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• How to store wiki sites (vcs)

  - by Eugen

  Hello, as a personal project I am trying to write a wiki with the help of django. I'm a beginner when it comes to web development. I am at the (early) point where I need to decide how to store the wiki sites. I have three approaches in mind and would like to know your suggestion. Flat files I considered a flat file approach with a version control system like git or mercurial. Firstly, I would have some example wikis to look at like http://hatta.sheep.art.pl/. Secondly, the vcs would probably deal with editing conflicts and keeping the edit history, so I would not have to reinvent the wheel. And thirdly, I could probably easily clone the wiki repository, so I (or for that matter others) can have an offline copy of the wiki. On the other hand, as far as I know, I can not use django models with flat files. Then, if I wanted to add fields to a wiki site, like a category, I would need to somehow keep a reference to that flat file in order to associate the fields in the database with the flat file. Besides, I don't know if it is a good idea to have all the wiki sites in one repository. I imagine it is more natural to have kind of like a repository per wiki site resp. file. Last but not least, I'm not sure, but I think using flat files would limit my deploying capabilities because web hosts maybe don't allow creating files (I'm thinking, for example, of Google App Engine) Storing in a database By storing the wiki sites in the database I can utilize django models and associate arbitrary fields with the wiki site. I probably would also have an easier life deploying the wiki. But I would not get vcs features like history and conflict resolving per se. I searched for django-extensions to help me and I found django-reversion. However, I do not fully understand if it fit my needs. Does it track model changes like for example if I change the django model file, or does it track the content of the models (which would fit my need). Plus, I do not see if django reversion would help me with edit conflicts. Storing a vcs repository in a database field This would be my ideal solution. It would combine the advantages of both previous approaches without the disadvantages. That is; I would have vcs features but I would save the wiki sites in a database. The problem is: I have no idea how feasible that is. I just imagine saving a wiki site/source together with a git/mercurial repository in a database field. Yet, I somehow doubt database fields work like that. So, I'm open for any other approaches but this is what I came up with. Also, if you're interested, you can find the crappy early test I'm working on here http://github.com/eugenkiss/instantwiki-test

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• org.hibernate.TransientObjectException during Criteria.list()

  - by rancidfishbreath

  I have seen posts all over the internet that talk about how to fix the TransientObjectExceptions during save/update/delete but I am having this problem when calling list on my Criteria. I have two objects A and B. A has a field named b which is of type B. In my mapping b is mapped as a many-to-one. This all runs in a larger persistence framework (the framework is kind of like Core Data) and so I don't use any cascades in my hibernate mappings since cascades are handled at a higher level. This is the interesting code surrounding my criteria: A a = new A(); B b = new B(); a.setB(b); session.save("B", b); // Actually handled by the higher level session.save("A", a); // framework, this is just for clarity // transaction committed and session closed ... // new session opened Criteria criteria = session.createCriteria(A.class); criteria.add(Restrictions.eq("b", b)); List<?> objects = criteria.list(); Basically I am looking for all objects of type A such that A.b equals a particular instance of b (I actually tried restructuring a query so that I was passing in the id of b just to make sure that b wasn't causing me problems). Here is the stack trace that occurs when I call criteria.list(): org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: B at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:244) at org.hibernate.type.EntityType.getIdentifier(EntityType.java:449) at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:141) at org.hibernate.loader.Loader.bindPositionalParameters(Loader.java:1769) at org.hibernate.loader.Loader.bindParameterValues(Loader.java:1740) at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1612) at org.hibernate.loader.Loader.doQuery(Loader.java:717) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270) at org.hibernate.loader.Loader.doList(Loader.java:2294) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2172) at org.hibernate.loader.Loader.list(Loader.java:2167) at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1706) at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347) Here is my mapping: <class entity-name="A" lazy="false"> <tuplizer entity-mode="dynamic-map" class="MyTuplizer" /> <id type="long" column="id"> <generator class="native" /> </id> <many-to-one name="b" entity-name="B" column="b_id" lazy="false" /> </class> <class entity-name="B" lazy="false"> <tuplizer entity-mode="dynamic-map" class="MyTuplizer" /> <id type="long" column="id"> <generator class="native" /> </id> </class> Can anyone help me figure out why I would be getting a TransientObjectException during a fetch? Preferably I would like to find a solution that does not rely on cascades since they tend to mask problems that occur in the higher level framework.

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• Crystal reports .net visual studio 2008 bundled edition

  - by DeveloperChris

  I have a serious issue with crystal reports. when run in my development environment or debugged on my local machine it works fine. but when the application is published to a windows server 2003 it has the dreaded "The report you requested requires further information" Message I have had no luck trying to get rid of this message Anybody know what I can try? DC Here is a bunch more info. I use a placeholder in the aspx page and then set the user/password and database in the codebehind I could not get it to work with a dataset and found that I had to assign odbc connection in the cr designer. and then in the code behind change the above details as required. This is done because the same report can get the data from 3 different databases (live development and training) protected override void Page_Load(object sender, EventArgs e) { base.Page_Load(sender, e); CrystalReportSource1.ReportDocument.Load(Server.MapPath(@"~/Reports/Report5asp.rpt")); CrystalReportViewer1.ReportSource = ConfigureCrystalReports(CrystalReportSource1.ReportDocument,CrystalReportViewer1); // parameters CrystalReportViewer1.ParameterFieldInfo.Clear(); AddParameter("DIid", _app.Data["DIid"], CrystalReportViewer1.ParameterFieldInfo); AddParameter("EEid", _app.Data["EEid"], CrystalReportViewer1.ParameterFieldInfo); AddParameter("CTid", _app.Data["CTid"], CrystalReportViewer1.ParameterFieldInfo); } public ReportDocument ConfigureCrystalReports(ReportDocument report, CrystalReportViewer viewer) { String _connectionString = _app.ConnectionString(); String dsn = _app.DSN(); SqlConnectionStringBuilder SConn = new SqlConnectionStringBuilder(_connectionString); TableLogOnInfos crtableLogoninfos = new TableLogOnInfos(); TableLogOnInfo crtableLogoninfo = new TableLogOnInfo(); ConnectionInfo crConnectionInfo = new ConnectionInfo(); crConnectionInfo.ServerName = dsn;// SConn.DataSource; crConnectionInfo.DatabaseName = SConn.InitialCatalog; crConnectionInfo.UserID = SConn.UserID; crConnectionInfo.Password = SConn.Password; crConnectionInfo.Type = ConnectionInfoType.SQL; crConnectionInfo.IntegratedSecurity = false; foreach (CrystalDecisions.CrystalReports.Engine.Table CrTable in report.Database.Tables) { crtableLogoninfo = CrTable.LogOnInfo; crtableLogoninfo.ConnectionInfo = crConnectionInfo; CrTable.ApplyLogOnInfo(crtableLogoninfo); } return report; } As stated this works fine on my XP machine used for development when deployed on winserver 2003 I get the error DC Some interesting additional information I moved the development to my home machine so I could work on the problem this weekend. So now I am developing debugging and testing on the same machine! In VS2008 I can edit and preview the reports with no problems If I fire up the debugger I can view the reports in the browser with no problems But if I publish the website to another folder on the same machine and fire up IIS and try to browse to a report I get the aforementioned error. All else works as expected. IIS runs under different permissions than VS2008 so perhaps its something to do with that, but I have tried lots of different permissions and cannot get it to run. DC

