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• Need alternative field names for these reserved words

  - by MattSlay

  “type” and “class” are likely reserved or problematic words in C# and/or Ruby, two languages I may use to program against my new database schema in the future. So, in order to avoid potential conflicts with those languages, I’m looking for alternative names for these field names in my tables. In this case, it is from my Machines table, where I have: “class” field (values would be something like “manual” or “computerized”) and “type” field (values would be “lathe” or “mill”) I could call the fields “machineclass” and “machinetype”, but that is inconsistent with naming scheme in the rest of my schema (meaning, I do not re-use the table name in the field… For instance, I use Machine.name, not Machine.machinename) Any thought on this madness?

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• What division operator symbol would you pick?

  - by Mackenzie

  I am currently designing and implementing a small programming language as an extra-credit project in a class I'm taking. My problem is that the language has three numeric types: Long, Double, and Fraction. Fractions can be written in the language as proper or improper fractions (e.g. "2 1/3" or "1/2"). This fact leads to problems such as "2/3.5" (Long/Double) and "2/3"(Long/Long) not being handled correctly by the lexer.The best solution that I see is to change the division operator. So far, I think "\" is the best solution since "//" starts comments. Would you pick "\", if you were designing the language? Would you pick something else? If so, what? Note: changing the way fractions are written is not possible. Thanks in advance for your help,

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• Why do Pascal control structures appear to be inconsistent?

  - by 70Mike

  Most Pascal control structures make sense to me, like: for ... do {statement}; if (condition) then {statement}; while (condition) do {statement}; where the {statement} is either a single statement, or a begin ... end block. I have a problem with: repeat {statement-list} until (expression); try {statement-list} except {statement-list} end; Wouldn't it be better that repeat and try have the same general structure, accepting only a single statement or a begin ... end block, instead of having a statement-list that's not formally blocked with a begin and an end?

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• Using inheritance and polymorphism to solve a common game problem

  - by Barry Brown

  I have two classes; let's call them Ogre and Wizard. (All fields are public to make the example easier to type in.) public class Ogre { int weight; int height; int axeLength; } public class Wizard { int age; int IQ; int height; } In each class I can create a method called, say, battle() that will determine who will win if an Ogre meets and Ogre or a Wizard meets a Wizard. Here's an example. If an Ogre meets an Ogre, the heavier one wins. But if the weight is the same, the one with the longer axe wins. public Ogre battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else if (this.axeLength > o.axeLength) return this; else if (this.axeLength < o.axeLength) return o; else return this; // default case } We can make a similar method for Wizards. But what if a Wizard meets an Ogre? We could of course make a method for that, comparing, say, just the heights. public Wizard battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else return this; } And we'd make a similar one for Ogres that meet Wizard. But things get out of hand if we have to add more character types to the program. This is where I get stuck. One obvious solution is to create a Character class with the common traits. Ogre and Wizard inherit from the Character and extend it to include the other traits that define each one. public class Character { int height; public Character battle(Character c) { if (this.height > c.height) return this; else if (this.height < c.height) return c; else return this; } } Is there a better way to organize the classes? I've looked at the strategy pattern and the mediator pattern, but I'm not sure how either of them (if any) could help here. My goal is to reach some kind of common battle method, so that if an Ogre meets an Ogre it uses the Ogre-vs-Ogre battle, but if an Ogre meets a Wizard, it uses a more generic one. Further, what if the characters that meet share no common traits? How can we decide who wins a battle?

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• Implementing the procducer-consumer with .NET 4.0 new

  - by bitbonk

  With alle the new paralell programming features in .NET 4.0, what would be a a simple and fast way to implement the producer-consumer pattern (where at least one thread is producing and enqueuing task items and one other thread executes (dequeues) these tasks). Can we benfit from all these new APIs? What is your preferred implementation of this pattern?

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• Use of base class object by child class reference - java

  - by JavaUser

  Hi, What is the use of creating base class object using child class reference in Java

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• capturing user identity for an online application

  - by Samuel

  We are designing an online application (college admission form) which mandates the user to upload a scanned copy of his photo along with his signature, so that this information can be used to cross verify the applicant when he appears for a exam + personal interview at a later point in time. This entire process requires a scanner for the applicant to scan his photo / signature into an appropriate size. Is there a better way to capture user identity for such purposes as usage of scanner for capturing signature, photo is a painful process.

