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  • Type patterns and generic classes in Haskell

    - by finnsson
    I'm trying to understand type patterns and generic classes in Haskell but can't seem to get it. Could someone explain it in laymen's terms? In [1] I've read that "To apply functions generically to all data types, we view data types in a uniform manner: except for basic predefined types such as Float, IO, and ?, every Haskell data type can be viewed as a labeled sum of possibly labeled products." and then Unit, :*: and :+: are mentioned. Are all data types in Haskell automatically versions of the above mentioned and if so how do I figure out how a specific data type is represented in terms of :*:, etc? The users guide for generic classes (ch. 7.16) at haskell.org doesn't mention the predefined types but shouldn't they be handled in every function if the type patterns should be exhaustive? [1] Comparing Approaches to Generic Programming in Haskell, Ralf Hinze, Johan Jeuring, and Andres Löh

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  • Using C# Type as generic

    - by I Clark
    I'm trying to create a generic list from a specific Type that is retrieved from elsewhere: Type listType; // Passed in to function, could be anything var list = _service.GetAll<listType>(); However I get a build error of: The type or namespace name 'listType' could not be found (are you missing a using directive or an assembly reference?) Is this even possible or am I setting foot onto C# 4 Dynamic territory? As a background: I want to automatically load all lists with data from the repository. The code below get's passed a Form Model whose properties are iterated for any IEnum (where T inherits from DomainEntity). I want to fill the list with objects of the Type the list made of from the repository. public void LoadLists(object model) { foreach (var property in model.GetType() .GetProperties(BindingFlags.Public | BindingFlags.Instance | BindingFlags.SetProperty)) { if (IsEnumerableOfNssEntities(property.PropertyType)) { var listType = property.PropertyType.GetGenericArguments()[0]; var list = _repository.Query<listType>().ToList(); property.SetValue(model, list, null); } } }

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  • .NET generic class instance - passing a variable data type

    - by FerretallicA
    As the title suggests, I'm tyring to pass a variable data type to a template class. Something like this: frmExample = New LookupForm(Of Models.MyClass) 'Works fine Dim SelectedType As Type = InstanceOfMyClass.GetType() 'Works fine frmExample = New LookupForm(Of SelectedType) 'Ba-bow! frmExample = New LookupForm(Of InstanceOfMyClass.GetType()) 'Ba-bow! LookupForm<Models.MyClass> frmExample; Type SelectedType = InstanceOfMyClass.GetType(); frmExample = new LookupForm<SelectedType.GetType()>(); //Ba-bow frmExample = new LookupForm<(Type)SelectedType>(); //Ba-bow I'm assuming it's something to do with the template being processed at compile time but even if I'm off the mark there, it wouldn't solve my problem anyway. I can't find any relevant information on using Reflection to instance template classes either. (How) can I create an instance of a dynamically typed repository at runtime?

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  • Error loading SQL_VARIANT data type using Python

    - by Brett D
    I am using Python and SQLAlchemy to query a database that I did not create. I have run into a problem querying a table that contains the SQL_VARIANT data type. I get the error: sqlalchemy.exc.DBAPIError: (Error) ('ODBC data type -150 is not supported. Cannot read column Value.', 'HY000') I confirmed with the database creator that the "Value" column is of type SQL_VARIANT. Does anyone know a way to load this data type using Python? I am currently using mssql with pyodbc. Thank you for any help you can offer! Versions: Python 2.7, SQLAlchemy 0.7.8

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  • 'Lexical' scoping of type parameters in C#

    - by leppie
    I have 2 scenarios. This fails: class F<X> { public X X { get; set; } } error CS0102: The type 'F' already contains a definition for 'X' This works: class F<X> { class G { public X X { get; set; } } } The only logical explanation is that in the second snippet the type parameter X is out of scope, which is not true... Why should a type parameter affect my definitions in a type? IMO, for consistency, either both should work or neither should work. Any other ideas? PS: I call it 'lexical', but it probably is not not the correct term.

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  • $_POST goes empty after adding a new input type "file"

    - by heldrida
    Hi, I'm not finding a way to understand and fix this and I've done a lot. I've got a script, wish is a simple form, that sends a file trough POST. The second file, process the info. By default, I give to the user a few fields, one of them being a input field of type "file" and there's also, a few "hidden" one's, that gives me values to work with on POST. I found that, when adding a new input of type "file", the $_POST returns array 0, even $_FILES returns nothing. I have no idea how to fix this, and it works just fine when keeping the default input box of type "file". This is the form http://pastie.org/872488 This only happens when: Exists! var_dump( $_POST ), or $_FILES, print_r(), etc Returns nothing. I've tryed to create a array on the input of type "files", like img_p_child[], but nothing. How to solve this ? Thanks for taking your time!

