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Workflow engine BPMN, Drools, etc or ESB?

- by Tom

We currently have an application that is based on an in-house developed workflow engine with YAML based DSL. We are looking to move parts of it to Java. I have discovered a number of java solutions like Intalio, JBPM, Drools Expert, Drools Flow etc. They appear to be aimed at businesses where the business analyst creates the workflows using a graphical editor and submits them to the workflow engine. They seem geared towards ease of use for non-technical people rather than for developers with a focus on human interaction. The workflows tend to look like. Discover-a-file -\ -> join -> process-file -> move-file -> register-file Discover-some-metadata -/ If any step fails we need to retry it X times. We also need to be able to stop the system and be able to restart it and have it continue from where it was (durable). Some of our workflows can be defined by a set of goals we need to achieve so Jess's backwards rule chaining sounds interesting but it is not open source. It might be that what we are after is a Finite State Machine engine or just an Enterprise Service Bus and do everything as JMS queues. Is there a good open source workflow engine that is both standards-based but also geared towards developers. We don't particular want to use a graphical workflow designer or write reams of XML and it should ideally be in Java or language agnostic (makes REST/Soap calls to external services). Thanks, Tom

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How to implement RSA-CBC?(I have uploaded the request document)

- by tq0fqeu

I don't konw more about cipher, I just want to implement RSA-CBC which maybe mean that the result of RSA encrypt in CBC mode, and I have implemented RSA. any code languages will be ok, java will be appreciated thx I copy the request as follow(maybe has spelling wrong), but that's French I don't konw that: Pr´esentation du mini-projet Le but du mini-projet est d’impl´ementer une version ´el´ementaire du chi?rement d’un bloc par RSA et d’inclure cette primitive dans un systeme de chi?rement par bloc avec chaˆinage de blocs et IV (Initial Vector ) al´eatoire. Dans ce systeme, un texte clair (`a chi?rer) est d´ecompos´e en blocs de taille t (?x´ee par l’utilisa- teur), chaque bloc (clair) est chi?r´e par RSA en un bloc crypt´e de mˆeme taille, puis le cryptogramme associ´e au texte clair initial est obtenu en chaˆinant les blocs crypt´es par la m´ethode CBC (cipher- block chaining) d´ecrite dans le cours (voir poly “Block Ciphers”) Votre programme devra demander a l’utilisateur la taille t, puis, apres g´en´eration des cl´es publique et priv´ee, lui proposer de chi?rer ou d´echi?rer un (court) ?chier ASCII. Il est indispensable que votre programme soit au moins capable de traiter le cas (tres peu r´ealiste du point de vue de la s´ecurit´e) t = 32. Pour les traiter des blocs plus grands, il vous faudra impl´ementer des routines d’arithm´etique multi-pr´ecision ; pour cela, je vous conseille de faire appela des bibliotheques libres comme GMP (GNU Multiprecision Library). Pour la g´en´eration al´eatoire des nombres premiers p et q, vous pouvez ´egalement faire appela des bibliotheques sp´ecialis´ees,a condition de me donner toutes les pr´ecisions n´ecessaires. Vous devez m’envoyer (avant une date qui reste a ?xer)a mon adresse ´electronique ([email protected]) un courriel (sujet : [MI1-crypto] : devoir, corps du message : les noms des ´etudiants ayant travaill´e sur le mini-projet) auquel sera attach´e un dossier compress´e regroupant vos sources C ou Java comment´ees, votre programme ex´ecutable, et un ?chier texte ou PDF donnant toutes les pr´ecisions sur les biblioth`eques utilis´ees, vos choix algorithmiques et d’impl´ementation, et les raisons de ces choix (complexit´e algorithmique, robus- tesse, facilit´e d’impl´ementation, etc.). Vous pouvez travailler en binˆome ou en trinˆome, mais je serai nettement plus exigeant avec les trinˆomes I have uploaded the request at http://uploading.com/files/22emmm6b/enonce_projet.pdf/ thx

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SHLoadImageFile(L"\\Program Files\\TrainingApp\\background.png"); whats that L in the argument for?

- by ashishsony

Hi, ive been working on c++ on linux for the past 2 years,and switched to windows c++ programming recently. can anyone tell me what that L is there in the argument of the function: SHLoadImageFile(L"\\Program Files\\TrainingApp\\background.png"); and on viewing certain sample code in MSVS C++ i came across hundereds of typedefs like.. LPARAM// typedef LONG_PTR LPARAM... here LONG_PTR is again typedef as __w64 long WPARAM// typedef UINT_PTR WPARAM... so there is a lot of chained typedefs.. I never saw this much of typedef chaining on c++ programming on linux using gcc.. what i want to say is that it just creates more confusion in this way for windows application programming.. while ive seen application programming on linux using frameworks like Qt.. there such things are rarely used.. so is there specific purpose in typedefining again and again on MSVSC++?? for eg.. there are typdefs like typedef int BOOL; whats the use of this when normal bool is available already..?? there are hundred other cases ive come across where just to decide what data type to use becomes so difficult.. it becomes difficult to understand a pre written code in this fashion too.. Thanks.

