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  • Operator overloading in generic struct: can I create overloads for specific kinds(?) of generic?

    - by Carson Myers
    I'm defining physical units in C#, using generic structs, and it was going okay until I got the error: One of the parameters of a binary operator must be the containing type when trying to overload the mathematical operators so that they convert between different units. So, I have something like this: public interface ScalarUnit { } public class Duration : ScalarUnit { } public struct Scalar<T> where T : ScalarUnit { public readonly double Value; public Scalar(double Value) { this.Value = Value; } public static implicit operator double(Scalar<T> Value) { return Value.Value; } } public interface VectorUnit { } public class Displacement : VectorUnit { } public class Velocity : VectorUnit { } public struct Vector<T> where T : VectorUnit { #... public static Vector<Velocity> operator /(Vector<Displacement> v1, Scalar<Duration> v2) { return new Vector<Velocity>(v1.Magnitude / v2, v1.Direction); } } There aren't any errors for the + and - operators, where I'm just working on a Vector<T>, but when I substitute a unit for T, suddenly it doesn't like it. Is there a way to make this work? I figured it would work, since Displacement implements the VectorUnit interface, and I have where T : VectorUnit in the struct header. Am I at least on the right track here? I'm new to C# so I have difficulty understanding what's going on sometimes.

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  • Java - How to pass a Generic parameter as Class<T> to a constructor

    - by Joe Almore
    I have a problem here that still cannot solve, the thing is I have this abstract class: public abstract class AbstractBean<T> { private Class<T> entityClass; public AbstractBean(Class<T> entityClass) { this.entityClass = entityClass; }... Now I have another class that inherits this abstract: @Stateless @LocalBean public class BasicUserBean<T extends BasicUser> extends AbstractBean<T> { private Class<T> user; public BasicUserBean() { super(user); // Error: cannot reference user before supertype contructor has been called. } My question is how can I make this to work?, I am trying to make the class BasicUserBean inheritable, so if I have class PersonBean which inherits BasicUserBean then I could set in the Generic the entity Person which also inherits the entity BasicUser. And it will end up being: @Stateless @LocalBean public class PersonBean extends BasicUserBean<Person> { public PersonBean() { super(Person.class); } ... I just want to inherit the basic functionality from BasicUserBean to all descendants, so I do not have to repeat the same code among all descendants. Thanks!.

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  • Making Extension method Generic

    - by Ian
    In this post there's a very interesting way of updating UI threads using a static extension method. public static void InvokeIfRequired(this Control c, Action<Control> action) { if(c.InvokeRequired) { c.Invoke(() => action(c)); } else { action(c); } } What I want to do, is to make a generic version, so I'm not constrained by a control. This would allow me to do the following for example (because I'm no longer constrained to just being a Control) this.progressBar1.InvokeIfRequired(pb => pb.Value = e.Progress); I've tried the following: public static void InvokeIfRequired<T>(this T c, Action<T> action) where T : Control { if (c.InvokeRequired) { c.Invoke(() => action(c)); } else { action(c); } } But I get the following error that I'm not sure how to fix. Anyone any suggestions? Error 5 Cannot convert lambda expression to type 'System.Delegate' because it is not a delegate type

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  • Type contraint problem of C#

    - by user351565
    I meet a problem about type contraint of c# now. I wrote a pair of methods that can convert object to string and convert string to object. ex. static string ConvertToString(Type type, object val) { if (type == typeof(string)) return (string)val; if (type == typeof(int)) return val.ToString(); if (type.InSubclassOf(typeof(CodeObject))) return ((CodeObject)val).Code; } static T ConvertToObject<T>(string str) { Type type = typeof(T); if (type == typeof(string)) return (T)(object)val; if (type == typeof(int)) return (T)(object)int.Parse(val); if (type.InSubclassOf(typeof(CodeObject))) return Codes.Get<T>(val); } where CodeObject is a base class of Employees, Offices ..., which can fetch by static method Godes.Get where T: CodeObject but the code above cannot be compiled because error #CS0314 the generic type T of method ConvertToObject have no any constraint but Codes.Get request T must be subclass of CodeObject i tried use overloading to solve the problem but not ok. is there any way to clear up the problem? like reflection?

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  • Why can't these generic type parameters be inferred?

