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  • How do C++ compilers actually pass reference parameters?

    - by T.E.D.
    This question came about as a result of some mixed-langauge programming. I had a Fortran routine I wanted to call from C++ code. Fortran passes all its parameters by reference (unless you tell it otherwise). So I thought I'd be clever (bad start right there) in my C++ code and define the Fortran routine something like this: extern "C" void FORTRAN_ROUTINE (unsigned & flag); This code worked for a while but (of course right when I needed to leave) suddenly started blowing up on a return call. Clear indication of a munged call stack. Another engineer came behind me and fixed the problem, declaring that the routine had to be deinfed in C++ as extern "C" void FORTRAN_ROUTINE (unsigned * flag); I'd accept that except for two things. One is that it seems rather counter-intuitive for the compiler to not pass reference parameters by reference, and I can find no documentation anywhere that says that. The other is that he changed a whole raft of other code in there at the same time, so it theoretically could have been another change that fixed whatever the issue was. So the question is, how does C++ actually pass reference parameters? Is it perhaps free to do copy-in, copy-out for small values or something? In other words, are reference parameters utterly useless in mixed-language programming? I'd like to know so I don't make this same code-killing mistake ever again.

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  • `enable_shared_from_this` has a non-virtual destructor

    - by Shtééf
    I have a pet project with which I experiment with new features of the upcoming C++0x standard. While I have experience with C, I'm fairly new to C++. To train myself into best practices, (besides reading a lot), I have enabled some strict compiler parameters (using GCC 4.4.1): -std=c++0x -Werror -Wall -Winline -Weffc++ -pedantic-errors This has worked fine for me. Until now, I have been able to resolve all obstacles. However, I have a need for enable_shared_from_this, and this is causing me problems. I get the following warning (error, in my case) when compiling my code (probably triggered by -Weffc++): base class ‘class std::enable_shared_from_this<Package>’ has a non-virtual destructor So basically, I'm a bit bugged by this implementation of enable_shared_from_this, because: A destructor of a class that is intended for subclassing should always be virtual, IMHO. The destructor is empty, why have it at all? I can't imagine anyone would want to delete their instance by reference to enable_shared_from_this. But I'm looking for ways to deal with this, so my question is really, is there a proper way to deal with this? And: am I correct in thinking that this destructor is bogus, or is there a real purpose to it?

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  • Nesting arbitrary objects in Java

    - by user1502381
    I am having trouble solving a particular problem in Java (which I did not find by search). I do not know how to create a nested lists of objects - with a different type of object/primitive type at the end. For example: *Note: only an example. I am actually doing this below with something other than Employee, but it serves as simple example. I have an array of an object Employee. It contains information on the Employee. public class Employee { int age int salary int yearsWorking public Employee () { // constructor... } // Accessors } What I need to do is organize the Employees by quantiles/percentiles. I have done so by the following: import org.apache.commons.math.stat.descriptive.rank.Percentile; public class EmployeeSort { public void main(String args[]) { Percentile p = new Percentile(); Employee[] employeeArray = new Employee(100); // filled employeeArray double[] ageArray new double[100]; // filled ageArray with ages from employeeArray int q = 25; // Percentile cutoff for (int i = 1; i*q < 100; i++) { // assign percentile cutoff to some array to contain the values } } } Now, the problem I have is that I need to organize the Employees first by the percentiles of age, then percentiles of yearsWorking, and finally by percentiles of salary. My Java knowledge is inadequate right now to solve this problem, but the project I was handed was in Java. I am primarily a python guy, so this problem would have been a lot easier in that language. No such luck.

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  • Type errors when using same name