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• Calling DI Container directly in method code (MVC Actions)

  - by fearofawhackplanet

  I'm playing with DI (using Unity). I've learned how to do Constructor and Property injection. I have a static container exposed through a property in my Global.asax file (MvcApplication class). I have a need for a number of different objects in my Controller. It doesn't seem right to inject these throught the constructor, partly because of the high quantity of them, and partly because they are only needed in some Actions methods. The question is, is there anything wrong with just calling my container directly from within the Action methods? public ActionResult Foo() { IBar bar = (Bar)MvcApplication.Container.Resolve(IBar); // ... Bar uses a default constructor, I'm not actually doing any // injection here, I'm just telling my conatiner to give me Bar // when I ask for IBar so I can hide the existence of the concrete // Bar from my Controller. } This seems the simplest and most efficient way of doing things, but I've never seen an example used in this way. Is there anything wrong with this? Am I missing the concept in some way?

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• Are there any MVP Frameworks projects out there?

  - by Greg Malcolm

  MVC is used a number of popular frameworks. To name just a few, Ruby on Rails, ASP.NET MVC, Monorail, Spring MVC. Are there any equivalent frameworks using any variant of MVP? Most of the examples I've found online seem to be custom implementations of the pattern rather than reusable frameworks. Suggestions need not be specific to any particular programming language, my interest is mostly academic.

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• How to color textblock on mouse over?

  - by DeanMc

  I'm looking to see if there is a way to change the color of a textblock in silverlight on mouse over. I have tried a trigger which I read now doesn't work. I would like to avoid having to do it in the codebehind if at all possible.

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• Saving Abstract and Sub classes to database

  - by bretddog

  Hi, I have an abstract class "StrategyBase", and a set of sub classes, StrategyA/B/C etc. The sub classes use some of the properties of the base class, and have some individual properties. My question is how to save this to a database. I'm currently using SqlCE, and Linq-To-Sql by creating entity classes automatically with SqlMetal.exe. I've seen there are three solutions shown in this question, but I'm not able to see how these solutions will work or not with SqlMetal/entity classes. Though it seems to me the "concrete table inheritance" would probably work without any manual modifying. What about the other two, would they be problematic? For "Single Table Inheritance" wouldn't all classes get all variables, even though they don't need them? And for the "Class table inheritance" solution I can't really see at all how that will map into the entity-classes for a useful purpose. I may note that I extend these partial entity classes for making the classes of my business objects. I may also consider moving to EntityFramework instead of SqlMetal/Linq2Sql, so would be nice also to know if that makes any difference to what schema is easy to implement. One likely important thing to note is that I will constantly be develop new strategies, which makes me have to modify the program code, and probably the database shcema; when adding a new strategy. Sorry the question is a bit "all over the place", but hopefully it's some clear advantages/disadvantages here that you may be able to advice. ? Cheers!

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• Do I have to create a static library to test my application?

  - by Christopher Gateley

  I'm just getting started with TDD and am curious as to what approaches others take to run their tests. For reference, I am using the google testing framework, but I believe the question is applicable to most other testing frameworks and to languages other than C/C++. My general approach so far has been to do either one of three things: Write the majority of the application in a static library, then create two executables. One executable is the application itself, while the other is the test runner with all of the tests. Both link to the static library. Embed the testing code directly into the application itself, and enable or disable the testing code using compiler flags. This is probably the best approach I've used so far, but clutters up the code a bit. Embed the testing code directly into the application itself, and, given certain command-line switches either run the application itself or run the tests embedded in the application. None of these solutions are particularly elegant... How do you do it?

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• Placement of defensive structures in a game

  - by Martin

  I am working on an AI bot for the game Defcon. The game has cities, with varying populations, and defensive structures with limited range. I'm trying to work out a good algorithm for placing defence towers. Cities with higher populations are more important to defend Losing a defence tower is a blow, so towers should be placed reasonably close together Towers and cities can only be placed on land So, with these three rules, we see that the best kind of placement is towers being placed in a ring around the largest population areas (although I don't want an algorithm just to blindly place a ring around the highest area of population, sometime there might be 2 sets of cities far apart, in which case the algorithm should make 2 circles, each one half my total towers). I'm wondering what kind of algorithms might be used for determining placement of towers?