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Get the parent id..

- by tixrus

I have a bunch of elements like the following: <div class="droppableP" id="s-NSW" style="width:78px; height:63px; position: absolute; top: 223px; left: 532px;"> </div> They all have class droppableP but different id's obviously and I would like to factor the code in this script I am hacking on. The original script just has a specific selector for each of one of these divs, but the code is all alike except for the id it does things to, which is either the id of the parent or another div with a name that's related to it. Here is the original code specifically for this div: $("#s-NSW > .sensible").droppable( { accept : "#i-NSW", tolerance : 'intersect', activeClass : 'droppable-active', hoverClass : 'droppable-hover', drop : function() { $('#s-NSW').addClass('s-NSW'); $('#s-NSW').addClass('encastrada'); //can't move any more.. $('#i-NSW').remove(); $('#s-NSW').animate( { opacity: 0.25 },200, 'linear'); checkWin(); } }); Here is how I would like to factor so the same code can do all of them and I will eventually do chaining as well and maybe get rid of the inline styles but here is my first go: $(".droppableP > .sensible").droppable( { accept : "#i" + $(this).parent().attr('id').substring(2), tolerance : 'intersect', activeClass : 'droppable-active', hoverClass : 'droppable-hover', drop : function() { $(this).parent().addClass($(this).parent().attr('id')); $(this).parent().addClass('encastrada'); $("#i" + ($this).parent().attr('id').substring(2)).remove(); $(this).parent().animate( { opacity: 0.25 },200, 'linear'); checkWin(); } }); The error I get is $(this).parent().attr("id") is undefined Many thanks. I have browsed related questions the one I understand that's closest to mine, turns out they didn't need parent function at all. I'm kind of a noob so please don't yell at me too hard if this is a stupid question.

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How do I unit test a finalizer?

- by GraemeF

I have the following class which is a decorator for an IDisposable object (I have omitted the stuff it adds) which itself implements IDisposable using a common pattern: public class DisposableDecorator : IDisposable { private readonly IDisposable _innerDisposable; public DisposableDecorator(IDisposable innerDisposable) { _innerDisposable = innerDisposable; } #region IDisposable Members public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } #endregion ~DisposableDecorator() { Dispose(false); } protected virtual void Dispose(bool disposing) { if (disposing) _innerDisposable.Dispose(); } } I can easily test that innerDisposable is disposed when Dispose() is called: [Test] public void Dispose__DisposesInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object).Dispose(); mockInnerDisposable.Verify(x => x.Dispose()); } But how do I write a test to make sure innerDisposable does not get disposed by the finalizer? I want to write something like this but it fails, presumably because the finalizer hasn't been called by the GC thread: [Test] public void Finalizer__DoesNotDisposeInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object); GC.Collect(); mockInnerDisposable.Verify(x => x.Dispose(), Times.Never()); }

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Which Javascript framework (jQuery vs Dojo vs ... )?

- by cletus

There are a few Javascript frameworks/toolets out there, such as: jQuery; Dojo; Prototype; YUI; MooTools; ExtJS; SmartClient; and others I'm sure. It certainly seems that jQuery is ascendant in terms of mindshare at the moment. For example, Microsoft (ASP.NET MVC) and Nokia will use it. I also found this this performance comparison of Dojo, jQuery, MooTools and Prototype (Edit: Updated Comparison), which looks highly favourable to Dojo and jQuery. Now my previous experience with Javascript has been the old school HTML + Javascript most of us have done and RIA frameworks like Google Web Toolkit ("GWT") and Ext-GWT, which were a fairly low-stress entry into the Ajax world for someone from a Java background, such as myself. But, after all this, I find myself leaning towards the more PHP + Ajax type solution, which just seems that much more lightweight. So I've been looking into jQuery and I really like it's use of commands, the use of fluent interfaces and method chaining, it's cross-browser CSS selector superset, the fact that it's lightweight and extensible, the brevity of the syntax, unobtrusive Javascript and the plug-in framework. Now obviously many of these aren't unique to jQuery but on the basis that some things are greater than their sum of parts, it just seems that it all fits together and works well. So jQuery seems to have a lot going for it and it looks to the frontrunner for what I choose to concentrate on. Is there anything else I should be aware of or any particular reasons not to choose it or to choose something else? EDIT: Just wanted to add this trend comparison of Javascript frameworks.

