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  • Misunderstanding function pointer - passing it as an argument

    - by Stef
    I want to pass a member function of class A to class B via a function pointer as argument. Please advise whether this road is leading somewhere and help me fill the pothole. #include <iostream> using namespace std; class A{ public: int dosomeA(int x){ cout<< "doing some A to "<<x <<endl; return(0); } }; class B{ public: B(int (*ptr)(int)){ptr(0);}; }; int main() { A a; int (*APtr)(int)=&A::dosomeA; B b(APtr); return 0; } This brilliant piece of code leaves me with the compiler error: cannot convert int (A::*)(int)' toint (*)(int)' in initialization Firstly I want it to compile. Secondly I don't want dosomeA to be STATIC.

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  • What is wrong in this bit of MyID3 code? (error code is just Exceptions)

    - by user3697621
    Okay, so, this was supposed to get the paths of all mp3 files in a folder, read their metadata and put in an arraylist. public static List<String> OrgMetadata(List<String> rawgenrelist){ File folder = new File("C:\\SOM\\"); File[] listOfFiles = folder.listFiles(); //File path = listOfFiles; for (int i = 0; i < listOfFiles.length; i++) { String pt = listOfFiles[i].getAbsolutePath(); File src = new File(pt); MusicMetadataSet src_set = new MyID3().read(src); if (src_set != null && listOfFiles[i].isFile()) { IMusicMetadata metadata = src_set.getSimplified(); rawgenrelist.add(metadata.getGenreName()); } } List<String> genrelist; genrelist = new ArrayList(new HashSet(rawgenrelist)); return genrelist; }

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  • Normalize database or not? Read only MyISAM table, performance is the main priority (MySQL)

    - by hello
    I'm importing data to a future database that will have one, static MyISAM table (will only be read from). I chose MyISAM because as far as I understand it's faster for my requirements (I'm not very experienced with MySQL / SQL at all). That table will have various columns such as ID, Name, Gender, Phone, Status... and Country, City, Street columns. Now the question is, should I create tables (e.g Country: Country_ID, Country_Name) for the last 3 columns and refer to them in the main table by ID (normalize...[?]), or just store them as VARCHAR in the main table (having duplicates, obviously)? My primary concern is speed - since the table won't be written into, data integrity is not a priority. The only actions will be selecting a specific row or searching for rows that much a certain criteria. Would searching by the Country, City and/or Street columns (and possibly other columns in the same search) be faster if I simply use VARCHAR?

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  • Bash redirection: save stderr/stdout to different files and still print them out on a console

    - by Alby
    Here is a simple program. class Redirection { public static void main (String args[]){ System.out.println("Hello World_Stdout"); System.err.println("Hello World_Stderr"); } } I want to see the all the outputs on a console, but at the same time I want to store stdout and stderr in different files. I tried the following command, to no avail. $java Redirection 3>&1 2>stderr 1>stdout 1>&3 2>&3 stderr& stdout files have the file size of 0. So basically I want to do what "tee" command does but I also want to capture stderr as well.

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  • Correct approach to validate attributes of an instance of class

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters declaration ? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • Why Timer does not work if we do not generate a window?

    - by Roman
    Here is the code: import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JFrame; import javax.swing.Timer; public class TimerSample { public static void main(String args[]) { new JFrame().setVisible(true); ActionListener actionListener = new ActionListener() { public void actionPerformed(ActionEvent actionEvent) { System.out.println("Hello World Timer"); } }; Timer timer = new Timer(500, actionListener); timer.start(); } } It generates a window and then periodically prints "Hello World Timer" in the terminal (Command Prompt). If I comment this line new JFrame().setVisible(true); the application do not print anything to the command line. Why?

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  • Void pointer cast C++ and GTK

    - by Tarantula
    See this GTK callback function: static gboolean callback(GtkWidget *widget, GdkEventButton *event, gpointer *data) { AnyClass *obj = (AnyClass*) data; // using obj works } (please note the gpointer* on the data). And then the signal is connected using: AnyClass *obj2 = new AnyClass(); gtk_signal_connect(/*GTK params (...)*/, callback, obj2); See that the *AnyClass is going to be cast to gpointer* (void**). In fact, this is working now. The callback prototype in GTK documentation is "gpointer data" and not "gpointer *data" as shown in code, what I want to know is: how this can work ? Is this safe ?

