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  • Is there any reason for an object pool to not be treated as a singleton?

    - by Chris Charabaruk
    I don't necessarily mean implemented using the singleton pattern, but rather, only having and using one instance of a pool. I don't like the idea of having just one pool (or one per pooled type). However, I can't really come up with any concrete situations where there's an advantage to multiple pools for mutable types, at least not any where a single pool can function just as well. What advantages are there to having multiple pools over a singleton pool?

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  • Interface in a dynamic language?

    - by Bryan
    Interface (or an abstract class with all the methods abstract) is a powerful weapon in a static language. It allows different derived types to be used in a uniformed way. However, in a dynamic language, all objects can be used in a uniformed way as long as they define certain methods. Does interface exist in dynamic languages? It seems unnecessary to me.

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  • what is session and session variables ? Plz guide

    - by haansi
    hello, I am new to asp.net Can you please guide me what is session and session variables ? Please I don't need a comparision of asp session and asp.net session because I don't know anything about asp. I have saw many articles on types of session as well. But still I cant understand erectly what is session and what are session variables in asp.net ? Please guide me. thanks

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  • How to implement an interface member that returns void in F#

    - by Drew Noakes
    Imagine the following interface in C#: interface IFoo { void Bar(); } How can I implement this in F#? All the examples I've found during 30 minutes of searching online show only examples that have return types which I suppose is more common in a functional style, but something I can't avoid in this instance. Here's what I have so far: type Bar() = interface IFoo with member this.Bar = void Fails with FS0010: Unexpected keyword 'void' in expression.

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  • How to build a gmail chat-bot?

    - by Jack
    I have read similar questions but they talk of AI models. What I want to do is build a simple bot which accepts predefined commands and performs required action. No learning needed. I have the whole flowchart prepared. What I need is to get the commands that a user types in his/her chat.

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  • Why does gcc generate verbose assembly code?

    - by Jared Nash
    I have a question about assembly code generated by GCC (-S option). Since, I am new to assembly language and know very little about it, the question will be very primitive. Still, I hope somebody will answer: Suppose, I have this C code: main(){ int x = 15; int y = 6; int z = x - y; return 0; } If we look at the assembly code (especially the part corresponding to int z = x - y ), we see: main: ... subl $16, %esp movl $15, -4(%ebp) movl $6, -8(%ebp) movl -8(%ebp), %eax movl -4(%ebp), %edx movl %edx, %ecx subl %eax, %ecx movl %ecx, %eax movl %eax, -12(%ebp) ... Why doesn't GCC generate something like this, which is less copying things around. main: ... movl $15, -4(%ebp) movl $6, -8(%ebp) movl -8(%ebp), %edx movl -4(%ebp), %eax subl %edx, %eax movl %eax, -12(%ebp) ... P.S. Linux zion-5 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i686 GNU/Linux gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)

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  • some troubles with WPF and Windows XP

    - by Sorush Rabiee
    is .net framework 3 compatible with xp? i install visual studio 9.0 (.net 3.5) on win XP. when i compile a WPF project and try to run it, this error occurs: cannot initialize application ...... at address 0x<some digits> (antivirus protection is off) after first fail of wpf, all other project types (windows application, console &...) after compiling don't run. where is problem?

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  • Tutorials and Introductions to C++ Expression Templates

    - by grrussel
    What are good introductions to the creation of C++ expression template systems? I would like to express arithmetic on user defined types while avoiding temporary values (which may be large), and to learn how to do this directly rather than applying an existing library. I have found Todd Veldhuizen's original paper and an example from the Josuttis C++ Templates book, and an article by Kreft & Langer. I am looking for simple, clear expositions.

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  • AD-DirectoryServices: .NET2.0 - Speaking architecture, approach and best practices... Suggestions?

    - by Will Marcouiller
    I've been mandated to write an application to migrate the Active Directory access models to another environment. Here's the context: I'm stuck with VB.NET 2005 and .NET Framework 2.0; The application must use the Windows authenticated user to manage AD; The objects I have to handle are Groups, Users and OrganizationalUnits; I intend to use the Façade design pattern to provider ease of use and a fully reusable code; I plan to write a factory for each of the objects managed (group, ou, user); The use of Attributes should be useful here, I guess; As everything is about the DirectoryEntry class when accessing the AD, it seems a good candidate for generic types. Obligatory features: User creates new OUs manually; User creates new group manually; User creates new user (these users are services accounts) manually; Application reads an XML file which contains the OUs, groups and users to create; Application informs the user about the OUs, groups and users that shall be created; User specifies the domain environment where to migrate the XML input file designated objects; User makes changes if needed, and launches the task operations; Application performs required by the XML input file operations against the underlying AD as specified by the user; Application informs the user upon completion. Linear features: User fetches OUs, groups, users; User changes OUs, groups, users; User deletes OUs, groups, users; The application logs AD entries and operations performed, plus errors and exceptions; Nice-to-have features: Application rollbacks operations on error or exception. I've been working for weeks now to get acquainted with the AD and the System.DirectoryServices assembly. But I don't seem to find a way to be fully satisfied with what I'm doing and always looking for better. I have studied Bret de Smet's Linq to AD on CodePlex, but then again, I can't use it as I'm stuck with .NET 2.0, so no Linq! But I've learned about Attributes, and seen that he's working with generic types as he codes a DirectorySource class to perform the operations for OUs, groups and users. I have been able to add groups to the AD; I have been able to add users to the AD; The created user is automatically disabled? I seem to get confused with the use of a LDAP path to add objects. For instance, one needs two instances of a System.DirectoryServices.DirectoryEntry class to add a group, for instance. Why this? Any suggestions? Thanks for any help, code sample, ideas, architural solution, everything!

