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  • Looking for a better way to integrate a static list into a set of classes

    - by EvilTeach
    I'm trying to expand my sons interest from Warcraft 3 programming into C++ to broaden his horizons to a degree. We are planning on porting a little game that he wrote. The context goes something like this. There are Ships and Missiles, for which Ships will use Missiles and interact with them A Container exists which will hold 'a list' of ships. A Container exists which will hold 'a list' of planets. One can apply a function over all elements in the Container (for_each) Ships and Missles can be created/destroyed at any time New objects automatically insert themselves into the proper container. I cobbled a small example together to do that job, so we can talk about topics (list, templates etc) but I am not pleased with the results. #include <iostream> #include <list> using namespace std; /* Base class to hold static list in common with various object groups */ template<class T> class ObjectManager { public : ObjectManager ( void ) { cout << "Construct ObjectManager at " << this << endl; objectList.push_back(this); } virtual ~ObjectManager ( void ) { cout << "Destroy ObjectManager at " << this << endl; } void for_each ( void (*function)(T *) ) { for (objectListIter = objectList.begin(); objectListIter != objectList.end(); ++objectListIter) { (*function)((T *) *objectListIter); } } list<ObjectManager<T> *>::iterator objectListIter; static list<ObjectManager<T> *> objectList; }; /* initializer for static list */ template<class T> list<ObjectManager<T> *> ObjectManager<T>::objectList; /* A simple ship for testing */ class Ship : public ObjectManager<Ship> { public : Ship ( void ) : ObjectManager<Ship>() { cout << "Construct Ship at " << this << endl; } ~Ship ( void ) { cout << "Destroy Ship at " << this << endl; } friend ostream &operator<< ( ostream &out, const Ship &that ) { out << "I am a ship"; return out; } }; /* A simple missile for testing */ class Missile : public ObjectManager<Missile> { public : Missile ( void ) : ObjectManager<Missile>() { cout << "Construct Missile at " << this << endl; } ~Missile ( void ) { cout << "Destroy Missile at " << this << endl; } friend ostream &operator<< ( ostream &out, const Missile &that ) { out << "I am a missile"; return out; } }; /* A function suitable for the for_each function */ template <class T> void show ( T *it ) { cout << "Show: " << *it << " at " << it << endl; } int main ( void ) { /* Create dummy planets for testing */ Missile p1; Missile p2; /* Demonstrate Iterator */ p1.for_each(show); /* Create dummy ships for testing */ Ship s1; Ship s2; Ship s3; /* Demonstrate Iterator */ s1.for_each(show); return 0; } Specifically, The list is effectively embedded in each ship though the inheritance mechanism. One must have a ship, in order to access the list of ships. One must have a missile in order to be able to access the list of missiles. That feels awkward. My question boils down to "Is there a better way to do this?" Automatic object container creation Automatic object insertion Container access without requiring an object in the list to access it. I am looking for better ideas. All helpful entries get an upvote. Thanks Evil.

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  • Ajax In Firefox Plugin

    - by Jishnu
    Hi, Is there any way to send Ajax request to server from Firefox plugin? If yes how? If no, how do we have client server communication in Firefox plugin? I want to get some json data from server and manipulate dom object according to the client input. I am pretty beginner in plugin programming Regards, Jishnu

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  • Why does the Java Collections Framework offer two different ways to sort?

    - by dvanaria
    If I have a list of elements I would like to sort, Java offers two ways to go about this. For example, lets say I have a list of Movie objects and I’d like to sort them by title. One way I could do this is by calling the one-argument version of the static java.util.Collections.sort( ) method with my movie list as the single argument. So I would call Collections.sort(myMovieList). In order for this to work, the Movie class would have to be declared to implement the java.lang.Comparable interface, and the required method compareTo( ) would have to be implemented inside this class. Another way to sort is by calling the two-argument version of the static java.util.Collections.sort( ) method with the movie list and a java.util.Comparator object as it’s arguments. I would call Collections.sort(myMovieList, titleComparator). In this case, the Movie class wouldn’t implement the Comparable interface. Instead, inside the main class that builds and maintains the movie list itself, I would create an inner class that implements the java.util.Comparator interface, and implement the one required method compare( ). Then I'd create an instance of this class and call the two-argument version of sort( ). The benefit of this second method is you can create an unlimited number of these inner class Comparators, so you can sort a list of objects in different ways. In the example above, you could have another Comparator to sort by the year a movie was made, for example. My question is, why bother to learn both ways to sort in Java, when the two-argument version of Collections.sort( ) does everything the first one-argument version does, but with the added benefit of being able to sort the list’s elements based on several different criteria? It would be one less thing to have to keep in your mind while coding. You’d have one basic mechanism of sorting lists in Java to know.

