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• How to handle monetary values in PHP and MySql?

  - by Songo

  I've inherited a huge pile of legacy code written in PHP on top of a MySQL database. The thing I noticed is that the application uses doubles for storage and manipulation of data. Now I came across of numerous posts mentioning how double are not suited for monetary operations because of the rounding errors. However, I have yet to come across a complete solution to how monetary values should be handled in PHP code and stored in a MySQL database. Is there a best practice when it comes to handling money specifically in PHP? Things I'm looking for are: How should the data be stored in the database? column type? size? How should the data be handling in normal addition, subtraction. multiplication or division? When should I round the values? How much rounding is acceptable if any? Is there a difference between handling large monetary values and low ones? Note: A VERY simplified sample code of how I might encounter money values in everyday life: $a= $_POST['price_in_dollars']; //-->(ex: 25.06) will be read as a string should it be cast to double? $b= $_POST['discount_rate'];//-->(ex: 0.35) value will always be less than 1 $valueToBeStored= $a * $b; //--> any hint here is welcomed $valueFromDatabase= $row['price']; //--> price column in database could be double, decimal,...etc. $priceToPrint=$valueFromDatabase * 0.25; //again cast needed or not? I hope you use this sample code as a means to bring out more use cases and not to take it literally of course. Bonus Question If I'm to use an ORM such as Doctrine or PROPEL, how different will it be to use money in my code.

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• What is a 'good number' of exceptions to implement for my library?

  - by Fuzz

  I've always wondered how many different exception classes I should implement and throw for various pieces of my software. My particular development is usually C++/C#/Java related, but I believe this is a question for all languages. I want to understand what is a good number of different exceptions to throw, and what the developer community expect of a good library. The trade-offs I see include: More exception classes can allow very fine grain levels of error handling for API users (prone to user configuration or data errors, or files not being found) More exception classes allows error specific information to be embedded in the exception, rather than just a string message or error code More exception classes can mean more code maintenance More exception classes can mean the API is less approachable to users The scenarios I wish to understand exception usage in include: During 'configuration' stage, which might include loading files or setting parameters During an 'operation' type phase where the library might be running tasks and doing some work, perhaps in another thread Other patterns of error reporting without using exceptions, or less exceptions (as a comparison) might include: Less exceptions, but embedding an error code that can be used as a lookup Returning error codes and flags directly from functions (sometimes not possible from threads) Implemented an event or callback system upon error (avoids stack unwinding) As developers, what do you prefer to see? If there are MANY exceptions, do you bother error handling them separately anyway? Do you have a preference for error handling types depending on the stage of operation?

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• Expiring timed actions a good idea?

  - by Bart van Heukelom

  We have an online game where players sometimes have to wait a while (say 30 minutes) before a process they intiated completes. This encourages them to come back later. An example of this is growing crops in Farmville or basically any action in the Sims Play4Free. Now, however, there is the idea to let these processes expire, so if the player doesn't 'reap' them in time (e.g. within 4 hours) they are aborted. I'm a bit sceptical about this. How will this make players come back more often? Is not the reward of reaping the process enough for that? Can we expect players to fit their daily schedule around our game, maybe even set the alarm clock at night? Won't this just cause players to give up on starting these processes in the first place? I realise this may be too subjective for this site, so I'll end with a concrete question: Do (m)any other online free-to-play games employ this technique?

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• Cliché monsters to populate a steampunk fantasy setting dwarven dungeon?

  - by Alexander Gladysh

  I'm looking for a list of cliché monsters for a steampunk computer game (assume one kind or another of casual rogue-like RPG), to populate lower levels of ancient dwarven-built dungeons. Dwarves are a technology/science race in the setting I am aiming for. The world is a low-magic one. I'm stuck after listing various mechanical golems, gigantic spiders (every dungeon must have some of them!), and maybe a mechanical barlog as a megaboss. What would player expect? What are the key cultural references for such setting? I know a couple of games with suitable steampunk dwarves, but none are detailed enough in the underworld monsters area. Please point me in the right direction. (If you have a single funny monster suggestion, please mention it in comments, not in answer. ;-) )

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• Level Representation in a 2D Game

  - by meszar.imola

  I would like to create a 2D game, where a character should move on a stage/level. My stage would be static, constructed some little cubes, similar to the well-known Mario game: some of the elements should represent an element of the way where the character can step, but if the element is missing, the character should fall. My problem is, how to represent this programmatically? My first thought was to represent the stage with a vector, which should contain boolean elements, depending on the state of the element on the stage - if it's missing or not. But this means, I have to verify at my character's x or y position change if it has a stage element under or not (if not, to simulate the falling of the character) - I think it is not the best practice, it's not the beautiful solution. Can you help me with some advice, how to represent the stage?

