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• Harmful temptations in programming

  - by gaearon

  Just curious, what kinds of temptations in programming turned out to be really harmful in your projects? Like when you really feel the urge to do something and you believe it's going to benefit the project or else you just trick yourself into believing it is, and after a week you realize you haven't solved any real problems but instead created new ones or, in the best case, pleased your inner beast with no visible impact. Personally, I find it very hard to not refactor bad code. I work with a lot of bad legacy code, and it takes some deep breaths to not touch it when I have no tests to prove my refactoring doesn't not break anything. Another demon for me in user interface, I can literally spend hours changing UI layout just because I enjoy doing it. Sometimes I tell myself I'm working on usability, but the truth is just I love moving buttons around. What are your programming demons, and how do you avoid them?

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• How to refactor to cleaner version of maintaing states of the widget

  - by George

  Backstory I inherited a bunch of code that I'd like to refactor. It is a UI application written in javascript. Current state: We have main application which consist of several UI components. And each component has entry fields, textboxes, menus, etc), like "ticket", "customer information", etc. Based on input, where the application was called from, who is the user, we enable/disable, hide, show, change titles. Unfortunately, the app grew to the point where it is really hard to scale, add new features. Main the driver (application code) calls set/unset functions of the respective components. So a lot of the stuff look like this Main app unit function1() { **call_function2()** component1.setX(true); component1.setY(true); component2.setX(false); } call_function2() { // it may repeat some of the code function1 called } and we have a lot of this in the main union. I am cleaning this mess. What is the best way to maintain the state of widgets? Please let me know if you need me to clarify.

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• IoC containers and service locator pattern

  - by TheSilverBullet

  I am trying to get an understanding of Inversion of Control and the dos and donts of this. Of all the articles I read, there is one by Mark Seemann (which is widely linked to in SO) which strongly asks folks not to use the service locator pattern. Then somewhere along the way, I came across this article by Ken where he helps us build our own IoC. I noticed that is is nothing but an implementation of service locator pattern. Questions: Is my observation correct that this implementation is the service locator pattern? If the answer to 1. is yes, then Do all IoC containers (like Autofac) use the service locator pattern? If the answer to 1. is no, then why is this differen? Is there any other pattern (other than DI) for inversion of control?

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• What would be a good set of first programming problems that would help a non-CS graduate to learn programming ?

  - by shan23

  I'm looking at helping a friend learn programming (I'm NOT asking about the ideal first language to learn programming in). She's had a predominantly mathematical background (majoring in Maths for both her undergrads and graduate degree), and has had some rudimentary exposure to programming before (in the form of Matlab simulations/matrix operations in C etc) - but has never been required to design/execute complex projects. She is primarily interested in learning C/C++ - so, with respect to her background, what would be a set of suitable problems that would both engage her interest ?

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• Use decorator and factory together to extend objects?

  - by TheClue

  I'm new to OOP and design pattern. I've a simple app that handles the generation of Tables, Columns (that belong to Table), Rows (that belong to Column) and Values (that belong to Rows). Each of these object can have a collection of Property, which is in turn defined as an enum. They are all interfaces: I used factories to get concrete instances of these products, depending on circumnstances. Now I'm facing the problem of extending these classes. Let's say I need another product called "SpecialTable" which in turn has some special properties or new methods like 'getSomethingSpecial' or an extended set of Property. The only way is to extend/specialize all my elements (ie. build a SpecialTableFactory, a SpecialTable interface and a SpecialTableImpl concrete)? What to do if, let's say, I plan to use standard methods like addRow(Column column, String name) that doesn't need to be specialized? I don't like the idea to inherit factories and interfaces, but since SpecialTable has more methods than Table i guess it cannot share the same factory. Am I wrong? Another question: if I need to define product properties at run time (a Table that is upgraded to SpecialTable at runtime), i guess i should use a decorator. Is it possible (and how) to combine both factory and decorator design? Is it better to use a State or Strategy pattern, instead?

