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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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  • DataGridView not displaying data in ToolStripControlHost

    - by jblaske
    I'm utilizing the code posted by Jesper Palm here: http://stackoverflow.com/questions/280891/make-user-control-display-outside-of-form-boundry /// <summary> /// A simple popup window that can host any System.Windows.Forms.Control /// </summary> public class PopupWindow : System.Windows.Forms.ToolStripDropDown { private System.Windows.Forms.Control _content; private System.Windows.Forms.ToolStripControlHost _host; public PopupWindow(System.Windows.Forms.Control content) { //Basic setup... this.AutoSize = false; this.DoubleBuffered = true; this.ResizeRedraw = true; this._content = content; this._host = new System.Windows.Forms.ToolStripControlHost(content); //Positioning and Sizing this.MinimumSize = content.MinimumSize; this.MaximumSize = content.Size; this.Size = content.Size; content.Location = Point.Empty; //Add the host to the list this.Items.Add(this._host); } } I've translated it to VB: Public Class PopupWindow Inherits System.Windows.Forms.ToolStripDropDown Private _content As System.Windows.Forms.Control Private _host As System.Windows.Forms.ToolStripControlHost Public Sub New(ByVal content As System.Windows.Forms.Control) Me.AutoSize = False Me.DoubleBuffered = True Me.ResizeRedraw = True Me._content = content Me._host = New System.Windows.Forms.ToolStripControlHost(content) Me.MinimumSize = content.MinimumSize Me.MaximumSize = content.MaximumSize Me.Size = content.Size content.Location = Point.Empty Me.Items.Add(Me._host) End Sub End Class It works great with a PictureBox showing its information. But for some reason I cannot get the DataGridView to display anything when it is in the popup. If I pull the grid out of the popup it displays all of its information fine. If I pause during debug, the grid shows that it has all the data in it. It's just not displaying anything. Does anybody have any ideas?

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  • Thread.sleep vs Monitor.Wait vs RegisteredWaitHandle?

    - by Royi Namir
    (the following items has different goals , but im interesting knowing how they "PAUSEd") questions Thread.sleep - Does it impact performance on a system ?does it tie up a thread with its wait ? what about Monitor.Wait ? what is the difference in the way they "wait"? do they tie up a thread with their wait ? what aboutRegisteredWaitHandle ? This method accepts a delegate that is executed when a wait handle is signaled. While it’s waiting, it doesn’t tie up a thread. so some thread are paused and can be woken by a delegate , while others just wait ? spin ? can someone please make things clearer ? edit http://www.albahari.com/threading/part2.aspx

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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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  • When are predicates appropriate and what is the best pattern for usage

    - by Maxim Gershkovich
    When are predicates appropriate and what is the best pattern for usage? What are the advantages of predicates? It seems to me like most cases where a predicate can be employed a tight loop would accomplish the same functionality? I don’t see a reusability argument given you will probably only implement a predicate in one method right? They look and feel nice but besides that they seem like you would only employ them when you need a quick hack on the collection classes? UPDATE But why would you be rewriting the tight loop again and again? In my mind/code when it comes to collections I always end up with something like Class Person End Class Class PersonList Inherits List(Of Person) Function FindByName(Name) as Person tight loop.... End Function End Class @Ani By that same logic I could implement the method as such Class PersonList Inherits List(Of Person) Function FindByName(Name) as PersonList End Function Function FindByAge(Age) as PersonList End Function Function FindBySocialSecurityNumber(SocialSecurityNumber) as PersonList End Function End Class And call it as such Dim res as PersonList = MyList.FindByName("Max").FindByAge(25).FindBySocialSecurityNumber(1234) and the result along with the amount of code and its reusability is largely the same, no? I am not arguing just trying to understand.

