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• Incompatible Types in Initialization

  - by jack

  I have the following code in a subroutine that produces an incompatible types in initialization error on the varVal library in the subroutine evaluateExpression: NSDictionary *varVal; for (int i=0; i<varCount; i++) { [varVal setObject:[(i+1)*2 stringValue] forKey:[i stringValue]]; } double result =[[self brain] evaluateExpression:[[self brain] expression] usingVariableValues:varVal]; My subroutine declaration in the brain.h file is: +(double)evaluateExpression:(id)anExpression usingVariableValues:(NSDictionary *)variables; I'd appreciate any help.

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• Variable scope in javascript

  - by Rich Bradshaw

  This is a simple question, but I can't work it out. The specifics aren't important, but here's the gist. I have some code like this: var lat = 0; var lon = 0; if (navigator.geolocation) { navigator.geolocation.getCurrentPosition(function(position) { lat = position.coords.latitude; lon = position.coords.longitude; }); } What I think it's doing is: Set lat and lon to 0 If the browser has geolocation, overwrite those variables with real values However, at the end of that chunk, lat and lon are still 0. I've tried adding vars, passing lat and lon to the function etc but with no success... How do I make this work?

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• Programming language for fast calculations with big integers

  - by sub

  I'm doing Project Euler problems at the moment and I can solve most of them using my own programming language which uses direct C++ integers (so they are bound to 2^32 on my machine). However, at times there are problems which require me to work with very high numbers, I can't do that with native integers. So I implemented a BigInt library in my language which unfortunately gets extremely slow at times. Is there a programming language suitable for very efficient handling of big numbers? I mean that I want to do the things I could do in other programming languages with it (variables, loops, etc.), but in a faster way. If you have got tips for workarounds of the 2^32 limit in my language/C++/other languages, please tell me too!

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• Regexp to add attribute in any xml tags

  - by katsuo11

  Hello, I have well-formed xml documents into string variables. I want to use preg_replace to add a defined attribute to every xml tags. For example replace: <tag1> <tag2> some text </tag2> </tag1> by: <tag1 attr="myAttr"> <tag2 attr="myAttr"> some text </tag2> </tag1> So I basically need the regex expression to find any start tags and add my attribute, but I'm a complete regex noob. Thanks, kats

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• form Validation white page not showing errors

  - by Jess McKenzie

  In the example below I am wanting to do all of the 'safety' checks on the $_POST variables but it seems when I click submit I get a white page why? I am wanting it to show the errors etc Form Process: /* check if the form is submitted */ if (isset($_POST['submitButton'])) { $fullName = $_POST['fullname']; if($_SERVER['REQUEST_METHOD'] == 'POST' && !empty($fullName)) { if (!ctype_alpha(str_replace(array("'", "-"), "",$fullName))) { $errorfullName .= '<span class="errorfullName">*First name should be alpha characters only.</span>'; } if (strlen($fullName) < 3 OR strlen($fullName) > 40) { $errorfullName .= '<span class="errorfullName">*First name should be within 3-40 characters long.</span>'; } } }

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• C++ class initialisation containing class variable initialization

  - by Phil Hannent

  I noticed some code of a colleague today that initialized class variables in the initialization. However it was causing a warning, he says because of the order they are in. My question is why is it better to do variable initialization where it currently is and not within the curly brackets? DiagramScene::DiagramScene( int slideNo, QRectF screenRect, MainWindow* parent ) : QGraphicsScene( screenRect, parent ), myParent( parent ), slideUndoImageCurrentIndex(-1), nextGroupID(0), m_undoInProgress(false), m_deleteItemOnNextUndo(0) line(0), path(0) { /* Setup default brush for background */ scDetail->bgBrush.setStyle(Qt::SolidPattern); scDetail->bgBrush.setColor(Qt::white); setBackgroundBrush(scDetail->bgBrush); }

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• design patterns for hierarchical structures

  - by JLBarros

  Anyone knows some design patterns for hierarchical structures? For example, to manage inventory categories, accounting chart of accounts, divisions of human resources, etc.. Thank you very much in advance EDIT: Thanks for your interest. I am looking for a better way of dealing with hierarchical items to which they should apply operations depending on the level of hierarchy. I have been studying the patterns by Martin Fowler, for example Accounting, but I wonder if there are other more generic. The problem is that operations apply to the items must be possible to change even at run time and may depend on other external variables. I thought of a kind of strategy pattern but would like to combine it with the fact that it is a hierarchical scheme. I would appreciate any reference to hierarchical patterns and you'll take care of them in depth.

