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• How to know if a std::list has been modified

  - by Nick

  I have this class: class C { public: C* parent; std::list<C> children; }; I can use this class in this way for example: C root; C child; root.children.push_back(child); // or other method of std::list (es: push_front, insert, ...) // Here child.parent is root // How can I set the parent of child? I want to do this work internally to my class without losing the functionality of std::list, is it possible?

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• Is it good practise to blank out inherited functionality that will not be used?

  - by Timo Kosig

  I'm wondering if I should change the software architecture of one of my projects. I'm developing software for a project where two sides (in fact a host and a device) use shared code. That helps because shared data, e.g. enums can be stored in one central place. I'm working with what we call a "channel" to transfer data between device and host. Each channel has to be implemented on device and host side. We have different kinds of channels, ordinary ones and special channels which transfer measurement data. My current solution has the shared code in an abstract base class. From there on code is split between the two sides. As it has turned out there are a few cases when we would have shared code but we can't share it, we have to implement it on each side. The principle of DRY (don't repeat yourself) says that you shouldn't have code twice. My thought was now to concatenate the functionality of e.g. the abstract measurement channel on the device side and the host side in an abstract class with shared code. That means though that once we create an actual class for either the device or the host side for that channel we have to hide the functionality that is used by the other side. Is this an acceptable thing to do: public abstract class MeasurementChannelAbstract { protected void MethodUsedByDeviceSide() { } protected void MethodUsedByHostSide() { } } public class DeviceMeasurementChannel : MeasurementChannelAbstract { public new void MethodUsedByDeviceSide() { base.MethodUsedByDeviceSide(); } } Now, DeviceMeasurementChannel is only using the functionality for the device side from MeasurementChannelAbstract. By declaring all methods/members of MeasurementChannelAbstract protected you have to use the new keyword to enable that functionality to be accessed from the outside. Is that acceptable or are there any pitfalls, caveats, etc. that could arise later when using the code?

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• What else I must do allow my method to handle any type of objects

  - by NewHelpNeeder

  So to allow any type object I must use generics in my code. I have rewrote this method to do so, but then when I create an object, for example Milk, it won't let me pass it to my method. Ether there's something wrong with my generic revision, or Milk object I created is not good. How should I pass my object correctly and add it to linked list? This is a method that causes error when I insert an item: public void insertFirst(T dd) // insert at front of list { Link newLink = new Link(dd); // make new link if( isEmpty() ) // if empty list, last = newLink; // newLink <-- last else first.previous = newLink; // newLink <-- old first newLink.next = first; // newLink --> old first first = newLink; // first --> newLink } This is my class I try to insert into linked list: class Milk { String brand; double size; double price; Milk(String a, double b, double c) { brand = a; size = b; price = c; } } This is test method to insert the data: public static void main(String[] args) { // make a new list DoublyLinkedList theList = new DoublyLinkedList(); // this causes: // The method insertFirst(Comparable) in the type DoublyLinkedList is not applicable for the arguments (Milk) theList.insertFirst(new Milk("brand", 1, 2)); // insert at front theList.displayForward(); // display list forward theList.displayBackward(); // display list backward } // end main() } // end class DoublyLinkedApp Declarations: class Link<T extends Comparable<T>> {} class DoublyLinkedList<T extends Comparable<T>> {}

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• Vector of objects

  - by Paul

  I've got a abstract class class A { public: virtual void somefunction() = ; }; and some different classes that inherit this class: class Ab { public: void somefunction(); }; etc. I want to make a vector containing some objects of these classes (how many depends on input parameters) so I can access these easily later. However I'm a bit lost on how to do this. My best idea is vector<A> *objectsVector; Ab AbObject; objectsVector.push_back(AbObject); However this gives me a huge amout of errors from various .h files in /usr/include/c++ How should i solve this?

