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  • Existentials and Scrap your Boilerplate

    - by finnsson
    I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing existentials. I got the existential data type data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine existentials with Scrap your Boilerplate? If so: how do you implement gunfold for an existential data type?

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  • Where are the function address literals in c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). <UPDATE> After some reading with help from answer by Chris Dodd, what I'm looking for is literal function addresses as template parameters. Chris' answer indicates how to do this for standard functions, but how can the addresses of member functions be used as template parameters? Since the standard prohibits non-static member function addresses as template parameters (c++03 14.3.2.3), I suspect the work around is quite complicated. Any ideas for a workaround? Below the original form of the question is left as is for context. </UPDATE> The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one. Edit The intent of this question is not to implement delegates, rather to identify a pattern that will embed a conventional function call, (in immediate mode) directly into third party code, possibly a template.

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  • Java: how do I get a class literal from a generic type?

    - by Tom
    Typically, I've seen people use the class literal like this: Class<Foo> cls = Foo.class; But what if the type is generic, e.g. List? This works fine, but has a warning since List should be parameterized: Class<List> cls = List.class So why not add a <?>? Well, this causes a type mismatch error: Class<List<?>> cls = List.class I figured something like this would work, but this is just a plain ol' a syntax error: Class<List<Foo>> cls = List<Foo>.class How can I get a Class<List<Foo>> statically, e.g. using the class literal? I could use @SuppressWarnings("unchecked") to get rid of the warnings caused by the non-parameterized use of List in the first example, Class<List> cls = List.class, but I'd rather not. Any suggestions? Thanks!

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  • Dynamically create textbox

    - by comii
    I need to dynamically create textbox. This is my code, but with this I create only one textbox: Public Sub CreateTextBox() Dim I As Integer Dim niz As Array For I = 1 To 5 Dim myTextBox = New TextBox myTextBox.Text = "Control Number:" & I Me.Controls.Add(myTextBox) Next End Sub So how i can dynamically create textbox? Thanks!

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  • Custom DataGridView column sort based on Value not Formatted value

    - by Dan Neely
    I have a custom DGV cell I'm using to display the contents of MyType objects. To control how they're being formatted I'm overriding the GetFormattedValue() and FormattedvalueType methods of DataGridViewTextBoxCell because in this case I don't want to use the default ToString() method. The problem is that when I do this the DGV is sorting the column by the string in FormattedValue instead of by Value. I'm not seeing a method I can override to change the sort behavior of the column. While I know I can, I don't want to have to write custom Sort mthods for the DGVs themselves because I'm using this in multiple DGV's.

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  • Why would an error get thrown inside my try-catch?

    - by George Johnston
    Why would my try-catch block still be throwing an error when it's handled? Exception Details: System.NullReferenceException: Object reference not set to an instance of an object. Try Here >> : _MemoryStream.Seek(6 * StartOffset, 0) _MemoryStream.Read(_Buffer, 0, 6) Catch ex As IOException // Handle Error End Try Edit: Cleaned the question up to remove the extraneous information.

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  • asp mvc: how to pass parameter to controller using jquery api?

    - by Grayson Mitchell
    I am following the following tutorial (http://www.highoncoding.com/Articles/642_Creating_a_Stock_Widget_in_ASP_NET_MVC_Application.aspx) on using ajax to render a partial form , but in this example parameters are not passed, and I have not been able to work out how to do it... This code works with no parameter function GetDetails() { $("#divDetails").load('Details'); } This is my attempt to add a parameter, but does not work (cant find action) function GetDetails() { $("#divDetails").load('Details?Id=20'); }

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  • Passing an empty IEnumerable argument to a method

    - by avance70
    I have this method (simplified): void DoSomething(IEnumerable<int> numbers); And I invoke it like this: DoSomething(condition==true?results:new List<int>()); The variable results is formed with a LINQ select condition (IEnumerable). I was wondering is this List<int>() the best way (the fastest?) to pass an empty collection, or is new int[0] better? Or, something else would be faster, a Collection, etc.? In my example null wouldn't be ok.

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  • Eliminating static properties - What patterns do I have at my disposal?

    - by Jamie Dixon
    I currently have a type that I inject into my controllers that's used for getting and setting session data. I use this so that I can obtain relevant session information as _sessionData.Username rather than using Session["username"]. I'd like to use this session information across all of my views and would previously have done this by making the SessionData members static instead of injecting the SessionData class into my controller. I want to avoid using static members as well as having to pass the object to the view in each controller. What patterns best suit this type of scenario? What do you do to solve this same problem?

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  • html.actionlink doesn't passing parameter to controller action

    - by FosterZ
    hi, m having problem in passing parameter to controller action, i have done the following Url.Action("SchoolDetails","School",new{id=item.SchoolId}) and my controller action follows public ActionResult SchoolDetails(string schoolId,_ASI_School schoolDetail) { schoolDetail = SchoolRepository.GetSchoolById(schoolId); return View(schoolDetail); } i dn't know why the schoolId above in action is getting null..

