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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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• Collision Systems Implementation

  - by hrr4

  Just curious what might be a good way to implement a decent collision system. As a class inherited by a base Entity class? Currently I'm stuck and could just use a couple better ideas than my own. Any help is appreciated! Edit: Sorry, it's 2D Collisioning but honestly, I'm not looking for specific collision methods. I'm looking more about the lines of implementation. Just curious of some of the common methods of how to implement collision systems such as: Should the entire collision system be it's own class? What, if anything, should be inheritable? These are some of my questions. Sorry for the confusion.

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• How to Structure a Trinary state in DB and Application

  - by ABMagil

  How should I structure, in the DB especially, but also in the application, a trinary state? For instance, I have user feedback records which need to be reviewed before they are presented to the general public. This means a feedback reviewer must see the unreviewed feedback, then approve or reject them. I can think of a couple ways to represent this: Two boolean flags: Seen/Unseen and Approved/Rejected. This is the simplest and probably the smallest database solution (presumably boolean fields are simple bits). The downside is that there are really only three states I care about (unseen/approved/rejected) and this creates four states, including one I don't care about (a record which is seen but not approved or rejected is essentially unseen). String column in the DB with constants/enum in application. Using Rating::APPROVED_STATE within the application and letting it equal whatever it wants in the DB. This is a larger column in the db and I'm concerned about doing string comparisons whenever I need these records. Perhaps mitigatable with an index? Single boolean column, but allow nulls. A true is approved, a false is rejected. A null is unseen. Not sure the pros/cons of this solution. What are the rules I should use to guide my choice? I'm already thinking in terms of DB size and the cost of finding records based on state, as well as the readability of code the ends up using this structure.

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• What is MVC, really?

  - by NickC

  As a serious programmer, how do you answer the question What is MVC? In my mind, MVC is sort of a nebulous topic — and because of that, if your audience is a learner, then you're free to describe it in general terms that are unlikely to be controversial. However, if you are speaking to a knowledgeable audience, especially an interviewer, I have a hard time thinking of a direction to take that doesn't risk a reaction of "well that's not right!...". We all have different real-world experience, and I haven't truly met the same MVC implementation pattern twice. Specifically, there seem to be disagreements regarding strictness, component definition, separation of parts (what piece fits where), etc. So, how should I explain MVC in a way that is correct, concise, and uncontroversial?

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• Layout Columns - Equal Height

  - by Kyle

  I remember first starting out using tables for layouts and learned that I should not be doing that. I am working on a new site and can not seem to do equal height columns without using tables. Here is an example of the attempt with div tags. <div class="row"> <div class="column">column1</div> <div class="column">column2</div> <div class="column">column3</div> <div style="clear:both"></div> </div> Now what I tried with that was doing making columns float left and setting their widths to 33% which works fine, I use the clear:both div so that the row would be the size of the biggest column, but the columns will be different sizes based on how much content they have. I have found many fixes which mostly involve css hacks and just making it look like its right but that's not what I want. I thought of just doing it in javascript but then it would look different for those who choose to disable their javascript. The only true way of doing it that I can think of is using tables since the cells all have equal heights in the same row. But I know its bad to use tables. After searching forever I than came across this: http://intangiblestyle.com/lab/equal-height-columns-with-css/ What it seems to do is exactly the same as tables since its just setting its display exactly like tables. Would using that be just as bad as using tables? I honestly can't find anything else that I could do. edit @Su' I have looked into "faux columns" and do not think that is what I want. I think I would be able to implement better designs for my site using the display:table method. I posted this question because I just wasn't sure if I should since I have always heard its bad using tables in website layouts.

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• How one could use a live editor

  - by Sathvik

  I was thinking about a live editing environment where code / a source file is synchronized so that, changes made by one user would be carried across to all others editing the file. Something like Google Wave, but for code. Could this kind of an environment be better for the code, as changes are shared instantly? (with revision-control, of course) Has anyone tried (or has had a need for) using a shared environment for code?

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• Gathering IP address and workstation information; does it belong in a state class?

