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• The algorithm used to generate recommendations in Google News?

  - by Siddhant

  Hi everyone. I'm study recommendation engines, and I went through the paper that defines how Google News generates recommendations to users for news items which might be of their interest, based on collaborative filtering. One interesting technique that they mention is Minhashing. I went through what it does, but I'm pretty sure that what I have is a fuzzy idea and there is a strong chance that I'm wrong. The following is what I could make out of it :- Collect a set of all news items. Define a hash function for a user. This hash function returns the index of the first item from the news items which this user viewed, in the list of all news items. Collect, say "n" number of such values, and represent a user with this list of values. Based on the similarity count between these lists, we can calculate the similarity between users as the number of common items. This reduces the number of comparisons a lot. Based on these similarity measures, group users into different clusters. This is just what I think it might be. In Step 2, instead of defining a constant hash function, it might be possible that we vary the hash function in a way that it returns the index of a different element. So one hash function could return the index of the first element from the user's list, another hash function could return the index of the second element from the user's list, and so on. So the nature of the hash function satisfying the minwise independent permutations condition, this does sound like a possible approach. Could anyone please confirm if what I think is correct? Or the minhashing portion of Google News Recommendations, functions in some other way? I'm new to internal implementations of recommendations. Any help is appreciated a lot. Thanks!

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• How large a role does subjectiveness play in programming?

  - by Bob

  I often read about the importance of readability and maintainability. Or, I read very strong opinions about which syntax features are bad or good. Or discussions about the values of certain paradigms, like OOP. Aside from that, this same question floats about in my mind whenever I read debates on SO or Meta about subjective questions. Or read questions about best practices and sometimes find myself or others disagreeing. What role does subjectiveness play within the programming realm? Sometimes I think it plays a large role. Software developers are engineers in a way, but also people. A large part of programming is dealing with code that's human readable. This is very different from Math or Physics or other disciplines with very exact and structured rules. Here the exact structure and rules are largely up in the air, changeable on a whim, and hence the amount of languages in existence. And one person may find one language very readable, and another person may find their own language the most comforting. The same with practices. One person may not like certain accepted practices. I myself find splitting classes into different files very unreadable, for instance. But, I can't say rules haven't helped in general. Certain practices have and do make life easier. And new languages have given rise to syntax and structure that make life easier. There's certainly been a progression towards code that is easier to read and maintain even given a largely diverse group of people. So maybe these things aren't as subjective as I thought. It reminds me, in a way, of UI design. Certainly it's subjective, but then there's an entire discipline involved in crafting good UI and it tends to work. Is there something non-subjective about the ideas behind maintainability, readability, and other best practices? Is there something tangible to grasp when one develops a new language or thinks of new practices?

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• Renaming TurboGears 2's Repoze Fields with TGAdmin

  - by William Chambers

  I've been working on renaming TurboGears 2's Repoze 'groups' field to 'roles' to free the namespace and db tables for other purposes. Also roles makes much more sense to me then groups because I have a strong Drupal background. Now I have found some of the docs to do this such as these: http://www.turbogears.org/2.1/docs/main/Auth/Customization.html#customizing-the-model-structure-assumed-by-the-quickstart http://code.gustavonarea.net/repoze.what-quickstart/#customizing-the-model-definition However these only go part of the way. I have made (I'm pretty sure at least, I've double checked a few times.) all the changes required as you can see in this diff. This seems to work fine however I've ran into a rather major issue with the TurboGears Admin system. I've tried http://turbogears.org/2.0/docs/main/Extensions/Admin/index.html and it didn't seem to make any difference, however I'm not 100% sure I did it correctly. The problem occurs when I attempt to go to localhost/admin/permissions/. It causes a Internal Server Error and outputs the following error. http://pastebin.com/YWMH3SiU This error does not happen on the Roles/Users pages and the permissions /edit/1 also works. I'm running kubuntu 10.04 with TG 2.1b2. (I'm running the beta mostly for easier mako support which is really important.) Any help would be very appreciated.