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• MVC and conditional formatting - strategies for implementation

  - by Extrakun

  Right now I am writing a simulation program which output is formatted according to certain factors. The question is in a MVC architecture, where is the conditional formatting to be taken place? What are some strategies for implement this feature? FYI, The platform I am using is rather bare-bone in its GUI/front-end execution. To change color and formatting, it requires a change to the formatting state (much like OpenGL).

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• JavaScript inheritance

  - by Tower

  Hi, Douglas Crockford seems to like the following inheritance approach: if (typeof Object.create !== 'function') { Object.create = function (o) { function F() {} F.prototype = o; return new F(); }; } newObject = Object.create(oldObject); It looks OK to me, but how does it differ from John Resig's simple inheritance approach? Basically it goes down to newObject = Object.create(oldObject); versus newObject = Object.extend(); And I am interested in theories. Implementation wise there does not seem to be much difference.

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• Primary key/foreign Key naming convention

  - by Jeremy

  In our dev group we have a raging debate regarding the naming convention for Primary and Foreign Keys. There's basically two schools of thought in our group: 1) Primary Table (Employee) Primary Key is called ID Foreign table (Event) Foreign key is called EmployeeID 2) Primary Table (Employee) Primary Key is called EmployeeID Foreign table (Event) Foreign key is called EmployeeID I prefer not to duplicate the name of the table in any of the columns (So I prefer option 1 above). Conceptually, it is consisted with a lot of the recommended practices in other languages, where you don't use the name of the object in its property names. I think that naming the foreign key EmployeeID (or Employee_ID might be better) tells the reader that it is the ID column of the Employee Table. Some others prefer option 2 where you name the primary key prefixed with the table name so that the column name is the same throughout the database. I see that point, but you now can not visually distinguish a primary key from a foreign key. Also, I think it's redundant to have the table name in the column name, because if you think of the table as an entity and a column as a property or attribute of that entity, you think of it as the ID attribute of the Employee, not the EmployeeID attribute of an employee. I don't go an ask my coworker what his PersonAge or PersonGender is. I ask him what his Age is. So like I said, it's a raging debate and we go on and on and on about it. I'm interested to get some new perspective.

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• Planning a database app

  - by ChrisC

  I am in the planning stages of a database app for personal use. I have a good bit of the database structure planned, but as I think about how I'm going to write the program, it made me wonder if I'm doing this in the right order. Which should I be planning first, the db structure or the classes?

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• Good tool to visualise database schema?

  - by Mat

  Are there any good tools for visualising a pre-existing database schema? I'm using MySQL if it matters. I'm currently using MySQL Workbench to process an SQL create script dump, but it's clunky, slow and a manual process to drag all the tables about (which would be okay if it wasn't so slow).

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• Meta Search Engine Architecture

  - by Loki

  The question wasn't clear enough, I think; here's an updated straight to the point question: What are the common architectures used in building a meta search engine and is there any libraries available to build that type of search engine? I'm looking at building an "enterprise" type of search engine where the indexed data could be coming from proprietary (like Autonomy or a Google Box) or public search engines (like Google Web or Yahoo Web).

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• Vertex Buffers in opengl

  - by JB

  I'm making a small 3d graphics game/demo for personal learning. I know d3d9 and quite a bit about d3d11 but little about opengl at the moment so I'm intending to abstract out the actual rendering of the graphics so that my scene graph and everything "above" it needs to know little about how to actually draw the graphics. I intend to make it work with d3d9 then add d3d11 support and finally opengl support. Just as a learning exercise to learn about 3d graphics and abstraction. I don't know much about opengl at this point though, and don't want my abstract interface to expose anything that isn't simple to implement in opengl. Specifically I'm looking at vertex buffers. In d3d they are essentially an array of structures, but looking at the opengl interface the equivalent seems to be vertex arrays. However these seem to be organised rather differently where you need a separate array for vertices, one for normals, one for texture coordinates etc and set the with glVertexPointer, glTexCoordPointer etc. I was hoping to be able to implement a VertexBuffer interface much like the the directx one but it looks like in d3d you have an array of structures and in opengl you need a separate array for each element which makes finding a common abstraction quite hard to make efficient. Is there any way to use opengl in a similar way to directx? Or any suggestions on how to come up with a higher level abstraction that will work efficiently with both systems?