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• Serializing an extended form object

  - by andyperfect

  I've been reading up on this whole subject, but I never came across this specific problem. I already understand that the whole idea of serializing an entire form is a horrible idea and just doesn't work. But, I am encountering a bit of a different problem. I have a class that inherits the "button" form object, that I call DataButton. Now for my problem. I want to be able to serialize this class, but I don't need any of the information from the actual button class. Is there any way to bypass the fact that I can't set the button form object to Serializable() and notify VB that when serialization is to occur, it should simply skip over that information? Theoretically, if such a procedure were possible, I'd be able to do the entire serialization without a hitch. I came up with the idea earlier of removing the "inherits" feature from the class, and having simply a button within the class, but that makes my program really difficult to work with as I am constantly changing the location, size, backgroundImage, text, and whatnot. Thus, immediate updates would be much tougher to work with. Any help would be greatly appreciated.

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• How to save to two tables using one SQLAlchemy model

  - by Oatman

  I have an SQLAlchemy ORM class, linked to MySQL, which works great at saving the data I need down to the underlying table. However, I would like to also save the identical data to a second archive table. Here's some psudocode to try and explain what I mean my_data = Data() #An ORM Class my_data.name = "foo" #This saves just to the 'data' table session.add(my_data) #This will save it to the identical 'backup_data' table my_data_archive = my_data my_data_archive.__tablename__ = 'backup_data' session.add(my_data_archive) #And commits them both session.commit() Just a heads up, I am not interested in mapping a class to a JOIN, as in: http://www.sqlalchemy.org/docs/05/mappers.html#mapping-a-class-against-multiple-tables

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• How to make the generic return type of a method dependend of the parameter type?

  - by deamon

  I have a convert method, which takes a String and a class as arguments and constructs an object of the given class, which will be returned. The usage should look like this Something s = Converter.convert("...", Something.class) Is it possible to express this with Java generics? Something like: public static <T> T convert(String source, ??? TClass) What would be ????

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• Adding behaviour to a set of classes

  - by devoured elysium

  I have defined an Event class: Event and all the following classes inherit from Event: SportEventType1 SportEventType2 SportEventType3 SportEventType4 Right now I will only have SportEvents but I don't know if in the future I'll want some other kind of events that doesn't even have anything to do with Sports. Later, I will want to draw some graphics with info taken from Events, and the drawing logic can be a bit complex. But, for the moment, I think I shouldn't think of how the drawing will be done and I believe that maybe it'd be better if that drawing part was not put as an integral part of the Event/SportEventX class chain. I am looking for solutions for this problem. I know I could just make Event have an instance variable(attribute, for the java crowds) pointing to something as an IDrawInterface, but that would make the Event class "assume" it will be later used for drawing. I would like to make the Event class oblivious to this if possible. Thanks!

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• css displaying divs inside a Tr fine in FireFox, but IE increases the width of the row...

  - by Ronedog

  I'm having some difficulty figuring out what is going on and how to fix it. I have some divs that contain some icons that are causing a width problem when displaying tabular data. If I remove the div's that contain the icons, the row width ends up the way I want it (See the firefox example below). Here's the view in Firefox which is what I want (notice the positioning of the icons circled in red, which is aligned on the same y coordinate, or thereabouts): Here's the view in IE7 (Notice what happens to the icons and the width of the grey line, which is the table row): Here's the HTML: <table> <tbody> <tr> <td> <span>stuff 1</span> <span>stuff 2</span> <div class="prop_edit"><img class="img_height14" src="edit.jpg"></div> <div class="prop_archive"><img class="img_height14" src="archive.jpg"></div> <div class="prop_delete"><img class="img_height14" src="delete.jpg"></div> <div style="display:none;"> <div>Links Here</div> </div> </td> </tr> </tbody> Heres the CSS: .prop_edit{ float:right; position: relative; top: 0px; right:50px; } .prop_archive{ float:right; position: relative; top: 0px; right:10px; } .prop_delete{ float:right; position: relative; top: 0px; right: -30px; } .img_height14{ height:14px; vertical-align:top; position:relative; } I've tried a bunch of different css things, but really am just hacking away hoping to figure something out. Anyone got some tips that could help me? Thanks in advance.

