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• Proper Data Structure for Commentable Comments

  - by Wesley

  Been struggling with this on an architectural level. I have an object which can be commented on, let's call it a Post. Every post has a unique ID. Now I want to comment on that Post, and I can use ID as a foreign key, and each PostComment has an ItemID field which correlates to the Post. Since each Post has a unique ID, it is very easy to assign "Top Level" comments. When I comment on a comment however, I feel like I now need a PostCommentComment, which attaches to the ID of the PostComment. Since ID's are assigned sequentially, I can no longer simply use ItemID to differentiate where in the tree the comment is assigned. I.E. both a Post and a Post Comment might have an ID of '5', so my foreign key relationship is invalid. This seems like it could go on infinitely, with PostCommentCommentComment's etc... What's the best way to solve this? Should I have a field in the comment called "IsPostComment" or something of the like to know which collection to attach the ID to? This strikes me as the best solution I've seen so far, but now I feel like I need to make recursive DataBase calls which start to get expensive. Meaning, I get a Post and get all PostComments where ItemID == Post.ID && where IsPostComment == true Then I take that as a collection, gather all the ID's of the PostComments, and do another search where ItemID == PostComment[all].ID && where IsPostComment == false, then repeat infinitely. This means I make a call for every layer, and if I'm calling 100 Posts, I might make 1000 DB calls to get 10 layers of comments each. What is the right way to do this?

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• Data structure for pattern matching.

  - by alvonellos

  Let's say you have an input file with many entries like these: date, ticker, open, high, low, close, <and some other values> And you want to execute a pattern matching routine on the entries(rows) in that file, using a candlestick pattern, for example. (See, Doji) And that pattern can appear on any uniform time interval (let t = 1s, 5s, 10s, 1d, 7d, 2w, 2y, and so on...). Say a pattern matching routine can take an arbitrary number of rows to perform an analysis and contain an arbitrary number of subpatterns. In other words, some patterns may require 4 entries to operate on. Say also that the routine (may) later have to find and classify extrema (local and global maxima and minima as well as inflection points) for the ticker over a closed interval, for example, you could say that a cubic function (x^3) has the extrema on the interval [-1, 1]. (See link) What would be the most natural choice in terms of a data structure? What about an interface that conforms a Ticker object containing one row of data to a collection of Ticker so that an arbitrary pattern can be applied to the data. What's the first thing that comes to mind? I chose a doubly-linked circular linked list that has the following methods: push_front() push_back() pop_front() pop_back() [] //overloaded, can be used with negative parameters But that data structure seems very clumsy, since so much pushing and popping is going on, I have to make a deep copy of the data structure before running an analysis on it. So, I don't know if I made my question very clear -- but the main points are: What kind of data structures should be considered when analyzing sequential data points to conform to a pattern that does NOT require random access? What kind of data structures should be considered when classifying extrema of a set of data points?

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• C++ - Constructor or Initialize Method to Startup

  - by Bob Fincheimer

  I want to determine when to do non-trivial initialization of a class. I see two times to do initialization: constructor and other method. I want to figure out when to use each. Choice 1: Constructor does initialization MyClass::MyClass(Data const& data) : m_data() { // does non-trivial initialization here } MyClass::~MyClass() { // cleans up here } Choice 2: Defer initialization to an initialize method MyClass::MyClass() : m_data() {} MyClass::Initialize(Data const& data) { // does non-trivial initialization here } MyClass::~MyClass() { // cleans up here } So to try and remove any subjectivity I want to figure out which is better in a couple of situations: Class that encapsulates a resource (window/font/some sort of handle) Class that composites resources to do something (a control/domain object) Data structure classes (tree/list/etc.) [Anything else you can think of] Things to analyze: Performance Ease of use by other developers How error-prone/opportunities for bugs [Anything else you can think of]

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• Using virtual functions

  - by Tucker Morgan

  I am starting to use virtual functions, and i am programming a simple text game, my question is this, if i have a virtual function called spec_abil with in a Super class called rpg_class. If you allow the player to class what class they want to play, say a mage class, a archer class, and a warrior class, which all have their own spec_abil function. How do you write it so that the program knows which one to use depending on the chosen class.