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• EAV - is it really bad in all scenarios?

  - by Giedrius

  I'm thinking to use EAV for some of the stuff in one of the projects, but all questions about it in stackoverflow end up to answers calling EAV an anti pattern. But I'm wondering, if is it that wrong in all cases? Let's say shop product entity, it has common features, like name, description, image, price, etc., that take part in logic many places and has (semi)unique features, like watch and beach ball would be described by completely different aspects. So I think EAV would fit for storing those (semi)unique features? All this is assuming, that for showing product list, it is enough info in product table (that means no EAV is involved) and just when showing one product/comparing up to 5 products/etc. data saved using EAV is used. I've seen such approach in Magento commerce and it is quite popular, so may be there are cases, when EAV is reasonable?

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• Earliest use of Comments as Semantically Meaningful Things in a Program?

  - by Alan Storm

  In certain corners of the PHP meta-programming world, it's become fashionable to use PHPDoc comments as a mechanism for providing semantically meaningful information to a program. That is, other code will parse the doc blocks and do something significant with the information encoded in those comments. Doctrine's annotations and code generation are an example of this. What's the earliest (or some early) use of this technique? I have vague memories of some early java Design by Contract implementations doing similar things, but I'm not sure of those folks were inventing the technique, or if they got it from somewhere. Mainly asking so I can provide some historical context for PHP developers who haven't come across the technique before, and are distrustful of it because it seems a little crazy pants.

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• Updating query results

  - by Francisco Garcia

  Within a DDD and CQRS context, a query result is displayed as table rows. Whenever new rows are inserted or deleted, their positions must be calculated by comparing the previous query result with the most recent one. This is needed to visualize with an animation new or deleted rows. The model of my view contains an array of the displayed query results. But I need a place to compare its contents against the latest query. Right now I consider my model view part of my application layer, but the comparison of two query result sets seems something that must be done within the domain layer. Which component should cache a query result and which one compare them? Are view models (and their cached contents) supposed to be in the application layer?

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• does class reference itself static anti pattern in prism

  - by Michael Riva

  I have an application and my desing approach look like this: class Manager { public int State; static Manager _instance = null; public static Manager Instance { get { return _instance; } set { if (_instance == value) return; _instance = value; } } public Manager() { State = 0; Instance=this; } } class Module1 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module2 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module3 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } Manager class already registered in Bootstrapper like : protected override void ConfigureContainer() { base.ConfigureContainer(); Container.RegisterType<Manager>(new ContainerControlledLifetimeManager()); } protected override void InitializeModules() { Manager man= Container.Resolve<Manager>(); } Question is do I need to define my manager object as static in its field to be able to reach its state? Or this is anti pattern or bad for performance?

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• What Pattern will solve this - fetching dependent record from database

  - by tunmise fasipe

  I have these classes class Match { int MatchID, int TeamID, //used to reference Team ... other fields } Note: Match actually have 2 teams which means 2 TeamID class Team { int TeamID, string TeamName } In my view I need to display List<Match> showing the TeamName. So I added another field class Match { int MatchID, int TeamID, //used to reference Team ... other fields string TeamName; } I can now do Match m = getMatch(id); m.TeamName = getTeamName(m.TeamId); //get name from database But for a List<Match>, getTeamName(TeamId) will go to the database to fetch TeamName for each TeamID. For a page of 10 Matches per page, that could be (10x2Teams)=20 trip to database. To avoid this, I had the idea of loading everything once, store it in memory and only lookup the TeamName in memory. This made me have a rethink that what if the records are 5000 or more. What pattern is used to solve this and how?

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• Is there a name for this use of the State design pattern?