    - by Jon M
    Given the following interfaces/classes: public interface IRequest<TResponse> { } public interface IHandler<TRequest, TResponse> where TRequest : IRequest<TResponse> { TResponse Handle(TRequest request); } public class HandlingService { public TResponse Handle<TRequest, TResponse>(TRequest request) where TRequest : IRequest<TResponse> { var handler = container.GetInstance<IHandler<TRequest, TResponse>>(); return handler.Handle(request); } } public class CustomerResponse { public Customer Customer { get; set; } } public class GetCustomerByIdRequest : IRequest<CustomerResponse> { public int CustomerId { get; set; } } Why can't the compiler infer the correct types, if I try and write something like the following: var service = new HandlingService(); var request = new GetCustomerByIdRequest { CustomerId = 1234 }; var response = service.Handle(request); // Shouldn't this know that response is going to be CustomerResponse? I just get the 'type arguments cannot be inferred' message. Is this a limitation with generic type inference in general, or is there a way to make this work?

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  • Using overloaded operator== in a generic function

    - by Dimitri C.
    Consider the following code: class CustomClass { public CustomClass(string value) { m_value = value; } public static bool operator==(CustomClass a, CustomClass b) { return a.m_value == b.m_value; } public static bool operator!=(CustomClass a, CustomClass b) { return a.m_value != b.m_value; } public override bool Equals(object o) { return m_value == (o as CustomClass).m_value; } public override int GetHashCode() { return 0; /* not needed */ } string m_value; } class G { public static bool enericFunction1<T>(T a1, T a2) where T : class { return a1.Equals(a2); } public static bool enericFunction2<T>(T a1, T a2) where T : class { return a1==a2; } } Now when I call both generic functions, one succeeds and one fails: var a = new CustomClass("same value"); var b = new CustomClass("same value"); Debug.Assert(G.enericFunction1(a, b)); // Succeeds Debug.Assert(G.enericFunction2(a, b)); // Fails Apparently, G.enericFunction2 executes the default operator== implementation instead of my override. Can anybody explain why this happens?

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  • A generic Re-usable C# Property Parser utility

    - by Shyam K Pananghat
    This is about a utility i have happened to write which can parse through the properties of a data contracts at runtime using reflection. The input required is a look like XPath string. since this is using reflection, you dont have to add the reference to any of your data contracts thus making pure generic and re- usable.. you can read about this and get the full c# sourcecode here. Property-Parser-A-C-utility-to-retrieve-values-from-any-Net-Data-contracts-at-runtime Now about the doubts which i have about this utility. i am using this utility enormously i many places of my code I am using Regex repetedly inside a recursion method. does this affect the memmory usage or GC collection badly ?do i have to dispose this manually. if yes how ?. The statements like obj.GetType().GetProperty() and obj.GetType().GetField() returns .net "object" which makes difficult or imposible to introduce generics here. Does this cause to have any overheads like boxing ? on an overall, please suggest to make this utility performance efficient and more light weight on memmory

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  • List to TreeSet conversion produces: "java.lang.ClassCastException: MyClass cannot be cast to java.l

    - by Chuck
    List<MyClass> myclassList = (List<MyClass>) rs.get(); TreeSet<MyClass> myclassSet = new TreeSet<MyClass>(myclassList); I don't understand why this code generates this: java.lang.ClassCastException: MyClass cannot be cast to java.lang.Comparable MyClass does not implement Comparable. I just want to use a Set to filter the unique elements of the List since my List contains unncessary duplicates.

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  • Does hibernate query result always return a list?

    - by Phoenix
    Does a query execution always have to return a list ? How do I replace the code below if I am sure it will only return a single object ? @Override public List<DocInfo> findAllByDocId(String docId) { Query q = getCurrentSession().createQuery("from DocInfo item where item.id = :docId"); q.setString("docId", docId); List<DocInfo> docInfoList = q.list(); return docInfoList; }

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  • Can we use the task list from "another" web site of same site collection as task list for Sharepoint

    - by Khurram Aziz
    Can I specify/use an existing task list from "another" website but from same site collection to be used in my Sequential Sharepoint Workflow? I am using Visual Studio to code the workflow, and it will be deployed in /subsite, the root site already has a task list to which everyone has connected to Outlook etc...Instead of creating a new task list in /subsite and asking concerned to subscribe to this new task list...I want to use the existing one..