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• What was your the most impressive technical programming achievement performed to impress a romantic

  - by DVK

  OK, so the archetypal human story is for a guy to go out and impress the girl with some wonderful achievement like slaying a dragon or building a monument or conquering neighboring tribe. This being enlightened 21st century on SO, let's morph this into a: StackOverflower performing a feat of programming to impress a romantic interest. There are two ways to do this: Technical achievement: Impressing a person with suitable background/understanding of programming with actual coding powerss you displayed. A dumb movie example would be that kid in "Hackers" move showing off his hacking skills in front of Angeline Jolie. Artistic achievement: Impressing a person with a result of running said code, whether they understand just how incredible the code itself is. An example is the animated ANSI rose (for a guy who actually wrote the ANSI code) This question is only about the first kind (technical achievements) - e.g. the person of interest was presented with impressive code/design that (s)he was able to properly appreciate. Rules (what doesn't qualify): The target audience must have been a person of romantic interest (prospective or present significant other or random hook-up). E.g. showing your program to your sister who's also a software developer doesn't count. The achievement must have been done specifically with the goal to impress such a person. However, it is OK if the achievement was done to impress a generic qualifying person, not someone specific. Although... if you write code to impress girls in general, I'd say "get a better idea of the opposite sex" The achievement must have been done with the goal of impressing the person. In other words, if you would have done it without romantic interest's knowledge anyway, it doesn't count. As examples, the following does not count: programming for your job. Programming for a coding contest. Open Source program that you'd have done anyway. The precise nature of the awesomeness of the achievement is somewhat irrelevant - from learning entire J2EE in 2 days to writing fancy game engine to implementing Python compiler in LOGO. As long as it's programming/software development related. The achievement should preferably be something other people would rank highly as well. If your date was impressed with your skill at calculating Fibonacci sequence without recursive function calls, it doesn't mean most developers will be. But it does mean you need to start finding better things to do on dates ;)

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• To detect if the user is closing the IE browser apart from onunload event, as it is triggerred when

  - by AndAars

  hi, After being through numerous forums available on the net for last 5 days, I am still not able to completely track down the browser close event. My requirement is to generate a popup message, when user tries to close the browser. I have called my javascript function on body 'onbeforeunload' event. And I have hardcoded the conditions to check the mouse-coordinates for the red 'X' buton of browser, refresh, File-close or Alt-F4. My code works fine when browser window is Maximized, but fails if we shrink it after a limit. Please help me, if some body has already found the solution to a similar problem. Thank you. Aggregated Responses of OP Ok, just tell me if it is possible to detect if a user has clicked on the Refresh button of the browser. Also, Refresh can be triggered by Right-click - Refresh or Ctrl-R. My requirement is to make a variable false on Refresh. I am just able to do it on F5, but all other ways are still out of my reach. The same would be applied to Back buton. Hi ppl, Thanks for all who replied atleast. I have talked to my seniors regarding this and they have now understood and have compromised with the browser menu buttons. So now my task has become easy. Now, I am using a variable and making it true by default. As, I mentioned earlier I just have to catch the onbeforeunload and popup a message when user tries to leave. The message will not popup when user is navigating to other pages, as I have made the variable as false on all the links of my page using following piece of code: document.onclick = function() { //To check if user is navigating from the page by clicking on a hyperlink. if (event.srcElement.tagName == 'A') blnShowMsg = false; //To not popup the warning message else blnShowMsg = true; //To popup the warning message } In my case still the message is shown when user does Refresh, back or goes to any link in Favorites, etc. Thanks buddy, but I have already gone through that and didn't find much help there too. My seniors are not happy with that solution as putting a flag on evry link of my application is a complicated job and they fear of breaking the application. Any other suggestions would be appreciated. Thanks once again. Is there no one who can think of a solution here!!! where are all the experts???

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• Custom EntityNotFoundDelegate

  - by Felix

  Hi all, I get a org.hibernate.ObjectNotFoundException when I want to delete an object which doesn't exist anymore via hibernate. I just want this exception to be ignored. I could catch the exception and ignore, this would be a solution maybe. But, since there is a hibernate support for ignoring this exception through org.hibernate.cfg.Configuration#entityNotFoundDelegate, I would like to use its advantage and control it using configuration. The question is then, how can I introduce my own/custom implementation of EntityNotFoundDelegate to the org.hibernate.cfg.Configuration? Does anybody have a sample code for me? Just an additional tip, I use Spring Framework as well in my project. Here is the exception that I get: Caused by: org.springframework.orm.hibernate3.HibernateObjectRetrievalFailureException: No row with the given identifier exists: [de.mycompany.domain.ResultObject#810b1334-32d3-02b0-e044-769e0ab48e48]; nested exception is org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [de.mycompany.domain.ResultObject#810b1334-32d3-02b0-e044-769e0ab48e48] at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:660) at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:424) at org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374) at org.springframework.orm.hibernate3.HibernateTemplate.delete(HibernateTemplate.java:865) at org.springframework.orm.hibernate3.HibernateTemplate.delete(HibernateTemplate.java:859) at de.mycompany.utils.dao.impl.PersistentDaoImpl.delete(PersistentDaoImpl.java:50) at de.mycompany.utils.service.ServiceImpl.delete(ServiceImpl.java:68) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149) at de.mycompany.utils.service.ServiceInterceptor.invoke(ServiceInterceptor.java:43) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) at $Proxy3.delete(Unknown Source) ... 14 more Caused by: org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [de.mycompany.domain.ResultObject#810b1334-32d3-02b0-e044-769e0ab48e48] at org.hibernate.impl.SessionFactoryImpl$2.handleEntityNotFound(SessionFactoryImpl.java:409) at org.hibernate.proxy.AbstractLazyInitializer.checkTargetState(AbstractLazyInitializer.java:108) at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:97) at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:140) at org.hibernate.engine.StatefulPersistenceContext.unproxyAndReassociate(StatefulPersistenceContext.java:594) at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:90) at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:74) at org.hibernate.impl.SessionImpl.fireDelete(SessionImpl.java:793) at org.hibernate.impl.SessionImpl.delete(SessionImpl.java:778) at org.springframework.orm.hibernate3.HibernateTemplate$26.doInHibernate(HibernateTemplate.java:871) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:419) ... 30 more And my versions: Hibernate: 3.3.1 Spring: 2.5.6 Thanks in advance! Felix