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  • How to stable_sort without copying?

    - by Mehrdad
    Why does stable_sort need a copy constructor? (swap should suffice, right?) Or rather, how do I stable_sort a range without copying any elements? #include <algorithm> class Person { Person(Person const &); // Disable copying public: Person() : age(0) { } int age; void swap(Person &other) { using std::swap; swap(this->age, other.age); } friend void swap(Person &a, Person &b) { a.swap(b); } bool operator <(Person const &other) const { return this->age < other.age; } }; int main() { static size_t const n = 10; Person people[n]; std::stable_sort(people, people + n); }

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  • is this code correct? [closed]

    - by davit-datuashvili
    hi i have poste this code from this title http://stackoverflow.com/questions/2896363/hi-i-have-question-here-is-pseudo-code-about-sift-up-and-sift-down-on-heaps i have following code of siftup on heap is it correct?i have put here because i have changed at old place my question and it became unreadable so i have posted here public class siftup{ public static void main(String[]args){ int p; int n=12; int a[]=new int[]{15,20,12,29,23,17,22,35,40,26,51,19}; int i=n-1; while (i!=0){ if (i==1) break; p=i/2; if (a[p]<=a[i]){ int t=a[p]; a[p]=a[i]; a[i]=t; } i=p; } for (int j=0;j<n;j++){ System.out.println(a[j]); } } } //result is this 15 20 19 29 23 12 22 35 40 26 51 17 is it correct?

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  • iqueryable select/where not working

    - by Steve
    I have two tables Boxer and Prospect. Boxers has general stuff like name and and dob etc and a BoxerId While Prospect contains only one value (at the moment) which is a boxerId. If a boxer is a prospect(up and coming boxer) there Id will be in the prospect table. This works fine but now I want to select all boxers that are prospects public static IQueryable<Boxer> IsProspect(this IQueryable<Boxer> query) { //this does not filter down to only prospects!!! return query.Where(x => x.Prospect != null); } This is the function I call using: var repository = GetRepository<Boxer>(); var boxers = repository.Query().IsProspect(); I would hope this would filter my collection of all boxers down to just boxers that are prospects! Oddly it doesnt filter it but if i hover over my boxers object and look at each boxer during debugging I can see "IsProspect" true or false correctly

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  • PHP object cannot find method

    - by Daniel Hertz
    Hello, So I have a very simple class that has a method called getThumbUrl() but when I try calling this method on an instance I get Notice: Undefined property: FlickrImage::$getFullUrl But it is clearly there. Here is the code of the function: public function getThumbUrl() { return "http://farm".$this->_farm.".static.flickr.com/".$this->_server."/".$this->_id."_".$this->_secret."_t.jpg"; } And here is where it fails: foreach($photos as $photo) { echo "<img src='$photo->getFullUrl()' />"; } Any ideas? Thanks!

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  • How to set up Node server for production on own machine?

    - by Matt Hintzke
    This must be a pretty basic thing to do, but I cannot find any good guide on how to do it on the internet. I only find how to set up a development environment for Node. I want to be able to forward my R-Pi's port 80 to my Node server, which I want to obviously listen on port 80. How can I close the native port 80 so that I can let me Node server listen on that port. Ultimately, I want to be able to access my pi from any remote location. I know how to set up a static IP and forward the port on my router, but now how do I allow Node into port 80?

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  • syntax problem crating a method that returns an object (java)

    - by David
    I'm trying to create a method that will sum two timeO objects and return a new TimeO object called sum. Here is the relevant code snippet: public static TimeO add (TimeO t1, TimeO t2) { TimeO sum = new TimeO ; ... } When i try to compile it i get this error message: TimeO.java:15: '(' or '[' expected TimeO sum = new TimeO ; ^ 1 error i cant think of any reason why it would want me to open a set of parenthasies or brackets here but its possible that i dont' quite understand the syntax. Whats going wrong here?

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  • Why StringWriter.ToString return `System.Byte[]` and not the data?