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  • org.hibernate.TransientObjectException during Criteria.list()

    - by rancidfishbreath
    I have seen posts all over the internet that talk about how to fix the TransientObjectExceptions during save/update/delete but I am having this problem when calling list on my Criteria. I have two objects A and B. A has a field named b which is of type B. In my mapping b is mapped as a many-to-one. This all runs in a larger persistence framework (the framework is kind of like Core Data) and so I don't use any cascades in my hibernate mappings since cascades are handled at a higher level. This is the interesting code surrounding my criteria: A a = new A(); B b = new B(); a.setB(b); session.save("B", b); // Actually handled by the higher level session.save("A", a); // framework, this is just for clarity // transaction committed and session closed ... // new session opened Criteria criteria = session.createCriteria(A.class); criteria.add(Restrictions.eq("b", b)); List<?> objects = criteria.list(); Basically I am looking for all objects of type A such that A.b equals a particular instance of b (I actually tried restructuring a query so that I was passing in the id of b just to make sure that b wasn't causing me problems). Here is the stack trace that occurs when I call criteria.list(): org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: B at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:244) at org.hibernate.type.EntityType.getIdentifier(EntityType.java:449) at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:141) at org.hibernate.loader.Loader.bindPositionalParameters(Loader.java:1769) at org.hibernate.loader.Loader.bindParameterValues(Loader.java:1740) at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1612) at org.hibernate.loader.Loader.doQuery(Loader.java:717) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270) at org.hibernate.loader.Loader.doList(Loader.java:2294) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2172) at org.hibernate.loader.Loader.list(Loader.java:2167) at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1706) at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347) Here is my mapping: <class entity-name="A" lazy="false"> <tuplizer entity-mode="dynamic-map" class="MyTuplizer" /> <id type="long" column="id"> <generator class="native" /> </id> <many-to-one name="b" entity-name="B" column="b_id" lazy="false" /> </class> <class entity-name="B" lazy="false"> <tuplizer entity-mode="dynamic-map" class="MyTuplizer" /> <id type="long" column="id"> <generator class="native" /> </id> </class> Can anyone help me figure out why I would be getting a TransientObjectException during a fetch? Preferably I would like to find a solution that does not rely on cascades since they tend to mask problems that occur in the higher level framework.

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  • Linked List Design

    - by Jim Scott
    The other day in a local .NET group I attend the following question came up: "Is it a valid interview question to ask about Linked Lists when hiring someone for a .NET development position?" Not having a computer sciense degree and being a self taught developer my response was that I did not feel it was appropriate as I in 5 years of developer with .NET had never been exposed to linked lists and did not hear any compeling reason for a use for one. However the person commented that it is a very common interview question so I decided when I left that I would do some reasearch on linked lists and see what I might be missing. I have read a number of posts on stack overflow and various google searches and decided the best way to learn about them was to write my own .NET classes to see how they worked from the inside out. Here is my class structure Single Linked List Constructor public SingleLinkedList(object value) Public Properties public bool IsTail public bool IsHead public object Value public int Index public int Count private fields not exposed to a property private SingleNode firstNode; private SingleNode lastNode; private SingleNode currentNode; Methods public void MoveToFirst() public void MoveToLast() public void Next() public void MoveTo(int index) public void Add(object value) public void InsertAt(int index, object value) public void Remove(object value) public void RemoveAt(int index) Questions I have: What are typical methods you would expect in a linked list? What is typical behaviour when adding new records? For example if I have 4 nodes and I am currently positioned in the second node and perform Add() should it be added after or before the current node? Or should it be added to the end of the list? Some of the designs I have seen explaining things seem to expose outside of the LinkedList class the Node object. In my design you simply add, get, remove values and know nothing about any node object. Should the Head and Tail be placeholder objects that are only used to define the head/tail of the list? I require my Linked List be instantiated with a value which creates the first node of the list which is essentially the head and tail of the list. Would you change that ? What should the rules be when it comes to removing nodes. Should someone be able to remove all nodes? Here is my Double Linked List Constructor public DoubleLinkedList(object value) Properties public bool IsHead public bool IsTail public object Value public int Index public int Count Private fields not exposed via property private DoubleNode currentNode; Methods public void AddFirst(object value) public void AddLast(object value) public void AddBefore(object existingValue, object value) public void AddAfter(object existingValue, object value) public void Add(int index, object value) public void Add(object value) public void Remove(int index) public void Next() public void Previous() public void MoveTo(int index)

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  • alternative ways to display a list

    - by joshua
    Hi everyone, I know on how to display a list by using loop. For example, choice(a):-write('This is the top 15 countries list:'),nl, loop(X). loop(X):-country(X),write(X),nl,fail. Unfortunately,I don't know on how to display list by using list.anyone can guide me?