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  • Design Patterns: What is a type

    - by contactmatt
    A very basic question, but after reading the "Design Patterns: Elements of reusable OO Software" book, I'm a little confused. The book states, "An object's type only refers to its interface-the set of request to which it can respond. An object can have many types, and objects of different classes can have the same type." Could someone please better explain what a Type is? I also don't understand how one object can have multiple types...unless the book is speaking of polymorphism....

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  • mapping Field with variable type using Hibernate Annotaion

    - by Zahra
    Hi. how can I have a field with variable type in my class? I use hibernate annotation for mapping to DB. I tried to use java.io.Serializable as field's type, but it mapped to database as a 01 amount which is true if I get it's object and cast it to it's true type. but I need to run a query on this objects that needs true amount of field.(right now I can't compare an integer field with a number) Does anyone have any idea how can I do this? Thanks in advance.

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  • I can't change HTTP request header Content-Type value using jQuery

    - by Matt
    Hi I tried to override HTTP request header content by using jQuery's AJAX function. It looks like this $.ajax({ type : "POST", url : url, data : data, contentType: "application/x-www-form-urlencoded;charset=big5", beforeSend: function(xhr) { xhr.setRequestHeader("Accept-Charset","big5"); xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=big5"); }, success: function(rs) { target.html(rs); } }); Content-Type header is default to "application/x-www-form-urlencoded; charset=UTF-8", but it obviously I can't override its value no matter I use 'contentType' or 'beforeSend' approaches. Could anyone adivse me a hint that how do I or can I change the HTTP request's content-type value? thanks a lot. btw, is there any good documentation that I can study JavaScript's XMLHttpRequest's encoding handling?

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  • Type or namespace name could not be found

    - by Pandiya Chendur
    I use this: public IQueryable<MaterialsView> FindAllMaterials() { var materials = from m in db.Materials join Mt in db.MeasurementTypes on m.MeasurementTypeId equals Mt.Id select new MaterialsView { MatId = m.Mat_Name, MesName = Mt.Name, MesType = m.Mat_Type }; return materials; } It gives me the following errors: The type or namespace name MaterialsView could not be found (are you missing a using directive or an assembly reference?) Cannot implicitly convert type System.Collections.Generic.IEnumerable<MaterialsView> to System.Linq.IQueryable<MaterialsView>. An explicit conversion exists (are you missing a cast?) The type arguments for method System.Linq.Enumerable.ToList<TSource>(System.Collections.Generic.IEnumerable<TSource>) cannot be inferred from the usage. Try specifying the type arguments explicitly. I have googled it and found this SO question but it doesn't help. What's wrong?

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  • How to display formated Calendar type in JSTL?

    - by maectpo
    Hi, I am using Calendar type in Java and I would like to display formated date in jstl. I was trying: <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %> <fmt:parseDate var="date" type="date" dateStyle="short" value="${photo.dateCreated}" /> <c:out value="${data}" /> But it doesn't work: java.text.ParseException: Unparseable date Can JSP format "Calendar" type?

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  • Apache Content negotiation returns wrong Content-Type with Mulitviews :(

    - by edbras
    I am using Apache webserver 2.2 with Content Negotiation through Multiviews. I have: <Directory /home/develop/web/prodBuild> Options +MultiViews AddEncoding x-gzip .gz </Directory> This directory contains the gzip files. So if a browser requests the file bla.js, the server will return the file bla.js.gz as the file bla.js doesn't exists. However, the Content-Type on my Ubuntu server is set to be "application/x-gzip" which is wrong as it's a javascript file, so is has be "application/javascript" I have this working on my local Windows Apache server, but don't seem to get it working on the remote Ubuntu server. :(... NO idea why... Who/why is it setting this wrong Content-Type ? BTW: I don't have this line "AddType application/x-gzip .gz .tgz" somwhere in my config, as then I understand why it goes wrong. My workaround: add the following line under the above "AddEncoding": AddType "" .gz It will then set an empty string as Content-Type and then it works.. I think that the browser will try to discover the content type itself... I hope somebody can explain to me why this is not working and why this content type is set ? :(

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  • How to implement table-per-concrete-type strategy using entity framework

    - by SDReyes
    Hello Guys! I'm mapping a set of tables that share a common set of fields: So as you can see I'm using a table-per-concrete-type strategy to map the inheritance. But... I have not could to relate them to an abstract type containing these common properties. It's possible to do it using EF? BONUS: The only non documented Entity Data Model Mapping Scenario is Table-per-concrete-type inheritance http://msdn.microsoft.com/en-us/library/cc716779.aspx : P

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  • Java method get the inheriting type

    - by DrDro
    I have several classes that extend C and I would need a method that accepts any argument of type C. But in this method I would like to know if I'm dealing with A or B. * public A extends C public B extends C public void goForIt(C c)() If I cast how can I retrieve the type in a clean way (I just read using getClass or instanceof is often not the best way). PS: Fell free to edit an explicit title. *Sorry but I can't type closing braces