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• Have I taken a wrong path in programming by being excessively worried about code elegance and style?

  - by Ygam

  I am in a major stump right now. I am a BSIT graduate, but I only started actual programming less than a year ago. I observed that I have the following attitude in programming: I tend to be more of a purist, scorning unelegant approaches to solving problems using code I tend to look at anything in a large scale, planning everything before I start coding, either in simple flowcharts or complex UML charts I have a really strong impulse on refactoring my code, even if I miss deadlines or prolong development times I am obsessed with good directory structures, file naming conventions, class, method, and variable naming conventions I tend to always want to study something new, even, as I said, at the cost of missing deadlines I tend to see software development as something to engineer, to architect; that is, seeing how things relate to each other and how blocks of code can interact (I am a huge fan of loose coupling) i.e the OOP thinking I tend to combine OOP and procedural coding whenever I see fit I want my code to execute fast (thus the elegant approaches and refactoring) This bothers me because I see my colleagues doing much better the other way around (aside from the fact that they started programming since our first year in college). By the other way around I mean, they fire up coding, gets the job done much faster because they don't have to really look at how clean their codes are or how elegant their algorithms are, they don't bother with OOP however big their projects are, they mostly use web APIs, piece them together and voila! Working code! CLients are happy, they get paid fast, at the expense of a really unmaintainable or hard-to-read code that lacks structure and conventions, or slow executions of certain actions (which the common reasoning against would be that internet connections are much faster these days, hardware is more powerful). The excuse I often receive is clients don't care about how you write the code, but they do care about how long you deliver it. If it works then all is good. Now, did my "purist" approach to programming may have been the wrong way to start programming? Should I just dump these purist concepts and just code the hell up because I have seen it: clients don't really care how beautifully coded it is?

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• NSMutableDictionary isn't stick around long enough

  - by Sean Danzeiser

  Sorry, beginner here . . . So I create an NSMutableDictionary in my app delegate when the application launches, and then later pass it on to a view controller, as it contains options for the VC like a background image, a url I want to parse, etc. Anyway, i wrote a custom init method for the VC, initWithOptions, where I pass the dictionary on. I'm trying to use this dictionary later on in other methods - so I created a NSMutableDictionary property for my VC and am trying to store the passed options dictionary there. However, when I go to get the contents of that property in later methods, it returns null. If i access it from the init method, it works. heres some sample code: -(id)initWithOptions:(NSMutableDictionary *)options { self = [super init]; if (self) { // Custom initialization self.optionsDict = [[NSMutableDictionary alloc]initWithDictionary:options]; NSLog(@"dictionary in init method %@",self.optionsDict); that NSLog logs the contents of the dictionary, and it looks like its working. then later when I do this: - (void)viewDidLoad { SDJConnection *connection = [[SDJConnection alloc]init]; self.dataArray = [connection getEventInfoWithURL:[dict objectForKey:@"urlkey"]]; NSLog(@"dictionary in connection contains: %@", [dict objectForKey:@"urlkey"]); [_tableView reloadData]; the dictionary returns null. Ive tried adjusting the property attributes, and it didn't work with either strong or retain. Any ideas?? THANKS!!

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• Common lisp, CFFI, and instantiating c structs

