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  • How to perform a binary search on IList<T>?

    - by Daniel Brückner
    Simple question - given an IList<T> how do you perform a binary search without writing the method yourself and without copying the data to a type with build-in binary search support. My current status is the following. List<T>.BinarySearch() is not a member of IList<T> There is no equivalent of the ArrayList.Adapter() method for List<T> IList<T> does not inherit from IList, hence using ArrayList.Adapter() is not possible I tend to believe that is not possible with build-in methods, but I cannot believe that such a basic method is missing from the BCL/FCL. If it is not possible, who can give the shortest, fastest, smartest, or most beatiful binary search implementation for IList<T>? UPDATE We all know that a list must be sorted before using binary search, hence you can assume that it is. But I assume (but did not verify) it is the same problem with sort - how do you sort IList<T>? CONCLUSION There seems to be no build-in binary search for IList<T>. One can use First() and OrderBy() LINQ methods to search and sort, but it will likly have a performance hit. Implementing it yourself (as an extension method) seems the best you can do.

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  • Java map with values limited by key's type parameter

    - by Ashley Mercer
    Is there a way in Java to have a map where the type parameter of a value is tied to the type parameter of a key? What I want to write is something like the following: public class Foo { // This declaration won't compile - what should it be? private static Map<Class<T>, T> defaultValues; // These two methods are just fine public static <T> void setDefaultValue(Class<T> clazz, T value) { defaultValues.put(clazz, value); } public static <T> T getDefaultValue(Class<T> clazz) { return defaultValues.get(clazz); } } That is, I can store any default value against a Class object, provided the value's type matches that of the Class object. I don't see why this shouldn't be allowed since I can ensure when setting/getting values that the types are correct. EDIT: Thanks to cletus for his answer. I don't actually need the type parameters on the map itself since I can ensure consistency in the methods which get/set values, even if it means using some slightly ugly casts.

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  • How can i convert this to a factory/abstract factory?

    - by Amitd
    I'm using MigraDoc to create a pdf document. I have business entities similar to the those used in MigraDoc. public class Page{ public List<PageContent> Content { get; set; } } public abstract class PageContent { public int Width { get; set; } public int Height { get; set; } public Margin Margin { get; set; } } public class Paragraph : PageContent{ public string Text { get; set; } } public class Table : PageContent{ public int Rows { get; set; } public int Columns { get; set; } //.... more } In my business logic, there are rendering classes for each type public interface IPdfRenderer<T> { T Render(MigraDoc.DocumentObjectModel.Section s); } class ParagraphRenderer : IPdfRenderer<MigraDoc.DocumentObjectModel.Paragraph> { BusinessEntities.PDF.Paragraph paragraph; public ParagraphRenderer(BusinessEntities.PDF.Paragraph p) { paragraph = p; } public MigraDoc.DocumentObjectModel.Paragraph Render(MigraDoc.DocumentObjectModel.Section s) { var paragraph = s.AddParagraph(); // add text from paragraph etc return paragraph; } } public class TableRenderer : IPdfRenderer<MigraDoc.DocumentObjectModel.Tables.Table> { BusinessEntities.PDF.Table table; public TableRenderer(BusinessEntities.PDF.Table t) { table =t; } public MigraDoc.DocumentObjectModel.Tables.Table Render(Section obj) { var table = obj.AddTable(); //fill table based on table } } I want to create a PDF page as : var document = new Document(); var section = document.AddSection();// section is a page in pdf var page = GetPage(1); // get a page from business classes foreach (var content in page.Content) { //var renderer = createRenderer(content); // // get Renderer based on Business type ?? // renderer.Render(section) } For createRenderer() i can use switch case/dictionary and return type. How can i get/create the renderer generically based on type ? How can I use factory or abstract factory here? Or which design pattern better suits this problem?

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  • Why does this return zero results?

    - by Jon
    I have a List<List<string>> and when I try to search with the List<string> it returns no results. Any ideas? Thanks List<List<string>> test = new List<List<string>>(); List<string> ff = new List<string>(); ff.Add("1"); ff.Add("ABC 1"); test.Add(ff); ff = new List<string>(); ff.Add("2"); ff.Add("ABC 2"); test.Add(ff); var result = test.Where(x=>x.Contains("ABC")); //result.Count(); is 0

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  • generic programming in C with void pointer.

    - by Nyan
    Hi everyone, even though it is possible to write generic code in C using void pointer(generic pointer), I find that it is quite difficult to debug the code since void pointer can take any pointer type without warning from compiler. (e.g function foo() take void pointer which is supposed to be pointer to struct, but compiler won't complain if char array is passed.) What kind of approach/strategy do you all use when using void pointer in C?