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What would you like to correct and/or improve in this java implementation of Chain Of Responsibility

- by Maciek Kreft

package design.pattern.behavioral; import design.pattern.behavioral.ChainOfResponsibility.*; public class ChainOfResponsibility { public static class Chain { private Request[] requests = null; private Handler[] handlers = null; public Chain(Handler[] handlers, Request[] requests){ this.handlers = handlers; this.requests = requests; } public void start() { for(Request r : requests) for (Handler h : handlers) if(h.handle(r)) break; } } public static class Request { private int value; public Request setValue(int value){ this.value = value; return this; } public int getValue() { return value; } } public static class Handler<T1> { private Lambda<T1> lambda = null; private Lambda<T1> command = null; public Handler(Lambda<T1> condition, Lambda<T1> command) { this.lambda = condition; this.command = command; } public boolean handle(T1 request) { if (lambda.lambda(request)) command.lambda(request); return lambda.lambda(request); } } public static abstract class Lambda<T1>{ public abstract Boolean lambda(T1 request); } } class TestChainOfResponsibility { public static void main(String[] args) { new TestChainOfResponsibility().test(); } private void test() { new Chain(new Handler[]{ // chain of responsibility new Handler<Request>( new Lambda<Request>(){ // command public Boolean lambda(Request condition) { return condition.getValue() >= 600; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are rich: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), new Handler<Request>( new Lambda<Request>(){ public Boolean lambda(Request condition) { return condition.getValue() >= 100; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are poor: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), }, new Request[]{ new Request().setValue(600), // chaining method new Request().setValue(100), } ).start(); } }

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Unittesting aspect-oriented features.

- by Tomas Brambora

Hi, I'd like to know what would you propose as the best way to unit test aspect-oriented application features (well, perhaps that's not the best name, but it's the best I was able to come up with :-) ) such as logging or security? These things are sort of omni-present in the application, so how to test them properly? E.g. say that I'm writing a Cherrypy web server in Python. I can use a decorator to check whether the logged-in user has the permission to access a given page. But then I'd need to write a test for every page to see whether it works oK (or more like to see that I had not forgotten to check security perms for that page). This could maybe (emphasis on maybe) be bearable if logging and/or security were implemented during the web server "normal business implementation". However, security and logging usually tend to be added to the app as an afterthough (or maybe that's just my experience, I'm usually given a server and then asked to implement security model :-) ). Any thoughts on this are very welcome. I have currently 'solved' this issue by, well - not testing this at all. Thanks.

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Best pattern to load enumerated values from DAL using WCF RIA Services

- by Dale Halliwell

I would like to be able to load several RIA entitysets in a single call without chaining/nesting several small LoadOperations together so that they load sequentially. I have several pages that have a number of comboboxes on them. These comboboxes are populated with static values from a database (for example status values). Right now I preload these values in my VM by one method that strings together a series of LoadOperations for each type that I want to load. For example: public void LoadEnums() { context.Load(context.GetMyStatusValues1Query()).Completed += (s, e) => { this.StatusValues1 = context.StatusValues1; context.Load(context.GetMyStatusValues2()).Completed += (s1, e1) => { this.StatusValues2 = context.StatusValues2; context.Load(context.GetMyStatusValues3Query()).Completed += (s2, e2) => { this.StatusValues3 = context.StatusValues3; (....and so on) }; }; }; }; While this works fine, it seems a bit nasty. Also, I would like to know when the last loadoperation completes so that I can load whatever entity I want to work on after this, so that these enumerated values resolve properly in form elements like comboboxes and listboxes. (I think) I can't do this easily above without creating a delegate and calling that on the completion of the last loadoperation. So my question is: does anyone out there know a better pattern to use, ideally where I can load all my static entitysets in a single LoadOperation?

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python 'with' statement

- by Stephen

Hi, I'm using Python 2.5. I'm trying to use this 'with' statement. from __future__ import with_statement a = [] with open('exampletxt.txt','r') as f: while True: a.append(f.next().strip().split()) print a The contents of 'exampletxt.txt' are simple: a b In this case, I get the error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/tmp/python-7036sVf.py", line 5, in <module> a.append(f.next().strip().split()) StopIteration And if I replace f.next() with f.read(), it seems to be caught in an infinite loop. I wonder if I have to write a decorator class that accepts the iterator object as an argument, and define an __exit__ method for it? I know it's more pythonic to use a for-loop for iterators, but I wanted to implement a while loop within a generator that's called by a for-loop... something like def g(f): while True: x = f.next() if test(x): a = x elif test(x): b = f.next() yield [a,x,b] a = [] with open(filename) as f: for x in g(f): a.append(x)

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Zend_Validate_Abstract custom validator not displaying correct error messages.

