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• Performance of concurrent software on multicore processors

  - by Giorgio

  Recently I have often read that, since the trend is to build processors with multiple cores, it will be increasingly important to have programming languages that support concurrent programming in order to better exploit the parallelism offered by these processors. In this respect, certain programming paradigms or models are considered well-suited for writing robust concurrent software: Functional programming languages, e.g. Haskell, Scala, etc. The actor model: Erlang, but also available for Scala / Java (Akka), C++ (Theron, Casablanca, ...), and other programming languages. My questions: What is the state of the art regarding the development of concurrent applications (e.g. using multi-threading) using the above languages / models? Is this area still being explored or are there well-established practices already? Will it be more complex to program applications with a higher level of concurrency, or is it just a matter of learning new paradigms and practices? How does the performance of highly concurrent software compare to the performance of more traditional software when executed on multiple core processors? For example, has anyone implemented a desktop application using C++ / Theron, or Java / Akka? Was there a boost in performance on a multiple core processor due to higher parallelism?

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• Strategy for clients to retrieve real-time log from HTTP server

  - by Jerry Dodge

  I have an HTTP Server Service application which has its own logging mechanism. It's written in Delphi. I would like to provide a way for multiple clients to connect to this service and get a real-time update of the log. The log in the service moves rather fast, there's a lot of things to log. There may be up to 50 messages within 1 second at times. The existing log which is already implemented is not saved, it's only kept in the memory of the server service - where I will need to distribute it to any client which needs it. Once all clients have a log message, it should be deleted. I intend to use HTTP to "ask" the server for the log, and respond with an XML packet. The connections are not keep-alive. The only problem is, the server should only send the client those log records which it needs, not everything. I have no way of the server pushing the log to the clients in real-time, so each client needs to repeatedly ask the server for the latest log records. This HTTP Server is very lightweight, and there is no session management. There isn't even any type of authentication. The only way I see is for a client to register its self on the server, and whenever a log is issued on the server, it creates a copy of the log for each client, where each client has a log queue (string list). However, suppose there are 100 clients connected and expecting to receive this log. That means the server must create 100 copies of each log, add this log to the end of each client log queue, and wait for the client to request it. At that point, when the server replies with the XML log, it should flush (delete) whatever's in the queue. I'm worried however that this could cause memory issues. Each client log queue might get 100 log messages before the client requests the latest logs. How should I go about doing this in the fastest way possible without hindering the performance of the server? I'm trying to avoid having to create a copy of each log for each client.

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• UML Diagrams of Multi-Threaded Applications

  - by PersonalNexus

  For single-threaded applications I like to use class diagrams to get an overview of the architecture of that application. This type of diagram, however, hasn’t been very helpful when trying to understand heavily multi-threaded/concurrent applications, for instance because different instances of a class "live" on different threads (meaning accessing an instance is save only from the one thread it lives on). Consequently, associations between classes don’t necessarily mean that I can call methods on those objects, but instead I have to make that call on the target object's thread. Most literature I have dug up on the topic such as Designing Concurrent, Distributed, and Real-Time Applications with UML by Hassan Gomaa had some nice ideas, such as drawing thread boundaries into object diagrams, but overall seemed a bit too academic and wordy to be really useful. I don’t want to use these diagrams as a high-level view of the problem domain, but rather as a detailed description of my classes/objects, their interactions and the limitations due to thread-boundaries I mentioned above. I would therefore like to know: What types of diagrams have you found to be most helpful in understanding multi-threaded applications? Are there any extensions to classic UML that take into account the peculiarities of multi-threaded applications, e.g. through annotations illustrating that some objects might live in a certain thread while others have no thread-affinity; some fields of an object may be read from any thread, but written to only from one; some methods are synchronous and return a result while others are asynchronous that get requests queued up and return results for instance via a callback on a different thread.

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• How to tackle a boss who thinks everybody in this world is wrong except him?