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  • Can someone please clarify my understanding of a mock's Verify concept?

    - by Pure.Krome
    Hi folks, I'm playing around with some unit tests and mocking. I'm trying to verify that some code, in my method, has been called. I don't think I understand the Verify part of mocking right, because I can only ever Verify main method .. which is silly because that is what I Act upon anyways. I'm trying to test that my logic is working - so I thought I use Verify to see that certain steps in the method have been reached and enacted upon. Lets use this example to highlight what I am doing wrong. public interface IAuthenticationService { bool Authenticate(string username, string password); SignOut(); } public class FormsAuthenticationService : IAuthenticationService { public bool Authenticate(string username, string password) { var user = _userService.FindSingle(x => x.UserName == username); if (user == null) return false; // Hash their password. var hashedPassword = EncodePassword(password, user.PasswordSalt); if (!hashedPassword.Equals(password, StringComparison.InvariantCulture)) return false; FormsAuthentication.SetAuthCookie(userName, true); return true; } } So now, I wish to verify that EncodePassword was called. FormsAuthentication.SetAuthCookie(..) was called. Now, I don't care about the implimentations of both of those. And more importantly, I do not want to test those methods. That has to be handled elsewhere. What I though I should do is Verify that those methods were called and .. if possible ... an expected result was returned. Is this the correct understanding of what 'Verify' means with mocking? If so, can someone show me how I can do this. Preferable with moq but i'm happy with anything. Cheers :)

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  • LINQ to SQL - Grouping categories by parentId

    - by creativeincode
    I am trying to construct a navigation menu using a Categories table from my db. I have a similar layout as below in Categories table. public List<Category> CategoryData = new List(new Category[] { new Category{ CategoryId = 1, Name = "Fruit", ParentCategoryId = null}, new Category{ CategoryId = 2, Name = "Vegetables", ParentCategoryId = null}, new Category{ CategoryId = 3, Name = "Apples", ParentCategoryId = 1}, new Category{ CategoryId = 4, Name = "Bananas", ParentCategoryId = 1}, new Category{ CategoryId = 5, Name = "Cucumber", ParentCategoryId = 2}, new Category{ CategoryId = 6, Name = "Onions", ParentCategoryId = 2} ); } The above should return something like Fruit (parent) "===Apples, Bananas (child) Vegetables (parent) "===Cucumber, Onions (child) I need to be able to pass this as some kind of 'grouped' (grouped by parentid) collection to my View. How to do this?

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  • When to use MVC Scaffolding via NuGet vs MVC Scaffolding via MVC3 Tools Update

    - by James
    I am a little confused about the various different "mainstream" scaffolding options for MVC3. There is a NuGet package called MVCScaffolding. It first showed up in Jan 2011, but seems to be active and have recent updates, and be developed by Scott Hanselman, among others. Then in May 2011 came the MVC3 Tools Update. This seems like it incorporated the original scaffolding ideas into an "out of the box" scaffolding options. However, this has not been updated since. So - what is the relationship between these two scaffoldings (if any). Are there cases when one should be used over the other, or is it just a matter of taste? Does Visual Studio 2012 or MVC4 change the game on any of this? Thanks for any input.

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  • Replace relative urls to absolute

    - by Rocky Singh
    I have the html source of a page in a form of string with me: <html> <head> <link rel="stylesheet" type="text/css" href="/css/all.css" /> </head> <body> <a href="/test.aspx">Test</a> <a href="http://mysite.com">Test</a> <img src="/images/test.jpg"/> <img src="http://mysite.com/images/test.jpg"/> </body> </html> I want to convert all the relative paths to absolute. I want the output be: <html> <head> <link rel="stylesheet" type="text/css" href="http://mysite.com/css/all.css" /> </head> <body> <a href="http://mysite.com/test.aspx">Test</a> <a href="http://mysite.com">Test</a> <img src="http://mysite.com/images/test.jpg"/> <img src="http://mysite.com/images/test.jpg"/> </body> </html> Note: I want only the relative paths to be converted to absolute ones in that string. The absolute ones which are already in that string should not be touched, they are fine to me as they are already absolute. Can this be done by regex or other means?

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  • Handle Enter Key on Website (ASP and VB)

    - by Andrew
    So I have a website with multiple asp controls. When I press enter inside by login form, the search function runs because it's the first thing found on the page. How would I handle the enter button so that when the active textbox is for the login form, the loginbutton code actually runs rather than the searchbutton. One last problem is that the login controls are inside a loginview so the hierarchy shows that the asp:textbox and asp:button for logging in are inside 3 tags like so: <loginview> <login> <logintemplate> //controls are here. </logintemplate> </login> Just a note that all controls are asp and that all code is prefered in VB. Thanks

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  • How do I build a class that shares a table with multiple columns in MVC3?

