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• Perl: reference to subroutine in external .pm file

  - by Pmarcoen

  I'm having some trouble figuring out how to make a reference to a subroutine in an external .pm file. Right now, I'm doing this : External file package settingsGeneral; sub printScreen { print $_[0]; } Main use settingsGeneral; my $printScreen = settingsGeneral::printScreen; &$printScreen("test"); but this result into an error: Can't use string ("1") as a subroutine ref while "strict refs" in use

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• Python - how to check if weak reference is still available

  - by Alex

  Hi all, I am passing some weakrefs from Python into C++ class, but C++ destructors are actively trying to access the ref when the real object is already dead, obviously it crashes... Is there any Python C/API approach to find out if Python reference is still alive or any other known workaround for this ? Thanks

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• How to self-assess your programming abilities?

  - by Ivo Danihelka

  What is a good test of your smartness vs. stupidity? Is Google Code Jam a good test for that? Or would you suggest something else? I want to know whether I'm a good programmer or not.

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• Pass a dynamic structure by reference? [C]

  - by Blackbinary

  How do i pass a structure like : struct data { int x; }; /*MAIN*/ struct data *root; by reference to a function? Thanks for any help!

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• Return reference from class to this.

  - by Thomas

  Hi, I have the following member of class foo. foo &foo::bar() { return this; } But I am getting compiler errors. What stupid thing am I doing wrong? Compiler error (gcc): error: invalid initialization of non-const reference of type 'foo&' from a temporary of type 'foo* const'

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• Self referential type

  - by pythonic metaphor

  What type T makes the following code compilable? T f(){ return &f; } I'd prefer a C answer, but I marked the question as C and C++ in case there is only an answer using templates.

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• Model self referential collections in Rails

  - by Najitaka

  I have written an application for an online clothing store in Rails 2.3.5. I want to show related Products when a customer views the Product Detail page. For example, if the customer views the detail page for a suit, I'd like to display the accessory products that match the dress such as a vest, shoes, and belt. I have named the related products an Ensemble. However, the vest, shoes, and belts are also Products which is what has me struggling. I have it working as follows but I know it's not the Rails way. I have a Products table for all of the products. Not important here but I also have a ProductDetails table. I have an Ensembles table that has the following columns: product_id - the main or origination product, the one displayed on the detail page outfit_id - the related or accessory product In setting up the data, on the Products list, for each Product I have an Ensemble link. This link takes you to the index action in the Ensembles controller. Using the id from the "main" Product, I find all of the associated Ensemble rows by product_id or I create a new ensemble and assign the id from the main product as the product_id. I'd like to just be able to do @product.related_products to get an Ensemble collection. Also on the index page I list the columns of the main product so the user can be sure their main product was the one they selected from the list. I also have a select list of the other products, with an Add to Ensemble action. Finally on the same index page, I have a table that displays the products that are already in the ensemble and in that list each row has a destroy link to remove a particular product from the ensemble. It would be nice if given a single Ensemble row @ensemble I could do @ensemble.product to get the Product related to the outfit_id of the ensemble row. I've got it working without associations but I have to run queries in the controller to build my own @product, @ensemble, and @ensembles collections. Also the only way I found to destroy an ensemble row is by Ensemble.connection.delete(sql to delete), simple @ensemble.destroy doesn't work. Anyone know how I would set up the associations or have a link to a site explaining a similar setup. None of the examples I found use the same table. They have A related to B through C. I want A related to other A through B.

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• C# - Does foreach() iterate by reference?

  - by sharkin

  Consider this: List<MyClass> obj_list = get_the_list(); foreach( MyClass obj in obj_list ) { obj.property = 42; } Is 'obj' a reference to the corresponding object within the list so that when I change the property the change will persist in the object instance once constructed somewhere?

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• C# Possible unintended reference comparison...

  - by Pandiya Chendur

  When i try to check Session["userId"] != null why i get this message Possible unintended reference comparrison; to get value comparrison; cast left hand side to string Any suggestion....