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• List input and output audio devices in Applet

  - by Jhonny Everson

  I am running a signed applet that needs to provide the ability for the user to select the input and output audio devices ( similar to what skype provides). I borrowed the following code from other thread: import javax.sound.sampled.*; public class SoundAudit { public static void main(String[] args) { try { System.out.println("OS: "+System.getProperty("os.name")+" "+ System.getProperty("os.version")+"/"+ System.getProperty("os.arch")+"\nJava: "+ System.getProperty("java.version")+" ("+ System.getProperty("java.vendor")+")\n"); for (Mixer.Info thisMixerInfo : AudioSystem.getMixerInfo()) { System.out.println("Mixer: "+thisMixerInfo.getDescription()+ " ["+thisMixerInfo.getName()+"]"); Mixer thisMixer = AudioSystem.getMixer(thisMixerInfo); for (Line.Info thisLineInfo:thisMixer.getSourceLineInfo()) { if (thisLineInfo.getLineClass().getName().equals( "javax.sound.sampled.Port")) { Line thisLine = thisMixer.getLine(thisLineInfo); thisLine.open(); System.out.println(" Source Port: " +thisLineInfo.toString()); for (Control thisControl : thisLine.getControls()) { System.out.println(AnalyzeControl(thisControl));} thisLine.close();}} for (Line.Info thisLineInfo:thisMixer.getTargetLineInfo()) { if (thisLineInfo.getLineClass().getName().equals( "javax.sound.sampled.Port")) { Line thisLine = thisMixer.getLine(thisLineInfo); thisLine.open(); System.out.println(" Target Port: " +thisLineInfo.toString()); for (Control thisControl : thisLine.getControls()) { System.out.println(AnalyzeControl(thisControl));} thisLine.close();}}} } catch (Exception e) {e.printStackTrace();}} public static String AnalyzeControl(Control thisControl) { String type = thisControl.getType().toString(); if (thisControl instanceof BooleanControl) { return " Control: "+type+" (boolean)"; } if (thisControl instanceof CompoundControl) { System.out.println(" Control: "+type+ " (compound - values below)"); String toReturn = ""; for (Control children: ((CompoundControl)thisControl).getMemberControls()) { toReturn+=" "+AnalyzeControl(children)+"\n";} return toReturn.substring(0, toReturn.length()-1);} if (thisControl instanceof EnumControl) { return " Control:"+type+" (enum: "+thisControl.toString()+")";} if (thisControl instanceof FloatControl) { return " Control: "+type+" (float: from "+ ((FloatControl) thisControl).getMinimum()+" to "+ ((FloatControl) thisControl).getMaximum()+")";} return " Control: unknown type";} } But what I get: Mixer: Software mixer and synthesizer [Java Sound Audio Engine] Mixer: No details available [Microphone (Pink Front)] I was expecting the get the real list of my devices (My preferences panels shows 3 output devices and 1 Microphone). I am running on Mac OS X 10.6.7. Is there other way to get that info from Java?

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• Form data sent to Node via Post is undefined

  - by user185812

  I know this has been asked countless times on here, however I tried all the solutions and am still having the issue. Most people say to set the content-type (which I did) and to name the inputs that I wish to Post to node. I have done both of these things, yet still get "undefined" when trying to send data from an HTML form to node. JADE Templating HTML Code (Sorry I can't seem to get the indenting to show up here, however I think I should leave the code intact when posting here instead of converting it to normal HTML so that if the error is in here, you are still able to help) Form(action="/registration", method="post", enctype="application/x-www-form-urlencoded") div(class="control-group-Username") label(class="control-group", for="username") Username: div.controls input#Username(id="Username", type="text", placeholder="Username Here", maxlength="23", name="username") //Other divs and stuff here button.btn#submit_button(type="submit") Submit app.js code /** * Module dependencies. */ express = require('express') , routes = require('./routes') , user = require('./routes/user') , http = require('http') , path = require('path'); app = express(); // all environments app.set('port', process.env.PORT || 3000); app.set('views', __dirname + '/views'); app.set('view engine','jade'); app.use(express.favicon()); app.use(express.logger('dev')); app.use(express.bodyParser()); app.use(express.methodOverride()); app.use(express.cookieParser('your secret here')); app.use(express.session()); app.use(app.router); app.use(require('less-middleware')({ src: __dirname + '/public' })); app.use(express.static(path.join(__dirname, 'public'))); // development only if ('development' == app.get('env')) { app.use(express.errorHandler()); } app.use(express.static(__dirname + '/public')); app.get('/', routes.index); app.get('/users', user.list); app.get('/register', routes.register); http.createServer(app).listen(app.get('port'), function(){ console.log('Express server listening on port ' + app.get('port')); }); require('./Register.js'); register.js code app.post('/registration', function(req, res) { var Email=req.body.username console.log(username); });

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• Which management tools would you recommend for software development?

