assembly-boundaries

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  • WPF, C# - Making Intellisense/Autocomplete list, fastest way to filter list of strings

    - by user559548
    Hello everyone, I'm writing an Intellisense/Autocomplete like the one you find in Visual Studio. It's all fine up until when the list contains probably 2000+ items. I'm using a simple LINQ statement for doing the filtering: var filterCollection = from s in listCollection where s.FilterValue.IndexOf(currentWord, StringComparison.OrdinalIgnoreCase) >= 0 orderby s.FilterValue select s; I then assign this collection to a WPF Listbox's ItemSource, and that's the end of it, works fine. Noting that, the Listbox is also virtualised as well, so there will only be at most 7-8 visual elements in memory and in the visual tree. However the caveat right now is that, when the user types extremely fast in the richtextbox, and on every key up I execute the filtering + binding, there's this semi-race condition, or out of sync filtering, like the first key stroke's filtering could still be doing it's filtering or binding work, while the fourth key stroke is also doing the same. I know I could put in a delay before applying the filter, but I'm trying to achieve a seamless filtering much like the one in Visual Studio. I'm not sure where my problem exactly lies, so I'm also attributing it to IndexOf's string operation, or perhaps my list of string's could be optimised in some kind of index, that could speed up searching. Any suggestions of code samples are much welcomed. Thanks.

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  • C: lseek() related question.

    - by Andrei Ciobanu
    I want to write some bogus text in a file ("helloworld" text in a file called helloworld), but not starting from the beginning. I was thinking to lseek() function. If I use the following code: #include <unistd.h> #include <fcntl.h> #include <sys/stat.h> #include <sys/types.h> #include <stdlib.h> #include <stdio.h> #define fname "helloworld" #define buf_size 16 int main(){ char buffer[buf_size]; int fildes, nbytes; off_t ret; fildes = open(fname, O_CREAT | O_TRUNC | O_WRONLY, S_IRUSR | S_IWUSR); if(fildes < 0){ printf("\nCannot create file + trunc file.\n"); } //modify offset if((ret = lseek(fildes, (off_t) 10, SEEK_END)) < (off_t) 0){ fprintf(stdout, "\nCannot modify offset.\n"); } printf("ret = %d\n", (int)ret); if(write(fildes, fname, buf_size) < 0){ fprintf(stdout, "\nWrite failed.\n"); } close(fildes); return (0); } , it compiles well and it runs without any apparent errors. Still if i : cat helloworld The output is not what I expected, but: helloworld Can Where is "Can" comming from, and where are my empty spaces ? Should i expect for "zeros" instead of spaces ? If i try to open helloworld with gedit, an error occurs, complaining that the file character encoding is unknown.

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  • Inheritance of list-style-type property in Firefox (bug in Firebug?)

    - by Marcel Korpel
    Let's have a look at some comments on a page generated by Wordpress (it's not a site I maintain, I'm just wondering what's going on here). As these pages might disappear in the near future, I've put some screenshots online. Here's what I saw: Obviously, the list-item markers shouldn't be there. So I decided to look at the source using Firebug. As you can see, Firebug claims that the list-style property (containing none) is inherited from ol.commentlist. But if that's the case, why are the circle and the square visible? When checking the computed style, Firebug shows the list-style-types correctly. What's the correct behaviour? I just did a quick check in Chromium, whose Web Inspector gave a better view of reality (the list item markers were also displayed in this browser): According to WebKit, list-style of ol.commentlist isn't inherited, only the default value of list-style-type from the rendering engine. So, we may conclude that the output of both browsers is correct and that Firefox (Firebug) shows an incorrect representation of inherited styles. What does the CSS specification say? Inheritance will transfer the list-style values from OL and UL elements to LI elements. This is the recommended way to specify list style information. Not much about the inheritance of ol properties to uls. Is Firebug wrong in this respect? BTW, I managed to let the markers disappear by just changing line 312 of style.css to ol.commentlist, li.commentlist, ul.children { When also explicitly defining the list-style of ul.children to none, the markers are not painted. You can have a look at screenshots of Firebug and WebKit's Web Inspector in this case, if you like.

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  • Mixins, variadic templates, and CRTP in C++

    - by Eitan
    Here's the scenario: I'd like to have a host class that can have a variable number of mixins (not too hard with variadic templates--see for example http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.103.144). However, I'd also like the mixins to be parameterized by the host class, so that they can refer to its public types (using the CRTP idiom). The problem arises when trying to mix the too--the correct syntax is unclear to me. For example, the following code fails to compile with g++ 4.4.1: template <template<class> class... Mixins> class Host : public Mixins<Host<Mixins>>... { public: template <class... Args> Host(Args&&... args) : Mixins<Host>(std::forward<Args>(args))... {} }; template <class Host> struct Mix1 {}; template <class Host> struct Mix2 {}; typedef Host<Mix1, Mix2> TopHost; TopHost *th = new TopHost(Mix1<TopHost>(), Mix2<TopHost>()); With the error: tst.cpp: In constructor ‘Host<Mixins>::Host(Args&& ...) [with Args = Mix1<Host<Mix1, Mix2> >, Mix2<Host<Mix1, Mix2> >, Mixins = Mix1, Mix2]’: tst.cpp:33: instantiated from here tst.cpp:18: error: type ‘Mix1<Host<Mix1, Mix2> >’ is not a direct base of ‘Host<Mix1, Mix2>’ tst.cpp:18: error: type ‘Mix2<Host<Mix1, Mix2> >’ is not a direct base of ‘Host<Mix1, Mix2>’ Does anyone have successful experience mixing variadic templates with CRTP?

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  • Is it approproate it use django signals withing the same app

    - by Alex Lebedev
    Trying to add email notification to my app in the cleanest way possible. When certain fields of a model change, app should send a notification to a user. Here's my old solution: from django.contrib.auth import User class MyModel(models.Model): user = models.ForeignKey(User) field_a = models.CharField() field_b = models.CharField() def save(self, *args, **kwargs): old = self.__class__.objects.get(pk=self.pk) if self.pk else None super(MyModel, self).save(*args, **kwargs) if old and old.field_b != self.field_b: self.notify("b-changed") # Sevelar more events here # ... def notify(self, event) subj, text = self._prepare_notification(event) send_mail(subj, body, settings.DEFAULT_FROM_EMAIL, [self.user.email], fail_silently=True) This worked fine while I had one or two notification types, but after that just felt wrong to have so much code in my save() method. So, I changed code to signal-based: from django.db.models import signals def remember_old(sender, instance, **kwargs): """pre_save hanlder to save clean copy of original record into `old` attribute """ instance.old = None if instance.pk: try: instance.old = sender.objects.get(pk=instance.pk) except ObjectDoesNotExist: pass def on_mymodel_save(sender, instance, created, **kwargs): old = instance.old if old and old.field_b != instance.field_b: self.notify("b-changed") # Sevelar more events here # ... signals.pre_save.connect(remember_old, sender=MyModel, dispatch_uid="mymodel-remember-old") signals.post_save.connect(on_mymodel_save, sender=MyModel, dispatch_uid="mymodel-on-save") The benefit is that I can separate event handlers into different module, reducing size of models.py and I can enable/disable them individually. The downside is that this solution is more code and signal handlers are separated from model itself and unknowing reader can miss them altogether. So, colleagues, do you think it's worth it?

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  • Design suggestion for expression tree evaluation with time-series data

    - by Lirik
    I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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