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• Using 'new' in a projection?

  - by davenewza

  I wish to project a collection from one type (Something) to another type (SomethingElse). Yes, this is a very open-eneded question, but which of the two options below do you prefer? Creating a new instance using new: var result = query.Select(something => new SomethingElse(something)); Using a factory: var result = query.Select(something => SomethingElse.FromSomething(something)); When I think of a projection, I generally think of it as a conversion. Using new gives me this idea that I'm creating new objects during a conversion, which doesn't feel right. Semantically, SomethingElse.FromSomething() most definitely fits better. Although, the second option does require addition code to setup a factory, which could become unnecessarily compulsive.

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• Is there an antipattern to describe this method of coding?

  - by P.Brian.Mackey

  I have a codebase where the programmer tended to wrap things up in areas that don't make sense. For example, given an Error log we have you can log via ErrorLog.Log(ex, "friendly message"); He added various other means to accomplish the exact same task. E.G. SomeClass.Log(ex, "friendly message"); Which simply turns around and calls the first method. This adds levels of complexity with no added benefit. Is there an anti-pattern to describe this?

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• Designing a simple snake A.I

  - by DillPixel

  I've looked at some stuff online regarding this specific topic, and a lot of the info that I read involved graphs and path finding. I really don't want to get involved in something too complex & out of my level, and also I don't need my snake to be that intelligent (it will be a large board with the snake not growing in size on every munch). How could you structure a simpler AI for the snake that gets the job done relatively well? I would be able to get the snake to move towards the food item correctly, but my issue is that I'm not sure how to deal with the snake colliding with itself. Say the snake has a look ahead, and it finds that its tail is in the way, it could change direction, but what happens next? Any ideas on how to tackle this? Should the snake build an instruction set from every square, or should it think on the go?

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• Does MVC apply only to web

  - by Deeptechtons

  It is almost and instantaneous whenever I talk to developers about Model View Controller (MVC) they say you make a request to a url the server builds a entity (MODEL) and provides you with visual representation of that model. So does this mean MVC is only for the web or have I been meeting people who are just developers who employ MVC for writing web applications? Are there usages for MVC on desktop style applications? I for one am new to paradigm and would like to know of any super-set to MVC

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• The balance between client and server functionality

  - by Eugen Martynov

  I want to bring the discussion that started in our teams and get your opinion about it. Assume we have an user account which could have different credentials for authentication and associated email to recover. An user has possibility to do signup with an email or use his social profile to complete signup process. As an Rest API from the backend to client looks like: Create account Authorise Update user data Link social account Register email Verify email In addition our BE is distributed and divided between several services/servers/clusters. So different calls are related to different end points. In case of the social sign up some of steps should be skipped or simplified. For example, with Facebook signup we could already skip email registration and verification step (we ask email permission form user), linking the social account and pre-fill user displayed name. So we proposed to have another end point which will hide/combine different calls on BE and return whole process result to the clients. The pros for this approach: No more duplication of functionality between clients Speed up the networking and user experience The cons for this approach: Additional work for backend Probably most complex scenarios in future updates I would like to get your opinion or experience with this situation. Especially if you already experienced point #2 from against reasons.

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• Is acoustic fingerprinting too broad for one audio file only?

  - by IBG

  We were looking for some topics related to audio analysis and found acoustic fingerprinting. As it is, it seems like the most famous application for it is for identification of music. Enter our manager, who requested us to research and possible find an algorithm or existing code that we can use for this very simple approach (like it's easy, source codes don't show up like mushrooms): Always-on app for listening Compare the audio patterns to a single audio file (assume sound is a simple beep) If beep is detected, send notification to server With a flow this simple, do you think acoustic fingerprinting is a broad approach to use? Should we stop and take another approach? Where to best start? We haven't started anything yet (on the development side) on this regard, so I want to get other opinion if this is pursuit is worth it or moot.

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• ASP.NET MVC 3 (C#) Software Architecture