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• Resetting a partial using RJS, and passing an instance variable?

  - by Elliot

  Hey guys here is my code (roughly): books.html.erb <% @books.each do |book| %> <% @bookid = book.id %> <div id="enter_stuff"> <%= render "input", :bookid => @bookid %> </div> <%end%> _input.html.erb <% @book = Book.find_by_id(@bookid) %> <strong>your book is: <%=h @book.name %></strong> create.rjs page.replace_html :enter_stuff, :partial => 'input2', :object => @bookid Only create.js doesn't seem to work though, if instead of passing the partial I passed "..." it does work, so I know its that there are instance variables in the partial that aren't being reset. Any ideas?

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• Displaying Fields (and/instead of Properties) in a PropertyGrid

  - by Jenk

  I'd like to use a PropertyGrid to manipulate the data on some objects, however these objects don't have properties, they have fields. Thus a property grid doesn't display them (high five MS!) Before anyone posts "just use properties": I can't at the moment.. these objects are DTOs and are used to send data to a VB6 Interop dll, thus all the parameters for the method calls are "ref" parameters (high five MS!), and C# won't compile if you use a property instead of a field or variable (high five MS!). No, I am not going to create local variables for every property on any given object. There many, many fields, and many, many test cases that would need updating, as well as the production code it self, and this post/question may be the path of least resistance. :)

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• How do I dynamically assign the Model for a .find in Ruby on Rails?

  - by Angela

  I am trying to create a Single Table Inheritance. However, the Controller must be able to know which class to find or create. These are based on another class. For example, ContactEvent with type = Letter needs to grab attributes from a corresponding Model called Letter. Here's what I've tried to do and hit a snag, labelled below. I need to be able to dynamically call assign a value of EventClass so that it can be Letter.find(:conditions =) or Calls.find(:conditions =) depending on which type the controller is acting on. def new @contact_event = ContactEvent.new @contact_event.type = params[:event_type] # can be letter, call, postcard, email @contact_event.event_id = params[:event_id] # that ID to the corresponding Model @contact_event.contact_id = params[:contact] @EventClass = case when @contact_event.type == 'letter' then 'Letter' when @contact_event.type == 'call' then 'Call' when @contact_event.type == 'email' then 'Email' SNAG BELOW: @event = @EventClass.find(@contact_letter.letter_id) #how do I make @EventClass actually the Class?SNAG # substitution of variables into the body of the contact_event @event.body.gsub!("{FirstName}", @contact.first_name) @event.body.gsub!("{Company}", @contact.company_name) @evebt.body.gsub!("{Colleagues}", @colleagues.to_sentence) @contact_event.body = @event.body @contact_event.status = "sent" end

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• Style question: Writing "this." before instance variable and methods: good or bad idea?

  - by Uri

  One of my nasty (?) programming habits in C++ and Java is to always precede calls or accesses to members with a this. For example: this.process(this.event). A few of my students commented on this, and I'm wondering if I am teaching bad habits. My rationale is: 1) Makes code more readable — Easier to distinguish fields from local variables. 2) Makes it easier to distinguish standard calls from static calls (especially in Java) 3) Makes me remember that this call (unless the target is final) could end up on a different target, for example in an overriding version in a subclass. Obviously, this has zero impact on the compiled program, it's just readability. So am I making it more or less readable? Related Question Note: I turned it into a CW since there really isn't a correct answer.

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• c# how to set up and use session state from preinit

  - by Praesagus

  OK so to set and read variables from the current session String Myvar =(string) System.Web.HttpContext.Current.Session[“MyVariable”] To set System.Web.HttpContext.Current.Session[“MyVariable”] = “NewValue” I can do neither, I get a System.NullReferenceException: Object reference not set to an instance of an object. from System.Web.HttpContext.Current.Session. In my web.config I have <sessionState mode="StateServer" stateConnectionString="tcpip=127.0.0.1:42424" cookieless="false" timeout="20"> </sessionState> I have read a dozen articles on the the necessity of IHttpHandler and an IRequiresSessionState interface. I think the issue may be caused because I am requesting this information in Page_PreInit. I found a solution in a stack overflow article but I don't seem be using it properly to actually make this go. I am not sure what I am missing. Thanks in advance.