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• Configuration data: single-row table vs. name-value-pair table

  - by Heinzi

  Let's say you write an application that can be configured by the user. For storing this "configuration data" into a database, two patterns are commonly used. The single-row table CompanyName | StartFullScreen | RefreshSeconds | ... ---------------+-------------------+------------------+-------- ACME Inc. | true | 20 | ... The name-value-pair table ConfigOption | Value -----------------+------------- CompanyName | ACME Inc. StartFullScreen | true (or 1, or Y, ...) RefreshSeconds | 20 ... | ... I've seen both options in the wild, and both have obvious advantages and disadvantages, for example: The single-row tables limits the number of configuration options you can have (since the number of columns in a row is usually limited). Every additional configuration option requires a DB schema change. In a name-value-pair table everything is "stringly typed" (you have to encode/decode your Boolean/Date/etc. parameters). (many more) Is there some consensus within the development community about which option is preferable?

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• Scene Graph Traversing Techniques

  - by Bunkai.Satori

  Scene Graph seems to be the most effective way of representing the game world. The game world usually tends to be as large as the memory and device can handle. In contrast, the screen of the device captures only a fraction of the Game World/Scene Graph. Ideally, I wish to process(update and render) only the visible game objects/nodes on per-frame basis. My question therefore is, how to traverse the scene graph so, that I will focus only on the game notes that are in the camera frustum? How to organize data so that I can easily focus only on the scene graph nodes visible to me? What are techniques to minimize scenegraph traversal time? Is there such way as more effective traversal, or do I have to traverse whole scene graph on per-frame basis?

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• Is it necessary to create a database with as few tables as possible

  - by Shaheer

  Should we create a database structure with a minimum number of tables? Should it be designed in a way that everything stays in one place or is it okay to have more tables? Will it in anyway affect anything? I am asking this question because a friend of mine modified some database structure in mediaWiki. In the end, instead of 20 tables he was using only 8, and it took him 8 months to do that (it was his college assignment). EDIT I am concluding the answer as: size of the tables does NOT matter, until the case is exceptional; in which case the denormalization may help. Thanks to everyone for the answers.

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• Should a domain expert make class diagrams?

  - by Matthieu

  The domain expert in our team uses UML class diagrams to model the domain model. As a result, the class diagrams are more of technical models rather than domain models (it serves of some sort of technical specifications for developpers because they don't have to do any conception, they just have to implement the model). In the end, the domain expert ends up doing the job of the architect/technical expert right? Is it normal for a domain expert (not a developer or technical profile) to do class diagrams? If not, what kind of modeling should he be using?

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• Distinction between API and frontend-backend

  - by Jason

  I'm trying to write a "standard" business web site. By "standard", I mean this site runs the usual HTML5, CSS and Javascript for the front-end, a back-end (to process stuff), and runs MySQL for the database. It's a basic CRUD site: the front-end just makes pretty whatever the database has in store; the backend writes to the database whatever the user enters and does some processing. Just like most sites out there. In creating my Github repositories to begin coding, I've realized I don't understand the distinction between the front-end back-end, and the API. Another way of phrasing my question is: where does the API come into this picture? I'm going to list some more details and then questions I have - hopefully this gives you guys a better idea of what my actual question is, because I'm so confused that I don't know the specific question to ask. Some more details: I'd like to try the Model-View-Controller pattern. I don't know if this changes the question/answer. The API will be RESTful I'd like my back-end to use my own API instead of allowing the back-end to cheat and call special queries. I think this style is more consistent. My questions: Does the front-end call the back-end which calls the API? Or does the front-end just call the API instead of calling the back-end? Does the back-end just execute an API and the API returns control to the back-end (where the back-end acts as the ultimate controller, delegating tasks)? Long and detailed answers explaining the role of the API alongside the front-end back-end are encouraged. If the answer depends on the model of programming (models other than the Model-View-Controller pattern), please describe these other ways of thinking of the API. Thanks. I'm very confused.