  - by p.campbell

  I'm writing an enterprisey utility that collects exception information and writes to the Windows Event Log, sends an email, etc. This utility class will be used by all applications in the corporation: web, BizTalk, Windows Services, etc. Currently this class: holds state given to it via public properties calls out to .NET Framework methods to gather information about runtime details. Included are call to various properties and methods from System.Environment, Reflection details, etc. This implementation has the benefit of allowing all those callers not to have to make these same calls themselves. This means less code for the caller to forget, screw up, etc. Should this state class (please what's the phrase I'm looking for [like DTO]?) know how to resolve/determine runtime details (like the IP address and machine name that it's running on)? It seems to me on second thought that it's meant to be a class that should hold state, and not know how to call out to the .NET Framework to find information. var myEx = new AppProblem{MachineName="Riker"}; //Will get "Riker 10.0.0.1" from property MachineLongDesc Console.WriteLine("full machine details: " + myEx.MachineLongDesc); public class AppProblem { public string MachineName{get;set;} public string MachineLongDesc{ get{ if(string.IsNullOrEmpty(this.MachineName) { this.MachineName = Environment.MachineName; } return this.MachineName + " " + GetCurrentIP(); } } private string GetCurrentIP() { return System.Net.Dns.GetHostEntry(this.MachineName) .AddressList.First().ToString(); } } This code was written by hand from memory, and presented for simplicity, trying to illustrate the concept.

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• What is best way to manage all images in a big project, inline images, background images, css sprite images?

  - by metal-gear-solid

  How do you manage all images in a big project, inline images, background images, css sprite images? Do you follow any naming convention? Do you create sub-folders to manage images? In a big project how to make it easy to find for new people in the development team if any images which they want to use (because it's in new PSD they received from designer) is already available in images folder of project and how they can find it easily.

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• Anemic Domain Model, Business Logic and DataMapper (PHP)

  - by sunwukung

  I've implemented a rudimentary ORM layer based on DataMapper (I don't want to use a full blown ORM like Propel/Doctrine - for anything beyond simple fetch/save ops I prefer to access the data directly layer using a SQL abstraction layer). Following the DataMapper pattern, I've endeavoured to keep all persistence operations in the Mapper - including the location of related entities. My Entities have access to their Mapper, although I try not to call Mapper logic from the Entity interface (although this would be simple enough). The result is: // get a mapper and produce an entity $ProductMapper = $di->get('product_mapper'); $Product = $ProductMapper->find('[email protected]','email'); //.. mutaute some values.. save $ProductMapper->save($Product) // uses __get to trigger relation acquisition $Manufacturer = $Product->manufacturer; I've read some articles regarding the concept of an Anemic Domain model, i.e. a Model that does not contain any "business logic". When demonstrating the sort of business logic ideally suited to a Domain Model, however, acquiring related data items is a common example. Therefore I wanted to ask this question: Is persistence logic appropriate in Domain Model objects?

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• Should I use a config file or database for storing business rules?

  - by foiseworth

  I have recently been reading The Pragmatic Programmer which states that: Details mess up our pristine code—especially if they change frequently. Every time we have to go in and change the code to accommodate some change in business logic, or in the law, or in management's personal tastes of the day, we run the risk of breaking the system—of introducing a new bug. Hunt, Andrew; Thomas, David (1999-10-20). The Pragmatic Programmer: From Journeyman to Master (Kindle Locations 2651-2653). Pearson Education (USA). Kindle Edition. I am currently programming a web app that has some models that have properties that can only be from a set of values, e.g. (not actual example as the web app data confidential): light-type = sphere / cube / cylinder The light type can only be the above three values but according to TPP I should always code as if they could change and place their values in a config file. As there are several incidents of this throughout the app, my question is: Should I store possibly values like these in: a config file: 'light-types' = array(sphere, cube, cylinder), 'other-type' = value, 'etc = etc-value a single table in a database with one line for each config item a database with a table for each config item (e.g. table: light_types; columns: id, name) some other way? Many thanks for any assistance / expertise offered.

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• Would it be possible to build a client portal on Squarespace6?

  - by aBathologist

  I'm helping a family member set up a site which will need to include a secure client portal, providing access to documents and a simple database. I have been encouraging them to go with a more established, open source CSM like drupal or joomla, whose capability in this area is evident. However, they have a strong preference for Squarespace. Does any one know if it would be possible to accomplish this with the new developer platform for squarespace 6? I've spent well over an hour searching google, the squarespace site and stackexchange, but can't seem to find any clear answer to this question. I'm grateful for any insight you all can provide.

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• Are null references really a bad thing?

  - by Tim Goodman

  I've heard it said that the inclusion of null references in programming languages is the "billion dollar mistake". But why? Sure, they can cause NullReferenceExceptions, but so what? Any element of the language can be a source of errors if used improperly. And what's the alternative? I suppose instead of saying this: Customer c = Customer.GetByLastName("Goodman"); // returns null if not found if (c != null) { Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } You could say this: if (Customer.ExistsWithLastName("Goodman")) { Customer c = Customer.GetByLastName("Goodman") // throws error if not found Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } But how is that better? Either way, if you forget to check that the customer exists, you get an exception. I suppose that a CustomerNotFoundException is a bit easier to debug than a NullReferenceException by virtue of being more descriptive. Is that all there is to it?