- by Jeremy Dowell

I have two text fields in a form that I need to make sure neither have empty values nor contain the same string. The custom validator that I wrote extends Zend_Validate_Abstract and works correctly in that it passes back the correct error messages. In this case either: isEmpty or isMatch. However, the documentation says to use addErrorMessages to define the correct error messages to be displayed. in this case, i have attached ->addErrorMessages(array("isEmpty"=>"foo", "isMatch"=>"bar")); to the form field. According to everything I've read, if I return "isEmpty" from isValid(), my error message should read "foo" and if i return "isMatch" then it should read "bar". This is not the case I'm running into though. If I return false from is valid, no matter what i set $this-_error() to be, my error message displays "foo", or whatever I have at index[0] of the error messages array. If I don't define errorMessages, then I just get the error code I passed back for the display and I get the proper one, depending on what I passed back. How do I catch the error code and display the correct error message in my form? The fix I have implemented, until I figure it out properly, is to pass back the full message as the errorcode from the custom validator. This will work in this instance, but the error message is specific to this page and doesn't really allow for re-use of code. Things I have already tried: I have already tried validator chaining so that my custom validator only checks for matches: ->setRequired("true") ->addValidator("NotEmpty") ->addErrorMessage("URL May Not Be Empty") ->addValidator([*customValidator]*) ->addErrorMessage("X and Y urls may not be the same") But again, if either throws an error, the last error message to be set displays, regardless of what the error truly is. I'm not entirely sure where to go from here. Any suggestions?

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javascript plugin - singleton pattern?

- by Adam Kiss

intro Hello, I'm trying to develop some plugin or/*and* object in javascript, which will control some properties over some object. It will also use jQuery, to ease development. idea This is in pseudocode to give you an idea, since I can't really describe it in english with the right words, it's impossible to go and use google to find out what I want to use (and learn). I will have plugin (maybe object?) with some variables and methods: plugin hideshow(startupconfig){ var c, //collection add: function(what){ c += what; }, do: function(){ c.show().hide().stop(); //example code } } and I will use it this way (or sort-of): var p = new Plugin(); p .add($('p#simple')) .add($('p#simple2')) .do(); note I'm not really looking for jQuery plugin tutorials - it's more like usage of singleton pattern in document in javascript, jQuery is mentione only because it will be used to modify dom and simplify selectors, jQuery plugin maybe just for that one little function add. I'm looking for something, that will sit on top of my document and call functions from itselft based on timer, or user actions, or whatever. problems I don't really know where to start with construction of this object/plugin I'm not really sure how to maintain one variable, which is collection of jQuery objects (something like $('#simple, #simple2');) I would maybe like to extedn jQuery with $.fn.addToPlugin to use chaining of objects, but that should be simple (really just each( p.add($(this)); )) I hope I make any sense, ideas, links or advices appreciated.

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Passing IDisposable objects through constructor chains

- by Matt Enright

I've got a small hierarchy of objects that in general gets constructed from data in a Stream, but for some particular subclasses, can be synthesized from a simpler argument list. In chaining the constructors from the subclasses, I'm running into an issue with ensuring the disposal of the synthesized stream that the base class constructor needs. Its not escaped me that the use of IDisposable objects this way is possibly just dirty pool (plz advise?) for reasons I've not considered, but, this issue aside, it seems fairly straightforward (and good encapsulation). Codes: abstract class Node { protected Node (Stream raw) { // calculate/generate some base class properties } } class FilesystemNode : Node { public FilesystemNode (FileStream fs) : base (fs) { // all good here; disposing of fs not our responsibility } } class CompositeNode : Node { public CompositeNode (IEnumerable some_stuff) : base (GenerateRaw (some_stuff)) { // rogue stream from GenerateRaw now loose in the wild! } static Stream GenerateRaw (IEnumerable some_stuff) { var content = new MemoryStream (); // molest elements of some_stuff into proper format, write to stream content.Seek (0, SeekOrigin.Begin); return content; } } I realize that not disposing of a MemoryStream is not exactly a world-stopping case of bad CLR citizenship, but it still gives me the heebie-jeebies (not to mention that I may not always be using a MemoryStream for other subtypes). It's not in scope, so I can't explicitly Dispose () it later in the constructor, and adding a using statement in GenerateRaw () is self-defeating since I need the stream returned. Is there a better way to do this? Preemptive strikes: yes, the properties calculated in the Node constructor should be part of the base class, and should not be calculated by (or accessible in) the subclasses I won't require that a stream be passed into CompositeNode (its format should be irrelevant to the caller) The previous iteration had the value calculation in the base class as a separate protected method, which I then just called at the end of each subtype constructor, moved the body of GenerateRaw () into a using statement in the body of the CompositeNode constructor. But the repetition of requiring that call for each constructor and not being able to guarantee that it be run for every subtype ever (a Node is not a Node, semantically, without these properties initialized) gave me heebie-jeebies far worse than the (potential) resource leak here does.

