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  • How to interview a natural scientist for a dev position?

    - by Silas
    I already did some interviews for my company, mostly computer scientists for dev positions but also some testers and project managers. Now I have to fill a vacancy in our research group within the R&D department (side note: “research” means that we try to solve problems in our professional domain/market niche using software in research projects together with universities, other companies, research centres and end user organisations. It’s not computer science research; we’re not going to solve the P=NP problem). Now we invited a guy holding an MSc in chemistry (with a lot of physics in his CV, too), who never had any computer science lesson. I already talked with him about half an hour at a local university’s career days and there’s no doubt the guy is smart. Also his marks are excellent and he graduated with distinction. For his BSc he needed to teach himself programming in Mathematica and told me believably that he liked programming a lot. Also he solved some physical chemistry problem that I probably don’t understand using his own software, implemented in Mathematica, for his MSc thesis. It includes a GUI and a notable size of 8,000 LoC. He seems to be very attracted by what we’re doing in our research group and to be honest it’s quite difficult for an SME like us to get good people. I also am very interested in hiring him since he could assist me in writing project proposals, reports, doing presentations and so on. He would probably fit to our team, too. The only question left is: How can I check if he will get the programming skills he needs to do software implementation in our projects since this will be a significant part of the job? Of course I will ask him what it is, that is fascinating him about programming. I’ll also ask how he proceeded to write his natural science software and how he structured it. I’ll ask about how he managed to obtain the skills and information about software development he needed. But is there something more I could ask? Something more concrete perhaps? Should I ask him to explain his Mathematica solution? To be clear: I’m not looking for knowledge in a particular language or technology stack. We’re a .NET shop in product development but I want to have a free choice for our research projects. So I’m interested in the meta-competence being able to learn whatever is actually needed. I hope this question is answerable and not open-ended since I really like to know if there is a default way to check for the ability to get further programming skills on the job. If something is not clear to you please give me some comments and let me improve my question.

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  • Interesting Topics in Comp. Sci. for New Students?

    - by SoulBeaver
    I hope this is the right forum to ask this question. Last friday I was in a discussion with my professors about the students' lack of motivation and interest in the field of Computer Science. All of the students are enrolled, but through questionnaires and other questions that my professor posed it was revealed that over 90% of all enrolled students are just in it for the reward of getting a job sometime in the future (since it's a growing field with high job potential) I asked my professor for the permission to take over the first couple of lectures and try and motivate, interest and inspire students for the field of Computer Science and programming in particular (this is the Intro to Programming course). This request was granted and I now have a week to come up with a lecture topic for my professor's five groups. My main goal isn't to teach, I just want to get students to be as interested in the field as I am. I want to show them what's possible, what awesome magical things have been done in the field, the future we are heading towards using programming and Comp. Sci. Therefore, I would like to pose this question: I have a few topics, materials and sample projects that I would like to talk about: -- Grace Hopper (It is my hope to interest the female programmers in the class. There are never more than two or three per group and they, more than males, are prone to jumping ship and abandoning Comp. Sci.) -- The Singularity Institute -- Alan Turing -- Robotics -- Programming not as a chore or a must, but the idea that we are, at our core, the nexus to which anything anybody does in the digital world is connected to. We are the problem solvers; we assemble all the parts together and we are the ones that, essentially, make the vision a reality. -- Give them an idea for a programming project which, through the help of the professor, could be significant to every student (I want students to not only feel interested in the topic, but they should feel important, that what they do here makes a difference) Do you have interesting topics worthy of discussion, something I can tell the students which they can get interested about? How would you approach the lecture? If you had 90 minutes worth of time to try and get students interested in the project, what would you do?

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  • Multiple Zend application code organisation