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  • JS: capture a static snapshot of an object at a point in time with a method

    - by Barney
    I have a JS object I use to store DOM info for easy reference in an elaborate GUI. It starts like this: var dom = { m:{ old:{}, page:{x:0,y:0}, view:{x:0,y:0}, update:function(){ this.old = this; this.page.x = $(window).width(); this.page.y = $(window).height(); this.view.x = $(document).width(); this.view.y = window.innerHeight || $(window).height(); } I call the function on window resize: $(window).resize(function(){dom.m.update()}); The problem is with dom.m.old. I would have thought that by calling it in the dom.m.update() method before the new values for the other properties are assigned, at any point in time dom.m.old would contain a snapshot of the dom.m object as of the last update – but instead, it's always identical to dom.m. I've just got a pointless recursion method. Why isn't this working? How can I get a static snapshot of the object that won't update without being specifically told to? Comments explaining how I shouldn't even want to be doing anything remotely like this in the first place are very welcome :)

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  • Changing save directory

    - by Nathan
    Disregard my previous pre-edit post. Rethought what I needed to do. This is what I'm currently doing: https://developer.mozilla.org/en/XPCOM_Interface_Reference/nsIScriptableIO downloadFile: function(httpLoc) { try { //new obj_URI object var obj_URI = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService). newURI(httpLoc, null, null); //new file object //set file with path obj_TargetFile.initWithPath("C:\\javascript\\cache\\test.pdf"); //if file doesn't exist, create if(!obj_TargetFile.exists()) { obj_TargetFile.create(0x00,0644); } //new persitence object var obj_Persist = Cc["@mozilla.org/embedding/browser/nsWebBrowserPersist;1"]. createInstance(Ci.nsIWebBrowserPersist); // with persist flags if desired const nsIWBP = Ci.nsIWebBrowserPersist; const flags = nsIWBP.PERSIST_FLAGS_REPLACE_EXISTING_FILES; obj_Persist.persistFlags = flags | nsIWBP.PERSIST_FLAGS_FROM_CACHE; //save file to target obj_Persist.saveURI(obj_URI,null,null,null,null,obj_TargetFile); return true; } catch (e) { alert(e); } },//end downloadFile As you can see the directory is hardcoded in there, I want to save the pdf file open in the active tab to a relative temporary directory, or anywhere that's out of the way enough that the user won't stumble along and delete it. I'm going to try that using File I/O, I was under the impression that what I was looking for was in scriptable file I/O and thus disabled.

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  • Ruby Doesn't Recognize Alias Method

    - by Jesse J
    I'm trying to debug someone else's code and having trouble figuring out what's wrong. When I run rake, one of the errors I get is: 2) Error: test_math(TestRubyUnits): NoMethodError: undefined method `unit_sin' for CMath:Module /home/user/ruby-units/lib/ruby_units/math.rb:21:in `sin' This is the function that calls the method: assert_equal Math.sin(pi), Math.sin("180 deg".unit) And this is what the class looks like: module Math alias unit_sin sin def sin(n) Unit === n ? unit_sin(n.to('radian').scalar) : unit_sin(n) end alias unit_cos cos def cos(n) Unit === n ? unit_cos(n.to('radian').scalar) : unit_cos(n) end ... module_function :unit_sin module_function :sin module_function :unit_cos module_function :cos ... end (The ellipsis means "more of the same"). As far as I can see, this is valid Ruby code. Is there something I'm missing here that's causing the error, or could the error be coming from something else? Update: I'm wondering if the problem has to do with namespaces. This code is attempting to extend CMath, so perhaps the alias and/or module_function isn't actually getting into CMath, or something like that....