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  • Extending both T and SomeInterface<T> in Java

    - by Graeme Moss
    I want to create a class that takes two parameters. One should be typed simply as T. The other should be typed as something that extends both T and SomeInterface. When I attempt this with public class SomeClass<T, S extends SomeInterface<T> & T> then Java complains with "The type T is not an interface; it cannot be specified as a bounded parameter" and if instead I attempt to create an interface for S with public interface TandSomeInterface<T> extends SomeInterface<T>, T then Java complains with "Cannot refer to the type parameter T as a supertype" Is there any way to do this in Java? I think you can do it in C++...?

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  • Do I have to allocate and free records when using TList<T> in Delphi?

    - by afrazier
    The question more or less says it all. Given the following record structure: type TPerson = record Name: string; Age: Integer; end; PPerson = ^TPerson; TPersonList = TList<TPerson>; Is the following code valid? procedure ReadPeople(DataSet: TDataSet; PersonList: TPersonList); begin PersonList.Count := DataSet.RecordCount; if DataSet.RecordCount = 0 then Exit; DataSet.First; while not DataSet.Eof do begin PersonList[DataSet.RecNo].Name := DataSet.FieldByName('Name').AsString; PersonList[DataSet.RecNo].Age := DataSet.FieldByName('Age').AsInteger; DataSet.Next; end; end; Do I have to use GetMem/FreeMem to allocate and free records an instance of TPersonList, or am I free to directly access the TPersonList entries directly? My gut says that the code should be valid, though I'm not sure if there's any wrinkles related to record initialization or finalization.

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  • .net runtime type casting when using reflection

    - by Mike
    I have need to cast a generic list of a concrete type to a generic list of an interface that the concrete types implement. This interface list is a property on an object and I am assigning the value using reflection. I only know the value at runtime. Below is a simple code example of what I am trying to accomplish: public void EmployeeTest() { IList<Employee> initialStaff = new List<Employee> { new Employee("John Smith"), new Employee("Jane Doe") }; Company testCompany = new Company("Acme Inc"); //testCompany.Staff = initialStaff; PropertyInfo staffProperty = testCompany.GetType().GetProperty("Staff"); staffProperty.SetValue(testCompany, (staffProperty.PropertyType)initialStaff, null); } Classes are defined like so: public class Company { private string _name; public string Name { get { return _name; } set { _name = value; } } private IList<IEmployee> _staff; public IList<IEmployee> Staff { get { return _staff; } set { _staff = value; } } public Company(string name) { _name = name; } } public class Employee : IEmployee { private string _name; public string Name { get { return _name; } set { _name = value; } } public Employee(string name) { _name = name; } } public interface IEmployee { string Name { get; set; } } Any thoughts? I am using .NET 4.0. Would the new covariant or contravariant features help? Thanks in advance.

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  • Java enums in generic type

    - by Marcin Cylke
    Hi, I'd like to create a generic enum-based mapper for IBatis. I'm doing this with the below code. This does have compile time errors, which I don't know how to fix. Maybe my solution is just plain wrong (keep in mind the use of IBatis), in such case please suggest something better. Any help appreciated. What I want to achieve is to define subsequent mappers as: public class XEnumTypeHandler extends CommonEnumTypeHandler<X> { } The current code: public class CommonEnumTypeHandler<T extends Enum> implements TypeHandlerCallback { public void setParameter(ParameterSetter ps, Object o) throws SQLException { if (o.getClass().isAssignableFrom(**T**)) { ps.setString(((**T**) o).value().toUpperCase()); } else throw new SQLException("Excpected ParameterType object than: " + o); } public Object getResult(ResultGetter rs) throws SQLException { Object o = valueOf(rs.getString()); if (o == null) throw new SQLException("Unknown parameter type: " + rs.getString()); return o; } public Object valueOf(String s) { for (T pt : T.**values()**) { if (pt.**value()**.equalsIgnoreCase(s)) return pt; } return null; } } I've added error markings to the above code, the error messages are in order: T cannot be resolved The method value() is undefined for the type T The method values() is undefined for the type T The method values() is undefined for the type T

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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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  • XML Serializing a class with a Dictionary<string, List<string>> object