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• What's wrong with JavaScript

  - by ts01

  There is a lot of buzz around Dart recently, often questioning Google motivations and utility of Dart as replacement for JavaScript. I was searching for rationale of creating Dart rather than investing more effort in ECMAScript. In well known leaked mail its author is saying that Javascript has historical baggage that cannot be solved without a clean break. But there is only one concrete example given (apart of performance concerns) of "fundamental language problems", which is an existence of a single Number primitive So, my questions are: How an existence of a single Number primitive can be a "fundamental problem"? Are there other known "fundamental problems" in JavaScript?

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• Callback Contract in WCF

  Callback contracts are a very powerful concept that is easily implemented in WCF. Using this, it is very easy to achieve event-like behavior between a service and client (duplex operations).

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• NCurses, scrolling of multiline items, "current item" pointer and "selected items"

  - by mjf

  I am looking for hints/ideas for the best (most effective) way on how to scroll multi-line items as well as emphasizing of the "current item" and "selected items" such as: 1 FOO ITEM 1 Foo sub-item 2 Foo sub-item 3 Foo sub-item 2 BAR ITEM 1 Bar sub-item 3 BAZ ITEM 1 Baz sub-item 2 Baz sub-item 4 RAB ITEM 5 ZZZ ITEM 1 Zzz sub-item 2 Zzz sub-item 3 Zzz sub-item 4 Zzz sub-item using NCurses (some combination of windows, sub-windows, pads, copywin? Uff! In fact, the lines could exceed the stdscr's width so that possibility to scroll left/right would be also nice - pads?)... The whole items (including the sub-items) are supposed to be emphasized as full-width window/pad areas. The "current item" (including it's set of lines) should be emphasized (i.e. using A_BOLD), selected set of items of choice (including the set of lines for each the selected item) should be emphasized in another way (i.e. using A_REVERSE). What would you choose to cope with it the most effective NCurses way? (The less redrawals/refreshes the better and terminal is supposed to have the ability to change it's size - such as XTerm running under "floating window" management.) Thank you for your ideas (or perhaps some piece of code where something similar is already solved - I was not able to find anything helpful on the Internet. I mean I am not going to copy/paste foreign code but programming NCurses properly is still somehow difficult to me). P.S.: Would you suggest to "smooth-scroll" +1/-1 screen line or rather "jump-scroll" +lines/-lines of the items? (I personally prefer the latter one.) Sincerely, -- mjf

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• Alchemy like game for the web, open source. Any ideas for element combinations?

  - by JohnDel

  I created a web game like the Android game Alchemy. It's open source and in the back-end you can create your own elements / your own game. I was wondering what elements - ideas would be good to implement as a prototype / demo? Some ideas are: Colors Programming languages Chemical Compounds Same as the original alchemy Evolution of biological organisms What do you think? Any specific combination ideas?

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• Adding a forum to an existing site

  - by Andrew Heath

  I've got a site with ~500 registered members, 300 of which are what you'd call "active". Site data is kept in a MySQL dbase. I'd like to add a myBB forum to the site, but this question applies to any forum really. What I very much want to avoid is requiring my users to register both on the site and on the forum because my userbase is not technically literate and this would confuse a lot of them. However the forum software has its own registration, login, cookie, and password management system which naturally are different from the site's mechanics. I envision the following possibilities: install myBB into the existing database and customize the login code to unify the two systems. This would probably mean changing the site's code to use the myBB system as that would likely be less painful to refactor and wouldn't hurt future myBB upgrade ability. install myBB into separate database and write a bridging script of some sort that auto-registers existing site users with the forum if they elect to participate. Also check new forum registrations against the site's username list to prevent newcomers from taking existing names. run them fully separate and force users to re-register (easiest for ME, but least desirable for them) I would like a suggested course of action from those who have trod this path before... Thank you.