  - by anon

  I mean seriously, how do you tackle a guy who even changes our variable names (even though they are reasonable) and sends back the code (after review) like 4 times? I know for sure I'm not that bad a developer! So many times, he enforces his ideals, which are not even best practices in the industry! I point out to him whatever link I can find on the internet trying to prove my point, but in the end he uses his authority to shut us out. Sick and tired. Frustrated. Do I have any way out other than quitting the job?

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• Is porting a Windows application to Mac worth it ?

  - by mikel

  I have a C# Windows application that sells for $35, and fairly regularly receive requests for a version for OS X too. I don't have any experience with Mac so far though, and so am not sure exactly how much work that would involve and if it would be worth it. If anyone's been in a similar position, it'd be very helpful to know: Roughly how many more (%) sales can you expect by porting to Mac ? Would you say it's worth the investment of a new Macbook Pro and the time of learning and porting to Objective-C ? Thanks in advance.

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• Precising definition of programming paradigm

  - by Kazark

  Wikipedia defines programming paradigm thus: a fundamental style of computer programming which is echoed in the descriptive text of the paradigms tag on this site. I find this a disappointing definition. Anyone who knows the words programming and paradigm could do about that well without knowing anything else about it. There are many styles of computer programming at many level of abstraction; within any given programming paradigm, multiple styles are possible. For example, Bob Martin says in Clean Code (13), Consider this book a description of the Object Mentor School of Clean Code. The techniques and teachings within are the way that we practice our art. We are willing to claim that if you follow these teachings, you will enjoy the benefits that we have enjoyed, and you will learn to write code that is clean and professional. But don't make the mistake of thinking that we are somehow "right" in any absolute sense. Thus Bob Martin is not claiming to have the correct style of Object-Oriented programming, even though he, if anyone, might have some claim to doing so. But even within his school of programming, we might have different styles of formatting the code (K&R, etc). There are many styles of programming at many levels. Sp how can we define programming paradigm rigorously, to distinguish it from other categories of programming styles? Fundamental is somewhat helpful, but not specific. How can we define the phrase in a way that will communicate more than the separate meanings of each of the two words—in other words, how can we define it in a way that will provide additional meaning for someone who speaks English but isn't familiar with a variety of paradigms?

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• As a person getting into mobile development, what's the best mobile platform in terms of profitability? [closed]

  - by Kyle Loman

  I realize this question can range very far so would love to hear any and all opinions on this. However, I'll be honest and say that I have been thinking of this in terms of most profitable. I know how this may sound either way but this is one of my main sticking points. I realize that I'm not guaranteed a single cent and success is never guaranteed but I'm going into this with the thought of making something out of it both financially and also for my own interest. I know that iOS gets a lot of attention on this front but Android commands a lot more market share. However, I know there are drawbacks to Android too, whether it's in the actual development process and programming (though I've heard conflicting reports on this, such as how easy/difficult it is for to address screen res in different devices) or the app ecosystem being flooded. But iOS's app ecosystem has been described as too saturated and harder to compete in for that reason. Since Windows Phone has fewer apps than both of those two, that might be the best place to start in order to be closer to the ground floor of the store and be noticed more? Less saturation = better chances of sales or differentiating? Something like the gold rush during the first years of the iOS App Store (not exactly but at least in concept)? Would it be that despite fewer users on the platform, there's more exposure due to less competition so that may translate to better success at sales? Plus, I know MS is in it for the long haul so I'm not too fearful of something like WebOS going away. Obviously RIM isn't very popular nowadays but I read a recent article that says Blackberry actually has the apps that make the most money, any thoughts on that: http://gigaom.com/mobile/which-mobile-oss-apps-make-most-money-surprise-its-blackberry/ Again, this is all I've heard or known about so if there's anything to add or correct here, please do. In addition, this has actually affected my next personal phone upgrade. I'm eligible for a carrier discount now and I've had my eye on the iPhone 5. However, the Lumia 920 is the one I'm holding out for and I'm open to trying an Android but I'm not sure I can wait that long for any new Nexus or even the Razr HD. Even the new Lumia in November is making me antsy, I'm so close to just getting an iPhone 5. But when I say this has affected my phone choice, I'd want to be able to carry the apps I write with me so that I'm able to pull my phone out to show people without having to carry around a second device to do so. So that's why I'd like to make my personal phone match the main platform I'm developing for. Of course, I will likely expand to other platforms if I gain any decent success but the one I target now would serve well as my personal phone I carry around so that I can use it as a marketing tool, in a sense, showing people my apps if the opportunity presents itself. So what's the best mobile platform to choose, and especially in regards to most lucrative? As said previously, this would influence my personal phone choice greatly. Thanks in advance and I hope this isn't taken the wrong way - I understand there are trade-offs and other factors that may balance this out but making some revenue is key among that. For some background, I have done software development and know programming language concepts so I'm not entirely new to it and I do get the notion of being familiar with these things so that I can translate this skill among a variety of languages but I'm currently just having difficulty choosing my first main mobile platform based on the criteria I've outlined above.