    - by lykimq
    I have 3 files: 1) cpf0.ml type string = char list type url = string type var = string type name = string type symbol = | Symbol_name of name 2) problem.ml: type symbol = | Ident of string 3) test.ml open Problem;; open Cpf0;; let symbol b = function | Symbol_name n -> Ident n When I combine test.ml: ocamlc -c test.ml. I received an error: This expression has type Cpf0.name = char list but an expression was expected of type string Could you please help me to correct it? Thank you very much EDIT: Thank you for your answer. I want to explain more about these 3 files: Because I am working with extraction in Coq to Ocaml type: cpf0.ml is generated from cpf.v : Require Import String. Definition string := string. Definition name := string. Inductive symbol := | Symbol_name : name -> symbol. The code extraction.v: Set Extraction Optimize. Extraction Language Ocaml. Require ExtrOcamlBasic ExtrOcamlString. Extraction Blacklist cpf list. where ExtrOcamlString I opened: open Cpf0;; in problem.ml, and I got a new problem because in problem.ml they have another definition for type string This expression has type Cpf0.string = char list but an expression was expected of type Util.StrSet.elt = string Here is a definition in util.ml defined type string: module Str = struct type t = string end;; module StrOrd = Ord.Make (Str);; module StrSet = Set.Make (StrOrd);; module StrMap = Map.Make (StrOrd);; let set_add_chk x s = if StrSet.mem x s then failwith (x ^ " already declared") else StrSet.add x s;; I was trying to change t = string to t = char list, but if I do that I have to change a lot of function it depend on (for example: set_add_chk above). Could you please give me a good idea? how I would do in this case.

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  • Where can I find my iPhone app's Core Data persistent store?

    - by Dr Dork
    I'm diving into iPhone development, so I apologize in advance if this is a ridiculous question, but in a new iPad app project using the Core Data framework, here's the generated code for creating the persistentStoreCoordinator... - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (persistentStoreCoordinator != nil) { return persistentStoreCoordinator; } NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"ApplicationName.sqlite"]]; NSError *error = nil; persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. Typical reasons for an error here include: * The persistent store is not accessible * The schema for the persistent store is incompatible with current managed object model Check the error message to determine what the actual problem was. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return persistentStoreCoordinator; } My questions are... The first time I run the app, is the ApplicationName.sqllite database created automatically if it doesn't exist? If not, when is it created? When data is added to it programmatically? Once the DB does exist, where can I locate the file? I'd like to open it with a different program so I can manually manipulate the data. Thanks so much in advance for your help! I'm going to continue researching these questions right now.

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  • What is the difference between these two linq implementations?

    - by Mahesh Velaga
    I was going through Jon Skeet's Reimplemnting Linq to Objects series. In the implementation of where article, I found the following snippets, but I don't get what is the advantage that we are gettting by splitting the original method into two. Original Method: // Naive validation - broken! public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Refactored Method: public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } return WhereImpl(source, predicate); } private static IEnumerable<TSource> WhereImpl<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Jon says - Its for eager validation and then defferring for the rest of the part. But, I don't get it. Could some one please explain it in a little more detail, whats the difference between these 2 functions and why will the validations be performed in one and not in the other eagerly? Conclusion/Solution: I got confused due to my lack of understanding on which functions are determined to be iterator-generators. I assumed that, it is based on signature of a method like IEnumerable<T>. But, based on the answers, now I get it, a method is an iterator-generator if it uses yield statements.

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  • What Test Environment Setup do Top Project Committers Use in the Ruby Community?

    - by viatropos
    Today I am going to get as far as I can setting up my testing environment and workflow. I'm looking for practical advice on how to setup the test environment from you guys who are very passionate and versed in Ruby Testing. By the end of the day (6am PST?) I would like to be able to: Type one 1-command to run test suites for ANY project I find on Github. Run autotest for ANY Github project so I can fork and make TESTABLE contributions. Build gems from the ground up with Autotest and Shoulda. For one reason or another, I hardly ever run tests for projects I clone from Github. The major reason is because unless they're using RSpec and have a Rake task to run the tests, I don't see the common pattern behind it all. I have built 3 or 4 gems writing tests with RSpec, and while I find the DSL fun, it's less than ideal because it just adds another layer/language of methods I have to learn and remember. So I'm going with Shoulda. But this isn't a question about which testing framework to choose. So the questions are: What is your, the SO reader and Github project committer, test environment setup using autotest so that whenever you git clone a gem, you can run the tests and autotest-develop them if desired? What are the guys who are writing the Paperclip Tests and Authlogic Tests doing? What is their setup? Thanks for the insight. Looking for answers that will make me a more effective tester.