  - by andrew

  Hi, I've been on google for about, oh, 3 hours looking for a solution to this "problem." I'm trying to figure out how to instantiate a C structure in lisp using CFFI. I have a struct in c: struct cpVect{cpFloat x,y;} Simple right? I have auto-generated CFFI bindings (swig, I think) to this struct: (cffi:defcstruct #.(chipmunk-lispify "cpVect" 'classname) (#.(chipmunk-lispify "x" 'slotname) :double) (#.(chipmunk-lispify "y" 'slotname) :double)) This generates a struct "VECT" with slots :X and :Y, which foreign-slot-names confirms (please note that I neither generated the bindings or programmed the C library (chipmunk physics), but the actual functions are being called from lisp just fine). I've searched far and wide, and maybe I've seen it 100 times and glossed over it, but I cannot figure out how to create a instance of cpVect in lisp to use in other functions. Note the function: cpShape *cpPolyShapeNew(cpBody *body, int numVerts, cpVect *verts, cpVect offset) Takes not only a cpVect, but also a pointer to a set of cpVects, which brings me to my second question: how do I create a pointer to a set of structs? I've been to http://common-lisp.net/project/cffi/manual/html_node/defcstruct.html and tried the code, but get "Error: Unbound variable: PTR" (I'm in Clozure CL), not to mention that looks to only return a pointer, not an instance. I'm new to lisp, been going pretty strong so far, but this is the first real problem I've hit that I can't figure out. Thanks!

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• Modify post data with a custom MVC extension?

  - by Jaxidian

  So I'm looking into writing some custom MVC extensions and the first one I'm attempting to tackle is a FormattedTextBox to handle things such as currency, dates, and times. I have the rendering of it working perfectly, formatting it, working with strong types and everything all golden. However, the problem I'm now running into is cleaning up the formatted stuff when the page posts the data back. Take for example, a currency format. Let's use USD for these examples. When an object has a property as a decimal, the value would be 79.95. Your edit view would be something like: <%= Html.FormattedTextBox(model => Model.Person.HourlyWage, "{0:C}") %> This is all well and good for the GET request, but upon POST, the value is going to be $79.95, which when you assign to that decimal, gets unhappy very quickly and ends up shoving a 0 in there. So my question is, how do I get code working somewhere to work with that value before the MVC Framework goes and starts shoving it back into my ViewModel? I'd much rather this be done server-side than client-side. Thanks!!

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• Hierarchical object model with property inheritance and event bubbling?

  - by Winston Fassett

  I'm writing a document-based client application and I need a DOM or WPF-like, but non-visual model that: Is a tree composed of elements Can accept an unlimited number of custom properties that get/set any CLR type, including collections. Can inherit their values from their parent Can inherit their default values from an ancestor Can be derived/calculated from other properties, ancestors, or descendants Support event bubbling / tunneling There will be a core set of properties but other plugins may add their own or even create custom documents Supports full inspection by the owning document in order to persist the tree and attributes in an XML format. I realize that's a tall order but I was really hoping there would be something out there to help me get started. Unfortunately WPF DependencyObjects are too closed, proprietary, and coupled to WPF to be of any use as a document model. My needs also have a strong resemblance to the HTML DOM but I haven't been able to find any clean DOM implementations that could be decoupled from HTML or ported to .NET. My current platform is .NET/C# but if anyone knows of anything that might be useful for inspiration or embedding, regardless of the platform, I'd love to know.

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• What is the best approach for creating a Common Information Model?

  - by Kaiser Advisor

  Hi, I would like to know the best approach to create a Common Information Model. Just to be clear, I've also heard it referred to as a canonical information model, semantic information model, and master data model - As far as I can tell, they are all referring to the same concept. I've heard in the past that a combined "top-down" and "bottom-up" approach is best. This has the advantage of incorporating "Ivory tower" architects and developers - The work will meet somewhere in the middle and usually be both logical and practical. However, this involves bringing in a lot of people with different skill sets. I've also seen a couple of references to the Distributed Management Task Force, but I can't glean much on best practices in terms of CIM development. This is something I'm quite interested in getting some feedback on since having a strong CIM is a prerequisite to SOA. Thanks for your help! KA Update I've heard another strategy goes along with overall SOA implementation: Get the business involved, and seek executive sponsorship. This would be part of the "Top-down" effort.

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• Python and a "time value of money" problem.