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• Best C# and SQL server reporting tool [closed]

  - by user65439

  What is the best reporting tool to use with C# applications? I have been playing around with Pentaho (a Java based reporting tool) but would prefer to work with something that integrate better with my c# and SQL server. The reporting requirements are extensive and I need a tool that can generate graphs etc. and can be called from within my c# code to automate and email these reports. Perhaps the people that is more experienced with report generation can help me out with some of the better applications used with C#

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• A way to return multiple return values from a method: put method inside class representing return value. Is it a good design?

  - by john smith optional

  I need to return 2 values from a method. My approach is as follows: create an inner class with 2 fields that will be used to keep those 2 values put the method inside that class instantiate the class and call the method. The only thing that will be changed in the method is that in the end it will assign those 2 values to the fields of the instance. Then I can address those values by referencing to the fields of that object. Is it a good design and why?

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• Does Microsoft really offer "support"?

  - by SpashHit

  One of the arguments against using Open Source is that there is no "support". However, do big vendors (e.g. Microsoft) really offer "support" of any kind? I'm sure there is some sort of 4-figure-per-hour "paid support" option out there, but is that really an "option" for any problem short of one that is going to bankrupt your business? To put it more concretely... I buy a Microsoft product... it has a bug... now what? And how is that better than what I get from Open Source?

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• New vs Clone Git in Eclipse with EGit

  - by Matty F

  I'm not sure I have either my new repo or clone repo workflow, or both, setup correctly. When I create a new project I create a repo on github, can't clone from it as it's empty so I create a new project which goes into my workspace and then the git init runs on the workspace copy. So I end up with everything in workspace\project-name. However, when I clone from github first I need to clone the repo and this goes into my default git directory (C:\git) as git\cloned-project-name, I then need to import this Git repo as a project into my workspace and I end up with workspace\cloned-project-name effectively duplicating the project folder in the git area. I've tried to clone to workspace\cloned-project-name but then it asks to import the git project and if I try to use workspace\cloned-project-name again, it errs. What am I doing wrong? Thanks, Matt.

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• Introducing Agile development after traditional project inception

  - by Riggy

  About a year and a half ago, I entered a workplace that claimed to do Agile development. What I learned was that this place has adopted several agile practices (such as daily standups, sprint plannings and sprint reviews) but none of the principles (just in time / just good enough mentality, exposing failure early, rich communication). I've now been tasked with making the team more agile and I've been assured that I have complete buy-in from the devs and the business team. As a pilot program, they've given me a project that just completed 15 months of requirements gathering, has a 110 page Analysis & Design document (to be considered as "written in stone"), and where I have no access to the end users (only to the committee made up of the users' managers who won't actually be using the product). I started small, giving them a list of expected deliverables for the first 5 sprints (leaving the future sprints undefined), a list of goals for the first sprint, and I dissected the A&D doc to get enough user stories to meet the first sprint's goals. Since then, they've asked why we don't have all the requirements for all the sprints, why I haven't started working on stuff for the third sprint (which they consider more important but is based off of the deliverables of the first 2 sprints) and are pressing for even more documentation that my entire IT team considers busy-work or un-related to us (such as writing the user manual up-front, documenting all the data fields from all the sprints up front, and more "up-front" work). This has been pretty rough for me as a new project manager, but there are improvements I have effectively implemented such as scrumban for story management, pair programming, and having the business give us customer acceptance tests up front (as part of the requirements documentation). So my questions are: What can I do to more effectively introduce change to a resistant business? Are there other practices that I can introduce on the IT side to help show the business the benefits of agile? The burden of documentation is strangling us - the business still sees it as a risk management strategy instead of as a risk. What can we do to alleviate their documentation concerns and demands (specifically the quantity of documentation and their need for all of it up front)? We are in a separate building from our business, about 3 blocks away and they refuse to have their people on the project co-habitate b/c that person "won't be able to work on their other projects while they're at our building." They expect us to always go over there and to bundle our questions so that we can ask them all at once and not waste that person's time with "constant interruptions." What can we do to get richer communication from them? Any additional advice would also be appreciated. Thanks!