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• Parse xml file with same tag multiple times iphone sdk

  - by neha

  Hi all, In my application, I have a tag multiple times. I'm using xml parser. I'm taking a corresponding element with similar name as the one in xml file in my class. So in case of: <photo>abc</photo> <photo>def</photo> What I get in photo element of my class is the second element i.e def, as the first one gets overwritten as there's only one photo element in my class. My question is am I wrong in taking similar elements in class as in case of xml? Is there any better method or a better parser? Or I'm on right path and have to do this manually by setting some flags etc? Thanx in advance.

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• Is it possible to create a C++ factory system that can create an instance of any "registered" object

  - by chrensli

  Hello, I've spent my entire day researching this topic, so it is with some scattered knowledge on the topic that i come to you with this inquiry. Please allow me to describe what I am attempting to accomplish, and maybe you can either suggest a solution to the immediate question, or another way to tackle the problem entirely. I am trying to mimic something related to how XAML files work in WPF, where you are essentially instantiating an object tree from an XML definition. If this is incorrect, please inform. This issue is otherwise unrelated to WPF, C#, or anything managed - I solely mention it because it is a similar concept.. So, I've created an XML parser class already, and generated a node tree based on ObjectNode objects. ObjectNode objects hold a string value called type, and they have an std::vector of child ObjectNode objects. The next step is to instantiate a tree of objects based on the data in the ObjectNode tree. This intermediate ObjectNode tree is needed because the same ObjectNode tree might be instantiated multiple times or delayed as needed. The tree of objects that is being created is such that the nodes in the tree are descendants of a common base class, which for now we can refer to as MyBase. Leaf nodes can be of any type, not necessarily derived from MyBase. To make this more challenging, I will not know what types of MyBase derived objects might be involved, so I need to allow for new types to be registered with the factory. I am aware of boost's factory. Their docs have an interesting little design paragraph on this page: o We may want a factory that takes some arguments that are forwarded to the constructor, o we will probably want to use smart pointers, o we may want several member functions to create different kinds of objects, o we might not necessarily need a polymorphic base class for the objects, o as we will see, we do not need a factory base class at all, o we might want to just call the constructor - without #new# to create an object on the stack, and o finally we might want to use customized memory management. I might not be understanding this all correctly, but that seems to state that what I'm trying to do can be accomplished with boost's factory. But all the examples I've located, seem to describe factories where all objects are derived from a base type. Any guidance on this would be greatly appreciated. Thanks for your time!

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• Debug.writeline locks

  - by Carra

  My program frequently stops with a deadlock. When I do a break-all and look at the threads I see that three threads are stuck in our logging function: public class Logging { public static void WriteClientLog(LogLevel logLevel, string message) { #if DEBUG System.Diagnostics.Debug.WriteLine(String.Format("{0} {1}", DateTime.Now.ToString("HH:mm:ss"), message)); //LOCK #endif //...Log4net logging } } If I let the program continue the threads are still stuck on that line. I can't see where this can lock. The debug class, string class & datetime class seem to be thread safe. The error goes away when I remove the "#if DEBUG System... #endif" code but I'm curious why this behavior happens. Thread one: public void CleanCache() { Logging.WriteClientLog(LogLevel.Debug, "Start clean cache.");//Stuck } Thread two: private void AliveThread() { Logging.WriteClientLog(LogLevel.Debug, "Check connection");//Stuck }

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• MVC + Repository Pattern - Still depends on Data Model?

  - by Jack

  I've started a project for school in which I am using ASP.NET MVC 2 + LINQ2SQL, and a business layer so my UI doesnt interact with the DB directly. My question is this: In my MVC project, when bringing up views and passing around data, I still have to include my Data project for access to the classes in my Linq2Sql project. Is this correct? Example: Controller: ClassesRepository cr = new ClassesRepository(); // this is from my Business project Class classToEdit = cr.GetByClassId(id); // "Class" is from my data project I still have to reference the Class class in my linq2sql data project - shouldn't my UI be completely independent of my data layer? Or maybe I'm going about this all wrong.