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• What are some ways to separate game logic from animations and the draw loop?

  - by TMV

  I have only previously made flash games, using MovieClips and such to separate out my animations from my game logic. Now I am getting into trying my hand at making a game for Android, but the game programming theory around separating these things still confuses me. I come from a background of developing non game web applications so I am versed in more MVC like patterns and am stuck in that mindset as I approach game programming. I want to do things like abstract my game by having, for example, a game board class that contains the data for a grid of tiles with instances of a tile class that each contain properties. I can give my draw loop access to this and have it draw the game board based on the properties of each tile on the game board, but I don't understand where exactly animation should go. As far as I can tell, animation sort of sits between the abstracted game logic (model) and the draw loop (view). With my MVC mindset, it's frustrating trying to decide where animation is actually supposed to go. It would have quite a bit of data associated with it like a model, but seemingly needs to be very closely coupled with the draw loop in order to have things like frame independent animation. How can I break out of this mindset and start thinking about patterns that make more sense for games?

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• Splitting Logic, Data, Layout and "Hacks"

  - by fjdumont

  Sure, we all heard of programming patterns such as MVVM, MVC and such. But that isn't really what I'm looking into as Layout, Data and Logic is already pretty much split up (XML-Layout markup, Database, insert your language of choice here). The platform I am developing for is hard to maintain over the updated versions and older OSes. The project significantly grew up over the last few months and dealing with different platform versions really is a pain. For example simply disabling an user interface control for all existing versions took me around 40 lines of code in the logic layer, wrangling around with invocation, delegation, singletons that provide UI handling and so on. Is there a clean way to keep track of those "hacks" by maybe excluding it into separate classes or even packages? Should I overwrite existing framework code in order to handle my requirements correctly? If so, does that concept have a name?

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• Patterns for a tree of persistent data with multiple storage options?

  - by Robin Winslow

  I have a real-world problem which I'll try to abstract into an illustrative example. So imagine I have data objects in a tree, where parent objects can access children, and children can access parents: // Interfaces interface IParent<TChild> { List<TChild> Children; } interface IChild<TParent> { TParent Parent; } // Classes class Top : IParent<Middle> {} class Middle : IParent<Bottom>, IChild<Top> {} class Bottom : IChild<Middle> {} // Usage var top = new Top(); var middles = top.Children; // List<Middle> foreach (var middle in middles) { var bottoms = middle.Children; // List<Bottom> foreach (var bottom in bottoms) { var middle = bottom.Parent; // Access the parent var top = middle.Parent; // Access the grandparent } } All three data objects have properties that are persisted in two data stores (e.g. a database and a web service), and they need to reflect and synchronise with the stores. Some objects only request from the web service, some only write to it. Data Mapper My favourite pattern for data access is Data Mapper, because it completely separates the data objects themselves from the communication with the data store: class TopMapper { public Top FetchById(int id) { var top = new Top(DataStore.TopDataById(id)); top.Children = MiddleMapper.FetchForTop(Top); return Top; } } class MiddleMapper { public Middle FetchById(int id) { var middle = new Middle(DataStore.MiddleDataById(id)); middle.Parent = TopMapper.FetchForMiddle(middle); middle.Children = BottomMapper.FetchForMiddle(bottom); return middle; } } This way I can have one mapper per data store, and build the object from the mapper I want, and then save it back using the mapper I want. There is a circular reference here, but I guess that's not a problem because most languages can just store memory references to the objects, so there won't actually be infinite data. The problem with this is that every time I want to construct a new Top, Middle or Bottom, it needs to build the entire object tree within that object's Parent or Children property, with all the data store requests and memory usage that that entails. And in real life my tree is much bigger than the one represented here, so that's a problem. Requests in the object In this the objects request their Parents and Children themselves: class Middle { private List<Bottom> _children = null; // cache public List<Bottom> Children { get { _children = _children ?? BottomMapper.FetchForMiddle(this); return _children; } set { BottomMapper.UpdateForMiddle(this, value); _children = value; } } } I think this is an example of the repository pattern. Is that correct? This solution seems neat - the data only gets requested from the data store when you need it, and thereafter it's stored in the object if you want to request it again, avoiding a further request. However, I have two different data sources. There's a database, but there's also a web service, and I need to be able to create an object from the web service and save it back to the database and then request it again from the database and update the web service. This also makes me uneasy because the data objects themselves are no longer ignorant of the data source. We've introduced a new dependency, not to mention a circular dependency, making it harder to test. And the objects now mask their communication with the database. Other solutions Are there any other solutions which could take care of the multiple stores problem but also mean that I don't need to build / request all the data every time?