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  • Namespace constraint with generic class decleration

    - by SomeGuy
    Good afternoon people, I would like to know if (and if so how) it is possible to define a namespace as a constraint parameter in a generic class declaration. What I have is this: namespace MyProject.Models.Entities <-- Contains my classes to be persisted in db namespace MyProject.Tests.BaseTest <-- Obvious i think Now the decleration of my 'BaseTest' class looks like so; public class BaseTest<T> This BaseTest does little more (at the time of writing) than remove all entities that were added to the database during testing. So typically I will have a test class declared as: public class MyEntityRepositoryTest : BaseTest<MyEntity> What i would LIKE to do is something similar to the following: public class BaseTest<T> where T : <is of the MyProject.Models.Entities namespace> Now i am aware that it would be entirely possible to simply declare a 'BaseEntity' class from which all entities created within the MyProject.Models.Entities namespace will inherit from; public class BaseTest<T> where T : MyBaseEntity but...I dont actually need to, or want to. Plus I am using an ORM and mapping entities with inheritance, although possible, adds a layer of complexity that is not required. So, is it possible to constrain a generic class parameter to a namespace and not a specific type ? Thank you for your time.

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  • ModelBindingContext ModelName

    - by user195910
    Can anyone explain where the ModelName gets populated from? Looked in MSDN documentation and no explaination here. I am creating a custom model binder and within it I get null for the following: var result = bindingContext.ModelName);

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  • Finding ALL positions of a substring in a large string in C#

    - by Tommy
    Alright, so what i have, is a large string i need to parse, and what i need to happen, is find all the instances of extract"(me,i-have lots. of]punctuation, and store them to a list. So say this piece of string was in the beginning and middle of the larger string, both of them would be found, and their index's would be added to the List. and the List would contain 0 and the other index whatever it would be. Ive been playing around, and the string.IndexOf does almost what i'm looking for, and ive written some code. But i cant seem to get it to work: List<int> inst = new List<int>(); int index = 0; while (index < source.LastIndexOf("extract\"(me,i-have lots. of]punctuation", 0) + 39) { int src = source.IndexOf("extract\"(me,i-have lots. of]punctuation", index); inst.Add(src); index = src + 40; } inst = The list source = The large string Any better ideas?

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  • Button in Update Panel doing full postback?

