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  • Is it possible in Scala to force the caller to specify a type parameter for a polymorphic method ?

    - by Alex Kravets
    //API class Node class Person extends Node object Finder { def find[T <: Node](name: String): T = doFind(name).asInstanceOf[T] } //Call site (correct) val person = find[Person]("joe") //Call site (dies with a ClassCast inside b/c inferred type is Nothing) val person = find("joe") In the code above the client site "forgot" to specify the type parameter, as the API writer I want that to mean "just return Node". Is there any way to define a generic method (not a class) to achieve this (or equivalent). Note: using a manifest inside the implementation to do the cast if (manifest != scala.reflect.Manifest.Nothing) won't compile ... I have a nagging feeling that some Scala Wizard knows how to use Predef.<:< for this :-) Ideas ?

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  • .BAT Switches Parsing

    - by giiYanJ
    Erm.. I'm working with a switches parsing in BAT files, which goes like this: <commands> -a -b -x -y -z -u abc ...... The user may input a lot of switch, or none. So I used looped shift to make parsing infinite switches possible: :loop IF "%1"=="-a" ... SHIFT GOTO loop But when the script ends, I always get cmd executing the switches and showing up error like '-n' is not recognized as an internal... So, someone got any idea? Thanks a lot... P/S: Make solution sticks with BAT script if possible as using other language may cause dependencies problem as this script is aimed on ANY computer with Windows. Finally, thanks again =) EDIT: Tried shf301 suggestion, i found out that I used DEL %0 to delete itself but it seems the %0 is shifted into the arguments because of the SHIFT command.

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  • Can you write to a file (on a disk) in JavaScript?

    - by asdfqwer
    I don't wanna come across as a troll, so please excuse my question's demeanor, but I am a novice-intermediate programmer taking a stab at AJAX. While reading up on JavaScript I found it curious that most of the examples I've been drawing on use PHP for such an operation. I know many of you may argue that 'I'm doing it wrong' or 'JavaScript is a client-side language' etc. but the question stands. . .can you write a file in only JavaScript? EDIT: Sorry, just read faq, failed to mention this my first post on Stackoverflow while I hope I'm not sounding argumentative, pompous, or subjective.

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  • How do i sort by: most viewed, most commented, most popular, best rating, etc?

    - by MrRioku
    Pretty basic question.. I kno.., I just don't know how its done. I see it everywhere. I want to be able to sort out my content in my websites by most viewed, most commented, most popular, best rating, etc...with a drop down list, check box, etc... but I don't know how "sort by" works? Which scripting language should it be written in? Javascript? PHP? Can it be done with XML? Do I have to have a database set up like MySQL? Is there a good tutorial anywhere that explains it? I need to be explained the exact process of how it works. As you can see I really need direction.. Your help is much appreciated :D

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  • Mapping C structure to an XML element

    - by EFraim
    Suppose I have a structure in C or C++, such as: struct ConfigurableElement { int ID; char* strName; long prop1; long prop2; ... }; I would like to load/save it to/from the following XML element: <ConfigurableElement ID="1" strName="namedElem" prop1="2" prop2="3" ... /> Such a mapping can be trivially done in Java/C# or any other language with run-time reflection for the matter. Can it be done in any non-tedious way in C++ with macros/template trickery? Bonus points for handling nested structures/unions.

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  • How does OfType<T>() Work?

    - by TheCloudlessSky
    How does OfType() Work? I read this link about what's going on but how exactly does the LINQ provider know how to get all objects matching the specified type. I know the IQueryable<T> "chains" up requests and then evaluates when GetEnumerator() is called (right?). Specifically I want to know how does the framework quickly do type comparison? I wrote a method in a .NET 2.0 project that went like this (since 2.0 doesn't support these kind of features): public IEnumerable<TResult> OfType<TResult>() where TResult : class { foreach (TItem item in this.InnerList) { TResult matchItem = item as TResult; if (matchItem != null) { yield return matchItem; } } } Is this the best implementation?

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  • Accessing object's method within string

    - by Wild One
    Recently I was reading php documentation and found interesting note in string section: Functions, method calls, static class variables, and class constants inside {$} work since PHP 5. However, the value accessed will be interpreted as the name of a variable in the scope in which the string is defined. Using single curly braces ({}) will not work for accessing the return values of functions or methods or the values of class constants or static class variables. See www.php.net/manual/en/language.types.string.php It says, that I can't use curly syntax to get value returned by object's method call. Is it a mistake in manual or I misunderstood it, because I tried the following code and it works just fine: <?php class HelloWorld { public static function hello() { echo 'hello'; } } $a = new HelloWorld(); echo "{$a->hello()} world";

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  • Algorithm of JavaScript "sort()" Function

    - by Knowledge Craving
    Recently when I was working with JavaScript "sort()" function, I found in one of the tutorials that this function does not sort the numbers properly. Instead to sort numbers, a function must be added that compares numbers, like the following code:- <script type="text/javascript"> function sortNumber(a,b) { return a - b; } var n = ["10", "5", "40", "25", "100", "1"]; document.write(n.sort(sortNumber)); </script> The output then comes as:- 1,5,10,25,40,100 Now what I didn't understand is that why is this occurring & can anybody please tell in details as to what type of algorithm is being used in this "sort()" function? This is because for any other language, I didn't find this problem where the function didn't sort the numbers correctly. Any help is greatly appreciated.