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  • Browser Issue: Charts are not rendered on IE8

    - by Rachel
    We have inhouse library which uses canvas for displaying charts in my application. And dojo as scripting language.Everything is fine, but my charts are not appearing in IE8. I google about this, and found that there is some VML issue in IE8. I found this: var printChart = function(time, freq){ if (!document.namespaces['g_vml_']) { document.namespaces.add('g_vml_', 'urn:schemas-microsoft-com:vml', '#default#VML'); } if (!document.namespaces['g_o_']) { document.namespaces.add('g_o_', 'urn:schemas-microsoft-com:office:office', '#default#VML'); } if (freq === undefined) { this.freq = "1mi"; } if (time === undefined) { this.time = "1dy"; } self.reload(); } Now I was trying to add this in my DOJO code and that is creating problem. As when I do document.namespace I get firebug error 'document.namespaces is undefined'. Q: How can we fix this, are the any better alternative approaches for the same, basic problem am having is browser related, charts are rendered properly on other browsers but not on IE8, any suggestions ? Update: What are ways to deal with such cross browser issue ?

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  • Deleting elements from stl set while iterating through it does not invalidate the iterators.

    - by pedromanoel
    I need to go through a set and remove elements that meet a predefined criteria. This is the test code I wrote: #include <set> #include <algorithm> void printElement(int value) { std::cout << value << " "; } int main() { int initNum[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; std::set<int> numbers(initNum, initNum + 10); // print '0 1 2 3 4 5 6 7 8 9' std::for_each(numbers.begin(), numbers.end(), printElement); std::set<int>::iterator it = numbers.begin(); // iterate through the set and erase all even numbers for (; it != numbers.end(); ++it) { int n = *it; if (n % 2 == 0) { // wouldn't invalidate the iterator? numbers.erase(it); } } // print '1 3 5 7 9' std::for_each(numbers.begin(), numbers.end(), printElement); return 0; } At first, I thought that erasing an element from the set while iterating through it would invalidate the iterator, and the increment at the for loop would have undefined behavior. Even though, I executed this test code and all went well, and I can't explain why. My question: Is this the defined behavior for std sets or is this implementation specific? I am using gcc 4.3.3 on ubuntu 10.04 (32-bit version), by the way. Thanks!

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  • If statement doesn't work? do download without filed name and email

    - by user1833871
    I've created some if / else statements to get a download when a user hit click jf he fields name and email but doesn"t work for my site http://my-easy-woodworking-projects.com because it is do download without field name and email contact.php is <?php $field_name = $_POST['cf_name']; $field_email = $_POST['cf_email']; $field_message = $_POST['cf_message']; $mail_to = '[email protected]'; $subject = 'Message from a site visitor '.$field_name; $body_message = 'From: '.$field_name."\n"; $body_message .= 'E-mail: '.$field_email."\n"; $body_message .= 'Message: '.$field_message; $headers = 'From: '.$field_email."\r\n"; $headers .= 'Reply-To: '.$field_email."\r\n"; $mail_status = mail($mail_to, $subject, $body_message, $headers); if ($mail_status) { echo <script>\n" echo "var str = \"download\"; \n"" echo "document.write(str.link("http://www.myshedplans.com/12BY8SHED.pdf"));\n" echo "</script>\n" } echo else { echo <script language="javascript" type="text/javascript"> echo // Print a message echo alert('Message failed. Please, send an email to [email protected]'); echo // Redirect to some page of the site. You can also specify full URL, e.g. http://template-help.com window.location = 'contact_page.html'; echo </script> }?>

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  • Memory Leak in returning NSMutableArray from class

    - by Structurer
    Hi I am quite new to Objective C for the iPhone, so I hope you wont kill me for asking a simple question. I have made an App that works fine, except that Instruments reports memory leaks from the class below. I use it to store settings from one class and then retrieve them from another class. These settings are stored on a file so they can be retrieved every time the App is ran. What can I do do release the "setting" and is there anything that can be done to call (use) the class in a smarter way? Thanks ----- Below is Settings.m ----- import "Settings.h" @implementation Settings @synthesize settings; -(NSString *)dataFilePath // Return path for settingfile, including filename { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; return [documentsDirectory stringByAppendingPathComponent:kUserSettingsFileName]; } -(NSMutableArray *)getParameters // Return settings from disk after checking if file exist (if not create with default values) { NSString *filePath = [self dataFilePath]; if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) // Getting data from file { settings = [[NSMutableArray alloc] initWithContentsOfFile:filePath]; } else // Creating default settings { settings = [[NSMutableArray alloc] initWithObjects: [NSNumber numberWithInteger:50], [NSNumber numberWithInteger:50], nil]; [settings writeToFile:[self dataFilePath] atomically:YES]; } return settings; } ----- Below is my other class from where I call my Settings class ----- // Get settings from file Settings *aSetting = [[Settings alloc] init]; mySettings = [aSetting getParameters]; [aSetting release];

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  • do the Python libraries have a natural dependence on the global namespace?