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c++ queue template

- by Dalton Conley

ALright, pardon my messy code please. Below is my queue class. #include <iostream> using namespace std; #ifndef QUEUE #define QUEUE /*---------------------------------------------------------------------------- Student Class # Methods # Student() // default constructor Student(string, int) // constructor display() // out puts a student # Data Members # Name // string name Id // int id ----------------------------------------------------------------------------*/ class Student { public: Student() { } Student(string iname, int iid) { name = iname; id = iid; } void display(ostream &out) const { out << "Student Name: " << name << "\tStudent Id: " << id << "\tAddress: " << this << endl; } private: string name; int id; }; // define a typedef of a pointer to a student. typedef Student * StudentPointer; template <typename T> class Queue { public: /*------------------------------------------------------------------------ Queue Default Constructor Preconditions: none Postconditions: assigns default values for front and back to 0 description: constructs a default empty Queue. ------------------------------------------------------------------------*/ Queue() : myFront(0), myBack(0) {} /*------------------------------------------------------------------------ Copy Constructor Preconditions: requres a reference to a value for which you are copying Postconditions: assigns a copy to the parent Queue. description: Copys a queue and assigns it to the parent Queue. ------------------------------------------------------------------------*/ Queue(const T & q) { myFront = myBack = 0; if(!q.empty()) { // copy the first node myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } /*------------------------------------------------------------------------ Destructor Preconditions: none Postconditions: deallocates the dynamic memory for the Queue description: deletes the memory stored for a Queue. ------------------------------------------------------------------------*/ ~Queue() { NodePointer prev = myFront, ptr; while(prev != NULL) { ptr = prev->next; delete prev; prev = ptr; } } /*------------------------------------------------------------------------ Empty() Preconditions: none Postconditions: returns a boolean value. description: returns true/false based on if the queue is empty or full. ------------------------------------------------------------------------*/ bool empty() const { return (myFront == NULL); } /*------------------------------------------------------------------------ Enqueue Preconditions: requires a constant reference Postconditions: allocates memory and appends a value at the end of a queue description: ------------------------------------------------------------------------*/ void enqueue(const T & value) { NodePointer newNodePtr = new Node(value); if(empty()) { myFront = myBack = newNodePtr; newNodePtr->next = NULL; } else { myBack->next = newNodePtr; myBack = newNodePtr; newNodePtr->next = NULL; } } /*------------------------------------------------------------------------ Display Preconditions: requires a reference of type ostream Postconditions: returns the ostream value (for chaining) description: outputs the contents of a queue. ------------------------------------------------------------------------*/ void display(ostream & out) const { NodePointer ptr; ptr = myFront; while(ptr != NULL) { out << ptr->data << " "; ptr = ptr->next; } out << endl; } /*------------------------------------------------------------------------ Front Preconditions: none Postconditions: returns a value of type T description: returns the first value in the parent Queue. ------------------------------------------------------------------------*/ T front() const { if ( !empty() ) return (myFront->data); else { cerr << "*** Queue is empty -- returning garbage value ***\n"; T * temp = new(T); T garbage = * temp; delete temp; return garbage; } } /*------------------------------------------------------------------------ Dequeue Preconditions: none Postconditions: removes the first value in a queue ------------------------------------------------------------------------*/ void dequeue() { if ( !empty() ) { NodePointer ptr = myFront; myFront = myFront->next; delete ptr; if(myFront == NULL) myBack = NULL; } else { cerr << "*** Queue is empty -- " "can't remove a value ***\n"; exit(1); } } /*------------------------------------------------------------------------ pverloaded = operator Preconditions: requires a constant reference Postconditions: returns a const type T description: this allows assigning of queues to queues ------------------------------------------------------------------------*/ Queue<T> & operator=(const T &q) { // make sure we arent reassigning ourself // e.g. thisQueue = thisQueue. if(this != &q) { this->~Queue(); if(q.empty()) { myFront = myBack = NULL; } else { myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } return *this; } private: class Node { public: T data; Node * next; Node(T value, Node * first = 0) : data(value), next(first) {} }; typedef Node * NodePointer; NodePointer myFront, myBack, queueSize; }; /*------------------------------------------------------------------------ join Preconditions: requires 2 queue values Postconditions: appends queue2 to the end of queue1 description: this function joins 2 queues into 1. ------------------------------------------------------------------------*/ template <typename T> Queue<T> join(Queue<T> q1, Queue<T> q2) { Queue<T> q1Copy(q1), q2Copy(q2); Queue<T> jQueue; while(!q1Copy.empty()) { jQueue.enqueue(q1Copy.front()); q1Copy.dequeue(); } while(!q2Copy.empty()) { jQueue.enqueue(q2Copy.front()); q2Copy.dequeue(); } cout << jQueue << endl; return jQueue; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a Queue of type T Postconditions: returns the ostream (for chaining) description: this function is overloaded for outputing a queue with << ----------------------------------------------------------------------------*/ template <typename T> ostream & operator<<(ostream &out, Queue<T> &s) { s.display(out); return out; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of type Student Postconditions: none description: this function is overloaded for outputing an object of type Student. ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, Student &s) { s.display(out); } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of a pointer to a Student object. Postconditions: none description: this function is overloaded for outputing pointers to Students ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, StudentPointer &s) { s->display(out); } #endif Now I'm having some issues with it. For one, when I add 0 to a queue and then I output the queue like so.. Queue<double> qdub; qdub.enqueue(0); cout << qdub << endl; That works, it will output 0. But for example, if I modify that queue in any way.. like.. assign it to a different queue.. Queue<double> qdub1; Queue<double> qdub2; qdub1.enqueue(0; qdub2 = qdub1; cout << qdub2 << endl; It will give me weird values for 0 like.. 7.86914e-316. Help on this would be much appreciated!