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  • Hide list Sharepoint Temprarly Javascript

    - by lerac
    Back again with a javascript question within sharepoint. I would like to hide a list temporarly while my javascript code is running. So lets say I have a to do list. Hide the list I run my javascript code (doesn't matter what it is, so plz don't ask). Show the list I know how to do it with a calendarview but not listview yet: HIDE CALENDAR--$(".ms-cal-gempty").hide();

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  • jQuery: List expands on page load

    - by Hasanah
    I've been looking for something very simple: How to make a side navigation expand with animation on page load, but all the tutorial websites I usually go to don't seem to have it. The closest I could find is this jQuery sample: http://codeblitz.wordpress.com/2009/04/15/jquery-animated-collapsible-list/ I've managed to strip down the list like so: <script type="text/javascript" src="jquery-1.3.2.min.js"></script> <script type="text/javascript"> $(function(){ $('li') .css('pointer','default') .css('list-style','none'); $('li:has(ul)') .click(function(event){ if (this == event.target) { $(this).css('list-style', (!$(this).children().is(':hidden')) ? 'none' : 'none'); $(this).children().toggle('slow'); } return false; }) .css({cursor:'pointer', 'list-style':'none'}) .children().hide(); $('li:not(:has(ul))').css({cursor:'default', 'list-style':'none'}); }); <body> <fieldset> <legend>Collapsable List Demo</legend> <ul> <li>A - F</li> <li>G - M <ul> <li>George Kent Technology Centre</li> <li>Hampshire Park</li> <li>George Kent Technology Centre</li> <li>Hampshire Park</li> </ul> </li> <li> N - R </li> <li>S - Z</li> </ul> </fieldset> My question is: Is there any way to make this list expand on page load instead of on click? I also don't need it to collapse at all; basically I need only the animating expansion. Thank you for your time and advice. :)

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  • Create list of variable type

    - by Jan
    I am trying to create a list of a certain type. I want to use the List notation but all I know is a "System.Type" The type a have is variable. How can I create a list of a variable type? I want something similar to this code. public IList createListOfMyType(Type myType) { return new List<myType>(); }

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  • list controls in flex3

    - by madhu
    Iam new to flex. in my work I have a problem. in my program i have to use three lists and one button. one is employees list,2nd is managers list and third is details list. depending on the selected items in the 2 lists i have display the items in detailed list can any one help me? thanks in advance.

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  • Shallow copying a list with downcasting

    - by Mohit
    I have the class herichary as follows CEntity----CNode---CElement I have a class Nodes : List<Cnode> and Class Elements : List<Element> Node class contain common item common across different project Element class has item specific to a project. I have to shallow copy the element list into the node list (basically down casting the elements to nodes)

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  • Splitting a list in python

    - by mglmnc
    Hey im new to python. How do you get a portion of a list by the relative value of its sorting key. example... list = [11,12,13,14,15,16,1,2,3,4,5,6,7,8,9,10] list.sort() newList = list.split("all numbers that are over 13") assert newList == [14,15,16]

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  • Best PHP timezone list

    - by jimbo
    I have looked over the PHP list of supported timezones, but the whole list is a little long to include in a drop-down menu, for the user to select his or her timezone. Is there a list with the main city/area on that can be used? My geography is terrible and add that to not knowing all the area and which timezone they fall into it could be a long day to construct the list my self! Thanks in advance

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  • Change a select list display value upon selecting description

    - by eli
    Hello, I would like a select list that does the following: When the select list is open, display the list of descriptions. When the user selects an item, the select list will close an only the value will be displayed. The reason for this is to conserve space as the values will be much shorter. I'm hoping that there's an answer in jQuery. Thanks.

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  • Prototype: Enable checkboxes list of a specific checkbox is checked

    - by BoDiE2003
    Guys, Ive been using jquery to do this, but now I need to do it with Prototype and Im little confused due lack of documentation I have 2 lists of check boxes First List: Check box 1 Check box 2 Second list: Check box x check box y check box z I need the JS code, using prototype to work like this: Second list, remains disabled unless I check one of the checkboxes of the First List. Any suggestions, or help, please! Thankyou.

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  • Javascript: Enable checkboxes list when a checkbox is checked (With Prototype)

    - by BoDiE2003
    Guys, Ive been using jquery to do this, but now I need to do it with Prototype and Im little confused due lack of documentation I have 2 lists of check boxes First List: Check box 1 Check box 2 Second list: Check box x check box y check box z I need the JS code, using prototype to work like this: Second list, remains disabled unless I check one of the checkboxes of the First List. Any suggestions, or help, please! Thankyou.

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