    - by msw
    I first ran into this when trying to determine the relative performance of two generators: t = timeit.repeat('g.get()', setup='g = my_generator()') So I dug into the timeit module and found that the setup and statement are evaluated with their own private, initially empty namespaces so naturally the binding of g never becomes accessible to the g.get() statement. The obvious solution is to wrap them into a class, thus adding to the global namespace. I bumped into this again when attempting, in another project, to use the multiprocessing module to divide a task among workers. I even bundled everything nicely into a class but unfortunately the call pool.apply_async(runmc, arg) fails with a PicklingError because buried inside the work object that runmc instantiates is (effectively) an assignment: self.predicate = lambda x, y: x > y so the whole object can't be (understandably) pickled and whereas: def foo(x, y): return x > y pickle.dumps(foo) is fine, the sequence bar = lambda x, y: x > y yields True from callable(bar) and from type(bar), but it Can't pickle <function <lambda> at 0xb759b764>: it's not found as __main__.<lambda>. I've given only code fragments because I can easily fix these cases by merely pulling them out into module or object level defs. The bug here appears to be in my understanding of the semantics of namespace use in general. If the nature of the language requires that I create more def statements I'll happily do so; I fear that I'm missing an essential concept though. Why is there such a strong reliance on the global namespace? Or, what am I failing to understand? Namespaces are one honking great idea -- let's do more of those!

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  • Is it OK to write code after [super dealloc]? (Objective-C)

    - by Richard J. Ross III
    I have a situation in my code, where I cannot clean up my classes objects without first calling [super dealloc]. It is something like this: // Baseclass.m @implmentation Baseclass ... -(void) dealloc { [self _removeAllData]; [aVariableThatBelongsToMe release]; [anotherVariableThatBelongsToMe release]; [super dealloc]; } ... @end This works great. My problem is, when I went to subclass this huge and nasty class (over 2000 lines of gross code), I ran into a problem: when I released my objects before calling [super dealloc] I had zombies running through the code that were activated when I called the [self _removeAllData] method. // Subclass.m @implementation Subclass ... -(void) deallloc { [super dealloc]; [someObjectUsedInTheRemoveAllDataMethod release]; } ... @end This works great, and It didn't require me to refactor any code. My question Is this: Is it safe for me to do this, or should I refactor my code? Or maybe autorelease the objects? I am programming for iPhone if that matters any.

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  • Tips for submitting a library to Boost?

    - by AraK
    Hi everyone, Summer is coming, and a group of friends and I are getting ready for it :) We decided to build a compile-time Arbitrary precision Unsigned Integers. We would like to provide a set of integers algorithms(functions) with the library. We have seen a number of requests for such a library(SoC2010, C++0x Standard Library wishlist). Also, a regular run-time bigint is requested usually with that, but we don't want to go into the hassle of memory management. The idea came to me from a library called TTMath, unfortunately this library works only on specific platforms because Assembly was used extensively in the library. We would like to write a standard library, depending on the C++ standard library and Boost. Also, we would like to use the available C++0x facilities in current compilers like user-defined literals and others. This would technically make the library non-standard for a while, but we think that it is a matter of time the new standards will be official. Your hints on the whole process including design, implementation, documentation, maintainable of the library are more than welcom. We are a group of students and fresh graduates who are looking for something interesting in the summer, but we see that Boost is full of gurus and we don't want to forget something too obvious. We are communicating on-line, so there is no shared white-boards :( Thanks,

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  • What is the simplest way to implement multithreading in c# to existing code