  - by ryanzec

  I am starting on a relatively large and ambitious ASP.NET MVC 3 project and just thinking about the best way to organize my code. The project is basically going to be a general management system that will be capable of supporting any type management system whether it be a blogging system, cms, reservation system, wikis, forums, project management system, etc…, each of them being just a separate 'module'. You can read more about it on my blog posted here : http://www.ryanzec.com/index.php/blog/details/8 (forgive me, the style of the site kinda sucks). For those who don't want to read the long blog post the basic idea is that the core system itself is nothing more than a users system with an admin interface to manage the users system. Then you just add on module as you need them and the module I will be creating is a simple blog post to test it out before I move on to the big module which is a project management system. Now I am just trying to think of the best way to structure this so that it is easy for users to add in there own modules but easy for me to update to core system without worrying about the user modifying the core code. I think the ideal way would be to have a number of core projects that user is specifically told not to modify otherwise the system may become unstable and future updates would not work. When the user wants to add in there own modules, they would just add in a new project (or multiple projects). The thing is I am not sure that it is even possible to use multiple projects all with their own controllers, razor view template, css, javascript, etc... in one web application. Ideally each module would have some of it own razor view templates, css, javascript, image files and also need access to some of the core razor view templates, css, javascript, image files which would is in a separate project. It is possible to have 1 web application run off of controllers, razor view templates, css, javascript, image files that are store in multiple projects? Is there a better was to structure this to allow the user to easily add in module with having to modify the core code?

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• How to determine if class meets single responsibility principle ?

  - by user1483278

  Single Responsibility Principle is based on high cohesion principle. The difference between the two is that highly cohesive classes feature a set of responsibilities that are strongly related, while classes adhering to SRP have just one responsibility. But how do we determine whether particular class features a set of responsibilities and is thus just highly cohesive, or whether it has only one responsibility and is thus adhering to SRP? Namely, isn't it more or less subjective, since some may find class very granular ( and as such will consider a class as adhering to SRP ), while others may find it not granular enough?

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• I need an approach to the problem of preventing inserting duplicate records into the database

  - by Maurice

  Apologies is this question is asked on the incorrect "stack" A webservice that I call returns a list of data. The data from the webservice is updated periodically, so a call to the webservice done in one hour could return the same data as a call done in an hour. Also, the data is returned based on a start and end date. We have multiple users that can run the webservice search, and duplicate data is most likely to be returned (especially for historical data). However I don't want to insert this duplicate data in the database. I've created a db table in which the data is stored (most important columns are) Id int autoincrement PK Date date not null --The date to which the data set belongs. LastUpdate date not null --The date the data set was last updated. UserName varchar(50) --The name of the user doing the search. I use sql server 2008 express with c# 4.0 and visual studio 2010. Entity Framework is used as the ORM. If stored procedures could be avoided in the proposed solution, then that will be a plus. Another way of looking interpreting what I'm asking a solution for is as follows: I have a million unique records in my table. A user does a new search. The search results from the user contains around 300k of the data that is already in the db. An efficient solution to finding an inserting only the unique records is needed.

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• Traverse tree with results. Maybe type in Java?

  - by Angelo.Hannes

  I need to check a tree's node state. It can either be OK or NOT_OK. But that state is dependent on its children. So for a node to be OK, every of its children needs to be OK. If one or more of its children is NOT_OK the whole node is NOT_OK. To determine the state of a node I need to aggregate some properties of the node. So I thought of two possible implementations. And they are more or less covered in this question: Why is Option/Maybe considered a good idea and checked exceptions are not? Exception I could pass the properties up the recursion path, and throw an exception if something went wrong. Maybe I implement an Maybe type and let it either hold an error or the aggregated properties. Maybe it is more an Either. I tend towards the last option. And I'm thinking of an enum with two objects. Where I can additionally set those aggregated properties. Am I on the right track? I'm not familiar with the new JDK8 functional stuff. But I'm stuck on JDK7 anyway, so please focus on JDK7.

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• Implementing traffic conditions in TORCS

  - by user1837811

  I am working on a project about "Effects of Traffic conditions and Track Complexity on Car Driving Behavior". Is it possible to implement traffic in TORCS, or should I use another car simulator? By the word "traffic" I mean there are cars running on both tracks in both directions and I can detect the distances, direction and speed of these cars. Depending on this information I can decide whether I should slow down, speed up and calculate the correct timing to overtake.

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• Is programming in layers real?

  - by Aura

  I am fairly new in product development and I am trying to work over a product. The problem that I have realized is that people draw diagrams and charts showing different modules and layers. But as I am working alone (I am my own team) I got a bit confused about the interaction I am facing in the development within the programs and I am wondering whether developing a product in modules is real or not? Maybe I am not a great programmer, but I see no boundaries when data start to travel from frontend to backend.

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• Should developers make their games easier with new versions?

  - by Gil Kalai

  It seems that the game Angry Birds is becoming gradually easier with new versions. Maybe so people get the illusion of progress and satisfaction of breaking new records? I would like to know if gradual small modifications of games to enhance the sense of improvement and learning by users is known/common/standard practice in game developing. (I don't mean to say that there is anything wrong with such a practice.)

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• Why do most programming languages only support returning a single value from a function?

  - by M4N

  Is there a reason or an explanation why functions in most(?) programming languages are designed to support any number of input parameters but only one return value? In most languages, it is possible to "work around" that limitation, e.g. by using out-parameters, returning pointers or by defining/returning structs/classes. But it seems strange, that programming languages were not designed to support multiple return values in a more "natural" way.