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  • Why do my raytraced spheres have dark lines when lit with multiple light sources?

    - by Curyous
    I have a simple raytracer that only works back up to the first intersection. The scene looks OK with two different light sources, but when both lights are in the scene, there are dark shadows where the lit area from one ends, even if in the middle of a lit area from the other light source (particularly noticeable on the green ball). The transition from the 'area lit by both light sources' to the 'area lit by just one light source' seems to be slightly darker than the 'area lit by just one light source'. The code where I'm adding the lighting effects is: // trace lights for ( int l=0; l<primitives.count; l++) { Primitive* p = [primitives objectAtIndex:l]; if (p.light) { Sphere * lightSource = (Sphere *)p; // calculate diffuse shading Vector3 *light = [[Vector3 alloc] init]; light.x = lightSource.centre.x - intersectionPoint.x; light.y = lightSource.centre.y - intersectionPoint.y; light.z = lightSource.centre.z - intersectionPoint.z; [light normalize]; Vector3 * normal = [[primitiveThatWasHit getNormalAt:intersectionPoint] retain]; if (primitiveThatWasHit.material.diffuse > 0) { float illumination = DOT(normal, light); if (illumination > 0) { float diff = illumination * primitiveThatWasHit.material.diffuse; // add diffuse component to ray color colour.red += diff * primitiveThatWasHit.material.colour.red * lightSource.material.colour.red; colour.blue += diff * primitiveThatWasHit.material.colour.blue * lightSource.material.colour.blue; colour.green += diff * primitiveThatWasHit.material.colour.green * lightSource.material.colour.green; } } [normal release]; [light release]; } } How can I make it look right?

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  • Cannot create the Silverlight ASP.NET website in Visual Studio 2008 Web Developer edition

    - by BALAMURUGAN
    I need to create a ASp.net website with silverlight controls. I am having only express editions of 2008 (Web developer edition and C# express editions). I have created the WPF application sing C# expression and create the new XAML files. Then I have created asp.net website in web developer edition and linked the xaml files with the . But nothing works. Note: I have not silverlight application project types and templates in Visual Studio 2008 web developer edition.

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  • Dynamic data-entry value store

    - by simendsjo
    I'm creating a data-entry application where users are allowed to create the entry schema. My first version of this just created a single table per entry schema with each entry spanning a single or multiple columns (for complex types) with the appropriate data type. This allowed for "fast" querying (on small datasets as I didn't index all columns) and simple synchronization where the data-entry was distributed on several databases. I'm not quite happy with this solution though; the only positive thing is the simplicity... I can only store a fixed number of columns. I need to create indexes on all columns. I need to recreate the table on schema changes. Some of my key design criterias are: Very fast querying (Using a simple domain specific query language) Writes doesn't have to be fast Many concurrent users Schemas will change often Schemas might contain many thousand columns The data-entries might be distributed and needs syncronization. Preferable MySQL and SQLite - Databases like DB2 and Oracle is out of the question. Using .Net/Mono I've been thinking of a couple of possible designs, but none of them seems like a good choice. Solution 1: Union like table containing a Type column and one nullable column per type. This avoids joins, but will definitly use a lot of space. Solution 2: Key/value store. All values are stored as string and converted when needed. Also use a lot of space, and of course, I hate having to convert everything to string. Solution 3: Use an xml database or store values as xml. Without any experience I would think this is quite slow (at least for the relational model unless there is some very good xpath support). I also would like to avoid an xml database as other parts of the application fits better as a relational model, and being able to join the data is helpful. I cannot help to think that someone has solved (some of) this already, but I'm unable to find anything. Not quite sure what to search for either... I know market research is doing something like this for their questionnaires, but there are few open source implementations, and the ones I've found doesn't quite fit the bill. PSPP has much of the logic I'm thinking of; primitive column types, many columns, many rows, fast querying and merging. Too bad it doesn't work against a database.. And of course... I don't need 99% of the provided functionality, but a lot of stuff not included. I'm not sure this is the right place to ask such a design related question, but I hope someone here has some tips, know of any existing work, or can point me to a better place to ask such a question. Thanks in advance!