    - by Kaeso
    I have already implemented a functionnal application that parses 26 pages of html all at once to produce an xml file with data contained on the web pages. I would need to implement a thread so that this method can work in the background without causing my app to seems unresponsive. Secondly, I have another function that is decoupled from the first one which compares two xml files to produce a third one and then transform this third xml file to produce an html page using XSLT. This would have to be on a thread, where I can click Cancel to stop the thread whithout crashing the app. What is the easiest best way to do this using WPF forms in VS 2010 ? I have chosen to use the BackgroundWorker. BackgroundWorker implementation: public partial class MainWindow : Window { private BackgroundWorker bw = new BackgroundWorker(); public MainWindow() { InitializeComponent(); bw.WorkerReportsProgress = true; bw.DoWork += new DoWorkEventHandler(bw_DoWork); bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted); } private void Window_Loaded(object sender, RoutedEventArgs e) { this.LoadFiles(); } private void btnCompare_Click(object sender, EventArgs e) { if (bw.IsBusy != true) { progressBar2.IsIndeterminate = true; // Start the asynchronous operation. bw.RunWorkerAsync(); } } private void bw_DoWork(object sender, DoWorkEventArgs e) { StatsProcessor proc = new StatsProcessor(); if (lstStatsBox1.SelectedItem != null) if (lstStatsBox2.SelectedItem != null) proc.CompareStats(lstStatsBox1.SelectedItem.ToString(), lstStatsBox2.SelectedItem.ToString()); } private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { progressBar2.IsIndeterminate = false; progressBar2.Value = 100; } I have started with the bgworker solution, but it seems that the bw_DoWork method is never called when btnCompare is clicked, I must be doing something wrong... I am new to threads.

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  • implementing a read/write field for an interface that only defines read

    - by PaulH
    I have a C# 2.0 application where a base interface allows read-only access to a value in a concrete class. But, within the concrete class, I'd like to have read/write access to that value. So, I have an implementation like this: public abstract class Base { public abstract DateTime StartTime { get; } } public class Foo : Base { DateTime start_time_; public override DateTime StartTime { get { return start_time_; } internal set { start_time_ = value; } } } But, this gives me the error: Foo.cs(200,22): error CS0546: 'Foo.StartTime.set': cannot override because 'Base.StartTime' does not have an overridable set accessor I don't want the base class to have write access. But, I do want the concrete class to provide read/write access. Is there a way to make this work? Thanks, PaulH Unfortunately, Base can't be changed to an interface as it contains non-abstract functionality also. Something I should have thought to put in the original problem description. public abstract class Base { public abstract DateTime StartTime { get; } public void Buzz() { // do something interesting... } } My solution is to do this: public class Foo : Base { DateTime start_time_; public override DateTime StartTime { get { return start_time_; } } internal void SetStartTime { start_time_ = value; } } It's not as nice as I'd like, but it works.

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  • OSGI, Servlets and JPA hello world / tutorial / example

    - by Kamil
    I want to build a web application which basically is a restful web-service serving json messages. I would like it to be as simple as possible. I was thinking about using servlets (with annotations). JPA as a database layer is a must - Toplink or Hibernate. Preferably working on Tomcat. I want to have app divided into modules serving different functionality (auth service, customer service, etc..). And I would like to be able to update those modules without reinstalling whole application on the server - like eclipse plugins, user is notified (when he enters webapp's home url) that update is available, clicks it, and app is downloading and installing updated module. I think this functionality can be made with OSGI, but I can't find any example code, or tutorial with simple hello world updatable servlet providing some data from database through jpa. I'm looking for an advice: - Is OSGI the right tool for this or it can be done with something simpler? - Where can I find some examples covering topic (or topics) which I need for this project. - Which OSGI implementation would be best-simplest for this task. *My knowledge of OSGI is basic. I know how bundles are described, I understand concept of OSGI container and what it does. I have never created any OSGI app yet.

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  • 3D and AI basics. The foundation before the coding.

    - by Allan
    Hi, everyone. (If you have the time and patience:) I've recently made the decision to study programming seriously and I'm about to order TAOCP and Concrete Mathematics to begin my studies (please don't get caught up on this). I'm very much interested in learning and understanding how 3D works but I'm aware that if I plan to do it right there's still a long walk before I get to actually play with 3D coding. Now to the question.. (tl;dr) Excluding programming itself, what disciplines do I have to be familiar with to code 3D? What kinds of mathematics? Physics? What else? What books do you recommend on such subjects? Now read it all again but replacing "3D" with "AI". Please don't recommend computer-specific books. The question is about the foundation to be learned before using the machine. Also, if possible, please keep the list brief; I plan to order one book on each subject but no more than that for now. Excuse me for any English mistakes, it's not my first language. Thank you.