    - by user966936
    For the past year I have been working on a series of applications all based on the Zend framework and centered on a complex business logic that all applications must have access to even if they don't use all (easier than having multiple library folders for each application as they are all linked together with a common center). Without going into much detail about what the project is specifically about, I am looking for some input (as I am working on the project alone) on how I have "grouped" my code. I have tried to split it all up in such a way that it removes dependencies as much as possible. I'm trying to keep it as decoupled as I logically can, so in 12 months time when my time is up anyone else coming in can have no problem extending on what I have produced. Example structure: applicationStorage\ (contains all applications and associated data) applicationStorage\Applications\ (contains the applications themselves) applicationStorage\Applications\external\ (application grouping folder) (contains all external customer access applications) applicationStorage\Applications\external\site\ (main external customer access application) applicationStorage\Applications\external\site\Modules\ applicationStorage\Applications\external\site\Config\ applicationStorage\Applications\external\site\Layouts\ applicationStorage\Applications\external\site\ZendExtended\ (contains extended Zend classes specific to this application example: ZendExtended_Controller_Action extends zend_controller_Action ) applicationStorage\Applications\external\mobile\ (mobile external customer access application different workflow limited capabilities compared to full site version) applicationStorage\Applications\internal\ (application grouping folder) (contains all internal company applications) applicationStorage\Applications\internal\site\ (main internal application) applicationStorage\Applications\internal\mobile\ (mobile access has different flow and limited abilities compared to main site version) applicationStorage\Tests\ (contains PHP unit tests) applicationStorage\Library\ applicationStorage\Library\Service\ (contains all business logic, services and servicelocator; these are completely decoupled from Zend framework and rely on models' interfaces) applicationStorage\Library\Zend\ (Zend framework) applicationStorage\Library\Models\ (doesn't know services but is linked to Zend framework for DB operations; contains model interfaces and model datamappers for all business objects; examples include Iorder/IorderMapper, Iworksheet/IWorksheetMapper, Icustomer/IcustomerMapper) (Note: the Modules, Config, Layouts and ZendExtended folders are duplicated in each application folder; but i have omitted them as they are not required for my purposes.) For the library this contains all "universal" code. The Zend framework is at the heart of all applications, but I wanted my business logic to be Zend-framework-independent. All model and mapper interfaces have no public references to Zend_Db but actually wrap around it in private. So my hope is that in the future I will be able to rewrite the mappers and dbtables (containing a Models_DbTable_Abstract that extends Zend_Db_Table_Abstract) in order to decouple my business logic from the Zend framework if I want to move my business logic (services) to a non-Zend framework environment (maybe some other PHP framework). Using a serviceLocator and registering the required services within the bootstrap of each application, I can use different versions of the same service depending on the request and which application is being accessed. Example: all external applications will have a service_auth_External implementing service_auth_Interface registered. Same with internal aplications with Service_Auth_Internal implementing service_auth_Interface Service_Locator::getService('Auth'). I'm concerned I may be missing some possible problems with this. One I'm half-thinking about is a config.ini file for all externals, then a separate application config.ini overriding or adding to the global external config.ini. If anyone has any suggestions I would be greatly appreciative. I have used contextswitching for AJAX functions within the individual applications, but there is a big chance both external and internal will get web services created for them. Again, these will be separated due to authorization and different available services. \applicationstorage\Applications\internal\webservice \applicationstorage\Applications\external\webservice

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  • Question on MVVM pattern on WPF ?

    - by Ashish Ashu
    I have a user control let say UC1 . This user control have viewmodel UC1_vm. In the usercontrol UC1 I have a canvas in which drawing curve logic is implemented. This drawing curve logic is based on the data points property in the view model ( UC1_vm). The data points property inside the view model change with different condition. The generation of data points is written in the View Model. I want to bind the data points property in the view model to the draw curve logic inside the User control (view). I want whenever the data point property is changed in the view model , the canvas calls the draw curve method. Can I set the set any property of canvas which when changed it calls the on paint logic auto matically? Please suggest me the approach of implementing this scenario!!

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  • How do you keep your business rules DRY?

    - by Mario
    I periodically ponder how to best design an application whose every business rule exists in just a single location. (While I know there is no proverbial “best way” and that designs are situational, people must have a leaning toward one practice or another.) I work for a shop where they prefer to house as much of the business rules as possible in the database. This requires developers in many cases to perform identical front-end validations to avoid sending data to the database that will result in an exception—not very DRY. It grates me anytime I find myself duplicating any kind of logic—even lowly validation logic. I am a single-point-of-truth purist to an anal degree. On the other end of the spectrum, I know of shops that create dumb databases (the Rails community leans in this direction) and handle all of the business logic in a separate tier (in Rails the models would house “most” of this). Note the word “most” which implies that some business logic does end up spilling into other places (in Rails it might spill over into the controllers). In way, a clean separation of concerns where all business logic exists in a single core location is a Utopian fantasy that’s hard to uphold (n-tiered architecture or not). Furthermore, is see the “Database as a fortress” and would agree that it should be built on constraints that cause it to reject bad data. As such, I hold principles that cause a degree of angst as I attempt to balance them. How do you balance the database-as-a-fortress view with the desire to have a single-point-of-truth?