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• Please recommend a patterns book for iOS development

  - by Brett Ryan

  I've read several books on iOS development and Objective-C, however what a lot of them teach is how to work with interfaces and all contain the model inside the view controller, i.e. a UITableViewController based view will simply have an NSArray as it's model. I'm interested in what the best practices are for designing the structure of an application. Specifically I'm interested in best practices for the following: How to separate a model from the view controller. I think I know how to do this by simply replacing the NSArray style example with a specific model object, however what I do not know how to do is alert the view when the model changes. For example in .NET I would solve this by conforming to INotifyPropertyChanged and databinding, and similarly with Java I would use PropertyChangeListener. How to create a service model for my domain objects. For example I want to learn the best way to create a service for a hypothetical Widget object to manage an internal DB and also services for communicating with remote endpoints. I need to learn the best ways to do this in a way that interface components can subscribe to events such as widgetUpdated. These services should be singleton classes and some how dependency injected into model/controller objects. Books I've read so far are: Programming in Objective-C (4th Edition) Beginning iOS 5 Development: Exploring the iOS SDK The iOS 5 Developer's Cookbook: Expanded Electronic Edition: Essentials and Advanced Recipes for iOS Programmers Learn Objective-C on the Mac: For OS X and iOS I've also purchased the following updated books but not yet read them. The Core iOS 6 Developer's Cookbook (4th edition Programming in Objective-C (5th Edition) I come from a Java and C# background with 15 years experience, I understand that many of the ways I would do things in these languages may not fit to the ObjC way of developing applications. Any guidance on the topic is very much appreciated.

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• What are current Biggest Challenges faced by Ecommerce Applications ?

  - by Rachel

  I am in the process to start Product Development for E-commerce and Online Retail domain but before starting I would like to know what are the biggest challenges faced by current state of Art E-Commerce Application ? Also I have not experience building e-commerce products and so what things should I keep in mind before developing one ? Is there are books, articles, blogs outside which I should refer to gain some knowledge before starting out ? Update: What are you thoughts on the recommendation engines for ecommerce applications ? What challenges we have with current state of recommendations engines for ecommerce web application and how can we overcome them ?

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• Should I comment Tables or Columns in my database?

  - by jako

  I like to comment my code with various information, and I think most people nowadays do so while writing some code. But when it comes to database tables or columns, I have never seen anyone setting some comments, and, to be honest, I don't even think of looking for comments there. So I am wondering if some people are commenting their DB strcuture here, and if I should bother commenting, for instance when I create a new column to an existing table?