  - by Robert Schneider

  What would you generally recommend for software developement? Which combination do you use or would you recommend? I assume that tools are needed for Version control, issues/bugs/task, Release management, Requirement management. Tools for Test management and Project management should be accounted for as well, I guess. Did I forget anything? Maybe tools for Continous Integration. I'm not interested in a halfway combination of one ore two tools like a Subversion + Bugzilla (I know they are good but for a company they might not be sufficient). And also tools like make/ant shouldn't be taken into account. I'd like to know a combination that covers all what is important for professional software development. However, it could be a single tool of course if it covers all the management issues. What do you think would be a good combination? I assume a combination should be regardes as good if the tools itself are good but also if they have good integrations. Udate: Something like Ant is just a script not a management tool. Okay: we do already have Perforce. But this is somehow generic. We have different projects that uses C-, VS/.NET-, Python-, PHP and we will be starting new projects in Java. Plenty of languages and frameworks, though some are going to be legacy. So the tools should be generic. Obviously we don't want to use Bugzilla for one project and Jira for another. The management tools have to be generic. Further thoughts: Think of sourceforge: For each project they offer a version control system, an issue tracker, a wiki, ... totally independent of what the project is about. Those are some management tools that a project usually needs. I would say that most companies need such a set of tools. But I could imagine, if a company has several projects, they need further tools too: for Project management, Quality management, ... And I could imagine there are some recommendable combinations of tools. A not really apropiate comparison to this could be LAMP (Linux, Apache, MySQL, PHP). A combination of software that has evolved since they work very well together, and are pretty useful for a lot of applications (or rather web sites). So maybe there are some recommendable management tool combinations that also fit toghether like LAMP. The integration is important. Thank you for the incredibly fast and helpful responses!!!

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• Oracle Coding Standards Feature Implementation

  - by Mike Hofer

  Okay, I have reached a sort of an impasse. In my open source project, a .NET-based Oracle database browser, I've implemented a bunch of refactoring tools. So far, so good. The one feature I was really hoping to implement was a big "Global Reformat" that would make the code (scripts, functions, procedures, packages, views, etc.) standards compliant. (I've always been saddened by the lack of decent SQL refactoring tools, and wanted to do something about it.) Unfortunatey, I am discovering, much to my chagrin, that there doesn't seem to be any one widely-used or even "generally accepted" standard for PL-SQL. That kind of puts a crimp on my implementation plans. My search has been fairly exhaustive. I've found lots of conflicting documents, threads and articles and the opinions are fairly diverse. (Comma placement, of all things, seems to generate quite a bit of debate.) So I'm faced with a couple of options: Add a feature that lets the user customize the standard and then reformat the code according to that standard. —OR— Add a feature that lets the user customize the standard and simply generate a violations list like StyleCop does, leaving the SQL untouched. In my mind, the first option saves the end-users a lot of work, but runs the risk of modifying SQL in potentially unwanted ways. The second option runs the risk of generating lots of warnings and doing no work whatsoever. (It'd just be generally annoying.) In either scenario, I still have no standard to go by. What I'd need to know from you guys is kind of poll-ish, but kind of not. If you were going to use a tool of this nature, what parts of your SQL code would you want it to warn you about or fix? Again, I'm just at a loss due to a lack of a cohesive standard. And given that there isn't anything out there that's officially published by Oracle, I think this is something the community could weigh in on. Also, given the way that voting works on SO, the votes would help to establish the popularity of a given "refactoring." P.S. The engine parses SQL into an expression tree so it can robustly analyze the SQL and reformat it. There should be quite a bit that we can do to correct the format of the SQL. But I am thinking that for the first release of the thing, layout is the primary concern. Though it is worth noting that the thing already has refactorings for converting keywords to upper case, and identifiers to lower case.

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• physics game programming box2d - orientating a turret-like object using torques

  - by egarcia

  This is a problem I hit when trying to implement a game using the LÖVE engine, which covers box2d with Lua scripting. The objective is simple: A turret-like object (seen from the top, on a 2D environment) needs to orientate itself so it points to a target. The turret is on the x,y coordinates, and the target is on tx, ty. We can consider that x,y are fixed, but tx, ty tend to vary from one instant to the other (i.e. they would be the mouse cursor). The turret has a rotor that can apply a rotational force (torque) on any given moment, clockwise or counter-clockwise. The magnitude of that force has an upper limit called maxTorque. The turret also has certain rotational inertia, which acts for angular movement the same way mass acts for linear movement. There's no friction of any kind, so the turret will keep spinning if it has an angular velocity. The turret has a small AI function that re-evaluates its orientation to verify that it points to the right direction, and activates the rotator. This happens every dt (~60 times per second). It looks like this right now: function Turret:update(dt) local x,y = self:getPositon() local tx,ty = self:getTarget() local maxTorque = self:getMaxTorque() -- max force of the turret rotor local inertia = self:getInertia() -- the rotational inertia local w = self:getAngularVelocity() -- current angular velocity of the turret local angle = self:getAngle() -- the angle the turret is facing currently -- the angle of the like that links the turret center with the target local targetAngle = math.atan2(oy-y,ox-x) local differenceAngle = _normalizeAngle(targetAngle - angle) if(differenceAngle <= math.pi) then -- counter-clockwise is the shortest path self:applyTorque(maxTorque) else -- clockwise is the shortest path self:applyTorque(-maxTorque) end end ... it fails. Let me explain with two illustrative situations: The turret "oscillates" around the targetAngle. If the target is "right behind the turret, just a little clock-wise", the turret will start applying clockwise torques, and keep applying them until the instant in which it surpasses the target angle. At that moment it will start applying torques on the opposite direction. But it will have gained a significant angular velocity, so it will keep going clockwise for some time... until the target will be "just behind, but a bit counter-clockwise". And it will start again. So the turret will oscillate or even go in round circles. I think that my turret should start applying torques in the "opposite direction of the shortest path" before it reaches the target angle (like a car braking before stopping). Intuitively, I think the turret should "start applying torques on the opposite direction of the shortest path when it is about half-way to the target objective". My intuition tells me that it has something to do with the angular velocity. And then there's the fact that the target is mobile - I don't know if I should take that into account somehow or just ignore it. How do I calculate when the turret must "start braking"?