    - by theateist
    UnZipFile method writes the data from inputStream to outputWriter. Why sr.ToString() returns System.Byte[] and not the data? using (var sr = new StringWriter()) { UnZipFile(response.GetResponseStream(), sr); var content = sr.ToString(); } public static void UnZipFile(Stream inputStream, TextWriter outputWriter) { using (var zipStream = new ZipInputStream(inputStream)) { ZipEntry currentEntry; if ((currentEntry = zipStream.GetNextEntry()) != null) { var size = 2048; var data = new byte[size]; while (true) { size = zipStream.Read(data, 0, size); if (size > 0) { outputWriter.Write(data); } else { break; } } } } }

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  • Return the difference between the lowest and highest key

    - by stan
    This is a past exam paper i am attempting and have no way to check if the out put is correct as i am not capable of building one of these things the question is in the title class Tree{ Tree left; Tree right; int key; public static int span(Tree tree) { if ( tree == null ){ return null; } if( tree.left != null) int min = span(tree.left); } if( tree.right != null){ int max = span(tree.right); } return max - min; } } Could anyone suggest what i need to change to get 5/5 marks :D - the only thing we have to do is write the span method, the header was given for us Thanks

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  • Godaddy registrar and Amazon Web Services EC2/Route 53

    - by soshannad
    Ok - I currently have a site hosted on Godaddy and they are the registrar for my domain. My goal is to have my site hosted on AWS with an EC2 server, which I have already set up and it is ready to go. In order to migrate my domain name to Amazon I have set up an A record with Godaddy and another A record with Route 53 (Amazon's routing service) with both of them pointing to the new static IP of the AWS site. My question is - Godaddy told me that I should leave my nameservers as Godaddy since my email is with them and set up an MX record wit Amazon pointing to it. Does this sound correct? Can you leave nameservers with Godaddy and have A records pointed to the new IP? Are there any benefits/cons to this? *FOR THE RECORD - My site is DOWN right now after doing the change - Godaddy says it will take 2 hours to come back, but I'm not sure if their nameserver recommendation is correct.

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  • Assign parameters to function according to parameter names

    - by Korcholis
    I have an assoc array with a list of what are parameters to me. Here's an example: array( 'param1' => 'value1', 'param4' => 'value4', 'param3' => 'value3', 'param2' => 'value2', ); Note that they may come unsorted. Now, is there a way I can make a call (static or from an instance, using call_user_func_array or similar) and correctly pass each value to each parameter? Just to be sure, an example function I'd like to call using that parameter array is one such this: exampleFunction($param1, $param2, $param3, $param4) { ... } PS: Reflection is great, but I'm concerned about execution times (which, at least, in Java tends to increase a lot when using Reflection). If you know any other way to do so, it would be awesome.

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  • Play 2.0 framework - POST parameters

    - by user1452715
    I'm trying to POST parameters to Action, and wrote in the routes: Home page GET / controllers.Application.index() POST /login/name:/password: controllers.Application.login(name, password) and I have an Action public static Result login(String name, String password) { return ok(name + " " + password); } my form is <form action="/login" method="post"> <input name="name" type="text" id="name"> <input name="password" type="password" id="password"> <input type="submit" value="Login"> </form> and it doesn't work For request 'POST /login' [Missing parameter: name] what am i doing wrong?

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  • Java using enum with switch statement

    - by MisterSquonk
    I've looked at various Q&As on SO similar to this question but haven't found a solution. What I have is an enum which represents different ways to view a TV Guide... static enum guideView { GUIDE_VIEW_SEVEN_DAY, GUIDE_VIEW_NOW_SHOWING, GUIDE_VIEW_ALL_TIMESLOTS } ...when the user changes the view an event handler receives an int from 0-2 and I'd like to do something like this... // 'which' is an int from 0-2 switch (which) { case NDroid.guideView.GUIDE_VIEW_SEVEN_DAY: ... break; } I'm used to C# enums and select/case statements which would allow something like the above and I know Java does things differently but I just can't make sense of what I need to do. Am I going to have to resort to if statements? There will likely only ever be 3 choices so I could do it but I wondered how it could be done with switch-case in Java.

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  • Is read-only auto-imlemented property possible?

    - by abatishchev
    Hello. I found a topic on MSDN that talks that yes, this is possible. I did a test that seems to break this statement: using System; namespace Test { class Program { static void Main(string[] args) { Foo f = new Foo("1"); Console.WriteLine(f.Bar); // prints 1 f.Test("2"); Console.WriteLine(f.Bar);// successfully prints 2 } } class Foo { public Foo(string b) { this.Bar = b; } public string Bar { get; private set; } public void Test(string b) { // this would be impossible for readonly field! // next error would be occur: CS0191 or CS0191 // A readonly field cannot be assigned to (except in a constructor or a variable initializer) this.Bar = b; } } } Where am I wrong?