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• Linear Search in Python? [closed]

  - by POTUS

  def find_interval(mesh,x): '''This function finds the interval containing x according to the following rules, mesh is an ordered list with n numbers return 0 if x < mesh[0] return n if mesh[n-1] < x return k if mesh[k-1] <= x < mesh[k] return n-1 if mesh[n-2] <= x <= mesh[n-1] This function does a Linear search. 08/29/2012 ''' for n in range(len(mesh)): for k in range(len(mesh)): if x == mesh[n]: print "Found x at index:" return n elif x<mesh[n]: return 0 elif mesh[n-1]<x: return n elif mesh[n-2]<=x<=mesh[n-1]: return n-1 elif mesh[k-1]<=x<mesh[k]: return k mesh = [0, 0.1, 0.25, 0.5, 0.6, 0.75, 0.9, 1] print mesh print find_interval(mesh, -1) print find_interval(mesh, 0) print find_interval(mesh, 0.1) print find_interval(mesh, 0.8) print find_interval(mesh, 0.9) print find_interval(mesh, 1) print find_interval(mesh, 1.01) Output: [0, 0.100000000000000, 0.250000000000000, 0.500000000000000, 0.600000000000000, 0.750000000000000, 0.900000000000000, 1] 0 Found x at index: 0 2 6 -1 -1 0 I don't think the output is correct. Can anyone help me fix it? Thanks.

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• Is it better to build HTML Code string on the server or on the client side?

  - by Ionut

  The result of the following process should be a html form. This form's structure varies from one to user. For example there might be a different number of rows or there may be the need for rowspan and colspan. When the user chooses to see this table an ajax call is made to the server where the structure of the table is decided from the database. Then I have to create the html code for the table structure which will be inserted in the DOM via JavaScript. The following problem comes to my mind: Where should I build the HTML code which will be inserted in the DOM? On the server side or should I send some parameters in the ajax call method and process the structure there? Therefore the main question involves good practice when it comes to decide between Server side processing or client side processing. Thank you!

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• Automatic Appointment Conflict Resolution

  - by Thomas

  I'm trying to figure out an algorithm for resolving appointment times. I currently have a naive algorithm that pushes down conflicting appointments repeatedly, until there are no more appointments. # The appointment list is always sorted on start time appointment_list = [ <Appointment: 10:00 -> 12:00>, <Appointment: 11:00 -> 12:30>, <Appointment: 13:00 -> 14:00>, <Appointment: 13:30 -> 14:30>, ] Constraints are that appointments: cannot be after 15:00 cannot be before 9:00 This is the naive algorithm for i, app in enumerate(appointment_list): for possible_conflict in appointment_list[i+1:]: if possible_conflict.start < app.end: difference = app.end - possible_conflict.start possible_conflict.end += difference possible_conflict.start += difference else: break This results in the following resolution, which obviously breaks those constraints, and the last appointment will have to be pushed to the following day. appointment_list = [ <Appointment: 10:00 -> 12:00>, <Appointment: 12:00 -> 13:30>, <Appointment: 13:30 -> 14:30>, <Appointment: 14:30 -> 15:30>, ] Obviously this is sub-optimal, It performs 3 appointment moves when the confict could have been resolved with one: if we were able to push the first appointment backwards, we could avoid moving all the subsequent appointments down. I'm thinking that there should be a sort of edit-distance approach that would calculate the least number of appointments that should be moved in order to resolve the scheduling conflict, but I can't get the a handle on the methodology. Should it be breadth-first or depth first solution search. When do I know if the solution is "good enough"?