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• Transposing and Untransposing a String in java

  - by Will

  I have been working on two methods that will Transpose and Untranspose a String respectively. The solutions that I have come up with both work to the best of my knowledge. I just want to know if I could have solved these problems in a simpler way. My code seems like it is too long for the task that is being performed. The first method, transpose(), will take a String as a parameter and transpose it. If "bridge" is entered, the output will be "bergid". Likewise, with the unTranspose() method, if the user enters "bergid", the output will be "bridge". public void transpose( String s ) { String t = ""; int end = s.length() - 1; for ( int i = 0; i < s.length() / 2; i++ ) { t += Character.toString( s.charAt( i ) ) + Character.toString( s.charAt( end ) ); end--; } // Lenth of String is odd if ( s.length() % 2 == 1 ) { // add character in middle of String to the end of the new String t+= Character.toString( s.charAt( s.length() / 2 ) ); } System.out.println( t ); } public void unTranspose( String s ) { String t = ""; // Length of String is odd if ( s.length() % 2 == 1 ) { for ( int i = 0; i < s.length(); i+=2 ) { t+= Character.toString( s.charAt( i ) ); } for ( int i = s.length() - 2; i > 0; i -= 2 ) { t += Character.toString( s.charAt( i ) ); } System.out.println( t ); } // Length of String is even else if ( s.length() % 2 == 0 ) { for ( int i = 0; i < s.length() - 1; i+=2 ) { t+= Character.toString( s.charAt( i ) ); } for ( int i = s.length() - 1; i > 0; i -= 2 ) { t+= Character.toString( s.charAt( i ) ); } System.out.println( t ); } } My code looks horrible. I'm still not used to formatting my code correctly. Please bear with me. Thanks for your time

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• SELECT SQL statement problem when getting info from an accdb in VB.Net

  - by Shane Fagan

  Hi again all, im getting the error below for this SQL statement in VB.Net SQLString = "SELECT AllPropertyDetails.PropertyID, Street, Town, County, Acres, Quotas, ResidenceDetails, Status, HighestBid, AskingPrice FROM AllPropertyDetails " SQLString += "INNER JOIN Land ON AllPropertyDetails.PropertyID = Land.PropertyID " SQLString += "WHERE Deleted = False " If PriceRadioButton.Checked = True Then SQLString += "ORDER BY AskingPrice ASC" ElseIf AcresRadioButton.Checked = True Then SQLString += "ORDER BY Acres ASC" End If Any ideas why its not working? The fields in the DB and the table names seem ok but its not working :/ System.InvalidOperationException was unhandled Message="An error occurred creating the form. See Exception.InnerException for details. The error is: No value given for one or more required parameters." Source="AuctioneerProject" StackTrace: at AuctioneerProject.My.MyProject.MyForms.Create__Instance__[T](T Instance) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 190 at AuctioneerProject.My.MyProject.MyForms.get_LandReport() at AuctioneerProject.ReportsMenu.LandButton_Click(Object sender, EventArgs e) in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\ReportsMenu.vb:line 4 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnClick(EventArgs e) at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ButtonBase.WndProc(Message& m) at System.Windows.Forms.Button.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.Run(ApplicationContext context) at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine) at AuctioneerProject.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException: System.Data.OleDb.OleDbException ErrorCode=-2147217904 Message="No value given for one or more required parameters." Source="Microsoft Office Access Database Engine" StackTrace: at System.Data.OleDb.OleDbCommand.ExecuteCommandTextErrorHandling(OleDbHResult hr) at System.Data.OleDb.OleDbCommand.ExecuteCommandTextForSingleResult(tagDBPARAMS dbParams, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommandText(Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommand(CommandBehavior behavior, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior, String method) at System.Data.OleDb.OleDbCommand.ExecuteReader(CommandBehavior behavior) at System.Data.OleDb.OleDbCommand.ExecuteReader() at AuctioneerProject.LandReport.load_Land() in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.vb:line 37 at AuctioneerProject.LandReport.PriceRadioButton_CheckedChanged(Object sender, EventArgs e) in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.vb:line 79 at System.Windows.Forms.RadioButton.OnCheckedChanged(EventArgs e) at System.Windows.Forms.RadioButton.set_Checked(Boolean value) at AuctioneerProject.LandReport.InitializeComponent() in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.designer.vb:line 40 at AuctioneerProject.LandReport..ctor() in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\LandReport.vb:line 5 InnerException:

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• Ant + JUnit = ClassNotFoundExceptions when running tests?

  - by rfkrocktk

  I'm trying to run some tests in Ant presently using JUnit, and all of my tests are failing with the following stacktrace: java.lang.ClassNotFoundException: com.mypackage.MyTestCase It doesn't make too much sense to me. I'm first compiling my test cases using <javac>, then directly running the <junit> task to run the tests. My buildfile looks like this: <target name="compile.webapp.tests"> <javac srcdir="${test.java.src.dir}" destdir="${test.java.bin.dir}"> <classpath> <filelist> <file name="${red5.home}/red5.jar"/> <file name="${red5.home}/boot.jar"/> <file name="${bin.dir}/${ant.project.name}.jar"/> </filelist> <fileset dir="${red5.lib.dir}" includes="**/*"/> <fileset dir="${main.java.lib.dir}" includes="**/*"/> <fileset dir="${test.java.lib.dir}" includes="**/*"/> </classpath> </javac> </target> <target name="run.webapp.tests"> <junit printsummary="true"> <classpath> <filelist> <file name="${red5.home}/red5.jar"/> <file name="${red5.home}/boot.jar"/> <file name="${bin.dir}/${ant.project.name}.jar"/> </filelist> <fileset dir="${red5.lib.dir}" includes="**/*.jar"/> <fileset dir="${main.java.lib.dir}" includes="**/*.jar"/> <fileset dir="${test.java.lib.dir}" includes="**/*.jar"/> </classpath> <formatter type="xml"/> <batchtest todir="${test.java.output.dir}"> <fileset dir="${test.java.bin.dir}" includes="**/*TestCase*"/> </batchtest> </junit> </target> This is really weird, I can't seem to fix this. Is there something I'm doing wrong here?

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• UNIX: Replace Newline w/ Colon, Preserving Newline Before EOF

  - by Maarx

  I have a text file ("INPUT.txt") of the format: A<LF> B<LF> C<LF> D<LF> X<LF> Y<LF> Z<LF> <EOF> which I need to reformat to: A:B:C:D:X:Y:Z<LF> <EOF> I know you can do this with 'sed'. There's a billion google hits for doing this with 'sed'. But I'm trying to emphasis readability, simplicity, and using the correct tool for the correct job. 'sed' is a line editor that consumes and hides newlines. Probably not the right tool for this job! I think the correct tool for this job would be 'tr'. I can replace all the newlines with colons with the command: cat INPUT.txt | tr '\n' ':' There's 99% of my work done. I have a problem, now, though. By replacing all the newlines with colons, I not only get an extraneous colon at the end of the sequence, but I also lose the carriage return at the end of the input. It looks like this: A:B:C:D:X:Y:Z:<EOF> Now, I need to remove the colon from the end of the input. However, if I attempt to pass this processed input through 'sed' to remove the final colon (which would now, I think, be a proper use of 'sed'), I find myself with a second problem. The input is no longer terminated by a newline at all! 'sed' fails outright, for all commands, because it never finds the end of the first line of input! It seems like appending a newline to the end of some input is a very, very common task, and considering I myself was just sorely tempted to write a program to do it in C (which would take about eight lines of code), I can't imagine there's not already a very simple way to do this with the tools already available to you in the Linux kernel.