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• Managed C++ Error 2504 Error

  - by Major

  I'm new to managed c++ and I'm attempting to design a program for a presentation. I am attempting to have a class inherit from an ABC and I'm getting the Error C2504. The code in question is as follows: ref class Item : Auction //Error C2504 here { //More code for the class Auction is defined in a different .h file. Let me know if there are any other questions or if you need to see more of the code. Thanks

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• Ruby on Rails: create records for multiple models with one form and one submit

  - by notblakeshelton

  I have a 3 models: quote, customer, and item. Each quote has one customer and one item. I would like to create a new quote, a new customer, and a new item in their respective tables when I press the submit button. I have looked at other questions and railscasts and either they don't work for my situation or I don't know how to implement them. I also want my index page to be the page where I can create everything. quote.rb class Quote < ActiveRecord::Base attr_accessible :quote_number has_one :customer has_one :item end customer.rb class Customer < ActiveRecord::Base #unsure of what to put here #a customer can have multiple quotes, so would i use: has_many :quotes #<----? end item.rb class Item < ActiveRecord::Base #also unsure about this #each item can also be in multiple quotes quotes_controller.rb class QuotesController < ApplicationController def index @quote = Quote.new @customer = Customer.new @item = item.new end def create @quote = Quote.new(params[:quote]) @quote.save @customer = Customer.new(params[:customer]) @customer.save @item = Item.new(params[:item]) @item.save end end items_controller.rb class ItemsController < ApplicationController def index end def new @item = Item.new end def create @item = Item.new(params[:item]) @item.save end end customers_controller.rb class CustomersController < ApplicationController def index end def new @customer = Customer.new end def create @customer = Customer.new(params[:customer]) @customer.save end end quotes/index.html.erb <%= form_for @quote do |f| %> <%= f.fields_for @customer do |builder| %> <%= label_tag :firstname %> <%= builder.text_field :firstname %> <%= label_tag :lastname %> <%= builder.text_field :lastname %> <% end %> <%= f.fields_for @item do |builder| %> <%= label_tag :name %> <%= builder.text_field :name %> <%= label_tag :description %> <%= builder.text_field :description %> <% end %> <%= label_tag :quote_number %> <%= f.text_field :quote_number %> <%= f.submit %> <% end %> When I try submitting that I get an error: Can't mass-assign protected attributes: item, customer So to try and fix it I updated the attr_accessible in quote.rb to include :item, :customer but then I get this error: Item(#) expected, got ActiveSupport::HashWithIndifferentAccess(#) Any help would be greatly appreciated.

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• catching erros and exiting

  - by apple pie

  In python, is there a way to exit a class after testing a condition, without exiting out of python? say i have the class class test(): def __init__(self): self.a = 2 def create_b(self): self.b = 3 def does_b_exist(self): if <self.b doesnt exist>: #terminate self.b += 1 try/except` doesnt work since the rest of the program doesnt terminate after failing. im basically trying to catch an error, and do what python does when it shows you errors, but i cant figure out how to do it

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• Hibernate not loading associated object

  - by Noor

  Hi, i am trying to load a hibernate object ForumMessage but in it contain another object Users and the Users object is not being loaded. My ForumMessage Mapping File: <?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Generated Jan 4, 2011 10:10:29 AM by Hibernate Tools 3.4.0.Beta1 --> <hibernate-mapping> <class name="com.BiddingSystem.Models.ForumMessage" table="FORUMMESSAGE"> <id name="ForumMessageId" type="long"> <column name="FORUMMESSAGEID" /> <generator class="native" /> </id> <property name="ForumMessage" type="java.lang.String"> <column name="FORUMMESSAGE" /> </property> <many-to-one name="User" class="com.BiddingSystem.Models.Users" fetch="join"> <column name="UserId" /> </many-to-one> <property name="DatePosted" type="java.util.Date"> <column name="DATEPOSTED" /> </property> <many-to-one name="Topic" class="com.BiddingSystem.Models.ForumTopic" fetch="join"> <column name="TopicId" /> </many-to-one> </class> </hibernate-mapping> and I am using the follwing code: Session session = gileadHibernateUtil.getSessionFactory().openSession(); SQL="from ForumMessage"; System.out.println(SQL); Query query=session.createQuery(SQL); System.out.println(query.list().size()); return new LinkedList <ForumMessage>(query.list());