  - by jamieb

  (I asked this question earlier today, but I did a poor job of explaining myself. Let me try again) I have a client who is an industrial maintenance company. They sell service agreements that are prepaid 20 hour blocks of a technician's time. Some of their larger customers might burn through that agreement in two weeks while customers with fewer problems might go eight months on that same contract. I would like to use Python to help model projected sales revenue and determine how many billable hours per month that they'll be on the hook for. If each customer only ever bought a single service contract (never renewed) it would be easy to figure sales as monthly_revenue = contract_value * qty_contracts_sold. Billable hours would also be easy: billable_hrs = hrs_per_contract * qty_contracts_sold. However, how do I account for renewals? Assuming that 90% (or some other arbitrary amount) of customers renew, then their monthly revenue ought to grow geometrically. Another important variable is how long the average customer burns through a contract. How do I determine what the revenue and billable hours will be 3, 6, or 12 months from now, based on various renewal and burn rates? I assume that I'd use some type of recursive function but math was never one of my strong points. Any suggestions please? Edit: I'm thinking that the best way to approach this is to think of it as a "time value of money" problem. I've retitled the question as such. The problem is probably a lot more common if you think of "monthly sales" as something similar to annuity payments.

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• Web development: Haskell or Scheme

  - by Robert E. Lester

  I would like to to choose one of these languages for building web applications. I'm not interested in framework per say, but have the following needs: Rapid development. Easy to scale. Strong community for the web. Quick and easy to deploy. I'm very familiar with Haskell, and have some familiarity with scheme (in particular PLT). Scheme appeals to me as good candidate for web development due to it's simple syntax which is homogenous across libraries. I state this despite my subjective opinion that Haskell is a 'cleaner' language. Haskell web apps seem to require learning and building a patchwork of different combinator libraries. On the plus side, I realise this can be quite expressive, although I'd prefer to eliminate impedance mismatches where possible. While scheme-plt looks to be a good fit, I can find but one example of it being used in the "real world". Haskell doesn't seem to fair too much better here, but there seems to be a bigger community behind the web side. Please help me make up my mind. For the most part I'm interested in real-world use cases.

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• How do I tell if an action is a lambda expression?

  - by Keith

  I am using the EventAgregator pattern to subscribe and publish events. If a user subscribes to the event using a lambda expression, they must use a strong reference, not a weak reference, otherwise the expression can be garbage collected before the publish will execute. I wanted to add a simple check in the DelegateReference so that if a programmer passes in a lambda expression and is using a weak reference, that I throw an argument exception. This is to help "police" the code. Example: eventAggregator.GetEvent<RuleScheduler.JobExecutedEvent>().Subscribe ( e => resetEvent.Set(), ThreadOption.PublisherThread, false, // filter event, only interested in the job that this object started e => e.Value1.JobDetail.Name == jobName ); public DelegateReference(Delegate @delegate, bool keepReferenceAlive) { if (@delegate == null) throw new ArgumentNullException("delegate"); if (keepReferenceAlive) { this._delegate = @delegate; } else { //TODO: throw exception if target is a lambda expression _weakReference = new WeakReference(@delegate.Target); _method = @delegate.Method; _delegateType = @delegate.GetType(); } } any ideas? I thought I could check for @delegate.Method.IsStatic but I don't believe that works... (is every lambda expression a static?)

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• How can I tackle 'profoundly found elsewhere' syndrome (inverse of NIH)?