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• SQLite with two python processes accessing it: one reading, one writing

  - by BBnyc

  I'm developing a small system with two components: one polls data from an internet resource and translates it into sql data to persist it locally; the second one reads that sql data from the local instance and serves it via json and a restful api. I was originally planning to persist the data with postgresql, but because the application will have a very low-volume of data to store and traffic to serve, I thought that was overkill. Is SQLite up to the job? I love the idea of the small footprint and no need to maintain yet another sql server for this one task, but am concerned about concurrency. It seems that with write ahead logging enabled, concurrently reading and writing a SQLite database can happen without locking either process out of the database. Can a single SQLite instance sustain two concurrent processes accessing it, if only one reads and the other writes? I started writing the code but was wondering if this is a misapplication of SQLite.

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• How long can a user remember what they were working on? [migrated]

  - by GlenPeterson

  A web application lets the user browse its screens for future or past months. The time period the user is currently viewing follows the user through every screen of the system. But users can be logged in for a month or more. After a certain period of inactivity, we will prompt the user: You were viewing November 2008 when you last clicked. Want to view the current (default) time period instead? How long between user clicks should we wait to show this message? I'm guessing somewhere between 30 minutes and 3 hours most people will forget what they were doing, but I'd love to have some data, or someone's experience to base it on. Other suggestions related to this issue?

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• How does this ruby error handling module code work

  - by Michael Durrant

  Trying to get a better handle on ruby exception handling. I have this code (from a book): def err_with_msg(pattern) m = Module.new (class << m; self; end).instance_eval do define_method(:===) do |e| pattern === e.msg end end m end So ok this is a method. We're creating a new Module. I think of module as mix-ins. Not sure what it's doing here. Not we add the module to the class. Fair enough. Then we have self on its own. What that for? I guess we have a little anonymouse method this is just about self. hmmm ok, now for each of the above, check the pattern match. but for each, I thought the above for for a new Module, did the module get to use instance's by being included? A better explanation of what's going on here would be most helpful.

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• Why should ViewModel route actions to Controller when using the MVCVM pattern?

  - by Lea Hayes

  When reading examples across the Internet (including the MSDN reference) I have found that code examples are all doing the following type of thing: public class FooViewModel : BaseViewModel { public FooViewModel(FooController controller) { Controller = controller; } protected FooController Controller { get; private set; } public void PerformSuperAction() { // This just routes action to controller... Controller.SuperAction(); } ... } and then for the view: public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.PerformSuperAction(); } } Why do we not just do the following? public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.Controller.SuperAction(); // or, even just use a shortcut property: Controller.SuperAction(); } }

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• What php programmer should know?

  - by emchinee

  I've dig the database here and didn't found any answer for my question. What is a standard for a php programmer to know? I mean, literally, what group of language functions, mechanisms, variables should person know to consider oneself a (good) php programmer? (I know 'being good' is beyond language syntax, still I'm considering syntax of plain php only) To give an example what I mean: functions to control http sessions, cookies functions to control connection with databases functions to control file handling functions to control xml etc.. I omit phrases like 'security' or 'patterns' or 'framework' intentionally as it applies to every programming language. Hope I made myself clear, any input appreciated :) Note: Michael J.V. is right claiming that databases are independent from language, so to put my question more precisely and emphasise differences: Practises or security, are some ideas to implement (there is no 'Pattern' object with 'Decorator()' method, is there?) while using databases means knowing a mysqli and a set of its methods.