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• Triggering Data Changes in N-Tier

  - by Ryan Kinal

  I've been studying n-tier architectures as of late, particularly in VB.NET with Entity Framework and/or LINQ to SQL. I understand the basic concepts, but have been wondering about best practices in regard to triggering CRUD-type operations from user input/action. So, the arcitecture looks something like the following: [presentation layer] - [business layer] - [data layer] - (database) Getting information from the database into the presentation layer is simple and abstracted. It's just a matter of instantiating a new object from the business layer, which in turn uses the data layer to get at the correct information. However, saving (updating and inserting), and deleting seem to require particular APIs on the relevant business objects. I have to assume this is standard practice, unless a business object will save itself on various operations (which seems inefficient), or on disposal (which seems like it just wouldn't work, or may be unwieldy and unreliable). Should my "savable" business objects all implement a particular "ISavable" or "IDatabaseObject" interface? Is this a recognized (anti-)pattern? Are there other, better patterns I should be using that I'm just unaware of? The TLDR question, I suppose, is How does the presentation layer trigger database changes?

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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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• How to handle new domain names?

  - by michael

  I have a new product which I'll call a pen ink reloader. I have a website using my products name, for example, www.inkywink.com which I want to have accessed by searches for keywords such as "pen ink", "pen out of ink" "ink for pens" etc. , since nobody knows that a pen ink reloader exists. I see that its quite difficult to get on front page for these keywords since they have lots of competition. However I notice that the exact phrases I want to rank highly for are available as domains. I purchase "www.penink.com" and "penoutofink.com" which for arguments sake are highly searched and the perfect keywords to get eyes on my money site www.inkywink.com . Two questions: 1. What is my best option to leverage those names so that they appear near top of searches so that I can get traffic to my money site? Do I just have them redirect 301 to inkywink.com or should I create small original content on each with links to my main site? 2. If I just have them redirected to inkywink.com, am I able to use keywords in metatag and headers for each site separately or do they all automatically obtain the same headers and tags as the site to which theyre redirected ? Thanks to anyone who can help as I'm a real newbie to all this.

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• is there a checklist that a small website should

  - by Mecon

  I am not a web developer - this would be my first foray. I can do HTML/CSS/Javascript, but never created a website for a company. If anybody is creating a site for small company (expecting some 10-15 static pages), what kinda things would it need to have? I am thinking of the following: Make the eventual owner buy in his/her name: Domain name, Web Hosting package and Email package. Q - DO Web Developers generally ask their clients to buy this stuff and then ask them to share their passwords? OR - Do Web Developers ship the source files to clients so that they can upload it? Create Cross Browser compatible HTML+CSS+javascript pages Add SEO stuff like Meta tags and xml file for crawler Buy professional images from stock website Q - IS there is a best-practice for this step? Add Copyright stuff. Q - ANY idea about how to do this? Add Faceboook widgets, so people can 'like' my website. Register website somewhere so that its searchable from multiple search-engine/yellopages. Q - DOES such a thing exist? Please check my checklist :) and let me know what you think could be missing? Thanks!

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• Why do programming languages allow shadowing/hiding of variables and functions?

  - by Simon

  Many of the most popular programming languges (such as C++, Java, Python etc.) have the concept of hiding / shadowing of variables or functions. When I've encountered hiding or shadowing they have been the cause of hard to find bugs and I've never seen a case where I found it necessary to use these features of the languages. To me it would seem better to disallow hiding and shadowing. Does anybody know of a good use of these concepts?

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• .NET app - Should we use SQL Server and duplicate some reference data from an external Oracle DB? Or use Oracle and have a DB link?