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  • Save object in CoreData

    - by John
    I am using CoreData with iPhone SDK. I am making a notes app. I have a table with note objects displayed from my model. When a button is pressed I want to save the text in the textview to the object being edited. How do I do this? I've been trying several things but none seem to work. Thanks EDIT: NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; [newManagedObject setValue:detailViewController.textView.text forKey:@"noteText"]; NSError *error; if (![context save:&error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } The above code saves it correctly but it saves it as a new object. I want it to be saved as the one I have selected in my tableView.

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  • JavaScript: why `null == 0` is false?

    - by lemonedo
    I had to write a routine that increments the value of a variable by 1 if it is a number, or assigns 0 to the variable if it is not a number. The variable can be incremented by the expression, or be assigned null. No other write access to the variable is allowed. So, the variable can be in three states: it is 0, a positive integer, or null. My first implementation was: v >= 0 ? v += 1 : v = 0 (Yes, I admit that v === null ? v = 0 : v += 1 is the exact solution, but I wanted to be concise then.) It failed since null >= 0 is true. I was confused, since if a value is not a number, an numeric expression involving it must be false always. Then I found that null is like 0, since null + 1 == 1, 1 / null == Infinity, Math.pow(2.718281828, null) == 1, ... Strangely enough, however, null == 0 is evaluated to false. I guess null is the only value that makes the following expression false: (v == 0) === (v >= 0 && v <= 0) So why null is so special in JavaScript?

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  • Imlpementations of an Interface with Different Types?

    - by b3njamin
    Searched as best I could but unfortunately I've learned nothing relevant; basically I'm trying to work around the following problem in C#... For example, I have three possible references (refA, refB, refC) and I need to load the correct one depending on a configuration option. So far however I can't see a way of doing it that doesn't require me to use the name of said referenced object all through the code (the referenced objects are provided, I can't change them). Hope the following code makes more sense: public ??? LoadedClass; public Init() { /* load the object, according to which version we need... */ if (Config.Version == "refA") { Namespace.refA LoadedClass = new refA(); } else if (Config.Version == "refB") { Namespace.refB LoadedClass = new refB(); } else if (Config.Version == "refC") { Namespace.refC LoadedClass = new refC(); } Run(); } private void Run(){ { LoadedClass.SomeProperty... LoadedClass.SomeMethod(){ etc... } } As you can see, I need the Loaded class to be public, so in my limited way I'm trying to change the type 'dynamically' as I load in which real class I want. Each of refA, refB and refC will implement the same properties and methods but with different names. Again, this is what I'm working with, not by my design. All that said, I tried to get my head around Interfaces (which sound like they're what I'm after) but I'm looking at them and seeing strict types - which makes sense to me, even if it's not useful to me. Any and all ideas and opinions are welcome and I'll clarify anything if necessary. Excuse any silly mistakes I've made in the terminology, I'm learning all this for the first time. I'm really enjoying working with an OOP language so far though - coming from PHP this stuff is blowing my mind :-)

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  • How to write to a Text File in Pipe delimited format from MS Sql Server / ASP.Net?

    - by NJTechGuy
    I have a text file which needs to be constantly updated (regular intervals). All I want is the syntax and possibly some code that outputs data from a MS Sql Database using ASP.Net. The code I have so far is : <%@ Import Namespace="System.IO" %> <script language="vb" runat="server"> sub Page_Load(sender as Object, e as EventArgs) Dim FILENAME as String = Server.MapPath("Output.txt") Dim objStreamWriter as StreamWriter ' If Len(Dir$(FILENAME)) > 0 Then Kill(FILENAME) objStreamWriter = File.AppendText(FILENAME) objStreamWriter.WriteLine("A user viewed this demo at: " & DateTime.Now.ToString()) objStreamWriter.Close() Dim objStreamReader as StreamReader objStreamReader = File.OpenText(FILENAME) Dim contents as String = objStreamReader.ReadToEnd() lblNicerOutput.Text = contents.Replace(vbCrLf, "<br>") objStreamReader.Close() end sub </script> <asp:label runat="server" id="lblNicerOutput" Font-Name="Verdana" /> With PHP, it is a breeze, but with .Net I have no clue. If you could help me with the database connectivity and how to write the data in pipe delimited format to an Output.txt file, that had be awesome. Thanks guys!