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• Python - copy by reference

  - by qba

  Is there any possibility to copy variable by reference no matter if its int or class instance? My goal is to have two lists of the same objects and when one changes, change is visible in second. In other words i need pointers:/

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• "undefined reference" error with namespace across multiple files

  - by user1330734

  I've looked at several related posts but no luck with this error. I receive this undefined reference error message below when my namespace exists across multiple files. If I compile only ConsoleTest.cpp with contents of Console.cpp dumped into it the source compiles. I would appreciate any feedback on this issue, thanks in advance. g++ Console.cpp ConsoleTest.cpp -o ConsoleTest.o -Wall /tmp/cc8KfSLh.o: In function `getValueTest()': ConsoleTest.cpp:(.text+0x132): undefined reference to `void Console::getValue<unsigned int>(unsigned int&)' collect2: ld returned 1 exit status Console.h #include <iostream> #include <sstream> #include <string> namespace Console { std::string getLine(); template <typename T> void getValue(T &value); } Console.cpp #include "Console.h" using namespace std; namespace Console { string getLine() { string str; while (true) { cin.clear(); if (cin.eof()) { break; // handle eof (Ctrl-D) gracefully } if (cin.good()) { char next = cin.get(); if (next == '\n') break; str += next; // add character to string } else { cin.clear(); // clear error state string badToken; cin >> badToken; cerr << "Bad input encountered: " << badToken << endl; } } return str; } template <typename T> void getValue(T &value) { string inputStr = Console::getLine(); istringstream strStream(inputStr); strStream >> value; } } ConsoleTest.cpp #include "Console.h" void getLineTest() { std::string str; std::cout << "getLinetest" << std::endl; while (str != "next") { str = Console::getLine(); std::cout << "<string>" << str << "</string>"<< std::endl; } } void getValueTest() { std::cout << "getValueTest" << std::endl; unsigned x = 0; while (x != 12345) { Console::getValue(x); std::cout << "x: " << x << std::endl; } } int main() { getLineTest(); getValueTest(); return 0; }

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• Passing arguments by value or by reference in objective C

  - by Rafael

  Hello, I'm kind of new with objective c and I'm trying to pass an argument by reference but is behaving like it were a value. Do you know why this doesn't work? This is the function: - (void) checkRedColorText:(UILabel *)labelToChange { NSComparisonResult startLaterThanEnd = [startDate compare:endDate]; if (startLaterThanEnd == NSOrderedDescending){ labelToChange.textColor = [UIColor redColor]; } else{ labelToChange.textColor = [UIColor blackColor]; } } And this the call: UILabel *startHourLabel; (this is properly initialized in other part of the code) [self checkRedColorText:startHourLabel]; Thanks for your help

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• R: Pass by reference

  - by Pierre

  Can you pass by reference with "R" ? for example, in the following code: setClass("MyClass", representation( name="character" )) instance1 <-new("MyClass",name="Hello1") instance2 <-new("MyClass",name="Hello2") array = c(instance1,instance2) instance1 array instance1@name="World!" instance1 array the output is > instance1 An object of class “MyClass” Slot "name": [1] "World!" > array [[1]] An object of class “MyClass” Slot "name": [1] "Hello1" [[2]] An object of class “MyClass” Slot "name": [1] "Hello2" but I wish it was > instance1 An object of class “MyClass” Slot "name": [1] "World!" > array [[1]] An object of class “MyClass” Slot "name": [1] "World!" [[2]] An object of class “MyClass” Slot "name": [1] "Hello2" is it possible ? Thanks Pierre

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• How to stop a QDialog from executing while still in the __init__ statement(or immediatly after)?