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• Character Stats and Power

  - by Stephen Furlani

  I'm making an RPG game system and I'm having a hard time deciding on doing detailed or abstract character statistics. These statistics define the character's natural - not learned - abilities. For example: Mass Effect: 0 (None that I can see) X20 (Xtreme Dungeon Mastery): 1 "STAT" Diablo: 4 "Strength, Magic, Dexterity, Vitality" Pendragon: 5 "SIZ, STR, DEX, CON, APP" Dungeons & Dragons (3.x, 4e): 6 "Str, Dex, Con, Wis, Int, Cha" Fallout 3: 7 "S.P.E.C.I.A.L." RIFTS: 8 "IQ, ME, MA, PS, PP, PE, PB, Spd" Warhammer Fantasy Roleplay (1st ed?): 12-ish "WS, BS, S, T, Ag, Int, WP, Fel, A, Mag, IP, FP" HERO (5th ed): 14 "Str, Dex, Con, Body, Int, Ego, Pre, Com, PD, ED, Spd, Rec, END, STUN" The more stats, the more complex and detailed your character becomes. This comes with a trade-off however, because you usually only have limited resources to describe your character. D&D made this infamous with the whole min/max-ing thing where strong characters were typically not also smart. But also, a character with a high Str typically also has high Con, Defenses, Hit Points/Health. Without high numbers in all those other stats, they might as well not be strong since they wouldn't hold up well in hand-to-hand combat. So things like that force trade-offs within the category of strength. So my original (now rejected) idea was to force players into deciding between offensive and defensive stats: Might / Body Dexterity / Speed Wit / Wisdom Heart Soul But this left some stat's without "opposites" (or opposites that were easily defined). I'm leaning more towards the following: Body (Physical Prowess) Mind (Mental Prowess) Heart (Social Prowess) Soul (Spiritual Prowess) This will define a character with just 4 numbers. Everything else gets based off of these numbers, which means they're pretty important. There won't, however, be ways of describing characters who are fast, but not strong or smart, but absent minded. Instead of defining the character with these numbers, they'll be detailing their character by buying skills and powers like these: Quickness Add a +2 Bonus to Body Rolls when Dodging. for a character that wants to be faster, or the following for a big, tough character Body Building Add a +2 Bonus to Body Rolls when Lifting, Pushing, or Throwing objects. [EDIT - removed subjectiveness] So my actual questions is what are some pitfalls with a small stat list and a large amount of descriptive powers? Is this more difficult to port cross-platform (pen&paper, PC) for example? Are there examples of this being done well/poorly? Thanks,

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• Designing a large database with multiple sources

  - by CatchingMonkey

  I have been tasked with redesigning, or at worst optimising the structure of a database for a data warehouse. Currently, the database has 4 other source databases (which is due to expand to X number of others), all of which have their own data structures, naming conventions etc. At the moment an overnight SSIS package pulls the data from the various source and then for each source coverts the data into a standardised, usable format. These tables are then appended to each other creating a 60m row, 40 column beast!. This table is then used in a variety of ways from an OLAP cube to a web front end. The structure has been in place for a very long time, and the work I have been able to prove the advantages of normalisation, and this is the way I would like to go. The problem for me is that the overnight process takes so long I don't then want to spend additional time normalising the last table into something usable. Can anyone offer any insight or ideas into the best way to restructure or optimise the database efficiently? Edit: All the databases are MS SQL Server 2008 R2 Thanks in advance CM

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• Will it hurt my website's SEO friendliness if I host a french targetted website at, let's say, godaddy.com?

  - by Suraj

  Hi guys, I have read that the server location is important for a website to be SEO friendly. I am planning to build a website from scratch which is targetted mainly to french audience (in france), but I am planning to host the web site at godaddy.com. My concern is will it hurt the website SEO friendliness? Or do you recommend me to host the website in france itself? I have also read that I need to have a static IP Address. If it's true, can anyone explain me for what reason? Can anyone suggest me some good web hosting companies, prefereable in france? Thanks in advance!

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• Architecture for Social Graph data that has a Time Frame Associated?

  - by Jay Stevens

  I am adding some "social" type features to an existing application. There are a limited # of node & edge types. Overall the data itself is relatively small (50,000 - 70,000 for each type of node) there will be a number of edges (relationships) between them (almost all directional). This, I know, is relatively easy to represent with an SDF store (such as BrightstarDB) or something like Microsoft's Trinity (or really many of the noSQL options). The thing that, I think, makes this a unique use case is that each relationship will have a timeframe associated with it (start and end dates). Right now, I'm thinking of just storing this in a relational structure and dealing with the headaches of "traversing the graph", but I'm looking for suggestions on a better approach (both in terms of data structure and server): Column ================ From_Node_ID Relationship To_Node_ID StartDate EndDate Any suggestions or thoughts are welcomed.

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• What are the downsides to using dependency injection?