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• What are good ways to find collaborators for a coding weekend?

  - by tarrasch

  Not sure if this belongs here, feel free to push it somewhere else if needed. When i was at university we would sometimes come together into a room full of beer and fast food and crank out software in a weekend. Unfortunately the group has kind of split up and its just not possible any more. My question is now: Where can i find like-minded people on the Internet that would like to do something like this? I have an idea what i wanted to do next, but of course other people have ideas too.

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• Trying to make a universe [on hold]

  - by caters

  I am wanting to program a universe so that it starts with a big bang and atoms form and then molecules form and stars start to form and planets start to form and then moons around those planets. I have a few questions. If 400 IPMUs(In Program Mass Units) = 1 solar mass than how would I calculate the number of IPMUs for a spectral class of star given the range of solar masses for a main sequence star in that spectral class? How can I have planets not look like stars? Since whether it is a subdwarf, main sequence star, subgiant, giant, bright giant, supergiant, or hypergiant is mainly dependent on the radius and luminosity how can I have the radius and luminosity independent of the mass?

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• Options for Application Registry

  - by Matt Felzani

  I work for a small software company (about 200 people building 8-10 applications) and I was hoping to get some advice on products that might be out there to manage the information of which clients are using which versions of our products? The most fundamental relationship would be that a "product" has "versions" and a given "version" is used by a "client." Uses would be: Determine which clients use which products Determine which clients are on which versions of a product Determine which clients are exposed to which vulnerabilities because of the version they use Determine which clients cannot move to a new version because of a vulnerability in the new version that they may hit Determine which clients should be approached for an upgrade Any thoughts or product reviews would be greatly appreciated! Thanks in advance.

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• Help identify the pattern for reacting on updates

  - by Mike

  There's an entity that gets updated from external sources. Update events are at random intervals. And the entity has to be processed once updated. Multiple updates may be multiplexed. In other words there's a need for the most current state of entity to be processed. There's a point of no-return during processing where the current state (and the state is consistent i.e. no partial update is made) of entity is saved somewhere else and processing goes on independently of any arriving updates. Every consequent set of updates has to trigger processing i.e. system should not forget about updates. And for each entity there should be no more than one running processing (before the point of no-return) i.e. the entity state should not be processed more than once. So what I'm looking for is a pattern to cancel current processing before the point of no return or abandon processing results if an update arrives. The main challenge is to minimize race conditions and maintain integrity. The entity sits mainly in database with some files on disk. And the system is in .NET with web-services and message queues. What comes to my mind is a database queue-like table. An arriving update inserts row in that table and the processing is launched. The processing gathers necessary data before the point of no-return and once it reaches this barrier it looks into the queue table and checks whether there're more recent updates for the entity. If there are new updates the processing simply shuts down and its data is discarded. Otherwise the processing data is persisted and it goes beyond the point of no-return. Though it looks like a solution to me it is not quite elegant and I believe this scenario may be supported by some sort of middleware. If I would use message queues for this then there's a need to access the queue API in the point of no-return to check for the existence of new messages. And this approach also lacks elegance. Is there a name for this pattern and an existing solution?

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• How do you prevent inflation in a virtual economy?

  - by Tetrad

  With your typical MMORPG, players can usually farm the world for raw materials essentially forever. Monsters/mineral veins/etc are usually on some respawn timer so, other than time, there really isn't a good way to limit the amount of new currency entering the system. So that really only leaves money sinks to try to take money out of the system. What are some strategies to prevent inflation of the in-game currency?

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• How to implement "bullet time" in a multiplayer game?

  - by Tom

  I have never seen such a feature before, but it should provide an interesting gameplay opportunity. So yes, in a multiplayer/real-time environment (imagine FPS), how could I implement a slow motion/bullet time effect? Something like an illusion for the player that's currently slo-mo'ed. So everybody sees him "real-time", but he sees everything slowed down. Update A sidenote: keep in mind that a FPS game has to be balanced in order for it to be fun. So yes, this bullet time feature has to be solid, giving a small advantage to the "player", while not taking away from other players. Plus, there is a possibility that two players could activate their bullet time at the same time. Furthermore: I'm going to implement this in the future no matter what it takes. And, the idea is to build a whole new game engine for all this. If that gives new options, I'm more then interested in hearing the ideas. Meanwhile, here with my team we're thinking about this too, when our theory will be crafted, I'm going to share it here. Is this even possible? So, the question on "is this even possible" has been answered, now it's time to find the best solution. I'm keeping the "answer" until something exceptionally good comes up, like a prototype theory with something close to working pseudo code.

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