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• Wpf application variable not changing

  - by Hasan Zubairi

  In my application I need some variables on almost all the pages so I declared them in Application.xaml like <sys:String x:key="First">First</sys:String> and on one page I change the value in code like Resources["First"] = "This is First"; on the second page when I call the variable like String f = (string)this.TryFindResource("First"); MessageBox.Show(f); the out put is "First" and not "This is First". I also tried like. Application.Current.Properties["First"]

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• POSIX Threads and signal masks

  - by Max

  Is there a way to change the signal mask of a thread from another thread? I am supposed to write a multithreaded C application that doesn't use mutex, semaphores and condition variables, only signals. So it would look like something like this: The main Thread sends SIGUSR1 to its process and and one of the 2 threads (not including the main thread), will respond to the signal and block SIGUSR1 from the sigmask and sleep. Then the main thread sends SIGUSR1 again, the other thread will respond, block SIGUSR1 from its sigmask, unblock SIGUSR1 from the other threads sigmask, so it will respond to SIGUSR1 again. So essentially whenever the main thread sends SIGUSR1 the two other threads swap between each other. Can somebody help?

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• Passing an array of data to a private function in CodeIgniter/PHP? [facepalm]

  - by Jack Webb-Heller

  So I thought this should be easy, but, I'm n00bing out here and failing epicly (as they say on teh interwebz). So here's my code: function xy() { $array['var1'] = x; $array['var2'] = y; echo $this->_z; } function _z($array) { $xy = $x.$y; return $xy; } So, why doesn't that seemingly simple code work? I know with views you can pass arrays and the variables are accessible in the views with just their array title, but, why doesn't it work in this case? Jack

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• Keeping Computer Science Writing Accessible and Eloquent

  - by Federer

  This question is particularly aimed at descriptions and explanations of what is happening in a computer program, as well as any general advice or approaches for undertaking technical reports in Computer Science at both undergraduate and graduate levels. You see, I am having particular difficulty in the best way to explain what is happening. As in, given any given program from a multi-agent system to a standard webservice, the best and most eloquent way to say exactly what is going on, the logic behind it and it's respective justifications. Should I avoid saying class names? Avoid specifying methods? Keep referring to class variables and any particular references? I'm banging my head against the wall at trying to keep a solid technical foundation and making it accessible to people of all backgrounds. Apologies for the rather vague question. Cheers.

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• reading a file that doesn't exist

  - by John

  Hi, I have got a small program that prints the contents of files using the system call - read. unsigned char buffer[8]; size_t offset=0; size_t bytes_read; int i; int fd = open(argv[1], O_RDONLY); do{ bytes_read = read(fd, buffer, sizeof(buffer)); printf("0x%06x : ", offset); for(i=0; i<bytes_read; ++i) { printf("%c ", buffer[i]); } printf("\n"); offset = offset + bytes_read; }while(bytes_read == sizeof(buffer)); Now while running I give a file name that doesn't exist. It prints some kind of data mixed with environment variables and a segmentation fault at the end. How is this possible? What is the program printing? Thanks, John

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• Retrieve a static variable using its name dynamically using reflection

  - by user2538438

  How to retrieve a static variable using its name dynamically using Java reflection? If I have class containing some variables: public class myClass { string [][] cfg1= {{"01"},{"02"},{"81"},{"82"}}; string [][]cfg2= {{"c01"},{"c02"},{"c81"},{"c82"}}; string [][] cfg3= {{"d01"},{"d02"},{"d81"}{"d82"}}; int cfg11 = 5; int cfg22 = 10; int cfg33 = 15; } And in another class I want variable name is input from user: class test { Scanner in = new Scanner(System.in); String userInput = in.nextLine(); // get variable from class myClass that has the same name as userInput System.out.println("variable name " + // correct variable from class) } Using reflection. Any help please?

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• php for loop varable names

  - by Stefan

  i got a code of 100-200 rules for making a table. but the whole time is happening the same. i got a variable $xm3, then i make a column . next row, i got $xm2 and make column. next row, i got $xm1 and make column. so my variables are going to $xm3, $xm2, $xm1, $xm0, $xp1, $xp2, $xp3. is there a way to make a forloop so i can fill $xm and after that a value from the for loop?