    - by sah302
    No this isn't a copy of this question: http://stackoverflow.com/questions/654423/button-in-update-panel-is-doing-a-full-postback I've got a drop down inside an update panel, and I am trying to get it to allow the person using the page to add users to a list that is bound to a gridview. The list is a global variable, and on page_load I set that to the gridview's datasource and databind it. However, anytime I click the 'add a user' button, or the button to remove the user from the list. It appears like it is doing a full post back even though all these elements are inside the update Panel. Code Behind: Public accomplishmentTypeDao As New AccomplishmentTypeDao() Public accomplishmentDao As New AccomplishmentDao() Public userDao As New UserDao() Public facultyDictionary As New Dictionary(Of Guid, String) Public facultyList As New List(Of User) Public associatedFaculty As New List(Of User) Public facultyId As New Guid Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load Page.Title = "Add a New Faculty Accomplishment" ddlAccomplishmentType.DataSource = accomplishmentTypeDao.getEntireTable() ddlAccomplishmentType.DataTextField = "Name" ddlAccomplishmentType.DataValueField = "Id" ddlAccomplishmentType.DataBind() facultyList = userDao.getListOfUsersByUserGroupName("Faculty") For Each faculty As User In facultyList facultyDictionary.Add(faculty.Id, faculty.LastName & ", " & faculty.FirstName) Next If Not Page.IsPostBack Then ddlFacultyList.DataSource = facultyDictionary ddlFacultyList.DataTextField = "Value" ddlFacultyList.DataValueField = "Key" ddlFacultyList.DataBind() End If gvAssociatedUsers.DataSource = associatedFaculty gvAssociatedUsers.DataBind() End Sub Protected Sub deleteUser(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.CommandEventArgs) facultyId = New Guid(e.CommandArgument.ToString()) associatedFaculty.Remove(associatedFaculty.Find(Function(user) user.Id = facultyId)) gvAssociatedUsers.DataBind() upAssociatedFaculty.Update() End Sub Protected Sub btnAddUser_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnAddUser.Click facultyId = New Guid(ddlFacultyList.SelectedValue) associatedFaculty.Add(facultyList.Find(Function(user) user.Id = facultyId)) gvAssociatedUsers.DataBind() upAssociatedFaculty.Update() End Sub Markup: <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> <asp:UpdatePanel ID="upAssociatedFaculty" runat="server" UpdateMode="Conditional"> <ContentTemplate> <p><b>Created By:</b> <asp:Label ID="lblCreatedBy" runat="server"></asp:Label></p> <p><b>Accomplishment Type: </b><asp:DropDownList ID="ddlAccomplishmentType" runat="server"></asp:DropDownList></p> <p><b>Accomplishment Applies To: </b><asp:DropDownList ID="ddlFacultyList" runat="server"></asp:DropDownList> &nbsp;<asp:Button ID="btnAddUser" runat="server" Text="Add Faculty" /></p> <p> <asp:GridView ID="gvAssociatedUsers" runat="server" AutoGenerateColumns="false" GridLines="None" ShowHeader="false"> <Columns> <asp:BoundField DataField="Id" HeaderText="Id" Visible="False" /> <asp:TemplateField ShowHeader="False"> <ItemTemplate> <span style="margin-left: 15px;"> <p><%#Eval("LastName")%>, <%#Eval("FirstName")%> <asp:Button ID="btnUnassignUser" runat="server" CausesValidation="false" CommandArgument='<%# Eval("Id") %>' CommandName="Delete" OnCommand="deleteUser" Text='Remove' /></p> </span> </ItemTemplate> </asp:TemplateField> </Columns> <EmptyDataTemplate> <em>There are currently no faculty associated with this accomplishment.</em> </EmptyDataTemplate> </asp:GridView> </p> </ContentTemplate> </asp:UpdatePanel> Now I thought the point of an update panel was to be able to update things inside of it without doing a full post_back and reloading the page. So if that's the case, why is it calling page_load everytime I click the buttons? I ran this code and debug and I see that even before any of the code associated with button press fires, page_load runs again. I tried putting the gvAssociatedUser.Datasource = associatedFaculty and the line below inside the Page.IsPostBack check, that prevented the page from working. I tried every combination of settings of the update panel for ChildrenAsTriggers and UpdateMode, and none of them worked. I know this is something simple, but all the combinations I've tried won't get it to work. How can I make this thing work?

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  • Java. Best procedure to de-serialize a Java generic object?

    - by Jake
    What is the best procedure for storing and retrieving, using native Java serialization, generic objects like ArrayList<String>? Edit: To clarify. When I serialize an object of type ArrayList<String> I'd like to de-serialize to the same type of object. However, I know of no way to cast back to this generic object without causing warnings.

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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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  • Create generic class instance throws TypeLoadException

    - by Elisa
    My TestLayer class has the namespace: "BLL.Infrastructure.TestLayer" and is inside the assembly: "BLL" public class LayerFactory<T, U> { public static IBaseLayer<T, U> Get() { var obj = Activator.CreateInstance("BLL", "BLL.Infrastructure.TestLayer", new object[] { (IBaseLayer<T, U>)null }); } } When I run the code the Activator throws an TypeLoadException with no more details Thats the concrete class it should create: GenericBaseLayer implements the IBaseLayer. public class TestLayer<T, U> : GenericBaseLayer<MyRequest, MyInfo.ActionType> { public TestLayer(IBaseLayer<MyRequest, MyInfo.ActionType> layer) : base(layer) { } } What do I wrong?

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  • IsAuthenticated is false!