  - by Jonathan

  I am wondering how I can go about stopping a dialog from opening if certain conditions are met in its __init__ statement. The following code tries to call the 'self.close()' function and it does, but (I'm assuming) since the dialog has not yet started its event loop, that it doesn't trigger the close event? So is there another way to close and/or stop the dialog from opening without triggering an event? Example code: from PyQt4 import QtCore, QtGui class dlg_closeInit(QtGui.QDialog): ''' Close the dialog if a certain condition is met in the __init__ statement ''' def __init__(self): QtGui.QDialog.__init__(self) self.txt_mytext = QtGui.QLineEdit('some text') self.btn_accept = QtGui.QPushButton('Accept') self.myLayout = QtGui.QVBoxLayout(self) self.myLayout.addWidget(self.txt_mytext) self.myLayout.addWidget(self.btn_accept) self.setLayout(self.myLayout) # Connect the button self.connect(self.btn_accept,QtCore.SIGNAL('clicked()'), self.on_accept) self.close() def on_accept(self): # Get the data... self.mydata = self.txt_mytext.text() self.accept() def get_data(self): return self.mydata def closeEvent(self, event): print 'Closing...' if __name__ == '__main__': import sys app = QtGui.QApplication(sys.argv) dialog = dlg_closeInit() if dialog.exec_(): print dialog.get_data() else: print "Failed"

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• reference to specific hash key

  - by dave

  How do I create a reference to the value in a specific hash key. I tried the following but $$foo is empty. Any help is much appreciated. $hash->{1} = "one"; $hash->{2} = "two"; $hash->{3} = "three"; $foo = \${$hash->{1}}; $hash->{1} = "ONE"; #I want "MONEY: ONE"; print "MONEY: $$foo\n";

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• Exception while trying to reference LINQ namespace

  - by MarceloRamires

  While trying to use linq in a .NET 2.0 winforms project I got: Namespace or type specified in the Imports 'System.Linq' doesn't contain any public member or cannot be found. Make sure the namespace or the type is defined and contains at least one public member. Make sure the imported element name doesn't use any aliases In both the lines that reference the following namespaces: System.Linq; System.Xml.Linq; How could I get these namespaces to work on .NET 2.0 without referencing an external DLL or anything ?

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• TMS320C64x Quick start reference for porgrammers

  - by osgx

  Hello Is thare any quickstart guide for programmers for writing DSP-accelerated appliations for TMS320C64x? I have a program with custom algorythm (not the fft, or usial filtering) and I want to accelerate it using multi-DSP coprocessor. So, how should I modify source to move computation from main CPU to DSPs? What limitations are there for DSP-running code? I have some experience with CUDA. In CUDA I should mark every function as being host, device, or entry point for device (kernel). There are also functions to start kernels and to upload/download data to/from GPU. There are also some limitations, for device code, described in CUDA Reference manual. I hope, there is an similar interface and a documentation for DSP.

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• The Community-Driven GDB Primer

  - by fbrereto

  I was reading this question and realized it might be helpful for entry- and pro-level developers alike (including myself) to have a common reference for best practices in using gdb. Many questions asked on Stack Overflow could easily be solved by taking some time to step some code in a debugger, and it would be good to have a community-approved resource to "teach them how to fish", so to speak. Even for those seasoned veterans who occasionally find themselves in gdb when they are accustomed to a GUI-tastic debugger might benefit from those who are much more familiar with the command line tool. For starters (both to gdb and to prime this thread) I submit: Ninefinger's gdb primer The gdb quick reference guide, which is useful for telling you what commands are available but not how best to use them. My hope is this thread is a seed planted that is of continued value to the community. If by "continued value" the community decides to nix it altogether, well then the masses have spoken.

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• pointer reference type

  - by Codenotguru

  I am trying to write a function that takes a pointer argument, modifies what the pointer points to, and then returns the destination of the pointer as a reference. I am gettin the following error: cannot convert int***' toint*' in return| Code: #include <iostream> using namespace std; int* increment(int** i) { i++; return &i;} int main() { int a=24; int *p=&a; int *p2; p2=increment(&p); cout<<p2; } Thanks for helping!