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  • What is good practice in .NET system architecture design concerning multiple models and aggregates

    - by BuzzBubba
    I'm designing a larger enterprise architecture and I'm in a doubt about how to separate the models and design those. There are several points I'd like suggestions for: - models to define - way to define models Currently my idea is to define: Core (domain) model Repositories to get data to that domain model from a database or other store Business logic model that would contain business logic, validation logic and more specific versions of forms of data retrieval methods View models prepared for specifically formated data output that would be parsed by views of different kind (web, silverlight, etc). For the first model I'm puzzled at what to use and how to define the mode. Should this model entities contain collections and in what form? IList, IEnumerable or IQueryable collections? - I'm thinking of immutable collections which IEnumerable is, but I'd like to avoid huge data collections and to offer my Business logic layer access with LINQ expressions so that query trees get executed at Data level and retrieve only really required data for situations like the one when I'm retrieving a very specific subset of elements amongst thousands or hundreds of thousands. What if I have an item with several thousands of bids? I can't just make an IEnumerable collection of those on the model and then retrieve an item list in some Repository method or even Business model method. Should it be IQueryable so that I actually pass my queries to Repository all the way from the Business logic model layer? Should I just avoid collections in my domain model? Should I void only some collections? Should I separate Domain model and BusinessLogic model or integrate those? Data would be dealt trough repositories which would use Domain model classes. Should repositories be used directly using only classes from domain model like data containers? This is an example of what I had in mind: So, my Domain objects would look like (e.g.) public class Item { public string ItemName { get; set; } public int Price { get; set; } public bool Available { get; set; } private IList<Bid> _bids; public IQueryable<Bid> Bids { get { return _bids.AsQueryable(); } private set { _bids = value; } } public AddNewBid(Bid newBid) { _bids.Add(new Bid {.... } } Where Bid would be defined as a normal class. Repositories would be defined as data retrieval factories and used to get data into another (Business logic) model which would again be used to get data to ViewModels which would then be rendered by different consumers. I would define IQueryable interfaces for all aggregating collections to get flexibility and minimize data retrieved from real data store. Or should I make Domain Model "anemic" with pure data store entities and all collections define for business logic model? One of the most important questions is, where to have IQueryable typed collections? - All the way from Repositories to Business model or not at all and expose only solid IList and IEnumerable from Repositories and deal with more specific queries inside Business model, but have more finer grained methods for data retrieval within Repositories. So, what do you think? Have any suggestions?

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  • Django1.1 model field value preprocessing before returning

    - by Satoru.Logic
    Hi, all. I have a model class like this: class Note(models.Model): author = models.ForeignKey(User, related_name='notes') content = NoteContentField(max_length=256) NoteContentField is a custom sub-class of CharField that override the to_python method in purpose of doing some twitter-text-conversion processing. class NoteContentField(models.CharField): __metaclass__ = models.SubfieldBase def to_python(self, value): value = super(NoteContentField, self).to_python(value) from ..utils import linkify return mark_safe(linkify(value)) However, this doesn't work. When I save a Note object like this: note = Note(author=request.use, content=form.cleaned_data['content']) note.save() The conversed value is saved into the database, which is not what I wanna see. What I'm trying to do is to save the raw content into the database, and only make the conversion when the content attribute is later accessed. Would you please tell me what's wrong with this? Thanks to Pierre and Daniel. I have figured out what's wrong. I thought the text-conversion code should be in either to_python or get_db_prep_value, and that's wrong. I should override both of them, make to_python do the conversion and get_db_prep_value return the unconversed value: from ..utils import linkify class NoteContentField(models.CharField): __metaclass__ = models.SubfieldBase def to_python(self, value): self._raw_value = super(NoteContentField, self).to_python(value) return mark_safe(linkify(self._raw_value)) def get_db_prep_value(self, value): return self._raw_value I wonder if there is a better way to implement this?

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  • How far does Dependency Injection reach?

    - by Baddie
    My web app solution consists of 3 projects: Web App (ASP.NET MVC) Business Logic Layer (Class Library) Database Layer (Entity Framework) I want to use Ninject to manage the lifetime of the DataContext generated by the Entity Framework in the Database Layer. The Business Logic layer consists of classes which reference repositories (located in the database layer) and my ASP.NET MVC app references the business logic layer's service classes to run code. Each repository creates an instance of the MyDataContext object from the Entity Framework Repository public class MyRepository { private MyDataContext db; public MyRepository { this.db = new MyDataContext(); } // methods } Business Logic Classes public class BizLogicClass { private MyRepository repos; public MyRepository { this.repos = new MyRepository(); } // do stuff with the repos } Will Ninject handle the lifetime of MyDataContext despite the lengthy dependency chain from the Web App to the Data Layer?