    - by Naor
    This is how I login ('user' holds the data of the user): HttpResponse Response = HttpContext.Current.Response; HttpRequest Request = HttpContext.Current.Request; FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(1, user.UserId.ToString(), DateTime.Now, DateTime.Now.AddHours(12), false, UserResolver.Serialize(user)); HttpCookie cookie = new HttpCookie(FormsAuthentication.FormsCookieName, FormsAuthentication.Encrypt(ticket)); cookie.Path = FormsAuthentication.FormsCookiePath; Response.Cookies.Add(cookie); string redirectUrl = user.HomePage; Response.Redirect(redirectUrl); After this login I get IsAuthenticated == false. Why?? It worked for me before an hour but I don't know what is wrong now.

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  • Does collections type conversion util methods already exist in any API?

    - by Delta
    interface TypeConverter<T, E> { T convert(E e); } class CollectionUtil() { public static <E> List<T> convertToList(List<E> fromList, TypeConverter<T, E> conv) { { if(fromList== null) return null; List<T> newList = new ArrayList<T>(fromList.size()) for(E e : fromList) { newList.add(conv.convert(e)); } return newList; } } Above code explains converting from List of String to List of Integer by implementing TypeConverter interface for String, Integer. Are there already any collections conversion utility methods exists in any API like list to set and so on?

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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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  • Access to an inner type

    - by sohum
    A colleague of mine posted a question on an internal forum which got me thinking about whether this was possible through C#. Basically, he's got an interface as follows: public interface IProvider<T> { T GetT(); } Is it possible to use something that implements that interface as a type parameter to another generic class and have access to the type T without re-specifying it? For example: public class Foo<P> where P : IProvider<T> { P p; T GetInnerT() { return p.GetT(); } } This does not compile, because the type T is not defined and hence can't be used as a parameter for IProvider. Is something like this even possible? Just curious!

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  • Replace {tag} with a value or completely remove {any-tag}

    - by HasanGursoy
    I've designed a multilingual web site and some values in database have a tag which will be replaced with it's language value, remove tags brackets ( in case {} ) or removed completely. There are two cases: Remove brackets: value {mm} >> value mm Remove completely: value {mm} >> value Also {tag} could be any length and can contain - Can anybody help me with regex?

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  • [C#] Problems with implementing generic IEnumerator and IComparable

    - by r0h
    Hi all! I'm working on an AVL Tree. The tree itself seems to be working but I need a iterator to walk through the values of the tree. Therefore I tried to implement the IEnumerator interace. Unfortunately I get a compile time error implementing IEnumerator and IComparable. First the code and below that the error. class AvlTreePreOrderEnumerator<T> : IEnumerator<T> where T :IComparable<T> { private AvlTreeNode<T> current = default(T); private AvlTreeNode<T> tree = null; private Queue<AvlTreeNode<T>> traverseQueue = null; public AvlTreePreOrderEnumerator(AvlTreeNode<T> tree) { this.tree = tree; //Build queue traverseQueue = new Queue<AvlTreeNode<T>>(); visitNode(this.tree.Root); } private void visitNode(AvlTreeNode<T> node) { if (node == null) return; else { traverseQueue.Enqueue(node); visitNode(node.LeftChild); visitNode(node.RightChild); } } public T Current { get { return current.Value; } } object IEnumerator.Current { get { return Current; } } public void Dispose() { current = null; tree = null; } public void Reset() { current = null; } public bool MoveNext() { if (traverseQueue.Count > 0) current = traverseQueue.Dequeue(); else current = null; return (current != null); } } The error given by VS2008: Error 1 The type 'T' cannot be used as type parameter 'T' in the generic type or method 'Opdr2_AvlTreeTest_Final.AvlTreeNode'. There is no boxing conversion or type parameter conversion from 'T' to 'System.IComparable'. For now I've not included the tree and node logic. I anybody thinks is necessary to resolve this probleem, just say so! Thx!

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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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