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• We're Subversion Geeks and we want to know the benefits of Mercurial

  - by Matt

  Having read I'm a Subversion geek, why should I consider or not consider Mercurial or Git or any other DVCS. I have a related follow up question. I read that question and read the recommended links and videos and I see the benefits but I don't see the overall mindshift people are talking about. Our team is of 8-10 developers that work on one large code base consisting of 60 projects. We use Subversion and have a main trunk. When a developer starts a new Fogbugz case they create a svn branch, do the work on the branch and when they're done they merge back to the trunk. Occasionally they may stay on the branch for an extended time and merge the trunk to the branch to pick up the changes. When I watched Linus talk about people creating a branch and never doing it again, that's not us at all. We create probably 50-100 branches a week without issue. The biggest challenge is the merging but we've gotten pretty good at that as well. I tend to merge by fogbugz case & checkin rather than the entire root of the branch. We never work remotely and we never make branches off of branches. If you're the only one working in that section of the code base then the merge to the trunk goes smoothly. If someone else had modified the same section of code then the merge can get messy and you might need to do some surgery. Conflicts are conflicts, I don't see how any system could get it right most of the time unless if was smart enough to understand the code. After creating a branch the following checkout of 60k+ files takes some time but that would be an issue with any source control system we'd use. Is there some benefit of any DVCS that we're not seeing that would be of great help to us?

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• Releasing a project under GPL v2 or later without the source code of libraries

  - by Luciano Silveira

  I wrote a system in Java that I want to release under the terms of GPL v2 or later. I've used Apache Maven to deal with all the dependencies of the system, so I don't have the source code of any of the libraries used. I've already checked, all the libraries were released under GPL-compatible licenses (Apache v2, 3-clause BSD, MIT, LGPL v2 and v2.1). I have 3 questions about this scenario: 1) Can I release a package with only the binaries of code I wrote, not including the libraries, and distribute only the source code I wrote? 2) Can I release a package with all the binaries, including the libraries, and distribute only the source code I wrote? 3) Can I release a package with all the binaries, including the libraries, and distribute only the source code I wrote plus the source code of the libraries licensed under the LGPL license?

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• find second smallest element in Fibonacci Heap

  - by Longeyes

  I need to describe an algorithm that finds the second smallest element in a Fibonacci-Heap using the Operations: Insert, ExtractMin, DecreaseKey and GetMin. The last one is an algorithm previously implemented to find and return the smallest element of the heap. I thought I'd start by extracting the minimum, which results in its children becoming roots. I could then use GetMin to find the second smallest element. But it seems to me that I'm overlooking other cases because I don't know when to use Insert and DecreaseKey, and the way the question is phrased seems to suggest I should need them.

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• Why would I want to install node.js in my Rails Application?

  - by Crazy JIm

  Okay guys, I'm super confused. I thought node.js was a sever side framwork, basically the js version of Ruby's Rails or PHP's Zend. However, I'm having some difficulty with turbolinks, and it seems to be the way to fix it is through installing node.js I mean, I don't understand this at all. How can two frameworks work together like this? Also, it's not a gem (that REALLY would have confused me), you have to install node.js it onto your local machine by running (in the case of Ubuntu) sudo apt-get install nodejs Firstly, how does this totally separate framwork have any bearing on rails? Secondly, surely this isn't fixing the problem forever? When you specify a gem in your gemfile, the server knows what external libraries to install. How does the server know to install nodejs?

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• Class Design for special business rules

  - by Samuel Front

  I'm developing an application that allows people to place custom manufacturing orders. However, while most require similar paperwork, some of them have custom paperwork that only they require. My current class design has a Manufacturer class, of which of one of the member variables is an array of RequiredSubmission objects. However, there are two issues that I am somewhat concerned about. First, some manufacturers are willing to accept either a standard form or their own custom form. I'm thinking of storing this in the RequiredSubmission object, with an array of alternate forms that are a valid substitute. I'm not sure that this is ideal, however. The major issue, however, is that some manufacturers have deadline cycles. For example, forms A, B and C have to be delivered by January 1, while payment must be rendered by January 10. If you miss those, you'll have to wait until the next cycle. I'm not exactly sure how I can get this to work with my existing classes—how can I say "this set of dates all belong to the same cycle, with date A for form A, date B for form B, etc." I would greatly appreciate any insights on how to best design these classes.

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