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• iPhone SDK / Core Data usage scenario, similar to GAE data store?

  - by boliva

  Hi all, I am currently rewriting a map based App which I wrote in the past, specifically for 2.2.1 devices. Originally I wrote it to make use of SQLite databases but I would like to try and migrate it over Core Data, now that it's available on 3.X (for which I am rewriting to). I am fairly experienced in iPhone/Obj-C development, SQL and server backend technologies, but I have never had the chance to work with Core Data so IDK really if it's the appropiate tool for what I am trying to accomplish. The App works on a limited area in a map over which there are about 4000 placemarks, with different kinds of icons and sizes. Of course not all 4000 placemarks are shown at once but only those currently visible in the map viewport, and depending on the zoom level. What I am doing right now is, after the user moves the map in any way (panning or zooming) I am requesting from the backend server the required information for the placemarks that would be visible given the viewport coordinates boundaries and zoom level, however the process isn't as smooth as I'd like (the backend is sending its response in XML and I am compressing it using gzip), it takes anywhere from 1 to 3 seconds to update the display of the placemarks after the user ends moving the map. What I would like to do is to prefetch all the placemarks data at the App launch and use it all through the app life time - I don't mind storing it for later use because the data should be dynamic. The way I would do it right now is, after retrieving all the data, to store it on an SQLite db which I would query later, whenever the user moves the map, to return only the placemarks inside the viewport coordinate boundaries and specific to a given zoom level. Now, the question itself is, if is it possible to use some more 'native', object driven way to carry this queries process, which got me thinking about Core Data and if it is in any way similar to what Google App Engine offers through its datastore where you can fetch a number of objects from the backend given a certain query or criteria, without resorting to an SQL query itself. Like I said before I don't have any experience on Core Data but I have a pretty deep understanding of Obj-C and iPhone development, as well as SQL databases. Any guides on how to achieve what I'm trying (if possible at all) would be greatly appreciated.

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• Glassfish V3 won't start

  - by Zakaria

  Hi everybody, I installed NetBeans 6.8 and tried to run the GlasshFish V3 server. I'm working under Windows Vista 32 Bits. First, it won't run. Then I modified the c:\Windows\System32\drivers\etc\hosts file and put the following line into it: 127.0.0.1 localhost And when I run the GlasshFish V3 Server, no error is showing but only "INFOs" are displayed: 3 avr. 2010 19:23:19 com.sun.enterprise.glassfish.bootstrap.ASMain main INFO: Launching GlassFish on Felix platform Welcome to Felix ================ INFO: Perform lazy SSL initialization for the listener 'http-listener-2' INFO: Starting Grizzly Framework 1.9.18-k - Sat Apr 03 19:23:24 CEST 2010 INFO: Starting Grizzly Framework 1.9.18-k - Sat Apr 03 19:23:25 CEST 2010 INFO: Grizzly Framework 1.9.18-k started in: 423ms listening on port 35127 INFO: GlassFish v3 (74.2) startup time : Felix(4456ms) startup services(1709ms) total(6165ms) INFO: Grizzly Framework 1.9.18-k started in: 459ms listening on port 35116 INFO: Grizzly Framework 1.9.18-k started in: 428ms listening on port 35155 INFO: Grizzly Framework 1.9.18-k started in: 470ms listening on port 35160 INFO: Grizzly Framework 1.9.18-k started in: 513ms listening on port 35159 INFO: javassist.util.proxy.ProxyFactory.classLoaderProvider = org.glassfish.weld.WeldActivator$GlassFishClassLoaderProvider@5be8f4 INFO: Hibernate Validator bean-validator-3.0-JBoss-4.0.2 INFO: Binding RMI port to *:35165 INFO: Instantiated an instance of org.hibernate.validator.engine.resolver.JPATraversableResolver. INFO: JMXStartupService: Started JMXConnector, JMXService URL = service:jmx:rmi://PC-de-Charlotte:35165/jndi/rmi://PC-de-Charlotte:35165/jmxrmi INFO: Using com.sun.enterprise.transaction.jts.JavaEETransactionManagerJTSDelegate as the delegate INFO: [Thread[GlassFish Kernel Main Thread,5,main]] started INFO: Grizzly Framework 1.9.18-k started in: 150ms listening on port 35159 INFO: Perform lazy SSL initialization for the listener 'http-listener-2' INFO: {felix.fileinstall.poll (ms) = 5000, felix.fileinstall.dir = C:\Program Files\sges-v3\glassfish\modules\autostart, felix.fileinstall.debug = 1, felix.fileinstall.bundles.new.start = true, felix.fileinstall.tmpdir = C:\Users\CHARLO~1\AppData\Local\Temp\fileinstall-330907148519261411, felix.fileinstall.filter = null} INFO: {felix.fileinstall.poll (ms) = 5000, felix.fileinstall.dir = C:\Users\Charlotte\.netbeans\6.8\GlassFish_v3\autodeploy\bundles, felix.fileinstall.debug = 1, felix.fileinstall.bundles.new.start = true, felix.fileinstall.tmpdir = C:\Users\CHARLO~1\AppData\Local\Temp\fileinstall-2938963288421854459, felix.fileinstall.filter = null} INFO: Grizzly Framework 1.9.18-k started in: 95ms listening on port 35160 INFO: Updating configuration from org.apache.felix.fileinstall-autodeploy-bundles.cfg INFO: Installed C:\Program Files\sges-v3\glassfish\modules\autostart\org.apache.felix.fileinstall-autodeploy-bundles.cfg INFO: {felix.fileinstall.poll (ms) = 5000, felix.fileinstall.dir = C:\Users\Charlotte\.netbeans\6.8\GlassFish_v3\autodeploy\bundles, felix.fileinstall.debug = 1, felix.fileinstall.bundles.new.start = true, felix.fileinstall.tmpdir = C:\Users\CHARLO~1\AppData\Local\Temp\fileinstall-6474085409014899009, felix.fileinstall.filter = null} And there is no message such as "Glassfish started"! So, when I try to access to the admin web interface: localhost:4848 or localhost:8080 or localhost:8181 , It doesn't work. What should I do? Thank you very much, Regards.