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  • Fastest way to clamp a real (fixed/floating point) value?

    - by Niklas
    Hi, Is there a more efficient way to clamp real numbers than using if statements or ternary operators? I want to do this both for doubles and for a 32-bit fixpoint implementation (16.16). I'm not asking for code that can handle both cases; they will be handled in separate functions. Obviously, I can do something like: double clampedA; double a = calculate(); clampedA = a > MY_MAX ? MY_MAX : a; clampedA = a < MY_MIN ? MY_MIN : a; or double a = calculate(); double clampedA = a; if(clampedA > MY_MAX) clampedA = MY_MAX; else if(clampedA < MY_MIN) clampedA = MY_MIN; The fixpoint version would use functions/macros for comparisons. This is done in a performance-critical part of the code, so I'm looking for an as efficient way to do it as possible (which I suspect would involve bit-manipulation) EDIT: It has to be standard/portable C, platform-specific functionality is not of any interest here. Also, MY_MIN and MY_MAX are the same type as the value I want clamped (doubles in the examples above).

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  • Streaming audio not working in Android

    - by user320293
    Hi, I'm sure that this question has been asked before but I've been unable to find a solid answer. I'm trying to load a streaming audio from a server. Its a audio/aac file http://3363.live.streamtheworld.com:80/CHUMFMAACCMP3 The code that I'm using is private void playAudio(String str) { try { final String path = str; if (path == null || path.length() == 0) { Toast.makeText(RadioPlayer.this, "File URL/path is empty", Toast.LENGTH_LONG).show(); } else { // If the path has not changed, just start the media player MediaPlayer mp = new MediaPlayer(); mp.setAudioStreamType(AudioManager.STREAM_MUSIC); try{ mp.setDataSource(getDataSource(path)); mp.prepareAsync(); mp.start(); }catch(IOException e){ Log.i("ONCREATE IOEXCEPTION", e.getMessage()); }catch(Exception e){ Log.i("ONCREATE EXCEPTION", e.getMessage()); } } } catch (Exception e) { Log.e("RPLAYER EXCEPTION", "error: " + e.getMessage(), e); } } private String getDataSource(String path) throws IOException { if (!URLUtil.isNetworkUrl(path)) { return path; } else { URL url = new URL(path); URLConnection cn = url.openConnection(); cn.connect(); InputStream stream = cn.getInputStream(); if (stream == null) throw new RuntimeException("stream is null"); File temp = File.createTempFile("mediaplayertmp", ".dat"); temp.deleteOnExit(); String tempPath = temp.getAbsolutePath(); FileOutputStream out = new FileOutputStream(temp); byte buf[] = new byte[128]; do { int numread = stream.read(buf); if (numread <= 0) break; out.write(buf, 0, numread); } while (true); try { stream.close(); } catch (IOException ex) { Log.e("RPLAYER IOEXCEPTION", "error: " + ex.getMessage(), ex); } return tempPath; } } Is this the correct implementation? I'm not sure where I'm going wrong. Can someone please please help me on this.

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  • Learning PHP - start out using a framework or no?

    - by Kevin Torrent
    I've noticed a lot of jobs in my area for PHP. I've never used PHP before, and figure if I can get more opportunities if I pick it up then it might be a good idea. The problem is that PHP without any framework is ugly and 99% of the time really bad code. All the tutorials and books I've seen are really lousy - it never shows any kind of good programming practice but always the quick and dirty kind of way of doing things. I'm afraid that trying to learn PHP this way will just imprint these bad practices in my head and make me waste time later trying to unlearn them. I've used C# in the past so I'm familiar with OOP and software design patterns and similar. Should I be trying to learn PHP by using one of the better known frameworks for it? I've looked at CakePHP, Symfony and the Zend Framework so far; Zend seems to be the most flexible without being too constraining like Cake and Symfony (although Symfony seemed less constraining than CakePHP which is trying too hard to be Ruby on Rails), but many tutorials for Zend I've seen assume you already know PHP and want to learn to use the framework. What would be my best opportunity for learning PHP, but learning GOOD PHP that uses real software engineering techniques instead of spaghetti code? It seems all the PHP books and resources either assume you are just using raw PHP and therefore showcase bade practices, or that you already know PHP and therefore don't even touch on parts of the language.

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