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  • Help System.Web.Compilation.BuildManager find a type in a non-referenced assembly

    - by asbjornu
    I'm trying to write a plug-in system where assemblies can be dropped in a folder that ASP.NET has no knowledge about. This plug-in system works fine for ASP.NET MVC based assemblies, but for old-school WebForm assemblies (where the .aspx files Inherits the System.Web.UI.Page derived classes) System.Web.Compilation.BuildManager is responsible for compiling the .aspx file into a dynamic assembly. My problem is that the BuildManager knows nothing about the assemblies within my plug-in folder and it seems to be absolutely nothing I can do to help it. If I do: BuildManager.GetType("Type.Defined.In.Plugin.Assembly", true, true) it throws. If I first get a reference to the Type and then try: var instance = BuildManager.CreateInstanceFromVirtualPath(path, type); it still throws, even though I've now passed in the specific type it needs to compile the .aspx file. Is there anything I can do to help BuildManager find the types it needs to compile the .aspx file?

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  • Using a Type object to create a generic

    - by Richard Neil Ilagan
    Hello all! I'm trying to create an instance of a generic class using a Type object. Basically, I'll have a collection of objects of varying types at runtime, and since there's no way for sure to know what types they exactly will be, I'm thinking that I'll have to use Reflection. I was working on something like: Type elType = Type.GetType(obj); Type genType = typeof(GenericType<>).MakeGenericType(elType); object obj = Activator.CreateInstance(genType); Which is well and good. ^_^ The problem is, I'd like to access a method of my GenericType< instance, which I can't because it's typed as an object class. I can't find a way to cast it obj into the specific GenericType<, because that was the problem in the first place (i.e., I just can't put in something like:) ((GenericType<elType>)obj).MyMethod(); How should one go about tackling this problem? Many thanks! ^_^

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  • C++ Function Template With Flexible Return Type

    - by Ignatius Reza
    Let's say that we have a function like so template <class T, class T2> T getMin(T a, T2 b) { if(a < b) return a; return b; } if we call the function like so int a, b; long c; a = getMin(b, c); if c is < a, then the value of c will be type casted to int. Is it possible to make the return type flexible so that it would return an int, or long, or any other type considered smaller by "<" without being type casted?

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  • Client validation of INPUT of type FILE without postback using jQuery

    - by Fixer
    I want to check on the client side that a file has been selected before the form can be submitted. <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script> @using (Html.BeginForm("Upload", "Files", FormMethod.Post, new { enctype = "multipart/form-data" })) { <input id="File" name="File" type="file" size="80" /> <input type="submit" name="name" value="Upload" /> } Currently this form is doing postbacks for validation. What is going wrong?

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  • Get annotations of return type in Java

    - by Apropos
    I'm using Spring MVC and am using aspects to advise my controllers. I'm running into one issue: controllers that return a value annotated with the @ResponseBody type. How are you able to find the annotations applied to the return type? @Around("myPointcut()") private Object checkAnnotations(ProceedingJoinPoint pjp) throws Throwable { Object result = pjp.proceed(); Method method = ((MethodSignature)pjp.getSignature()).getMethod(); System.out.println("Checking return type annotations."); for(Annotation annotation : method.getReturnType().getAnnotations()){ System.out.println(annotation.toString()); } System.out.println("Checking annotations on returned object."); for(Annotation annotation : result.getClass().getAnnotations()){ System.out.println(annotation.toString()); } return result; } Unfortunately, neither of these methods seem to have the desired effect. I can retrieve annotations on the type of object being returned, but not the ones being added at return time.

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  • Java method: retrieve the inheriting type

    - by DrDro
    I have several classes that extend C and I would need a method that accepts any argument of type C. But in this method I would like to know if I'm dealing with A or B. * public A extends C public B extends C public void goForIt(C c)() If I cast how can I retrieve the type in a clean way (I just read using getClass or instanceof is often not the best way). *Sorry but I can't type closing braces

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  • Post request to include 'Content-Type' and JSON

    - by Sangram Singh
    I'm to work with goo.gl for URL shortening. I need to make the following request: POST https://www.googleapis.com/urlshortener/v1/url Content-Type: application/json {"longUrl": "http://www.google.com/"} my html:- <form method="post" action="https://www.googleapis.com/urlshortener/v1/"> <button type="submit"> submit </button> </form> how do i add the 'content-type' and json here?

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  • Type is undefined MVC AJAX Script

    - by zsharp
    on one page of my app i get a Type is undefined on the ajax script. why would this be? EDIT Type is not defined MicrosoftMvcAjax.js()()Microsof...vcAjax.js (line 6) [Break on this error] Type.registerNamespace('Sys.Mvc');Sys.Mv...reate_AjaxOptions=function(){return {};}

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