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• Inheritance - initialization problem

  - by dumbquestion

  I have a c++ class derived from a base class in a framework. The derived class doesn't have any data members because I need it to be freely convertible into a base class and back - the framework is responsible for loading and saving the objects and I can't change it. My derived class just has functions for accessing the data. But there are a couple of places where I need to store some temporary local variables to speed up access to data in the base class. mydata* MyClass::getData() { if ( !m_mydata ) { // set to NULL in the constructor m_mydata = some_long_and complex_operation_to_get_the_data_in_the_base() } return m_mydata; } The problem is if I just access the object by casting the base class pointer returned from the framework to MyClass* the ctor for MyClass is never called and m_mydata is junk. Is there a way of only initializing the m_mydata pointer once?

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• MySQL Locking table from Stored FUNCTION

  - by Brandon

  I have a function in a MySQL Database that determines some sync parameters for a mobile device. The function determines the last date/time the user synchronized with the database. During my sync operation I call this server side function twice. As soon as I call it the second time - the entire Sync_Records table is locked. I cannot write to it from any other connection anywhere (note, after first call, the table is not locked). I changed the function to a Procedure - and all is fine - no locking after the second call. The entire sync operation (including both calls to the function/procedure) is within a transaction. This is an InnoDb table. The function/procedure simply does two select statements. They are storing results in local variables and then returning the date time variable. I don't understand why the tables are locked. Does anyone have any ideas?

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• Run batch file when argument contains quotes and spaces (from .NET framework)

  - by turtle

  I have a bat file which sets some environment variables, and then executes a command on the command line. I want to replace the hard coded command with one passed in via a parameter. So: :: Set up the required environment SET some_var=a SET another_var=b CALL some.bat :: Now call the command passed into this batch file %1 The problem is that the command is complex, and doesn't escape cleanly. It looks like this: an.exe -p="path with spaces" -t="some text" -f="another path with spaces" I'm trying to call the .bat from a .NET framework app, using: Dim cmd as String = "the cmd" System.Diagnostics.Process.Start( thebat.exe, cmd ) but I can't seem to get the escapes to work correctly. Can someone tell me how the string cmd should be entetered to get the command passed into the bat file as an argument correctly?

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• Why do C++ streams use char instead of unsigned char?

  - by Johannes Schaub - litb

  I've always wondered why the C++ Standard library has instantiated basic_[io]stream and all its variants using the char type instead of the unsigned char type. char means (depending on whether it is signed or not) you can have overflow and underflow for operations like get(), which will lead to implementation-defined value of the variables involved. Another example is when you want to output a byte, unformatted, to an ostream using its put function. Any ideas? Note: I'm still not really convinced. So if you know the definitive answer, you can still post it indeed.

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• Fetching JSON object from Servlet Java

  - by ChrisA

  I want to create an application that will fetch a JSON object from a servlet to deserialize it, and then use its variables to do other things. My servlet has the following code in the doPost: protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ObjectOutputStream os; os = new ObjectOutputStream(response.getOutputStream()); String s = new String("A String"); Gson gson = new Gson(); String gsonObject= gson.toJson(s); os.writeObject(gsonObject); os.close(); } Now, while the servlet is running, I can access it via a browser, if I post same code in the doGet method, that would download a servlet file, which is not what I want. What should I use in my second application that would connect to the servlet, fetch the object, so that I can manipulate it later? Thanks in advance.

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• PHP/MySQL - Special characters in URLs. How to avoid?

  - by RC

  Hey everyone, My database contains information extracted from an external feed. In this raw text feed, the following text is used in place of special characters: & - &amp; ' - &39; é - &eacute; I extract some of this text to form URLs. For example, a URL that I construct from data containing these characters might look like this: http://url.com/search/?brand=Franklin&Hédgson's I use the GET variables in this URL to construct further lookups, which leads to a couple of specific problems: The é and ' characters are sent back to MySQL as they appear, and so they don't trigger any results (because the characters take the full HTML form in the database text). The & within the URL separates the variable, and the GET returns only Franklin, when it should return the whole string. Are there any straightforward ways of dealing with this? Thanks.

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