  - by kerry

  I recently came across an interesting question on stack overflow with some interesting reponses.  I like this post for three reasons. First, I am a big fan of dependency injection, it forces you to decouple your code, create cohesive interfaces, and should result in testable classes. Second, the author took the approach I usually do when trying to evaluate a technique or technology; suspend personal feelings and try to find some compelling arguments against it. Third, it proved that it is very difficult to come up with a compelling argument against dependency injection. What are the downsides to using dependency injection?

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• Using XML as data storage

  - by Kian Mayne

  I was thinking about the XML format and the following quote: “XML is not a database. It was never meant to be a database. It is never going to be a database. Relational databases are proven technology with more than 20 years of implementation experience. They are solid, stable, useful products. They are not going away. XML is a very useful technology for moving data between different databases or between databases and other programs. However, it is not itself a database. Don't use it like one.“ -Effective XML: 50 Specific Ways to Improve Your XML by Elliotte Rusty Harold (page 230, Part 4, Item 41, 2nd paragraph) This seems to really stress that XML should not be used for data storage and should only be used for program to program interoperability. Personally, I disagree and .NET's app.config file that's used to store a program's settings is an example of data storage in an XML file. However for databases rather than configurations etc XML should not be used. To develop my point, I will use two examples: A) Data about customers with fields that are all on one level i.e. there are a number of fields all relating to one customer with no children B) Data about configuration of an application where nested fields and properties make a lot of sense So my question is, Is this still a valid statement and is it now acceptable to store data using XML? EDIT: I've sent an email to the author of that quote to ask for his input/extra context.

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• How to refactor a Python “god class”?

  - by Zearin

  Problem I’m working on a Python project whose main class is a bit “God Object”. There are so friggin’ many attributes and methods! I want to refactor the class. So Far… For the first step, I want to do something relatively simple; but when I tried the most straightforward approach, it broke some tests and existing examples. Basically, the class has a loooong list of attributes—but I can clearly look over them and think, “These 5 attributes are related…These 8 are also related…and then there’s the rest.” getattr I basically just wanted to group the related attributes into a dict-like helper class. I had a feeling __getattr__ would be ideal for the job. So I moved the attributes to a separate class, and, sure enough, __getattr__ worked its magic perfectly well… At first. But then I tried running one of the examples. The example subclass tries to set one of these attributes directly (at the class level). But since the attribute was no longer “physically located” in the parent class, I got an error saying that the attribute did not exist. @property I then read up about the @property decorator. But then I also read that it creates problems for subclasses that want to do self.x = blah when x is a property of the parent class. Desired Have all client code continue to work using self.whatever, even if the parent’s whatever property is not “physically located” in the class (or instance) itself. Group related attributes into dict-like containers. Reduce the extreme noisiness of the code in the main class. For example, I don’t simply want to change this: larry = 2 curly = 'abcd' moe = self.doh() Into this: larry = something_else('larry') curly = something_else('curly') moe = yet_another_thing.moe() …because that’s still noisy. Although that successfully makes a simply attribute into something that can manage the data, the original had 3 variables and the tweaked version still has 3 variables. However, I would be fine with something like this: stooges = Stooges() And if a lookup for self.larry fails, something would check stooges and see if larry is there. (But it must also work if a subclass tries to do larry = 'blah' at the class level.) Summary Want to replace related groups of attributes in a parent class with a single attribute that stores all the data elsewhere Want to work with existing client code that uses (e.g.) larry = 'blah' at the class level Want to continue to allow subclasses to extend, override, and modify these refactored attributes without knowing anything has changed Is this possible? Or am I barking up the wrong tree?

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• Limit The Game Loop?

  - by user1758938

  How do I make a game go at the same speed? You probly dont understand that so here are examples: This Would Loop Too Fast while(true) { GetInput(); Render(); } This Just Wont Work, Hard To Exlplain while(true) { GetInput(); Render(); Sleep(16); } Basicly How Do I Sync It To Any FrameRate And Still Have To Input And Funtions Going At The Same Rate?

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