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  • Strange behavior of move with strings

    - by Umair Ahmed
    I am testing some enhanced string related functions with which I am trying to use move as a way to copy strings around for faster, more efficient use without delving into pointers. While testing a function for making a delimited string from a TStringList, I encountered a strange issue. The compiler referenced the bytes contained through the index when it was empty and when a string was added to it through move, index referenced the characters contained. Here is a small downsized barebone code sample:- unit UI; interface uses System.SysUtils, System.Types, System.UITypes, System.Rtti, System.Classes, System.Variants, FMX.Types, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.Layouts, FMX.Memo; type TForm1 = class(TForm) Results: TMemo; procedure FormCreate(Sender: TObject); end; var Form1: TForm1; implementation {$R *.fmx} function StringListToDelimitedString ( const AStringList: TStringList; const ADelimiter: String ): String; var Str : String; Temp1 : NativeInt; Temp2 : NativeInt; DelimiterSize : Byte; begin Result := ' '; Temp1 := 0; DelimiterSize := Length ( ADelimiter ) * 2; for Str in AStringList do Temp1 := Temp1 + Length ( Str ); SetLength ( Result, Temp1 ); Temp1 := 1; for Str in AStringList do begin Temp2 := Length ( Str ) * 2; // Here Index references bytes in Result Move ( Str [1], Result [Temp1], Temp2 ); // From here the index seems to address characters instead of bytes in Result Temp1 := Temp1 + Temp2; Move ( ADelimiter [1], Result [Temp1], DelimiterSize ); Temp1 := Temp1 + DelimiterSize; end; end; procedure TForm1.FormCreate(Sender: TObject); var StrList : TStringList; Str : String; begin // Test 1 : StringListToDelimitedString StrList := TStringList.Create; Str := ''; StrList.Add ( 'Hello1' ); StrList.Add ( 'Hello2' ); StrList.Add ( 'Hello3' ); StrList.Add ( 'Hello4' ); Str := StringListToDelimitedString ( StrList, ';' ); Results.Lines.Add ( Str ); StrList.Free; end; end. Please devise a solution and if possible, some explanation. Alternatives are welcome too.

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  • dual map structure implementation?

    - by Danra
    Hey, I'm looking for a standard dual-map structure - is there one implemented in std/boost/another standard C++ library? When I say "dual-map" I mean a map which can be indexed efficiently both by the key and the "value" (it actually has two key types instead of one key type and one value type). for example: dualmap<int,string> m; m[1] = "foo"; m["bar"] = 2 int a = m["bar"]; // a = 2 Thanks, Dan

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  • Another C datatypes question

    - by b-gen-jack-o-neill
    Hello. Well, I completely get the most basic datatypes of C, like short, int, long, float, to be exact, all numerical types.These types are needed to be known perform right operations with right numbers. For example to use FPU to add two float numbers. So the compiler must know what the type is. But, when it comes to characters I am little bit off. I know that basic C datatype char is there for ASCII characters coding. But what I don´t know is, why you even need another datatype for characters. Why could not you just use 1 byte integer value to store ASCII character. If you call printf, you apecify the datatype in the call, so you could say to printf that the integer represents ASCII character. I dont know how cout resolves datatype, but I guess you could just specify it somehow. Another thing is, when you want to use Unicode, you must use datatype wchar. But, what if I would like to use some another, for example ISO, or Windows coding instead of UTF? Becouse wchar codes characters as UTF-16 or UTF-32 (I read its compiler specific). And, what if I would want to use for example some imaginary new 8 byte text coding? What datatype should I use for it? I am actually pretty confused of this, becouse I always expected that if I want to use UTF-32 instead of ASCII, I just tell compiler "get UTF-32 value of the character I typed and save it into 4 char field." I thought that text coding is to be dealt with by the end, print function for example. That I just need to specify the coding for the compiler to use, since Windows doesent use ASCII in win32 apps, I guess C compiler must convert the char I typed to ASCII from whatever the type is that windows sends to the C editor. And the last thing is, what if I want to use for example 25 Byte integer for some high math operations? C has no specify-yourself datatype. Yes, I know that this would be difficult since all the math operations would need to be changed, becouse CPU can not add 25 Bytes numbers together. But is there a way to do it? Or is there some math library for it? What if I want to compute Pi to 1000000000000000 digits? :) I know my question is pretty long, but I just wanted to explain my thoughts the best I can in English, since its not my native language it is difficult. And I believe there is simple answer to my question(s), something I missed that explains everything. I read lot about text coding, C tutorials, but nothing about his. Thank you for your time.

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