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  • Dispatching generic tasks in WCF or .Net Remoting

    - by Eric
    Hello all, I've been researching for a couple days on and off, and have yet to figure out the best way to achieve the following goal. I would like to define either an interface or abstract class in C# which has an associated Run method, similar to the Java runnable interface. The goal would be to have a shared queue which contains a list of these objects. Then individual clients would be able to derive their own concrete runnable classes and add them to the queue hosted by the server. Clients would also be able to pop these runnable objects off the queue and execute them arbitrarily. This seems like it should be feasible in a VM based language without needing to place any of the concrete implementations in a shared assembly, but I have thus far had no luck finding a working example of such a system. Does anyone know how this might be achieved?

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  • Variable pre-fixes, Visual Studio 2010 onwards?

    - by thedixon
    I'm a bit bewildered on this subject, as I relate variable prefixes to being a thing of the past now, but with Visual Studio 2010 onwards (I'm currently using 2012), do people still do this and why? I only ask because, these days, you can hover over any variable and it'll tell you the variable type and scope. There's literally no requirement for pre-fixing being there for readability. By this I mean: string strHello int intHello etc. And I'm being language/tool biased here - as Visual Studio takes a lot of the legwork out for you in terms of seeing exactly what type the variable is, including after conversions in the code. This is not a "general programming" question.

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  • Feed char array into stdin

    - by Brian Lindsey
    I am writing a parser for a mini scripting language. Some of my grammar rules require jumping to a different location in the file to obtain information. There doesn't seem to be a straightforward way to accomplish this. So, I was thinking about loading my data files into a char array array and parsing line by line. This will allow me to jump all over the array with ease. My question is, is it possible to feed char arrays (i.e. char *) into stdin, so I can easily invoke the yyparse() function as needed.

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  • Guidance on using drop in DLLs

    - by Scott Chamberlain
    I have been giving the task to rewrite a internal utility in .net for my work. One of program requirements the new system has is have a dll that implements a set of interfaces and have the program call the DLL. Now this dll will be changed out a lot per deployment. My question is what is the best way to do it from a development standpoint? Do I add a template DLL (one that only has the interfaces but no implementation) to the project references like I would do any other dll that I would use. Or do I need to use somthing like this every time I want to use code from the dll? var DropIn = System.Reflection.Assembly.LoadFrom("DropInDll.dll"); var getActions = DropIn.GetType("Main").GetMethod("GetActions"); List<IAction> ActionList = (List<IAction>)getActions.Invoke(null, null);

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  • What scripts should not be ported from bash to python?

    - by Jack
    I decided to rewrite all our Bash scripts in Python (there are not so many of them) as my first Python project. The reason for it is that although being quite fluent in Bash I feel it's somewhat archaic language and since our system is in the first stages of its developments I think switching to Python now will be the right thing to do. Are there scripts that should always be written in Bash? For example, we have an init.d daemon script - is it OK to use Python for it? We run CentOS. Thanks.

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  • NSString inheritance

    - by Stef
    Hi, I'm doing an useless thing for my first step in Obj-C @interface String : NSString { int m_isnull; } - (id) init; - (int) isNull; @end @implementation String - (id) init { self = [super init]; m_isnull=1; return self; } - (int) isNull { return m_isnull; } @end test : String *a; a=@"ok"; Works fine, but just 2 little questions 1) When I'm compiling I have this warning warning: incompatible Objective-C types assigning 'struct NSString *', expected 'struct String *' I don't know how to avoid it !? 2) a=@"ok" is a fastest way to initialize a string, but when I'm debugging, I don't stop by at my init constructor why ?

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  • Force to call virtual base function instead of the overriden one.

    - by Roberto Sebestyen
    In the following example "Test that v1 function was called" fails. Is there a way to force call the base implementation of "RunFunction" through an instance of "class V2" ?? class V1 { public virtual string RunFunction() { return "V1"; } } class V2 : V1 { public override string RunFunction() { return "V2"; } } [Test] public void TestCall() { var v1 = (V1)new V2(); var v2 = new V2(); Assert.IsTrue(v1.RunFunction() == "V1", "Test that v1 function was called"); Assert.IsTrue(v2.RunFunction() == "V2", "Test that v2 function was called"); }

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  • class member access specifiers and binary code

    - by pdehaan
    I understand what the typical access specifiers are, and what they mean. 'public' members are accessible anywhere, 'private' members are accessible only by the same class and friends, etc. What I'm wondering is what, if anything, this equates to in lower-level terms. Are their any post-compilation functional differences between these beyond the high-level restrictions (what can access what) imposed by the language (c++ in this case) they're used in. Another way to put it - if this were a perfect world where programmers always made good choices (like not accessing members that may change later and using only well defined members that should stay the same between implementations), would their be any reason to use these things?