  - by Chris C

  I'm looking to see if there is a particular name for this style of programming a certain kind of behavior into a program. Said program runs in real time, in an update loop, and the program uses the State design pattern to do some work, but it's the specific way it does the work that I want to know about. Here's how it's used. - Object Foo constructed, with concrete StateA object in it - First loop runs --- Foo.Run function calls StateA.Bar --- in StateA.Bar replace Foo's state to StateB - Second loop runs --- Foo.Run calls StateB.Bar - Third loop runs --- Foo.Run calls StateB.Bar - Fourth loop --- etc. So in short, Foo doesn't have an explicit Initialize function. It will just have Run, but Run will do something unique in the first frame to initialize something for Foo and then replace it with a different action that will repeat in all the frames following it- thus not needing to check if Foo's already initialized. It's just a "press start and go" action. What would you call implementing this type of behavior?

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• Where ORMs blur the lines between code and data, how do you decide what logic should be a stored procedure, and what should be coded?

  - by PhonicUK

  Take the following pseudocode: CreateInvoiceAndCalculate(ItemsAndQuantities, DispatchAddress, User); And say CreateInvoice does the following: Create a new entry in an Invoices table belonging to the specified User to be sent to the given DispatchAddress. Create a new entry in an InvoiceItems table for each of the items in ItemsAndQuantities, storing the Item, the Quantity, and the cost of the item as of now (by looking it up from an Items table) Calculate the total amount of the invoice (ex shipping and taxes) and store it in the new Invoice row. At a glace you wouldn't be able to tell if this was a method in my applications code, or a stored procedure in the database that is being exposed as a function by the ORM. And to some extent it doesn't really matter. Now technically none of this is business logic. You're not making any decisions - just performing a calculation and creating records. However some may argue that because you are performing a calculation that affects the business (the total amount to be invoiced) that this isn't something that should be done in a stored procedure and instead should be in code. So for this specific example - why would it be more appropriate to do one or the other? And where do you draw the line? Or does it even particular matter as long as it's sufficiently well documented?

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• returning null vs returning zero, which would be better?

  - by Dark Star1

  I inherited a project that I am managing and having to maintain pending the redevelopment of the code base. At the moment I am being tasked with adding little feature all over the place and have gotten into the habit of returning null instead of zero in parts of the code where I am working on. The problem is we have a client that is using this code and parts of code that require data from my implemented features recieve a null and dump the stack trace in UI. I would like to avoid this entirely from my input but without the nullPointer exceptions there's the potential that errors would be introduced into the client's data which may go un-noticed. Usually I would have come up with my own error notification system but I have never inherited a project before. so I am unsure whether to continue down this path. I still believe that the stack dump is preferable to un-noticed data corruption/inaccuracies.

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• What is the good way of sharing specific data between ViewModels

  - by voroninp

  We have IAppContext which is injected into ViewModel. This service contains shared data: global filters and other application wide properties. But there are cases when data is very specific. For example one VM implements Master and the second one - Details of selected tree item. Thus DetailsVm must know about the selected item and its changes. We can store this information either in IAppContext or inside each concerned VM. In both cases update notifications are sent via Messenger. I see pros and cons for any of the approaches and can not decide which one is better. 1st: + explicitly exposed shared proerties, easy to follow dependencies - IAppContxt becomes cluttered with very specific data. 2nd: the exact opposite of the first and more memory load due to data duplication. May be someone can offer design alternatives or tell that one of the variants is objectively superior to the other cause I miss something important?

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• Entity Framework 5, separating business logic from model - Repository?