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  • How to import a class from default package

    - by mykhaylo
    Hi, I am using Eclipse 3.5 and I have created a project with some package structure along with the default package. I have one class in default package - Calculations.java and I want to make the use of that class in any of the package (for instance in com.company.calc). When I try to make the use of the class which is default package, its giving me compile error. Its not able to recognise the class in default package. Where is a problem? Calculations.java - source code public class Calculations{ native public int Calculate(int contextId); native public double GetProgress(int contextId); static { System.loadLibrary("Calc"); } } I can put my class in any other package. This class has some native method which is implemented in Delphi . If I put that class in any of the folder,I will have to make the change that DLL which I want to avoid(really - I can not). Thats why I put my class in the default package.

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  • Ruby module_function, invoking module's private method, invoked in class method style on module shows error

    - by Jignesh
    test_module.rb module MyModule def module_func_a puts "module_func_a invoked" private_b end module_function :module_func_a private def private_b puts "private_b invoked" end end class MyClass include MyModule def test_module module_func_a end end Invoking module function from class c = MyClass.new c.test_module Output 1: $ ruby test_module.rb module_func_a invoked private_b invoked Invoking module function on module in class method style ma = MyModule.module_func_a Output 2: module_func_a invoked test_module.rb:5:in `module_func_a': undefined local variable or method `private_b' for MyModule:Module (NameError) from test_module.rb:31 As can be seen from the Output 1 and Output 2 when including the module in a class, no issue occurs when a module's private method gets invoked from a module function while in case when directly invoking the module function on the module in class method style the module's private method, invoked from module function, is not found. Can anybody make me understand the reason behind above behavior and whether invoking module function (which in turn invokes module's private method) on module in class method style is possible or not? If possible, then what rectifications are required in my code to do the same? Thanks, Jignesh

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  • When is it better to use a method versus a property for a class definition?

    - by ccomet
    Partially related to an earlier question of mine, I have a system in which I have to store complex data as a string. Instead of parsing these strings as all kinds of separate objects, I just created one class that contains all of those objects, and it has some parser logic that will encode all properties into strings, or decode a string to get those objects. That's all fine and good. This question is not about the parser itself, but about where I should house the logic for the parser. Is it a better choice to put it as a property, or as a method? In the case of a property, say public string DataAsString, the get accessor would house the logic to encode all of the data into a string, while the set accessor would decode the input value and set all of the data in the class instance. It seems convenient because the input/output is indeed a string. In the case of a method, one method would be Encode(), which returns the encoded string. Then, either the constructor itself would house the logic for the decoding a string and require the string argument, or I write a Decode(string str) method which is called separately. In either case, it would be using a method instead of a property. So, is there a functional difference between these paths, in terms of the actual running of the code? Or are they basically equivalent and it then boils down to a choice of personal preference or which one looks better? And in that kind of question... which would look cleaner anyway?

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  • Getting started on thunderbird extensions

    - by Mike
    Hello there,       I have beein using Tunderbird for many years now and now i am interested in developing some of my own extensions.       I looked over the documentation on their official website but found little suport for getting started at this.       I have some experience with python, perl, php and would like if you can reccomend me some geting started materials, a "hello world" for this would be great Best regards, Mike

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  • Accessing non-static combbox property in the static method.

    - by Harikrishna
    I have one combobox on the window form and I have one method which is declared with static like private static DataTable ParseTable(HtmlNode table) Now I want to use combobox in that method for using combobox property but I can not access any property of combobox or combobox itself.If I made the combobox declaration as static then it can be accessed in that static method.But any alternative way to access combbox property in that static method because I don't want to make combobox declaration as static.

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  • How to get visual studio 10 to open .mk files in the same instance?

    - by Russ Schultz
    I've recently been migrated to windows 7, and upon re-installing VS2010, it seems to want to treat .mk files differently than it used to. For whatever reason, it insists on opening a new instance of visual studio to edit these files. It doesn't for .c, .h, etc. I've tried using types, a freeware association manager, to change how it is associated. I've deleted the association, recreated, etc. but it still seems to want to treat these separately. Anybody know how to beat this thing into submission?

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  • Fast ArgumentNullException with attributes. It is possible?

    - by Fraga
    Hi. Is there any fast way to verify null arguments via attributes or something? Convert this: public void Method(type arg1,type arg2,type arg3) { if (arg1== null) throw new ArgumentNullException("arg1"); if (arg2== null) throw new ArgumentNullException("arg2"); if (arg3== null) throw new ArgumentNullException("arg3"); //Business Logic } Into something like this: [VerifyNullArgument("arg1","arg2","arg3")] public void Method(type arg1,type arg2,type arg3) { //Business Logic } Ideas? thanks guys.