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• Extended Zend_Db_Table_Row_Abstract does not return values

  - by WesleyE

  Hi, I'm quite new to Zend and the database classes from it. I'm having problems mapping a Zend_Db_Table_Row_Abstract to my rows. The problem is that whenever I try to map it to a class (Job) that extends the Zend_Db_Table_Row_Abstract class, the database data is not receivable anymore. I'm not getting any errors, trying to get data simply returns null. Here is my code so far: Jobs: class Jobs extends Zend_Db_Table_Abstract { protected $_name = 'jobs'; protected $_rowsetClass = "Job"; public function getActiveJobs() { $select = $this->select()->where('jobs.jobDateOpen < UNIX_TIMESTAMP()')->limit(15,0); $rows = $this->fetchAll($select); return $rows; } } Job: class Job extends Zend_Db_Table_Row_Abstract { public function getCompanyName() { //Gets the companyName for this row (Is on another table), just for example } } Controller: $oJobs = new Jobs(); $aActiveJobs = $oJobs->getActiveJobs(); foreach ($aActiveJobs as $value) { var_dump($value->jobTitle); } When I remove the "protected $_rowsetClass = "Job";" line, so that the table row is not mapped to my own class, I get all the jobTitles perfectly. What am I doing wrong here? Thanks in advance, Wesley

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• conditionally enabling constructor

  - by MK

  Here is how I can conditionally enable a constructor of a class : struct Foo { template<class T> Foo( T* ptr, boost::enable_if<is_arithmetic<T> >::type* = NULL ) {} }; I would like to know why I need to do the enabling via a dummy parameter. Why can I not just write : struct Foo { template<class T> Foo( boost::enable_if<is_arithmetic<T>, T>::type* = NULL ) {} };

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• How can I get model names from inside my app?

  - by Cameron

  I have a bunch of models in a sub-directory that inherit from a model in the models root directory. I want to be able to set a class variable in another model that lists each inherited model class. i.e @@groups = sub_models.map do { |model| model.class.to_s } Not sure how to get at this info though...

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• STI and accepts_nested_attributes_for in rails

  - by ryanshackintosh

  I have models as follows: class Entity < ActiveRecord::Base has_many :addresses accepts_nested_attributes_for :addresses, :reject_if => lambda { |a| a[:label].blank?} , :allow_destroy => true end class Client < Entity before_save :set_type private def set_type self.type = "Client" end end class Address < ActiveRecord::Base belongs_to :entity end I have recently implemented accepts_nested_attributes_for on the /clients/new form, as follows: <% form_for(@client, :html => {:class => 'form'}) do |f| -%> <%= f.label :name %> <%= f.text_field :name -%> <%= f.label :phone %> <%= f.text_field :phone %> <% f.fields_for :addresses do |a| %> <%= a.label :street %> <%= a.text_field :street%> <%= a.label :city %> <%= a.text_field :city %> <% end %> <% end %> And my controller as follows: class ClientsController < ApplicationController before_filter :load_client , :except => [:index, :new, :create, :render_clients] def new @client = Client.new @client.addresses.build end def create @client = Client.new(params[:client]) if @client.save flash[:notice] = 'Client has been successfully added' redirect_to @client else render :action => 'new' end end The issue is that when the record is saved it gives an error stating: "Entity can't be blank" I assume it is something to do with the fact that a 'Client' and not an 'Entity' is being added. Can anyone point me in the right direction?