  - by bnice7

  I am working on my first public-facing web application and I’m using MVC 4 for the presentation layer and EF 5 for the DAL. The database structure is locked, and there are moderate differences between how the user inputs data and how the database itself gets populated. I have done a ton of reading on the repository pattern (which I have never used) but most of my research is pushing me away from using it since it supposedly creates an unnecessary level of abstraction for the latest versions of EF since repositories and unit-of-work are already built-in. My initial approach is to simply create a separate set of classes for my business objects in the BLL that can act as an intermediary between my Controllers and the DAL. Here’s an example class: public class MyBuilding { public int Id { get; private set; } public string Name { get; set; } public string Notes { get; set; } private readonly Entities _context = new Entities(); // Is this thread safe? private static readonly int UserId = WebSecurity.GetCurrentUser().UserId; public IEnumerable<MyBuilding> GetList() { IEnumerable<MyBuilding> buildingList = from p in _context.BuildingInfo where p.Building.UserProfile.UserId == UserId select new MyBuilding {Id = p.BuildingId, Name = p.BuildingName, Notes = p.Building.Notes}; return buildingList; } public void Create() { var b = new Building {UserId = UserId, Notes = this.Notes}; _context.Building.Add(b); _context.SaveChanges(); // Set the building ID this.Id = b.BuildingId; // Seed 1-to-1 tables with reference the new building _context.BuildingInfo.Add(new BuildingInfo {Building = b}); _context.GeneralInfo.Add(new GeneralInfo {Building = b}); _context.LocationInfo.Add(new LocationInfo {Building = b}); _context.SaveChanges(); } public static MyBuilding Find(int id) { using (var context = new Entities()) // Is this OK to do in a static method? { var b = context.Building.FirstOrDefault(p => p.BuildingId == id && p.UserId == UserId); if (b == null) throw new Exception("Error: Building not found or user does not have access."); return new MyBuilding {Id = b.BuildingId, Name = b.BuildingInfo.BuildingName, Notes = b.Notes}; } } } My primary concern: Is the way I am instantiating my DbContext as a private property thread-safe, and is it safe to have a static method that instantiates a separate DbContext? Or am I approaching this all wrong? I am not opposed to learning up on the repository pattern if I am taking the total wrong approach here.

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• What are the advantages and Disadvantages of Using an Aspect Orientated Programming Paradigm

  - by JHarley1

  Ok so here is the question: What are the advantages and Disadvantages of Using an Aspect Orientated Programming Paradigm. My advantages and disadvantages thus far: Advantages: Complements object orientation. Modularizes cross-cutting concerns improving code maintainability and understandability. Disadvantage: Not the easiest of concepts to grasp - not as well documented as O-O O-O goes far enough in the separation of concerns... List item Would anyone like to challenge any of these/ add their own? Many Thanks, J

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• Necessary Infrastructure for large project with many components communicating through IPCs

  - by jluzwick

  I have a fairly in depth question which probably doesn't have an exact answer. As a software engineer, I am usually tasked with working on a program or project with minimal understanding of how other components or programs in the project interact with each other. When one program fails in a sea of multiple components and processes, what infrastructure elements are necessary to ensure that the problem can be accurately tracked to the violating application? More specifically, what infrastructure elements should be necessary for this large project and which are optional but very helpful. One such example I can think of is some form of a common logging infrastructure that allows for a developer or tester to easily browse through a log that contains numerous components for messages that might allude to the culprit program along with a "trail" of what happened before the issue occurred. I'm thinking of something similar to Androids alogcat tool. These necessary infrastructure elements should be language-agnostic. While these elements should be understood by all engineers on the team in question, which elements should be understood at great detail by the technical system engineers and what should the individual software engineers be responsible for adding to their tools to allow for such infrastructures to take hold? Please feel free to ask for clarification if something does not make sense as I understand this question is very broad and needs some refinement. I will refine as necessary from the answers and comments I receive. Thanks for any help!

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• OO Software Architecture - base class that everything inherits from. Bad/good idea?

  - by ale

  I am reviewing a proposed OO software architecture that looks like this: Base Foo Something Bar SomethingElse Where Base is a static class. My immediate thought was that every object in any class will inherit all the methods in Base which would create a large object. Could this cause problems for a large system? The whole architecture is hierarchical.. the 'tree' is much bigger than this really. Does this sort of architecture have a name (hierarchical?!). What are the known pros and cons?