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  • passing different structs to a function in c

    - by clear2k
    I have different structures that need to be filled out the same way. The only difference is that they are filled based on different data. I was wondering if it's possible to pass different structures to a certain function. What I have in mind is something like: struct stu1 { char *a; int b; }; struct stu2 { char *a; int b; }; static struct not_sure **some_func(struct not_sure *not_sure_here, original_content_list) { // do something and return passed struct for(i=0; i<size_of_original_content_list; i++){ //fill out passed structure } return the_struct; } int main(int argc, char *argv[]) { return_struct1 = some_func(stu1); return_struct2 = some_func(stu2); // do something separate with each return struct... } Any comments will be appreciate it.

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  • Google App Engine: Difficulty with Users API (or maybe just a Python syntax problem)

    - by Rosarch
    I have a simple GAE app that includes a login/logout link. This app is running on the dev server at the moment. The base page handler gets the current user, and creates a login/logout url appropriately. It then puts this information into a _template_data dictionary, for convenience of subclasses. class BasePage(webapp.RequestHandler): _user = users.get_current_user() _login_logout_link = None if _user: _login_logout_link = users.create_logout_url('/') else: _login_logout_link = users.create_login_url('/') _template_data = {} _template_data['login_logout_link'] = _login_logout_link _template_data['user'] = _user def render(self, templateName, templateData): path = os.path.join(os.path.dirname(__file__), 'Static/Templates/%s.html' % templateName) self.response.out.write(template.render(path, templateData)) Here is one such subclass: class MainPage(BasePage): def get(self): self.render('start', self._template_data) The login/logout link is displayed fine, and going to the correct devserver login/logout page. However, it seems to have no effect - the server still seems to think the user is logged out. What am I doing wrong here?

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  • How do you like to define your module-wide variables in drupal 6?

    - by sprugman
    I'm in my module file. I want to define some complex variables for use throughout the module. For simple things, I'm doing this: function mymodule_init() { define('SOME_CONSTANT', 'foo bar'); } But that won't work for more complex structures. Here are some ideas that I've thought of: global: function mymodule_init() { $GLOBALS['mymodule_var'] = array('foo' => 'bar'); } variable_set: function mymodule_init() { variable_set('mymodule_var', array('foo' => 'bar')); } property of a module class: class MyModule { static $var = array('foo' => 'bar'); } Variable_set/_get seems like the most "drupal" way, but I'm drawn toward the class setup. Are there any drawbacks to that? Any other approaches out there?

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  • HashMap "WriteOnce" Implementation .. need help

    - by JavaNewbie
    import java.util.*; public class HashMapExample { public static class WriteOnceMap<K, V> extends HashMap<K, V> { public V put(K key, V value) { /* WriteOnceMap is a map that does not allow changing value for a particular key. It means that put() method should throw IllegalArgumentException if the key is already assosiated with some value in the map. Please implement this method to conform to the above description of WriteOnceMap. */ } public void putAll(Map<? extends K, ? extends V> m) { /* Pleaase implement this method to conform to the description of WriteOnceMap above. It should either (1) copy all of the mappings from the specified map to this map or (2) throw IllegalArgumentException and leave this map intact if the parameter already contains some keys from this map. */ } } }

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  • How do you pass objects between View Controllers in Objective-C?

    - by editor
    I've been trudging through some code for two days trying to figure out why I couldn't fetch a global NSMutableArray variable I declared in the .h and implemented in .m and set in a the viewDidLoad function. It finally dawned on me: there's no such thing as a global variable in Objective-C, at least not in the PHP sense I've come to know. I didn't ever really read the XCode error warnings, but there it was, even if not quite plain English: "Instance variable 'blah' accessed in class method." My question: What am I supposed to do now? I've got two View Controllers that need to access a central NSMutableDictionary I generate from a JSON file via URL. It's basically an extended menu for all my Table View drill downs, and I'd like to have couple other "global" (non-static) variables. Do I have to grab the JSON each time I want to generate this NSMutableDictionary or is there some way to set it once and access it from various classes via #import? Do I have to write data to a file, or is there another way people usually do this?

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