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How to display two ObservableCollections as a single list in WPF?

- by nareshbhatia

I have two ObservableCollections, say ObservableCollection<Cat> and ObservableCollections<Dog>. Cat and Dog both derive from class Pet. I want to display a list of all Pets. How do I do this? I prefer not want create a new ObservableCollection<Pet> by adding items from the two source lists because this list will become stale as more Cats and Dogs are added to the source lists. I can think of two approaches: 1) Create a "Decorator" ObservableCollection that keeps the two source collections as members and iterates over them every time. 2) Create an ObservableCollection<Pet> that does have the combined elements of the two source collections, but is also dependent on the source collections. Thus if a Cat is added to the Cat collection, this collection is notified and it adds the new Cat to itself. Is there a standard way to solve this issue? I don't want to reinvent the wheel!

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What does it mean to double license?

- by Adrian Panasiuk

What does it mean to double license code? I can't just put both licenses in the source files. That would mean that I mandate users to follow the rules of both of them, but the licenses will probably be contradictory (otherwise there'd be no reason to double license). I guess this is something like in cryptographic chaining, cipher = crypt_2(crypt_1(clear)) (generally) means, that cipher is neither the output of crypt_2 on clear nor the output of crypt_1 on clear. It's the output of the composition. Likewise, in double-licensing, in reality my code has one license, it's just that this new license says please follow all of the rules of license1, or all of the rules of license2, and you are hereby granted the right to redistribute this application under this "double" license, license1 or license2, or any license under which license1 or license2 allow you to redistribute this software, in which case you shall replace the relevant licensing information in this application with that of the new license. (Does this mean that before someone may use the app under license1, he has to perform the operation of redistributing to self? How would he document the fact that he did that operation?) Am I correct. What LICENSE file and what text to put in the source files would I need if I wanted to double license on, for the sake of example, Apachev2 and GPLv3 ?

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How do I rewrite .after( content, content )?

- by Evan Carroll

I've got this form working, but according to my previous question it might not be supported: it isn't in the docs either way -- but the intention is pretty obvious in the code. $(".section.warranty .warranty_checks :last").after( $('<div class="little check" />').click( function () { alert('hi') } ) , $('<span>OEM</span>') /*Notice this (a second) argument */ ); What this does is insert <div class="little check"> with a simple .click() callback, followed by a sibling of <span>OEM</span>. How else can I write this then? I'm having difficulty conjuring something working by chaining any combination of .after(), and .insertAfter()? I would expect this to work, but it doesn't: $(".section.warranty .warranty_checks :last").after( $('<div class="little check" />').click( function () { alert('hi') } ).after ( $('<span>OEM</span>') ) ); I would also expect this to work, but it doesn't: $(".section.warranty .warranty_checks :last").after( $('<span>OEM</span>').insertAfter( $('<div class="little check" />').click( function () { alert('hi') } ) ); );

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How to start/stop/restart jQuery animation

- by Emin

I have the following function that when I call displays a message to the user for a certain amount of time (5 secs in my case). During this "period" if I call the function again to display another message, practically it should hide, then re-appear with the new message for another 5 seconds. What happens with my code below, I call the function to display the message. Then, lets say on the 4th second, I call it again to display another message, the new message is displayed for 1 second. I need to somehow -reset- the time but can't figure out how. Tried stopping the animation, checking if the element was visible and hiding it if it was, and many other things. I believe the solution is a simple chaining issue but can't get it right. So any help would be appreciated! function display_message(msgType, message) { var elem = $('#ur_messagebox'); switch (msgType) { case 'confirm': elem.addClass('msg_confirm'); break; case 'error': elem.addClass('msg_error'); break; } elem.html(message); elem.show().delay(5000).fadeOut(1000); } thanks in advance...