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• reference parent class function in AS 3.0

  - by vasion

  I am trying to run a function of the main class, but even with casting it does not work. I get this error TypeError: Error #1009: Cannot access a property or method of a null object reference. at rpflash.communication::RPXMLReader/updateplaylist() at rpflash.communication::RPXMLReader/dataHandler() at flash.events::EventDispatcher/dispatchEventFunction() at flash.events::EventDispatcher/dispatchEvent() at flash.net::XMLSocket/scanAndSendEvent() this is the main class code package{ import flash.display.MovieClip; import rpflash.communication.RPXMLReader; public class Main extends MovieClip{ var reader:RPXMLReader = new RPXMLReader(); public function Main(){ trace('Main actionscript loaded'); } public function test(){ trace('test worked');} } } and this is the function trying to call it: private function updateplaylist(){ //xml to string var xmls:String= xml.toXMLString(); trace('playlist updated debug point'); MovieClip(this.parent).test();} what am i doing wrong?

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• Python Locking Implementation (with threading module)

  - by Matty

  This is probably a rudimentary question, but I'm new to threaded programming in Python and am not entirely sure what the correct practice is. Should I be creating a single lock object (either globally or being passed around) and using that everywhere that I need to do locking? Or, should I be creating multiple lock instances in each of the classes where I will be employing them. Take these 2 rudimentary code samples, which direction is best to go? The main difference being that a single lock instance is used in both class A and B in the second, while multiple instances are used in the first. Sample 1 class A(): def __init__(self, theList): self.theList = theList self.lock = threading.Lock() def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList): self.theList = theList self.lock = threading.Lock() self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": aList = [] for x in range(10): B(aList) A(aList).poll() Sample 2 class A(): def __init__(self, theList,lock): self.theList = theList self.lock = lock def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList,lock): self.theList = theList self.lock = lock self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": lock = threading.Lock() aList = [] for x in range(10): B(aList,lock) A(aList,lock).poll()

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• Add reference to .dll asp.net

  - by Andy

  Hi, I have a simple question about adding references to a .NET project. I'm adding reCAPTCHA to a website and i have downloaded the dll. After setting the reference to the dll i build and run the project and gets this error: [ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.] System.Reflection.Module._GetTypesInternal(StackCrawlMark& stackMark) +0 System.Reflection.Assembly.GetTypes() +96 StarSuite.Core.Settings.GetSingletonInstancesOfBaseType(Type baseType, String staticMethodName, Type returnType) +149 [ApplicationException: Unable to load types from 'Recaptcha, Version=1.0.5.0, Culture=neutral, PublicKeyToken=9afc4d65b28c38c2'. LoaderExceptions: [FileNotFoundException: Could not load file or assembly 'System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.] ] What am i missing, why do i get this error?

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• Silverlight 3-4 reference kind (e-)book.

  - by Bubba88

  Hello! I'm looking for a source of information about Microsoft Silverlight to begin practically efficient programming custom functionality applications. I want to pretend just for now that I don't need any ideologically correct refresher (SL tips, top patterns, VS tutorials :) and etc.). Basically, what I want is a reference kind e-book, where I could find any practically relevant info outlined in a minimalistic manner. If you do remember something fitting the above description, I ask you to give me a hint. Thank you very much!

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• Input system reference trouble

  - by Ockonal

  Hello, I'm using SFML for input system in my application. size_t WindowHandle; WindowHandle = ...; // Here I get the handler sf::Window InputWindow(WindowHandle); const sf::Input *InputHandle = &InputWindow.GetInput(); // [x] Error At the last lines I have to get reference for the input system. Here is declaration of GetInput from documentation: const Input & sf::Window::GetInput () const The problem is: >invalid conversion from ‘const sf::Input*’ to ‘sf::Input*’ What's wrong?

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• Model-Controller cyclic reference/design problem

  - by jasamer

  I have a CoreData entity X, and controllers for this entity, XController. Now there's another entity, XGroup, containing a collection of X entities, and a XGroupController. Now the problem is that XGroupController needs to interact with XController, and it would be nice to just pass XGroupController a XGroup to observe, and then get the XControllers from the X entities. So the question is: is it a good idea to store a (weak, to avoid retain cycles) reference to a controller in an entity? It just feels a bit "wrong". Is there another design pattern for this?

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