  - by Alistair Knock

  How can I encourage colleagues to embrace small-scale innovation within our team(s), in order to get things done quicker and to encourage skills development? (the term 'profoundly found elsewhere' comes from Wikipedia, although it is scarcely used anywhere else apart from a reference to Proctor & Gamble) I've worked in both environments where there is a strong opposition to software which hasn't been developed in-house (usually because there's a large community of developers), and more recently (with far fewer central developers) where off-the-shelf products are far more favoured for the usual reasons: maintenance, total cost over product lifecycle, risk management and so on. I think the off the shelf argument works in the majority of cases for the majority of users, even though as a developer the product never quite does what I'd like it to do. However, in some cases there are clear gaps where the market isn't able to provide specifically what we would need, or at least it isn't able to without charging astronomical consultancy rates for a bespoke solution. These can be small web applications which provide a short-term solution to a particular need in one specific department, or could be larger developments that have the potential to serve a wider audience, both across the organisation and into external markets. The problem is that while development of these applications would be incredibly cheap in terms of developer hours, and delivered very quickly without the need for glacial consultation, the proposal usually falls flat because of risk: 'Who'll maintain the project tracker that hasn't had any maintenance for the past 7 years while you're on holiday for 2 weeks?' 'What if one of our systems changes and the connector breaks?' 'How can you guarantee it's secure/better/faster/cheaper/holier than Company X's?' With one developer behind these little projects, the answers are invariably: 'Nobody, but...' 'It will break, just like any other application would...' 'I, uh...' How can I better answer these questions and encourage people to take a little risk in order to stimulate creativity and fast-paced, short-lifecycle development instead of using that 6 months to consult about what tender process we might use?

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• R: manipulating data.frames containing strings and booleans.

  - by Mike Dewar

  Hello. I have a data.frame in R; it's called p. Each element in the data.frame is either True or False. My variable p has, say, m rows and n columns. For every row there is strictly only one TRUE element. It also has column names, which are strings. What I would like to do is the following: For every row in p I see a TRUE I would like to replace with the name of the corresponding column I would then like to collapse the data.frame, which now contains FALSEs and column names, to a single vector, which will have m elements. I would like to do this in an R-thonic manner, so as to continue my enlightenment in R and contribute to a world without for-loops. I can do step 1 using the following for loop: for (i in seq(length(colnames(p)))) { p[p[,i]==TRUE,i]=colnames(p)[i] } but theres's no beauty here and I have totally subscribed to this for-loops-in-R-are-probably-wrong mentality. Maybe wrong is too strong but they're certainly not great. I don't really know how to do step 2. I kind of hoped that the sum of a string and FALSE would return the string but it doesn't. I kind of hoped I could use an OR operator of some kind but can't quite figure that out (Python responds to False or 'bob' with 'bob'). Hence, yet again, I appeal to you beautiful Rstats people for help!

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• How to keep track of objects for garbage collection

  - by Yman

  May I know what is the proper way to keep track of display objects created and hence allow me to remove it efficiently later, for garbage collection. For example: for(i=0; i<100; i++){ var dobj = new myClass(); //a sprite addChild(dobj); } From what i know, flash's garbage collection will only collect the objects without strong references and event listeners attached to it. Since the var dobj is strongly referenced to the new object created, I will have to "nullify" it too, am I correct? Should I create an array to keep track of all the objects created in the loop such as: var objectList:Array = new Array(); for(i=0; i<100; i++) { var dobj = new myClass(); //a sprite addChild(dobj); objectList.push(dobj); } //remove all children for each (var key in objectList) { removeChild(key as myClass); } Does this allow GC to collect it on sweep?

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• How to add objects to NSArray from a different class with ARC

  - by Space Dust

  I needed to convert my code to ARC. I have an NSArray that I use to draw a path. I fill the objects of NSArray values from a different class. Problem is after converting to ARC, NSArray returns always null I can not see what I am doing wrong. bug.h @interface Ladybug : CCSprite <CCTargetedTouchDelegate>{ CCArray *linePathPosition; } @property (nonatomic, strong) CCArray *linePathPosition; @end bug.m @synthesize linePathPosition; -(id) init { if( (self=[super init] )) { self.linePathPosition = [[CCArray alloc] init]; } return self; } -(void) updatePosition:(CGPoint) position { [self.linePathPosition addObject:[NSValue valueWithCGPoint:position]]; NSLog(@"line path %@",linePathPosition); } -(void) breakMoveLadyBug { [self.linePathPosition removeAllObjects]; } In main .m - (void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event { Ladybug *ladybug1 = (Ladybug *)[self getChildByTag:99]; CCMotionStreak* streak = (CCMotionStreak *)[self getChildByTag:999]; CGPoint touchLocation = [touch locationInView: [touch view]]; CGPoint curPosition = [[CCDirector sharedDirector] convertToGL:touchLocation]; if (ladybug1.isSelected) { streak.position = curPosition; [ladybug1 updatePosition:curPosition]; NSLog(@"Cur position %@",NSStringFromCGPoint(curPosition)); if (!ladybug1.isMoving) { [ladybug1 startMoveLadyBug]; } } } Log: Cur position {331, 110} line path (null) What am I doing wrong? What is the proper way to define and init NSArray with ARC?