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  • java multiple connections between server and one client

    - by user1507128
    I'm trying to make like a skype-instant messager, my idea for it is to have one server which handles multiple connections for the clients. What I now have is a friend list etc, but now I want to create Threads both for server and client to handle a conversation. The problem is that I need multiple connections between a server and one client for every conversation(I think). but i dont think it's possible. Does someone have another way for doing this or maybe a way to make multiple connections between the server and a client? Thanks for helping me out PS: English is not my main language so please excuse me for my grammar.

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  • Switching from php to python

    - by ts
    Hello I am trying to make a list of things which can be difficult/surprising to someone who is changing language from PHP to Python. so far i have rather short list: forget require / include, learn import (this was most difficult to me - to understand package - module - class - object hierarchy and its mapping to filesystem) you can't just upload file on server to have webpage (-mod_python, wsgi etc) learn the python way for use variable class names (new $class() vs import + getattr) / operator in python 2.x and all float-related horrors those were difficult to me, it takes few days before mind adapts a new paradigm after i found that there is few other areas which could be challenging for someone with (too) many years of php: everything is an object you have to live with exceptions array vs list, set, dictionary, tuple ... learn (effective) list comprehensions learn generators any other ideas / personal experiences ?

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  • Are there alternative ways to implementing an "active link" navigation without using server side languages?

    - by Mel
    By "active" I mean to have the link pointing to the current page classed as "active." This way the link's appearance can be modified using css. Is it possible to implement an active link navigation without using a server side language? I would like to only use CSS/HTML/jQuery if possible. If there are, what are those methods? Assuming you want to create the following structure: <ul id="nav"> <li class="active">Home</li> <li>About</li> <li>Contact</li> </ul>

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  • How to write an unit test for WCF behaviors?

    - by katie77
    I am new to unit testing. How do I write a unit test for a method when I am extending a WCF behavior. Since I am not sure of when the class is being instantiated, or I can not change the method signature. In the behavior implementation, I am getting the header and looking up a value in the config. public class IncomingValidator : IDispatchMessageInspector { public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext) { // Grab the header and see if one of the particular values(read from config) is there. } public void BeforeSendReply(ref Message reply, object correlationState) { } }

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  • 4D - is it any good?

    - by Pies
    Recently I found out that the company a friend of mine co-owns uses 4D, which I've never heard of before. They swear by it, but they're non-technical and what they say about it sounds like memorized marketing blurb. Unfortunately the 4D website also seems devoid of any actual information and is filled with words like "comprehensive", "solution", "platform" and "integrated" instead. Since that thing is rather expensive and uses a custom language that I don't have much inclination to learn just for one project, I'm cautious about it and I'm wondering if anyone had any experience with it? Would you recommend it? What is it good for? What competitive advantage would I gain by learning it as a programmer, or using it as a company?

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  • C++ Inheritance Question

    - by shaz
    I have a base class MessageHandler and 2 derived classes, MessageHandler_CB and MessageHandler_DQ. The derived classes redefine the handleMessage(...) method. MH_DQ processes a message and puts the result in a deque while MH_CB processes the message and then executes a callback function. The base class has a static callback function that I pass along with a this pointer to a library which calls the static callback when a new message is available for processing. My problem comes when I am in the static callback with a void * pointing to either a MH_DQ or a MH_CB. If I cast it to the base class the empty MessageHandler::handleMessage(...) method is called, rather than the version in the appropriate derived class. What is the best way to address this situation from a design perspective and/or what language features might help me to implement a solution to my problem? Thanks in advance!

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  • Find and list all functions/methods in a set of JavaScript files

    - by Dan Milstein
    Is there a way to read a set of JavaScript files, and output a description of where every function/method is defined? I realize that this is likely impossible in full generality, due to the extreme dynamic nature of the language. What I'm imagining is something which gets the (relatively) straightforward cases. Ideally, I'd want it figure out where, e.g. some method got attached to string or hash or some other fundamental class (and also just let you find all the classes/functions that get defined once in one place). Does such a tool exist?

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  • class member access specifiers

    - by pdehaan
    I understand what the typical access specifiers are, and what they mean. 'public' members are accessible anywhere, 'private' members are accessible only by the same class and friends, etc. What I'm wondering is what, if anything, this equates to in lower-level terms. Are their any post-compilation functional differences between these beyond the high-level restrictions (what can access what) imposed by the language (c++ in this case) they're used in. Another way to put it - if this were a perfect world where programmers always made good choices (like not accessing members that may change later and using only well defined members that should stay the same between implementations), would their be any reason to use these things?

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  • How to make use of Tags property of an xml node to get its information and attributes?

    - by user72731
    How would i make use of tags property of a node so that i can get the attributes of an xml node. I have to display an xml tree in a winform and then when i click on any node, its attributes should get displayed on a list box in same window. I want to make use of tags property, but for that i need to convert that tree node in the winform into an xml node. I wanted to store the tree node in the tag and then typecast that tag to an xml node. I dont know how to do it? I am a newbie at C# so there might be some discrpancy in language...please help

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