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• Static Javascript files not loaded in Express app

  - by Dave Long

  I have an express app that has a bunch of static javascript files that aren't being loaded even though they are registered in my app.js file. Even public scripts (like jQuery: http://ajax.googleapis.com/ajax/libs/jquery/1.6.3/jquery.min.js) aren't processing. I can see the script tags in the generated html, but none of the functionality runs and I can't see the files loading in the web inspector. Here is the code that I have: app.js var express = require('express') var app = module.exports = express.createServer(); // Configuration var port = process.env.PORT || 3000; app.configure(function(){ app.set('views', __dirname + '/views'); app.set('view engine', 'jade'); app.use(express.bodyParser()); app.use(express.methodOverride()); app.use(app.router); app.use(express.static(__dirname + '/public')); }); app.configure('development', function(){ app.use(express.errorHandler({ dumpExceptions: true, showStack: true })); }); app.configure('production', function(){ app.use(express.errorHandler()); }); // Routes app.get('/manage/new', function(req, res){ res.render('manage/new', { title: 'Create a new widget' }); }) app.listen(port); console.log("Express server listening on port %d in %s mode", app.address().port, app.settings.env); /views/manage/layout.jade !!! 5 html(lang="en") head title= title link(rel="stylesheet", href="/stylesheets/demo.css") link(rel="stylesheet", href="/stylesheets/jquery.qtip.css") script(type="text/javascript", href="http://ajax.googleapis.com/ajax/libs/jquery/1.6.3/jquery.min.js") body!= body script(type="text/javascript", href="/javascripts/jquery.formalize.js") script(type="text/javascript", href="/javascripts/jquery.form.js") script(type="text/javascript", href="/javascripts/jquery.qtip.js") script(type="text/javascript", href="/javascripts/formToWizard.js") script(type="text/javascript", href="/javascripts/widget.js") /views/manage/new.jade h1= title div(style="float:left;") form(action="/manage/generate", method="post", enctype="multipart/form-data", name="create-widget") .errors fieldset legend Band / Album Information fieldset legend Social Networks fieldset legend Download All of my javascript files are stored in /public/javascripts and all of my static CSS files are being served up just fine. I'm not sure what I've done wrong.

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• C#: BackgroundWorker cloning resources?

  - by Dav

  The problem I've been struggling with this partiular problem for two days now and just run out of ideas. A little... background: we have a WinForms app that needs to access a database, construct a list of related in-memory objects from that data, and then display on a DataGridView. Important point is that we first populate an app-wide cache (List), and then create a mirror of the cache local to the form on which the DGV lives (using List constructor param). Because fetching the data takes a good few seconds (DB sits on a LAN server) to load, we decided to use a BackgroundWorker, and only refresh the DGV once the data is loaded. However, it seems that doing the loading via a BGW results in some memory leak... or an error on my part. When loaded using a blocking method call, the app consumes about 30MB of RAM; with a BGW this jumps to 80MB! While it may not seem as much anyway, our clients are not too happy about it. Relevant code Form private void MyForm_Load(object sender, EventArgs e) { MyRepository.Instance.FinishedEvent += RefreshCache; } private void RefreshCache(object sender, EventArgs e) { dgvProducts.DataSource = new List<MyDataObj>(MyRepository.Products); } Repository private static List<MyDataObj> Products { get; set; } public event EventHandler ProductsLoaded; public void GetProductsSync() { List<MyDataObj> p; using (MyL2SDb db = new MyL2SDb(MyConfig.ConnectionString)) { p = db.PRODUCTS .Select(p => new MyDataObj {Id = p.ID, Description = p.DESCR}) .ToList(); } Products = p; // tell the form to refresh UI if (ProductsLoaded != null) ProductsLoaded(this, null); } public void GetProductsAsync() { using (BackgroundWorker myWorker = new BackgroundWorker()) { myWorker.DoWork += delegate { List<MyDataObj> p; using (MyL2SDb db = new MyL2SDb(MyConfig.ConnectionString)) { p = db.PRODUCTS .Select(p => new MyDataObj {Id = p.ID, Description = p.DESCR}) .ToList(); } Products = p; }; // tell the form to refresh UI when finished myWorker.RunWorkerCompleted += GetProductsCompleted; myWorker.RunWorkerAsync(); } } private void GetProductsCompleted(object sender, RunWorkerCompletedEventArgs e) { if (ProductsLoaded != null) ProductsLoaded(this, null); } End! GetProductsSync or GetProductsAsync are called on the main thread, not shown above. Could it be that the GarbageCollector just gets lost with two threads? Or is it the task manager that shows incorrect values? Will be greateful for any responses, suggestions, criticism.

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• Permutations of Varying Size

  - by waiwai933

  I'm trying to write a function in PHP that gets all permutations of all possible sizes. I think an example would be the best way to start off: $my_array = array(1,1,2,3); Possible permutations of varying size: 1 1 // * See Note 2 3 1,1 1,2 1,3 // And so forth, for all the sets of size 2 1,1,2 1,1,3 1,2,1 // And so forth, for all the sets of size 3 1,1,2,3 1,1,3,2 // And so forth, for all the sets of size 4 Note: I don't care if there's a duplicate or not. For the purposes of this example, all future duplicates have been omitted. What I have so far in PHP: function getPermutations($my_array){ $permutation_length = 1; $keep_going = true; while($keep_going){ while($there_are_still_permutations_with_this_length){ // Generate the next permutation and return it into an array // Of course, the actual important part of the code is what I'm having trouble with. } $permutation_length++; if($permutation_length>count($my_array)){ $keep_going = false; } else{ $keep_going = true; } } return $return_array; } The closest thing I can think of is shuffling the array, picking the first n elements, seeing if it's already in the results array, and if it's not, add it in, and then stop when there are mathematically no more possible permutations for that length. But it's ugly and resource-inefficient. Any pseudocode algorithms would be greatly appreciated. Also, for super-duper (worthless) bonus points, is there a way to get just 1 permutation with the function but make it so that it doesn't have to recalculate all previous permutations to get the next? For example, I pass it a parameter 3, which means it's already done 3 permutations, and it just generates number 4 without redoing the previous 3? (Passing it the parameter is not necessary, it could keep track in a global or static). The reason I ask this is because as the array grows, so does the number of possible combinations. Suffice it to say that one small data set with only a dozen elements grows quickly into the trillions of possible combinations and I don't want to task PHP with holding trillions of permutations in its memory at once.