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• How to bind data from a view of type List<List<MyViewModelClass>>?

  - by Robert Koritnik

  I have a strong type view of type List<List<MyViewModelClass>> The outer list will always have two lists of List<MyViewModelClass>. For each of the two outer lists I want to display a group of checkboxes. Each set can have an arbitrary number of choices. My view model class looks similar to this: public class MyViewModelClass { public Area Area { get; set; } public bool IsGeneric { get; set; } public string Code { get; set; } public bool IsChecked { get; set; } } So the final view will look something like: Please select those that apply: First set of choices: x Option 1 x Option 2 x Option 3 etc. Second set of choices: x Second Option 1 x Second Option 2 x Second Option 3 x Second Option 4 etc. Checkboxes should display MyViewModelClass.Area.Name, and their value should be related to MyViewModelClass.Area.Id. Checked state is of course related to MyViewModel.IsChecked. Question I wonder how should I use Html.CheckBox() or Html.CheckBoxFor() helper to display my checkboxes? I have to get these values back to the server on a postback of course. If it makes things simpler, I could make a separate view model type like: public class Options { public List<MyViewModelClass> General { get; set; } public List<MyViewModelClass> Others { get; set; } }

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• how to access anti aliasing method of a font with CSS

  - by Daniel Ramirez-Escudero

  I've had this problem in a lot of different webs. You have a font which has different anti-aliasing options, the designer uses the same font with different anti-aliasing options on different parts of the text on the web. So there is a difference between some elements. In this case I have sharp, crisp, strong and smooth. I've used a font generator to get the code to access it via @font-face. Even so, I also have the original .otf if important to know. Is there a method to access this? I upload a picture of what I mean and my actual code: ![@font-face { font-family: 'light'; src: url('../_fnt/light/gothamrnd-light.eot'); src: url('../_fnt/light/gothamrnd-light.eot?#iefix') format('embedded-opentype'), url('../_fnt/light/gothamrnd-light.woff') format('woff'), url('../_fnt/light/gothamrnd-light.ttf') format('truetype'), url('../_fnt/light/gothamrnd-light.svg#../_fnt/light/gothamrnd-light') format('svg'); font-weight: normal; font-style: normal; }]![enter image description here][1]

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• Using the same code in different (partial) views

  - by Danny Chen

  Maybe this question is quite simple because I'm new to MVC2. I have a simple demo MVC project. (1) A weak-typed view: Index.aspx <% Html.RenderPartial("ArticalList", ViewData["AllArticals"] as List<Artical>); %> (2) A strong-typed partical view: ArticalList.ascx <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<List<Artical>>" %> <% foreach (Artical a in Model) { %> <%= Html.ActionLink(a.Title, "About", new { id = a.ID })%><br /> <%} %> (3) Here is the HomeController.cs public ActionResult Index() { ViewData["AllArticals"] = Artical.GetArticals(); return View(); } public ActionResult ArticalList() { return PartialView(Artical.GetArticals()); } Sorry I'm using a Web-Form "angle", because if I'm using a Web-Form, when I visit Index.aspx, rendering ArticalList.ascx will call public ActionResult ArticalList(). But here I need to write Artical.GetArticals() twice in two actions. How can I put them in one?