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jQuery: one-liner for removing all children but one

- by user1352530

HTML code is: <li> <a href="#" /> <ul> <li> <a href="#"/> </li> </ul> </li> I want to delete any node under $(this) = li that is not a link. If there are more than one link, just the first one is saved, and if there are links inside the ul tag, they are not included because they are descendants and no childrens. Something like this (I am cloning and outputting html): $(this).clone().remove('not(a:first)').html(); //Assuming remove looks for "a" as a first child Does not work, so I try with this: $(this).clone().children().remove('not(a:first)').parent().html(); Does not work so I try with this: $(this).clone().remove('not(>a:first)').html(); I need the original element as a reference after removal for chaining more operations EDIT: Ok! Second one works with a little syntax correction as some appointed (:not( instead of not() but I would like to know if there is any other solution similar to the third line so I don't have to do children().remove().parent(). Thank you!

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jQuery "best practices" is an oxymoron [closed]

- by n00b

jQuery "best practices", oxymoron for several reasons sadly To speak candidly, the entire jQuery library has a HIGHLY inconsistent API, and virtually no coding standards. It's basically a subset of JavaScript, a new language if you will, which is probably the most confusing part for normal javascript developers. In my opinion, use normal JavaScript where possible to save on memory consumption. Or, better yet, use a professional tool like YUI. If you already come from a javascript background, you will appreciate it much more than jQuery because it doesn't have n00b wrappers around everything. In tools like YUI, you interact directly with the native DOM to do things, instead of a super-jQuery object that tries to do everything. I'll get voted down for saying the truth. Don't get me wrong, jQuery is cool if you wanna throw something flashy up quick, but if you're going to build a larger app you're going to need a more refined tool (especially since jQuery leaks memory like no other once you start chaining too much things). jQuery does have one of the lowest learning curves, and you won't outgrow it for awhile, but when you do it will be highly apparent and tedious to merge to something else. over 60 years programming experience someone clean this up and community wiki please

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Request for advice about class design, inheritance/aggregation

- by Lasse V. Karlsen

I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested way be to handle this: Implement all the methods and properties found inside HttpListener, just changing the class types where it matters (ie. the GetContext + EndGetContext methods would return a different class for WebDAV contexts), and storing and using a HttpListener object internally Construct WebDAVListener by passing it a HttpListener class to use? Create a wrapper for HttpListener with an interface, and constrct WebDAVListener by passing it an object implementing this interface? If going the route of passing a HttpListener (disguised or otherwise) to the WebDAVListener, would you expose the underlying listener object through a property, or would you expect the program that used the class to keep a reference to the underlying HttpListener? Also, in this case, would you expose some of the methods of HttpListener through the WebDAVListener, like Start and Stop, or would you again expect the program that used it to keep the HttpListener reference around for all those things? My initial reaction tells me that I want a combination. For one thing, I would like my WebDAVListener class to look like a complete implementation, hiding the fact that there is a HttpListener object beneath it. On the other hand, I would like to build unit-tests without actually spinning up a networked server, so some kind of mocking ability would be nice to have as well, which suggests I would like the interface-wrapper way. One way I could solve this would be this: public WebDAVListener() : WebDAVListener(new HttpListenerWrapper()) { } public WebDAVListener(IHttpListenerWrapper listener) { } And then I would implement all the methods of HttpListener (at least all those that makes sense) in my own class, by mostly just chaining the call to the underlying HttpListener object. What do you think? Final question: If I go the way of the interface, assuming the interface maps 1-to-1 onto the HttpListener class, and written just to add support for mocking, is such an interface called a wrapper or an adapter?

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How does the receiver of a cipher text know the IV used for encryption?

- by PatrickL

If a random IV is used in encrypting plain text, how does the receiver of the cipher text know what the IV is in order to decrypt it? This is a follow-up question to a response to the previous stackoverflow question on IVs here. The IV allows for plaintext to be encrypted such that the encrypted text is harder to decrypt for an attacker. Each bit of IV you use will double the possibilities of encrypted text from a given plain text. The point is that the attacker doesn't know what the IV is and therefore must compute every possible IV for a given plain text to find the matching cipher text. In this way, the IV acts like a password salt. Most commonly, an IV is used with a chaining cipher (either a stream or block cipher). ... So, if you have a random IV used to encrypt the plain text, how do you decrypt it? Simple. Pass the IV (in plain text) along with your encrypted text. Wait. You just said the IV is randomly generated. Then why pass it as plain text along with the encrypted text?