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• Entry level engineer question regarding memory mangement

  - by Ealianis

  It has been a few months since I started my position as an entry level software developer. Now that I am past some learning curves (e.g. the language, jargon, syntax of VB and C#) I'm starting to focus on more esoteric topics, as to write better software. A simple question I presented to a fellow coworker was responded with "I'm focusing on the wrong things." While I respect this coworker I do disagree that this is a "wrong thing" to focus upon. Here was the code (in VB) and followed by the question. Note: The Function GenerateAlert() returns an integer. Dim alertID as Integer = GenerateAlert() _errorDictionary.Add(argErrorID, NewErrorInfo(Now(), alertID)) vs... _errorDictionary.Add(argErrorID, New ErrorInfo(Now(), GenerateAlert())) I originally wrote the ladder and rewrote it with the "Dim alertID" so that someone else might find it easier to read. But here was my concern and question. "Should one write this with the Dim AlertID, it would in fact take up more memory; finite but more, and should this method be called many times could it lead to an issue? How will .NET handle this object AlertID. Outside of .NET should one manually dispose of the object after use (near the end of the sub)." I want to ensure I become a knowledgeable programmer that does not just rely upon garbage collection. Am I over thinking this? Am I focusing on the wrong things?

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• What is a good design pattern and terminology for decoupling output?

  - by User

  I have a program where I want to save some data record. And I want the output type to be flexible such that I could save the data record to a text file, xml file, database, push to a webservice. My take on it would be to create an interface such as DataStore with a Save() method, and the concrete subclasses such as TextFileDataStore, DatabaseDataStore, etc. What is the proper name/terminology for this type of pattern (I'm using the term "DataStore", log4net names things "appenders", .net they talk about "providers" and "persistence")? I want to come up with good class names (and method names) that fit with a convention if there is one. can you point me to a decent example, preferably in C#, C++, or java? Update Managed to find this stack overflow question, Object persistence terminology: 'repository' vs. 'store' vs. 'context' vs. 'retriever' vs. (…), which captures the terminology part of my question pretty well although there's not a decent answer yet.

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• Storing hierarchical template into a database

  - by pduersteler

  If this title is ambiguous, feel free to change it, I don't know how to put this in a one-liner. Example: Let's assume you have a html template which contains some custom tags, like <text_field />. We now create a page based on a template containing more of those custom tags. When a user wants to edit the page, he sees a text field. he can input things and save it. This looks fairly easy to set up. You either have something like a template_positions table which stores the content of those fields. Case: I now have a bit of a blockade keeping things as simple as possible. Assume you have the same tag given in your example, and additionally, <layout> and <repeat> tags. Here's an example how they should be used: <repeat> <layout name="image-left"> <image /> <text_field /> </layout> <layout name="image-right"> <text_field /> <image /> </layout> </repeat> We now have a block which can be repeated, obviously. This means: when creting/editing a page containing such a template block, I can choose between a layout image-left and image-right which then gets inserted as content element (where content for <image /> and <text_field /> gets stored). And because this is inside a <repeat>, content elements from the given layouts can be inserted multiple times. How do you store this? Simply said, this could be stored with the same setup I've wrote in the example above, I just need to add a parent_id or something similiar to maintain a hierarchy. but I think I am missing something. At least the relation between an inserted content element and the origin/insertion point is missing. And what happens when I update the template file? Do I have to give every custom tag that acts as editable part of a template an identifier that matches an identifier in the template to substitue them correctly? Or can you think of a clean solution that might be better?

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• How to solve cyclic dependencies in a visitor pattern

  - by Benjamin Rogge

  When programming at work we now and then face a problem with visitors and module/project dependencies. Say you have a class A in a module X. And there are subclasses B and C in module Y. That means that module Y is dependent on module X. If we want to implement a visitor pattern to the class hierarchy, thus introducing an interface with the handle Operations and an abstract accept method in A, we get a dependency from module Y to module X, which we cannot allow for architectural reasons. What we do is, use a direct comparison of the types (i.e. instanceof, since we program in Java), which is not satisfying. My question(s) would be: Do you encounter this kind of problem in your daily work (or do we make poor architectural choices) and if so, how is your approach to solve this?