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  • Rails NoMethodError in loop when method exists

    - by Kevin Whitaker
    Good day all. I'm running into a bit of a problem getting a script running on my production environment, even though it works just fine on my dev box. I've verified that all the requisite gems and such are the same version. I should mention that the script is intended to be run with the script/runner command. Here is a super-condensed version of what I'm trying to do, centered around the part that's broken: def currentDeal marketTime = self.convertToTimeZone(Time.new) deal = Deal.find(:first, :conditions = ["start_time ? AND market_id = ? AND published = ?", marketTime, marketTime, self.id, 1]) return deal end markets = Market.find(all) markets.each do |market| deal = market.currentDeal puts deal.subject end Now convertToTimeZone is a method attached to the model. So, this code works just fine on my dev machine, as stated. However, attempting to run it on my production machine results in: undefined method `subject' for nil:NilClass (NoMethodError) If, however, I go into the console on the production box and do this: def currentDeal marketTime = self.convertToTimeZone(Time.new) deal = Deal.find(:first, :conditions = ["start_time ? AND market_id = ? AND published = ?", marketTime, marketTime, self.id, 1]) return deal end market = Market.find(1) deal = market.currentDeal puts deal.subject It returns the correct value, no problem. So what is going on? This is on rails v 2.3.5, on both machines. Thanks for any help

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  • Runge-Kutta Method with adaptive step

    - by infoholic_anonymous
    I am implementing Runge-Kutta method with adaptive step in matlab. I get different results as compared to matlab's own ode45 and my own implementation of Runge-Kutta method with fixed step. What am I doing wrong in my code? Is it possible? function [ result ] = rk4_modh( f, int, init, h, h_min ) % % f - function handle % int - interval - pair (x_min, x_max) % init - initial conditions - pair (y1(0),y2(0)) % h_min - lower limit for h (step length) % h - initial step length % x - independent variable ( for example time ) % y - dependent variable - vertical vector - in our case ( y1, y2 ) function [ k1, k2, k3, k4, ka, y ] = iteration( f, h, x, y ) % core functionality performed within loop k1 = h * f(x,y); k2 = h * f(x+h/2, y+k1/2); k3 = h * f(x+h/2, y+k2/2); k4 = h * f(x+h, y+k3); ka = (k1 + 2*k2 + 2*k3 + k4)/6; y = y + ka; end % constants % relative error eW = 1e-10; % absolute error eB = 1e-10; s = 0.9; b = 5; % initialization i = 1; x = int(1); y = init; while true hy = y; hx = x; %algorithm [ k1, k2, k3, k4, ka, y ] = iteration( f, h, x, y ); % error estimation for j=1:2 [ hk1, hk2, hk3, hk4, hka, hy ] = iteration( f, h/2, hx, hy ); hx = hx + h/2; end err(:,i) = abs(hy - y); % step adjustment e = abs( hy ) * eW + eB; a = min( e ./ err(:,i) )^(0.2); mul = a * s; if mul >= 1 % step length admitted keepH(i) = h; k(:,:,i) = [ k1, k2, k3, k4, ka ]; previous(i,:) = [ x+h, y' ]; %' i = i + 1; if floor( x + h + eB ) == int(2) break; else h = min( [mul*h, b*h, int(2)-x] ); x = x + keepH(i-1); end else % step length requires further adjustments h = mul * h; if ( h < h_min ) error('Computation with given precision impossible'); end end end result = struct( 'val', previous, 'k', k, 'err', err, 'h', keepH ); end The function in question is: function [ res ] = fun( x, y ) % res(1) = y(2) + y(1) * ( 0.9 - y(1)^2 - y(2)^2 ); res(2) = -y(1) + y(2) * ( 0.9 - y(1)^2 - y(2)^2 ); res = res'; %' end The call is: res = rk4( @fun, [0,20], [0.001; 0.001], 0.008 ); The resulting plot for x1 : The result of ode45( @fun, [0, 20], [0.001, 0.001] ) is:

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  • Lisp, OCaml or what for Runge Kutta?

    - by Eelvex
    Which language would you propose for solving a system with: first order differential equations complex variables N-dimensions using 4th order Runge Kutta or the like. Speed matters a lot but would sacrifice for: Elegant (clean and short) code Flexibility + scalability I'm mostly between a Lisp and OCaml but any other suggestion is welcomed. Thanks!