    - by Matt
    Is it possible to implement IXmlSerializable and in my XML file capture an object of type Dictionary ? I have the following public class coolio : IXmlSerializable { private int a; private bool b; private string c; private Dictionary<string, List<string>> coco; public coolio(int _a, bool _b, string _c, Dictionary<string, List<string>> _coco) { a=_a; b=_b; c=_c; coco=_coco; } public System.Xml.Schema.XmlSchema GetSchema() { return null; } public void WriteXml(XmlWriter writer) { const string myType = "coolio"; writer.WriteStartElement(myType); writer.WriteAttributeString("a", a.ToString()); writer.WriteAttributeString("b", b.ToString()); writer.WriteAttributeString("c", c); // How do I add a subelement for Dictionary<string, List<string>> coco? writer.WriteEndElement(); } public void ReadXml(XmlReader reader) { if (reader.MoveToContent() != XmlNodeType.Element || reader.LocalName != "coolio") return; a= int.Parse(reader["a"]); b = bool.Parse(reader["b"]); c= reader["c"]; // How do I read subelement into Dictionary<string, List<string>> coco? } } But I am stumped as to how I could add the Dictionary (XML seriliazed to my XML file)

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  • Hot to get generic type from object type

    - by Murat
    My Classes are; class BaseClass { } class DerivedClass1 : BaseClass { } class GenericClass<T> { } class DerivedClass2 : BaseClass { GenericClass<DerivedClass1> subItem; } I want to access all fields of DerivedClass2 class. I use System.Reflection and FieldInfo.GetValue() method; Bu I cant get subItem field. FieldInfo.GetValue() method return type is "object". And I cant cast to GenericClass<DerivedClass1> or I cant get DerivedClass1 type. I try this with BaseClass BaseClass instance = FieldInfo.Getvalue(this) as GenericClass<BaseClass>; but instance is null. How to get instance with type or how to get only type?

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  • Unchecked call to compareTo

    - by Dave Jarvis
    Background Create a Map that can be sorted by value. Problem The code executes as expected, but does not compile cleanly: http://pastebin.com/bWhbHQmT The syntax for passing Comparable as a generic parameter along to the Map.Entry<K, V> (where V must be Comparable?) -- so that the (Comparable) typecast shown in the warning can be dropped -- eludes me. Warning Compiler's cantankerous complaint: SortableValueMap.java:24: warning: [unchecked] unchecked call to compareTo(T) as a member of the raw type java.lang.Comparable return ((Comparable)entry1.getValue()).compareTo( entry2.getValue() ); Question How can the code be changed to compile without any warnings (without suppressing them while compiling with -Xlint:unchecked)? Related TreeMap sort by value How to sort a Map on the values in Java? http://paaloliver.wordpress.com/2006/01/24/sorting-maps-in-java/ Thank you!

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  • I can't find the cause of an "unchecked or unsafe operations" warning in Java.

    - by Peter
    Hello, as per the title I am struggling to find the cause of an "unchecked or unsafe operations" warning in some code. If I have the following code, it compiles without any warnings: public void test() { Set<String> mySet = new HashSet<String>(); Set<String> myNewSet = mySet; //do stuff } Now, if I change where mySet comes from, specifically as the result of a method call, I get the "unchecked yadda yadda" warning: public void test() { Set<String> myNewSet = this.getSet(); //do stuff } public Set getSet() { Set<String> set = new HashSet<String>(); return set; } I have tried and tried to work out what the problem is and I am completely stumped. The issue is present whether I use Sets or Lists. Why would the Set returned by the getSet method be any different to the Set in the first example? Any help would be greatly appreciated as while the warning isn't the end of the world, it is bugging the hell out of me! :( Regards

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  • Is there a way to achieve covariance of generic types in C# 3.0?

    - by nullDev
    This has been introduced in C# 4.0, but is there a way to achieve this in c# 3.0? For e.g., consider the following code: class Base { } class Derived1 : Base { } class Derived2 : Base { } class User<T> where T : Base { } class User1 : User<Derived1> { } Now, I would like to have a list of User<T>, in which I can store User<Derived1> as well as User<Derived2>, but the following code fails to compile in C# 3.0: List<User<Base>> users = new List<User<Base>>(); users.Add(new User1()); Any ideas?

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  • Casting Generic Types

    - by David Rutten
    Public Function CastToT(Of T)(ByVal GenericType(Of Object) data) As GenericType(Of T) Return DirectCast(data, GenericType(Of T)) End Function The above clearly does not work. Is there any way to perform this cast if I know that all objects inside data are in fact of Type T?

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  • Generic overriding tells me this is the same function. Not agree.