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  • Django model manager didn't work with related object when I do aggregated query

    - by Satoru.Logic
    Hi, all. I'm having trouble doing an aggregation query on a many-to-many related field. Let's begin with my models: class SortedTagManager(models.Manager): use_for_related_fields = True def get_query_set(self): orig_query_set = super(SortedTagManager, self).get_query_set() # FIXME `used` is wrongly counted return orig_query_set.distinct().annotate( used=models.Count('users')).order_by('-used') class Tag(models.Model): content = models.CharField(max_length=32, unique=True) creator = models.ForeignKey(User, related_name='tags_i_created') users = models.ManyToManyField(User, through='TaggedNote', related_name='tags_i_used') objects_sorted_by_used = SortedTagManager() class TaggedNote(models.Model): """Association table of both (Tag , Note) and (Tag, User)""" note = models.ForeignKey(Note) # Note is what's tagged in my app tag = models.ForeignKey(Tag) tagged_by = models.ForeignKey(User) class Meta: unique_together = (('note', 'tag'),) However, the value of the aggregated field used is only correct when the model is queried directly: for t in Tag.objects.all(): print t.used # this works correctly for t in user.tags_i_used.all(): print t.used #prints n^2 when it should give n Would you please tell me what's wrong with it? Thanks in advance.

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  • PlaySound linker error in C++

    - by logic-unit
    Hello, I'm getting this error: [Linker error] undefined reference to 'PlaySoundA@12' Id returned 1 exit status From this code: // c++ program to generate a random sequence of numbers then play corresponding audio files #include <windows.h> #include <mmsystem.h> #include <iostream> #pragma comment(lib, "winmm.lib") using namespace std; int main() { int i; i = 0; // set the value of i while (i <= 11) // set the loop to run 11 times { int number; number = rand() % 10 + 1; // generate a random number sequence // cycling through the numbers to find the right wav and play it if (number == 0) { PlaySound("0.wav", NULL, SND_FILENAME); // play the random number } else if (number == 1) { PlaySound("1.wav", NULL, SND_FILENAME); // play the random number } //else ifs repeat to 11... i++; // increment i } return 0; } I've tried absolute and relative paths for the wavs, the file size of them is under 1Mb each too. I've read another thread here on the subject: http://stackoverflow.com/questions/1565439/how-to-playsound-in-c As you may well have guessed this is my first C++ program, so my knowledge is limited with where to go next. I've tried pretty much every page Google has on the subject including MSDN usage page. Any ideas? Thanks in advance...

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  • CakePHP dynamic element

    - by Logic Artist
    I am trying to create a message-board type element in a CakePHP app. This element will be displayed on all pages and views that use a particular layout. I want it to display all the messages in the model, then show the add form when a link is clicked, then return to the updated message list when submitted. All this without affecting the current view/page. I have my message model/controller/index set up, with a message board element that requests the index action. This works fine. However I am perplexed about how to return back to the original page/action from which the link was clicked. I can't use $this-referer() because that will link back to the add() action; what I want rather is to link to the page/view before that. Any general pointers on how to achieve something like this?

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  • OO Design / Patterns - Fat Model Vs Transaction Script?

    - by ben
    Ok, 'Fat' Model and Transaction Script both solve design problems associated with where to keep business logic. I've done some research and popular thought says having all business logic encapsulated within the model is the way to go (mainly since Transaction Script can become really complex and often results in code duplication). However, how does this work if I want to use the TDG of a second Model in my business logic? Surely Transaction Script presents a neater, less coupled solution than using one Model inside the business logic of another? A practical example... I have two classes: User & Alert. When pushing User instances to the database (eg, creating new user accounts), there is a business rule that requires inserting some default Alerts records too (eg, a default 'welcome to the system' message etc). I see two options here: 1) Add this rule as a User method, and in the process create a dependency between User and Alert (or, at least, Alert's Table Data Gateway). 2) Use a Transaction Script, which avoids the dependency between models. (Also, means the business logic is kept in a 'neutral' class & easily accessible by Alert. That probably isn't too important here, though). User takes responsibility for it's own validation etc, however, but because we're talking about a business rule involving two Models, Transaction Script seems like a better choice to me. Anyone spot flaws with this approach?