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• Python threading question (Working with a method that blocks forever)

  - by Nix

  I am trying to wrap a thread around some receiving logic in python. Basically we have an app, that will have a thread in the background polling for messages, the problem I ran into is that piece that actually pulls the messages waits forever for a message. Making it impossible to terminate... I ended up wrapping the pull in another thread, but I wanted to make sure there wasn't a better way to do it. Original code: class Manager: def __init__(self): receiver = MessageReceiver() receiver.start() #do other stuff... class MessageReceiver(Thread): receiver = Receiver() def __init__(self): Thread.__init__(self) def run(self): #stop is a flag that i use to stop the thread... while(not stopped ): #can never stop because pull below blocks message = receiver.pull() print "Message" + message What I refectored to: class Manager: def __init__(self): receiver = MessageReceiver() receiver.start() class MessageReceiver(Thread): receiver = Receiver() def __init__(self): Thread.__init__(self) def run(self): pullThread = PullThread(self.receiver) pullThread.start() #stop is a flag that i use to stop the thread... while(not stopped and pullThread.last_message ==None): pass message = pullThread.last_message print "Message" + message class PullThread(Thread): last_message = None def __init__(self, receiver): Thread.__init(self, target=get_message, args=(receiver)) def get_message(self, receiver): self.last_message = None self.last_message = receiver.pull() return self.last_message I know the obvious locking issues exist, but is this the appropriate way to control a receive thread that waits forever for a message? One thing I did notice was this thing eats 100% cpu while waiting for a message... **If you need to see the stopping logic please let me know and I will post.

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• Help using recursion in Java

  - by Mercer

  I have a class Group. In the class I have two fields, idGroup IdGroupGroup. Groups may be part of other groups. My class Group is defined in a HashMap<Integer,Integer>; the key is IdGroupGroup and value is idGroup. I want to search the map for a particular idGroup; can I use recursion to do this?

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• Using classes for the first time,help in debugging

  - by kaushik

  here is post my code:this is no the entire code but enough to explain my doubt.please discard any code line which u find irrelavent enter code here saving_tree={} isLeaf=False class tree: global saving_tree rootNode=None lispTree=None def __init__(self,x): file=x string=file.readlines() #print string self.lispTree=S_expression(string) self.rootNode=BinaryDecisionNode(0,'Root',self.lispTree) class BinaryDecisionNode: global saving_tree def __init__(self,ind,name,lispTree,parent=None): self.parent=parent nodes=lispTree.getNodes(ind) print nodes self.isLeaf=(nodes[0]==1) nodes=nodes[1]#Nodes are stored self.name=name self.children=[] if self.isLeaf: #Leaf Node print nodes #Set the leaf data self.attribute=nodes print "LeafNode is ",nodes else: #Set the question self.attribute=lispTree.getString(nodes[0]) self.attribute=self.attribute.split() print "Question: ",self.attribute,self.name tree={} tree={str(self.name):self.attribute} saving_tree=tree #Add the children for i in range(1,len(nodes)):#Since node 0 is a question # print "Adding child ",nodes[i]," who has ",len(nodes)-1," siblings" self.children.append(BinaryDecisionNode(nodes[i],self.name+str(i),lispTree,self)) print saving_tree i wanted to save some data in saving_tree{},which i have declared previously and want to use that saving tree in the another function outside the class.when i asked to print saving_tree it printing but,only for that instance.i want the saving_tree{} to have the data to store data of all instance and access it outside. when i asked for print saving_tree outside the class it prints empty{}.. please tell me the required modification to get my required output and use saving_tree{} outside the class..

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• GTK+ with any programs

  - by user565739

  I recently knew a latex-editor "gummi", see http://gummi.midnightcoding.org/ , which is written by GTK+ graphical interface toolkit. There are two panels, one in the left which is an editor (using the library gtksourceview) and on in the right which is a viewer (using the library poppler). I am curious that if we can do similary things for every program. For example, replace the editor with "terminal"?"emacs"?"vim"?"terminator (a multi-windows terminal)"...etc. And replace the viewer with other viewers, which in my mind is Adobe Reader. With discussion with the author, he mentioned: The viewer component is also replacable, but doing it with Adobe Reader would not be easy or perhaps even impossible. The reason for this being that Adobe Reader is a complete program instead of a library, and also closed-source So I have some questions: a) We can only make "library" embedded as a panel, but we can't do this for a (any) program? b) Could we replace the editor with emacs? with terminal? c) Could we replace the viewer with Adobe Reader? If not, why? Because it's a program or it's closed-source? I know the questions in this thread are not very precise, sorry.

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