    - by Barrett Kuethen
    I have a Job table public class Job { public int JobId { get; set; } public int SalesManagerId { get; set; } public int SalesRepId { get; set; } } and a Person table public class Person { public int PersonId { get; set; } public int FirstName { get; set; } public int LastName { get; set; } } My question is, how do I link the SalesManagerId to the Person (or PersonId) as well as the SalesRepId to the Person (PersonId)? The Sales Manager and Sales Rep are independent of each other. I just don't want to make 2 different lists to support the Sales Manager and Sales Rep roles. I'm new to MVC3, but it seems public virtual Person Person {get; set; } would be the way to go, but that doesn't work. Any help would be appreciated! Thanks!

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  • Versioning issues with assemblies

    - by devoured elysium
    Let's assume I have two assemblies: MyExecutable.dll version 1.0.0 MyClassLibrary.dll version 1.0.0 Now, MyExecutable.dll currently uses MyClassLibrary.dll's classes and methods (which include some algorithms). Most of those algorithms were made on the run, being that later I'll want to refine them if needed. This means, I won't change the interface of those classes but the code itself will see some changes. The question at hand is, MyExecutable.dll will be expecting MyClassLibrary.dll 1.0.0 and I'll want it to use version 1.0.1 (or something like that). I don't want to have to recompile MyExecutable.dll(because actually there might be more than just one executable using MyClassLibrary.dll). Is there a solution for this problem? I've heard about the GAC, but if possible I'd like to stay away from it. Thanks

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  • Where are the function literals in c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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  • I want to get 2 values returned by my query. How to do, using linq-to-entity

    - by Shantanu Gupta
    var dept_list = (from map in DtMapGuestDepartment.AsEnumerable() where map.Field<Nullable<long>>("GUEST_ID") == DRowGuestPI.Field<Nullable<long>>("PK_GUEST_ID") join dept in DtDepartment.AsEnumerable() on map.Field<Nullable<long>>("DEPARTMENT_ID") equals dept.Field<Nullable<long>>("DEPARTMENT_ID") select new { dept_id=dept.Field<long>("DEPARTMENT_ID") ,dept_name=dept.Field<long>("DEPARTMENT_NAME") }).Distinct(); DataTable dt = new DataTable(); dt.Columns.Add("DEPARTMENT_ID"); dt.Columns.Add("DEPARTMENT_NAME"); foreach (long? dept_ in dept_list) { dt.Rows.Add(dept_[0], dept_[1]); } EDIT In the previous question asked by me. I got an answer like this for single value. What is the difference between the two ? foreach (long? dept in dept_list) { dt.Rows.Add(dept); }

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  • How to create a generic list in this wierd case in c#

    - by Marc Bettex
    Hello, In my program, I have a class A which is extended by B, C and many more classes. I have a method GetInstance() which returns a instance of B or C (or of one of the other child), but I don't know which one, so the return type of the method is A. In the method CreateGenericList(), I have a variable v of type A, which is in fact either a B, a C or another child type and I want to create a generic list of the proper type, i.e. List<B> if v is a B or List<C> if v is a C, ... Currently I do it by using reflection, which works, but this is extremely slow. I wanted to know if there is another way to to it, which doesn't use reflection. Here is an example of the code of my problem: class A { } class B : A { } class C : A { } // More childs of A. class Program { static A GetInstance() { // returns an instance of B or C } static void CreateGenericList() { A v = Program.GetInstance(); IList genericList = // Here I want an instance of List<B> or List<C> or ... depending of the real type of v, not a List<A>. } } I tried the following hack. I call the following method, hoping the type inferencer will guess the type of model, but it doesn't work and return a List<A>. I believe that because c# is statically typed, T is resolved as A and not as the real type of model at runtime. static List<T> CreateGenericListFromModel<T>(T model) where T : A { return new List<T> (); } Does anybody have a solution to that problem that doesn't use reflection or that it is impossible to solve that problem without reflection? Thank you very much, Marc

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  • Change the output of the Html.menu() asp control .

    - by user327893
    Im creating a asp mvc application and im using a sitemap to create my menu. Is it possible to change the output of the Html.menu() asp control? normal output: <ul> <li><a href="#">Item 1</li> <li><a href="#">Item 2</li> </ul> needed output: <ul> <li><a href="#"><span>Item 1</span></li> <li><a href="#"><span>Item 2</span></li> </ul> Or should i filter true the nodes of the sitemap to get the format i want?? TY in advance:)

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  • MasterPage Page_Load hits before Grid_ItemCommand

    - by Raheel Khan
    I am using the session object to store success/error messages based on user actions. On each postback, the message is set on ItemCommend and retrieved on the Page_Load of the master page. Once retrieved, the message is deleted from the session. The problem is that the master page's Page_Load gets called before the ItemCommand gets called so the message does not show up until the next refresh or postback. How is this situation normally handled? Is there some other event we can code against?

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