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  • Django model field value preprocessing before returning

    - by Satoru.Logic
    Hi, all. I have a Note model class like this: class Note(models.Model): author = models.ForeignKey(User, related_name='notes') content = NoteContentField(max_length=256) NoteContentField is a custom sub-class of CharField that override the to_python method in purpose of doing some twitter-text-conversion processing. class NoteContentField(models.CharField): __metaclass__ = models.SubfieldBase def to_python(self, value): value = super(NoteContentField, self).to_python(value) from ..utils import linkify return mark_safe(linkify(value)) However, this doesn't work. When I save a Note object like this: note = Note(author=request.use, content=form.cleaned_data['content']) The conversed value is saved into the database, which is not what I wanna see. Would you please tell me what's wrong with this? Thanks in advance.

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  • Is ASP.NET MVC is really MVC? Or how to separate model from controller?

    - by Andrey
    Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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  • UITableView - Select nearest row after row deletion.

    - by sunnycmf
    like build in apple notes app, after you swipe to delete the selected row, it will select the nearest available row automatically. The logic should be: if row count 0 then if deleted_row == last row then select deleted_row_index-1 row else select deleted_row_index+1 row end end i have try to implement the above logic in the commitEditingStyle event, but the selection fail. the selectRowAtIndexPath logic just don't work in this event, if i apply it in a button, it works. any idea?

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  • how to get an html anchor effect with JQuery

    - by frosty
    I have a click handler, which has "event.preventDefault". There is whole lot of logic that occurs within this function. At the end of this logic i would like the page to scroll up to the top. ie the same effect as an anchor. ie " $('.vod-playlist-film a').bind("click", function(event) { // some logic // now i need the browser to goto the top of the page event.preventDefault(); });

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  • Grails: Services VS Groovy classes

    - by Olexandr
    Documentation says: The Grails team discourages the embedding of core application logic inside controllers, as it does not promote re-use and a clean separation of concerns. I have one API controller and a few Groovy classes in src/groovy folder. Those classes just implements my application logic so actions in API controller works in this way: //index page def index = { render new IndexApi().index(params) as JSON } I'm curious - is there any reason to move my application logic from plain groovy classes into services ?

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  • ASP.NET: How to initialize when *user control* is initially loaded

    - by kendor
    I have an ASP.NET user control that I'm embedding in another user control. This works fine. I need to know the best logic/method for detecting when the control is loaded. In other words, I have some display initialization logic that needs to run when the control is initially displayed. Surely there is a pattern for this. The typical method is to put (!IsPostBack) logic in the Page_Load method of the control. This works great until you end up with a state when the Parent page has already posted back many times. My user control gets added to the page but its display does not intialize properly. I'm hoping to find a way that keeps this logic inside the control, versus various hacking around in the codebehind of the parent page.

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  • How to convert tag-and-username-like text into proper links in a twitter message?

    - by Satoru.Logic
    Hi, all. I'm writing a twitter-like note-taking web app. In a page the latest 20 notes of the user will be listed, and when the user scroll to the bottom of the browser window more items will be loaded and rendered. The initial 20 notes are part of the generated html of my django template, but the other dynamically loaded items are in json format. I want to know how do I do the tag-and-username converting consistently. Thanks in advance.

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  • Implement Exception Handling in ASP.NET C# Project

    - by Shrewd Demon
    hi, I have an application that has many tiers. as in, i have... Presentation Layer (PL) - contains all the html My Codes Layer (CL) - has all my code Entity Layer (EL) - has all the container entities Business Logic Layer (BLL) - has the necessary business logic Data Logic Layer (DLL) - any logic against data Data Access Layer (DAL) - one that accesses data from the database Now i want to provide error handling in my DLL since it is responsible for executing statement like ExecureScalar and all.... And i am confused as to how to go about it...i mean do i catch the error in the DLL and throw it back to the BLL and from there throw it back to my code or what.... can any one please help me how do i implement a clean and easy error handling techinque help you be really appreciated. Thank you.

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  • Designing a Tag table that tells how many times it's used

    - by Satoru.Logic
    Hi, all. I am trying to design a tagging system with a model like this: Tag: content = CharField creator = ForeignKey used = IntergerField It is a many-to-many relationship between tags and what's been tagged. Everytime I insert a record into the assotication table, Tag.used is incremented by one, and decremented by one in case of deletion. Tag.used is maintained because I want to speed up answering the question 'How many times this tag is used?'. However, this seems to slow insertion down obviously. Please tell me how to improve this design. Thanks in advance.

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