  - by Daventry

  We're looking to migrate some existing Excel/Access processes into a new system which will provide the users with a Silverlight frontend to run and view the reports instead of using MS Access. The initial idea was to have SQL Server 2008 as RDBMS. The problem is that we've got some static data such as country codes, counterparties, etc which live in an existing Oracle DB. Since we do not want to duplicate that data (if possible), we were thinking of having a DB link between SQL Server and Oracle, but our firm does not allow that. So the options are either duplicate the data or use Oracle as RDBMS - surprise, the firm does allow DB links between Oracle databases. The initial idea was also to use WCF RIA Services, Entity Framework, etc which we're not sure they play well with Oracle, that's why it was decided to go with SQL Server in the first place. Would you advise to go for Oracle so that we can just link the static data? Or use SQL Server 2008 and replicate it because it's "safer" to stay within the Microsoft land? To use or not to use Entity Framework and WCF RIA Services at all? Regards. UPDATE: Thanks everyone for your answers. Nothing is set in stone yet. We'll try to import the data instead of linking, as if the other DB goes down, our system can still carry on. We're likely to use SQL Server just because most developers are more experienced with it. Even if we used RIA Services, we can swap out the Data Access Layer and use other frameworks such those mentioned below.

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• What kind of graphics would you like better? [ pictures ] [closed]

  - by Roger Travis

  I am looking forward to make an android game, something angrybirds style. I've already made my own engine and now have to decide what kind of graphics should I make. It could be either realistic, like that or a doodle-style like this Right now the first one looks more appealing to me... on the other hand, doodle-graphics are very easy to draw and their transparency doesn't seem to slow down the engine much. What do you think?

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• Centrally managing 100+ websites without bankrupting a small company

  - by palintropos

  I'm mainly interested in opinions on the trade-offs between having a single central server all the websites connect to as opposed to each website mirroring a subset of the master database with all the products in it. For example, will I run into severe performance issues (or even security issues, or restrictions) making queries to an offsite database? Will we hit scalability issues we can't handle early on from the sheer bandwidth required to maintain this? If we do go with something like a script that keeps smaller databases (each containing a subset of the central master data) in sync, what sorts of issues will we likely encounter there? I would really like the opinions of people far more knowledgeable than I am regarding the pros and cons of both setups and what headaches we are likely to encounter. CLARIFICATION: This should not be viewed as a question about whether we should implement one database vs multiple databases. This question has been answered numerous times. The question is regarding the pros and cons for a deployment like this having the ability to manage all the websites centrally (one server) vs trying to keep them all in sync if they each have their own db (multiple servers). REAL-WORLD EXAMPLE: We are a t-shirt company, and we have individual websites for our different kinds of t-shirts, but we're looking at a central order management integrated with our single shopping cart (which is ColdFusion + MySQL). Now, let's say we have a t-shirt that's on 10 of our websites and we change an image for it. Ideally we would change that in one place and the change would propagate, but how would we set this up?

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• Logic or Algorithm to solve this problem [closed]

  - by jade

  I have two lists. List1 {a,b,c,d,e} and List2 {f,g,h,i,j} The relation between the two list is as follows a->g,a->h,h->c,h->d,d->i,d->j Now I have these two lists displayed. Based on the relation above on selecting element a from List1, List2 shows g,h. On selecting h from List2, in List1 c,d are shown in List1. On selecting d from List1 it shows i,j in List2. How to trace back to initial state by deselecting the elements in reverse order in which they have been selected?

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• Player & Level class structure in 2D python console game?

  - by Markus Meskanen

  I'm trying to create a 2D console game, where I have a player who can freely move around in a level (~map, but map is a reserved keyword) and interfere with other objects. Levels construct out of multiple Blocks, such as player(s), rocks, etc. Here's the Block class: class Block(object): def __init__(self, x=0, y=0, char=' ', solid=False): self.x = x self.y = y self.char = char self.solid = solid As you see, each block has a position (x, y) and a character to represent the block when it's printed. Each block also has a solid attribute, defining whether it can overlap with other solids or not. (Two solid blocks cannot overlap) I've now created few subclasses from Block (Rock might be useless for now) class Rock(Block): def __init__(self, x=0, y=0): super(Rock, self).__init__(x, y, 'x', True) class Player(Block): def __init__(self, x=0, y=0): super(Player, self).__init__(x, y, 'i', True) def move_left(self, x=1): ... # How do I make sure Player wont overlap with rocks? self.x -= x And here's the Level class: class Level(object): def __init__(self, name='', blocks=None): self.name = name self.blocks = blocks or [] Only way I can think of is to store a Player instance into Level's attributes (self.player=Player(), or so) and then give Level a method: def player_move_left(self): for block in self.blocks: if block.x == self.player.x - 1 and block.solid: return False But this doesn't really make any sense, why have a Player class if it can't even be moved without Level? Imo. player should be moved by a method inside Player. Am I wrong at something here, if not, how could I implement such behavior?

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