    - by serhio
    base class: Class List(Of T) Function Contains(ByVal value As T) As Boolean derived class: Class Bar : List(Of Exception) ' Exception type as example ' Function Contains(Of U)(ByVal value As U) As Boolean compiler tells me that that two are the same, so I need to declare Overloads/new this second function. But I want use U to differentiate the type (one logic) like NullReferenceException, ArgumentNull Exception, etc. but want to leave the base function(no differentiation by type - other logic) as well.

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  • Use component id in Castle Windsor generic object configuration

    - by ChoccyButton
    2 questions in one, but very much related. Is it possible with Castle Windsor to resolve a configuration entry such as - Assembly.Namespace.Object1`2[[${ComponentId1}],[${ComponentId2}]], Assembly Where ComponentId1 and ComponentId2 are defined as components. Castle Windsor doesn't seem to be resolving the ComponentId, it is just looking for ComponentId1 in the Castle.Windsor assembly. The second question comes in to play if you can't do the first question. If you have to use a full assembly reference instead of a ComponentId, how can you pass any parameters to the object being created? eg to set ComponentId1.Field1 = "blah", or pass something to the constructor of ComponentId1 Hope that makes sense Update - Following the request for code I've knocked together the following - Objects public class Wrapper<T, T1> where T : ICollector where T1:IProcessor { private T _collector; private T1 _processor; public Wrapper(T collector, T1 processor) { _collector = collector; _processor = processor; } public void GetData() { _collector.CollectData(); _processor.ProcessData(); } } public class Collector1 : ICollector { public void CollectData() { Console.WriteLine("Collecting data from Collector1 ..."); } } public class Processor1 : IProcessor { public void ProcessData() { Console.WriteLine("Processing data from Processor1 ..."); } } repeated so 3 of each type of object in the example Config <components> <component id="Collector1" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector1, CastleWindsorPlay"/> <component id="Collector2" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector2, CastleWindsorPlay"/> <component id="Collector3" service="CastleWindsorPlay.ICollector, CastleWindsorPlay" type="CastleWindsorPlay.Collector3, CastleWindsorPlay"/> <component id="Processor1" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor1, CastleWindsorPlay"/> <component id="Processor2" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor2, CastleWindsorPlay"/> <component id="Processor3" service="CastleWindsorPlay.IProcessor, CastleWindsorPlay" type="CastleWindsorPlay.Processor3, CastleWindsorPlay"/> <component id="Wrapper1" type="CastleWindsorPlay.Wrapper`2[[CastleWindsorPlay.Collector1, CastleWindsorPlay],[CastleWindsorPlay.Processor3, CastleWindsorPlay]], CastleWindsorPlay" /> </components> Instantiation var wrapper = (Wrapper<ICollector, IProcessor>) container.Resolve("Wrapper1"); wrapper.GetData(); This brief example errors with this error message though - Can't create component 'Wrapper1' as it has dependencies to be satisfied. Wrapper1 is waiting for the following dependencies: Services: - CastleWindsorPlay.Collector1 which was not registered. - CastleWindsorPlay.Processor3 which was not registered. The curious part about this is that I can get it to resolve Collector1 and Processor3 individually before the call to the wrapper, but the wrapper still can't see them. This is a basic example, the next thing I'd like to be able to do is when instantiating the Wrapper, set a property on the collector and/or processor. So it could be something like Collector.Id = 10, but set in the config where the wrapper is defined. Setting against the Collector component definition wouldn't work as I'd want to be able to instantiate multiple copies of each Collector, using different Id's Update 2 What I'm actually trying to do is have - <components> <component id="Wrapper1" type="CastleWindsorPlay.Wrapper`2[${Collector1}(id=1)],[${Processor3}]], CastleWindsorPlay" /> <component id="Wrapper2" type="CastleWindsorPlay.Wrapper`2[${Collector1}(id=3)],[${Processor3}]], CastleWindsorPlay" /> </components> Then have another object defined as <component id="Manager" type="CastleWindsorPlay.Manager,CastleWindsorPlay"> <parameters> <wrappers> <array> <item>${Wrapper1}</item> <item>${Wrapper2}</item> </array> </wrappers> </parameters> Then finally in code just be able to call - var manager = (Manager)container.Resolve("Manager"); This should return the manager object, with an array of wrappers populated and the wrappers configured with the correct Collector and Convertor. I know there are errors in the Castle config here, that's why I'm asking the question, I don't know how to set the config up to do what I'm after, or even if it's possible to do it in Castle Windsor

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