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• Spring + iBatis + Hessian caching

  - by ILya

  Hi. I have a Hessian service on Spring + iBatis working on Tomcat. I'm wondering how to cache results... I've made the following config in my sqlmap file: <sqlMap namespace="Account"> <cacheModel id="accountCache" type="MEMORY" readOnly="true" serialize="false"> <flushInterval hours="24"/> <flushOnExecute statement="Account.addAccount"/> <flushOnExecute statement="Account.deleteAccount"/> <property name="reference-type" value="STRONG" /> </cacheModel> <typeAlias alias="Account" type="domain.Account" /> <select id="getAccounts" resultClass="Account" cacheModel="accountCache"> fix all; select id, name, pin from accounts; </select> <select id="getAccount" parameterClass="Long" resultClass="Account" cacheModel="accountCache"> fix all; select id, name, pin from accounts where id=#id#; </select> <insert id="addAccount" parameterClass="Account"> fix all; insert into accounts (id, name, pin) values (#id#, #name#, #pin#); </insert> <delete id="deleteAccount" parameterClass="Long"> fix all; delete from accounts where id = #id#; </delete> </sqlMap> Then i've done some tests... I have a hessian client application. I'm calling getAccounts several times and after each call it's a query to DBMS. How to make my service to query DBMS only a first time (after server restart) getAccounts called and for the following calls to use a cache?

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• Dealing with SQLException with spring,hibernate & Postgres

  - by mad

  Hi im working on a project using HibernateDaoSUpport from my Daos from Spring & spring-ws & hibernate & postgres who will be used in a national application (means a lot of users) Actually, every exception from hibernate is automatically transformed into some specific Spring dataAccesException. I have a table with a keyword on the dabatase & a unique constraint on the keywords : no duplicate keywords is allowed. I have found twows ways to deal with with that in the Insert Dao: 1- Check for the duplicate manually (with a select) prior to doing your insert. I means that the spring transaction will have a SERIALIZABLE isolation level. The obvious drawback is that we have now 2 queries for a simple insert.Advantage: independent of the database 2-let the insert gone & catch the SqlException & convert it to a userfriendly message & errorcode to the final consumer of our webservices. Solution 2: Spring has developped a way to translate specific exeptions into customized exceptions. see http://www.oracle.com/technology/pub/articles/marx_spring.html In my case i would have a ConstraintViolationException. Ideally i would like to write a custom SQLExceptionTranslator to map the duplicate word constraint in the database with a DuplicateWordException. But i can have many unique constraints on the same table. So i have to get the message of the SQLEXceptions in order to find the name of the constraint declared in the create table "uq_duplicate-constraint" for example. Now i have a strong dependency with the database. Thanks in advance for your answers & excuse me for my poor english (it is not my mother tongue)

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• java.math.BigInteger pow(exponent) question

  - by Jan Kraus

  Hi, I did some tests on pow(exponent) method. Unfortunately, my math skills are not strong enough to handle the following problem. I'm using this code: BigInteger.valueOf(2).pow(var); Results: var | time in ms 2000000 | 11450 2500000 | 12471 3000000 | 22379 3500000 | 32147 4000000 | 46270 4500000 | 31459 5000000 | 49922 See? 2,500,000 exponent is calculated almost as fast as 2,000,000. 4,500,000 is calculated much faster then 4,000,000. Why is that? To give you some help, here's the original implementation of BigInteger.pow(exponent): public BigInteger pow(int exponent) { if (exponent < 0) throw new ArithmeticException("Negative exponent"); if (signum==0) return (exponent==0 ? ONE : this); // Perform exponentiation using repeated squaring trick int newSign = (signum<0 && (exponent&1)==1 ? -1 : 1); int[] baseToPow2 = this.mag; int[] result = {1}; while (exponent != 0) { if ((exponent & 1)==1) { result = multiplyToLen(result, result.length, baseToPow2, baseToPow2.length, null); result = trustedStripLeadingZeroInts(result); } if ((exponent >>>= 1) != 0) { baseToPow2 = squareToLen(baseToPow2, baseToPow2.length, null); baseToPow2 = trustedStripLeadingZeroInts(baseToPow2); } } return new BigInteger(result, newSign); }