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Change a finder method w/ parameters to an association

- by Sai Emrys

How do I turn this into a has_one association? (Possibly has_one + a named scope for size.) class User < ActiveRecord::Base has_many :assets, :foreign_key => 'creator_id' def avatar_asset size = :thumb # The LIKE is because it might be a .jpg, .png, or .gif. # More efficient methods that can handle that are OK. ;) self.assets.find :first, :conditions => ["thumbnail = '#{size}' and filename LIKE ?", self.login + "_#{size}.%"] end end EDIT: Cuing from AnalogHole on Freenode #rubyonrails, we can do this: has_many :assets, :foreign_key => 'creator_id' do def avatar size = :thumb find :first, :conditions => ["thumbnail = ? and filename LIKE ?", size.to_s, proxy_owner.login + "_#{size}.%"] end end ... which is fairly cool, and makes syntax a bit better at least. However, this still doesn't behave as well as I would like. Particularly, it doesn't allow for further nice find chaining (such that it doesn't execute this find until it's gotten all its conditions). More importantly, it doesn't allow for use in an :include. Ideally I want to do something like this: PostsController def show post = Post.get_cache(params[:id]) { Post.find(params[:id], :include => {:comments => {:users => {:avatar_asset => :thumb}} } ... end ... so that I can cache the assets together with the post. Or cache them at all, really - e.g. get_cache(user_id){User.find(user_id, :include => :avatar_assets)} would be a good first pass. This doesn't actually work (self == User), but is correct in spirit: has_many :avatar_assets, :foreign_key => 'creator_id', :class_name => 'Asset', :conditions => ["filename LIKE ?", self.login + "_%"] (Also posted on Refactor My Code.)

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Django, url tag in template doesn't work: NoReverseMatch

- by Lukasz Jocz

I've encountered a problem with generating reverse url in templates in django. I'm trying to solve it since a few hours and I have no idea what the problem might be. URL reversing works great in models and views: # like this in models.py @models.permalink def get_absolute_url(self): return ('entry', (), { 'entry_id': self.entry.id, }) # or this in views.py return HttpResponseRedirect(reverse('entry',args=(entry_id,))) but when I'm trying to make it in template I get such an error: NoReverseMatch at /entry/1/ Reverse for ''add_comment'' with arguments '(1L,)' and keyword arguments '{}' not found. My file structure looks like this: project/ +-- frontend ¦ +-- models.py ¦ +-- urls.py ¦ +-- views.py +-- settings.py +-- templates ¦ +-- add_comment.html ¦ +-- entry.html +-- utils ¦ +-- with_template.py +-- wsgi.py My urls.py: from project.frontend.views import * from django.conf.urls import patterns, include, url urlpatterns = patterns('project.frontend.views', url(r'^entry/(?P<entry_id>\d+)/', 'entry', name="entry"), (r'^entry_list/', 'entry_list'), Then entry_list.html: {% extends "base.html" %} {% block content %} {% for entry in entries %} {% url 'entry' entry.id %} {% endfor %} {% endblock %} In views.py I have: @with_template def entry(request, entry_id): entry = Entry.objects.get(id=entry_id) entry.comments = entry.get_comments() return locals() where with_template is following decorator(but I don't think this is a case): class TheWrapper(object): def __init__(self, default_template_name): self.default_template_name = default_template_name def __call__(self, func): def decorated_func(request, *args, **kwargs): extra_context = kwargs.pop('extra_context', {}) dictionary = {} ret = func(request, *args, **kwargs) if isinstance(ret, HttpResponse): return ret dictionary.update(ret) dictionary.update(extra_context) return render_to_response(dictionary.get('template_name', self.default_template_name), context_instance=RequestContext(request), dictionary=dictionary) update_wrapper(decorated_func, func) return decorated_func if not callable(arg): return TheWrapper(arg) else: default_template_name = ''.join([ arg.__name__, '.html']) return TheWrapper(default_template_name)(arg) Do you have any idea, what may cause the problem? Great thanks in advance!

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Reusing named_scope to define another named_scope

- by Sergei Kozlov

The problem essence as I see it One day, if I'm not mistaken, I have seen an example of reusing a named_scope to define another named_scope. Something like this (can't remember the exact syntax, but that's exactly my question): named_scope :billable, :conditions => ... named_scope :billable_by_tom, :conditions => { :billable => true, :user => User.find_by_name('Tom') } The question is: what is the exact syntax, if it's possible at all? I can't find it back, and Google was of no help either. Some explanations Why I actually want it, is that I'm using Searchlogic to define a complex search, which can result in an expression like this: Card.user_group_managers_salary_greater_than(100) But it's too long to be put everywhere. Because, as far as I know, Searchlogic simply defines named_scopes on the fly, I would like to set a named_scope on the Card class like this: named_scope from_big_guys, { user_group_managers_salary_greater_than(100) } - this is where I would use that long Searchlogic method inside my named_scope. But, again, what would be the syntax? Can't figure it out. Resume So, is named_scope nesting (and I do not mean chaining) actually possible?

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