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• Database: Storing Dates as Numeric Values

  - by Chin

  I'm considering storing some date values as ints. i.e 201003150900 Excepting the fact that I lose any timezone information, is there anything else I should be concerned about with his solution? Any queries using this column would be simple 'where after or before' type lookups. i.e Where datefield is less than 201103000000 (before March next year). currently the app is using MSSQL2005. Any pointers to pitfalls appreciated.

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• Upgrade .NET 1.1 WinForm/Service to what?

  - by Conor

  Hi Folks, We have a current WinForm/Windows Service running in .NET 1.1 out on various customer sites that is getting data from internal systems, transforming it and then calling a Web Service synchronously. This client app will no longer work in Vista or Windows 7 etc.. and its time to update!! I was looking for ideas on what I could do here, I didn't write the App and I have the Business team telling me they want the world but I need to be realistic :) Things the service must be able to do: - Handle multiple formats from internal system and transform to a schema SAP, ERP etc.. - Run silently and just work on customer sites (it does currently albeit .NET 1.1) - The Customers are unable to call our web service from their sites as they are not technical enough. - Upgrade it's self when updates occur (currently don't have this capability) Is there anything I can do here other than upgrade the service to run in .NET and add a few more transformation capabilities e..g they want the customer to be able to give us a flat file, an xml file, a csv and the service transforms it and calls the Web Service? I was hoping in this day and age we could use the Web, but automating this 100% rules it out in my eyes? I could be totally wrong!! Any help would be gratefully appreciated! Cheers. Conor

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• How to create a view and update it later?

  - by Tommy

  Is it possible to update the same view with new data? Using UPDATE after CREATE didn't seem to work. Create view ID 1-10 if it does not exist. . . // . // . Update view **ID** 2-10 Any help is appreciated.

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• Should I use custom exceptions to control the flow of application?

  - by bonefisher

  Is it a good practise to use custom business exceptions (e.g. BusinessRuleViolationException) to control the flow of user-errors/user-incorrect-inputs??? The classic approach: I have a web service, where I have 2 methods, one is the 'checker' (UsernameAlreadyExists()) and the other one is 'creator' (CreateUsername())... So if I want to create a username, I have to do 2 roundtrips to webservice, 1.check, 2.if check is OK, create. What about using UsernameAlreadyExistsException? So I call only the 2. web service method (CrateUsername()), which contains the check and if not successfull, it throws the UsernameAlreadyExistsException. So the end goal is to have only one round trip to web service and the checking can be contained also in other web service methods (so I avoid calling the UsernameAlreadyExists() all the times..). Furthermore I can use this kind of business error handling with other web service calls completely avoiding the checking prior the call.

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• Cleanly handling events

  - by nkr1pt

  I have code similar to this in all my observer classes that handle events fired by an event bus class. As you can see there are a lot of instanceof checks to choose the path of action needed to appropriately handle events, and I was wondering if this could be done more cleanly, eliminating the instanceof tests? @Override public void handleEvent(Event event) { if (event instanceof DownloadStartedEvent) { DownloadStartedEvent dsEvent = (DownloadStartedEvent)event; dsEvent.getDownloadCandidateItem().setState(new BusyDownloadingState()); } else if (event instanceof DownloadCompletedEvent) { DownloadCompletedEvent dcEvent = (DownloadCompletedEvent)event; dcEvent.getDownloadCandidateItem().setState(new FinishedDownloadingState()); DownloadCandidate downloadCandidate = dcEvent.getDownloadCandidateItem(). getDownloadCandidate(); if (downloadCandidate.isComplete()) { // start extracting } } else if (event instanceof DownloadFailedEvent) { DownloadFailedEvent dfEvent = (DownloadFailedEvent)event; dfEvent.getDownloadCandidateItem().setState(new FailedDownloadingState()); } }

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