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  • Does Java support default parameter values?

    - by gnavi
    I came across some Java code that had the following structure: public MyParameterizedFunction(String param1, int param2) { this(param1, param2, false); } public MyParameterizedFunction(String param1, int param2, boolean param3) { //use all three parameters here } I know that in C++ I can assign a parameter a default value. For example: void MyParameterizedFunction(String param1, int param2, bool param3=false); Does Java support this kind of syntax? Are there any reasons why this two step syntax is preferable?

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  • Managing logs/warnings in Python extensions

    - by Dimitri Tcaciuc
    TL;DR version: What do you use for configurable (and preferably captured) logging inside your C++ bits in a Python project? Details follow. Say you have a a few compiled .so modules that may need to do some error checking and warn user of (partially) incorrect data. Currently I'm having a pretty simplistic setup where I'm using logging framework from Python code and log4cxx library from C/C++. log4cxx log level is defined in a file (log4cxx.properties) and is currently fixed and I'm thinking how to make it more flexible. Couple of choices that I see: One way to control it would be to have a module-wide configuration call. # foo/__init__.py import sys from _foo import import bar, baz, configure_log configure_log(sys.stdout, WARNING) # tests/test_foo.py def test_foo(): # Maybe a custom context to change the logfile for # the module and restore it at the end. with CaptureLog(foo) as log: assert foo.bar() == 5 assert log.read() == "124.24 - foo - INFO - Bar returning 5" Have every compiled function that does logging accept optional log parameters. # foo.c int bar(PyObject* x, PyObject* logfile, PyObject* loglevel) { LoggerPtr logger = default_logger("foo"); if (logfile != Py_None) logger = file_logger(logfile, loglevel); ... } # tests/test_foo.py def test_foo(): with TemporaryFile() as logfile: assert foo.bar(logfile=logfile, loglevel=DEBUG) == 5 assert logfile.read() == "124.24 - foo - INFO - Bar returning 5" Some other way? Second one seems to be somewhat cleaner, but it requires function signature alteration (or using kwargs and parsing them). First one is.. probably somewhat awkward but sets up entire module in one go and removes logic from each individual function. What are your thoughts on this? I'm all ears to alternative solutions as well. Thanks,

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  • Returning IEnumerable<T> vs IQueryable<T>

    - by stackoverflowuser
    what is the difference between returning iqueryable vs ienumerable. IQueryable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; IEnumerable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; Will both be deferred execution? When should one be preferred over the other?

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  • Kohana Database Library - How to Execute a Query with the Same Parameters More Than Once?

    - by Noah Goodrich
    With the following bit of code: $builder = ORM::factory('branch')->where('institution_id', $this->institution->id)->orderby('name'); I need to first execute: $count = $builder->count_all(); Then I need to execute: $rs = $builder->find_all($limit, $offset); However, it appears that when I execute the first query the stored query parameters are cleared so that a fresh query can be executed. Is there a way to avoid having the parameters cleared or at least copy them easily without having to reach directly into the Database driver object that stores the query parameters and copy them out? We are using Kohana 2.3.4 and upgrading is not an option.

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  • Fatal error: Function name must be a string in.. PHP error

    - by Jonesy
    Hi I have a class called User and a method called insertUser(). function insertUser($first_name, $last_name, $user_name, $password, $email_address, $group_house_id) { $first_name = mysql_real_escape_string($first_name); $last_name = mysql_real_escape_string($last_name); $user_name = mysql_real_escape_string($user_name); $password = mysql_real_escape_string($password); $email_address = mysql_real_escape_string($email_address); $query = "INSERT INTO Users (FirstName,LastName,UserName,Password,EmailAddress, GroupHouseID) VALUES ('$first_name','$last_name','$user_name','$password','$email_address','$group_house_id')"; $mysql_query($query); } And I call it like this: $newUser = new User(); $newUser->insertUser($first_name, $last_name, $user_name, $email, $password, $group_house_id); When I run the code I get this error: Fatal error: Function name must be a string in /Library/WebServer/Documents/ORIOnline/includes/class_lib.php on line 33 Anyone know what I am doing wronly? Also, this is my first attempt at OO PHP. Cheers, Jonesy

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