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• C++ Declarative Parsing Serialization

  - by Martin York

  Looking at Java and C# they manage to do some wicked processing based on special languaged based anotation (forgive me if that is the incorrect name). In C++ we have two problems with this: 1) There is no way to annotate a class with type information that is accessable at runtime. 2) Parsing the source to generate stuff is way to complex. But I was thinking that this could be done with some template meta-programming to achieve the same basic affect as anotations (still just thinking about it). Like char_traits that are specialised for the different types an xml_traits template could be used in a declaritive way. This traits class could be used to define how a class is serialised/deserialized by specializing the traits for the class you are trying to serialize. Example Thoughs: template<typename T> struct XML_traits { typedef XML_Empty Children; }; template<> struct XML_traits<Car> { typedef boost::mpl::vector<Body,Wheels,Engine> Children; }; template<typename T> std::ostream& Serialize(T const&) { // my template foo is not that strong. // but somthing like this. boost::mpl::for_each<typename XML_Traits<T>::Children,Serialize>(data); } template<> std::ostream& Serialize<XML_Empty>(T const&) { /* Do Nothing */ } My question is: Has anybody seen any projects/decumentation (not just XML) out there that uses techniques like this (template meta-programming) to emulate the concept of annotation used in languges like Java and C# that can then be used in code generation (to effectively automate the task by using a declaritive style). At this point in my research I am looking for more reading material and examples.

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• How can I intelligently group rows of integers for a faceted search?

  - by Alastair

  I'm not even quite sure what terms I should be using for what I want, so any advice on what I'm even asking for would be very welcome. Basically, my web site lists user-generated accommodations. Each has a rent price, which users will be able to query in our new faceted search box. Users search by city, and within each city I'd like to present a different rent grouping. That is to say that in City #1, if we have listings ranging from $200 - $1000, I'd like to present checkboxes for: less than $300 $301 - $500 $501 - $700 more than $700 However, if City #2 has values that range from $500 - $1500, I want the ranges above to change accordingly. So, if I say that I want 5 or 6 range options in each city, I think I have two options: Take the min and max values and just split the difference. I don't like this idea because one listing with a rent of $10,000 will throw the whole scale off. Intelligently calculate the ranges using means, medians etc. Number 2 is what I need help with. I'm a web developer that gets logic, but was never strong on math and statistics at school. Can anyone point me towards a guide that'll help me figure this out?

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• New desktop GUI developer; can choose any platform...

  - by alexantd

  I'm planning a client-server product for a tiny, low-volume, high-cost vertical market. One of the components of the product will be a desktop application, simple to moderate in complexity, for data entry and uploading to a central server from remote PCs and/or Macs via SOAP. The server is a Java web app. Customers will be choosing their platform (Windows or Mac) based on what the client app runs on, so my options are wide-open here. However, I will be developing on a Mac and have a strong allergy to MS-specific technologies (sorry). The app will not need to run on any non-desktop-computer devices and I have total freedom to say it will support X but not Y or Z without any negative consequences (quite the luxury, to be sure). I have a lot of experience in server-side development but very little in desktop GUI stuff, and am evaluating my options on the client - basically what do I want to commit to learning over the next 6+ months. I have server-side Java experience as well as a brief dabble in iPhone development, which went OK. Overall I'm looking for: Ease of learning & development IDE support Healthy surrounding ecosystem (libraries, tools, help, etc.) Quality documentation My options as I see them, in rough order of how I'm currently mentally ranking them: Java Swing Cocoa Java SWT JavaFX Adobe AIR XULRunner Am I leaving anything out?

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