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• How can I design my classes to include calendar events stored in a database?

  - by Gianluca78

  I'm developing a web calendar in php (using Symfony2) inspired by iCal for a project of mine. At this moment, I have two classes: a class "Calendar" and a class "CalendarCell". Here you are the two classes properties and method declarations. class Calendar { private $month; private $monthName; private $year; private $calendarCellList = array(); private $translator; public function __construct($month, $year, $translator) {} public function getCalendarCellList() {} public function getMonth() {} public function getMonthName() {} public function getNextMonth() {} public function getNextYear() {} public function getPreviousMonth() {} public function getPreviousYear() {} public function getYear() {} private function calculateDaysPreviousMonth() {} private function calculateNumericDayOfTheFirstDayOfTheWeek() {} private function isCurrentDay(\DateTime $dateTime) {} private function isDifferentMonth(\DateTime $dateTime) {} } class CalendarCell { private $day; private $month; private $dayNameAbbreviation; private $numericDayOfTheWeek; private $isCurrentDay; private $isDifferentMonth; private $translator; public function __construct(array $parameters) {} public function getDay() {} public function getMonth() {} public function getDayNameAbbreviation() {} public function isCurrentDay() {} public function isDifferentMonth() {} } Each calendar day can includes many calendar events (such as appointments or schedules) stored in a database. My question is: which is the best way to manage these calendar events in my classes? I think to add a eventList property in CalendarCell and populate it with an array of CalendarEvent objects fetched by the database. This kind of solution doesn't allow other coders to reuse the classes without db (because I should inject at least a repository services also) just to create and visualize a calendar... so maybe it could be better to extend CalendarCell (for instance in CalendarCellEvent) and add the database features? I feel like I'm missing some crucial design pattern! Any suggestion will be very appreciated!

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• I am the Webmaster now. Where do I start? [closed]

  - by John C

  I just changed jobs and will soon be in charge of a custom-built ASP.NET CMS and website for a fairly large corporation with global offices. I have IT and developer FTE resources available to me but I am trying to build a list of branding, project, and functionality points to review. What guides or lists can/should I use to evaluate this website before I begin adding features, creating new projects, or even redesigning and redeveloping the site? (I have been a webmaster/designer/developer for small, WordPress/Drupal sites for 10 years. I have been an unofficial webmaster (director/content manager) for a large site for 3 years (no direct development control over Sharepoint administration, IIS, or hosting ... but everything else, I did. Analytics, email, advertising, social, SEO, etc.).) Thank you!

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• Modular Architecture for Processing Pipeline

  - by anjruu

  I am trying to design the architecture of a system that I will be implementing in C++, and I was wondering if people could think of a good approach, or critique the approach that I have designed so far. First of all, the general problem is an image processing pipeline. It contains several stages, and the goal is to design a highly modular solution, so that any of the stages can be easily swapped out and replaced with a piece of custom code (so that the user can have a speed increase if s/he knows that a certain stage is constrained in a certain way in his or her problem). The current thinking is something like this: struct output; /*Contains the output values from the pipeline.*/ class input_routines{ public: virtual foo stage1(...){...} virtual bar stage2(...){...} virtual qux stage3(...){...} ... } output pipeline(input_routines stages); This would allow people to subclass input_routines and override whichever stage they wanted. That said, I've worked in systems like this before, and I find the subclassing and the default stuff tends to get messy, and can be difficult to use, so I'm not giddy about writing one myself. I was also thinking about a more STLish approach, where the different stages (there are 6 or 7) would be defaulted template parameters. Can anyone offer a critique of the pattern above, thoughts on the template approach, or any other architecture that comes to mind?

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