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• controlling threads flow

  - by owca

  I had a task to write simple game simulating two players picking up 1-3 matches one after another until the pile is gone. I managed to do it for computer choosing random value of matches but now I'd like to go further and allow humans to play the game. Here's what I already have : http://paste.pocoo.org/show/201761/ Class Player is a computer player, and PlayerMan should be human being. Problem is, that thread of PlayerMan should wait until proper value of matches is given but I cannot make it work this way. Logic is as follows: thread runs until matches equals to zero. If player number is correct at the moment function pickMatches() is called. After decreasing number of matches on table, thread should wait and another thread should be notified. I know I must use wait() and notify() but I can't place them right. Class Shared keeps the value of current player, and also amount of matches. public void suspendThread() { suspended = true; } public void resumeThread() { suspended = false; } @Override public void run(){ int matches=1; int which = 0; int tmp=0; Shared data = this.selectData(); String name = this.returnName(); int number = this.getNumber(); while(data.getMatches() != 0){ while(!suspended){ try{ which = data.getCurrent(); if(number == which){ matches = pickMatches(); tmp = data.getMatches() - matches; data.setMatches(tmp, number); if(data.getMatches() == 0){ System.out.println(" "+ name+" takes "+matches+" matches."); System.out.println("Winner is player: "+name); stop(); } System.out.println(" "+ name+" takes "+matches+" matches."); if(number != 0){ data.setCurrent(0); } else{ data.setCurrent(1); } } this.suspendThread(); notifyAll(); wait(); }catch(InterruptedException exc) {} } } } @Override synchronized public int pickMatches(){ Scanner scanner = new Scanner(System.in); int n = 0; Shared data = this.selectData(); System.out.println("Choose amount of matches (from 1 to 3): "); if(data.getMatches() == 1){ System.out.println("There's only 1 match left !"); while(n != 1){ n = scanner.nextInt(); } } else{ do{ n = scanner.nextInt(); } while(n <= 1 && n >= 3); } return n; } }

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• Some more multitasking java issues

  - by owca

  I had a task to write simple game simulating two players picking up 1-3 matches one after another until the pile is gone. I managed to do it for computer choosing random value of matches but now I'd like to go further and allow humans to play the game. Here's what I already have : http://paste.pocoo.org/show/200660/ Class Player is a computer player, and PlayerMan should be human being. Problem is, that thread of PlayerMan should wait until proper value of matches is given but I cannot make it work this way. When I type the values it sometimes catches them and decrease amount of matches but that's not exactly what I was up to :) Logics is : I check the value of current player. If it corresponds to this of the thread currently active I use scanner to catch the amount of matches. Else I wait one second (I know it's kinda harsh solution, but I have no other idea how to do it). Class Shared keeps the value of current player, and also amount of matches. By the way, is there any way I can make Player and Shared attributes private instead of public and still make the code work ? CONSOLE and INPUT-DIALOG is just for choosing way of inserting values. class PlayerMan extends Player{ static final int CONSOLE=0; static final int INPUT_DIALOG=1; private int input; public PlayerMan(String name, Shared data, int c){ super(name, data); input = c; } @Override public void run(){ Scanner scanner = new Scanner(System.in); int n = 0; System.out.println("Matches on table: "+data.matchesAmount); System.out.println("which: "+data.which); System.out.println("number: "+number); while(data.matchesAmount != 0){ if(number == data.which){ System.out.println("Choose amount of matches (from 1 to 3): "); n = scanner.nextInt(); if(data.matchesAmount == 1){ System.out.println("There's only 1 match left !"); while(n != 1){ n = scanner.nextInt(); } } else{ do{ n = scanner.nextInt(); } while(n <= 1 && n >= 3); } data.matchesAmount = data.matchesAmount - n; System.out.println(" "+ name+" takes "+n+" matches."); if(number != 0){ data.which = 0; } else{ data.which = 1; } } else{ try { Thread.sleep(1000); } catch(InterruptedException exc) { System.out.println("End of thread."); return; } } System.out.println("Matches on table: "+data.matchesAmount); } if(data.matchesAmount == 0){ System.out.println("Winner is player: "+name); stop(); } } }

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• Can you find a pattern to sync files knowing only dates and filenames?

  - by Robert MacLean

  Imagine if you will a operating system that had the following methods for files Create File: Creates (writes) a new file to disk. Calling this if a file exists causes a fault. Update File: Updates an existing file. Call this if a file doesn't exist causes a fault. Read File: Reads data from a file. Enumerate files: Gets all files in a folder. Files themselves in this operating system only have the following meta data: Created Time: The original date and time the file was created, by the Create File method. Modified Time: The date and time the file was last modified by the Update File method. If the file has never been modified, this will equal the Create Time. You have been given the task of writing an application which will sync the files between two directories (lets call them bill and ted) on a machine. However it is not that simple, the client has required that The application never faults (see methods above). That while the application is running the users can add and update files and those will be sync'd next time the application runs. Files can be added to either the ted or bill directories. File names cannot be altered. The application will perform one sync per time it is run. The application must be almost entirely in memory, in other words you cannot create a log of filenames and write that to disk and then check that the next time. The exception to point 6 is that you can store date and times between runs. Each date/time is associated with a key labeled A through J (so you have 10 to use) so you can compare keys between runs. There is no way to catch exceptions in the application. Answer will be accepted based on the following conditions: First answer to meet all requirements will be accepted. If there is no way to meet all requirements, the answer which ensures the smallest amount of missed changes per sync will be accepted. A bounty will be created (100 points) as soon as possible for the prize. The winner will be selected one day before the bounty ends. Please ask questions in the comments and I will gladly update and refine the question on those.

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• pointers to functions

  - by DevAno1

  I have two basic Cpp tasks, but still I have problems with them. First is to write functions mul1,div1,sub1,sum1, taking ints as arguments and returning ints. Then I need to create pointers ptrFun1 and ptrFun2 to functions mul1 and sum1, and print results of using them. Problem starts with defining those pointers. I thought I was doing it right, but devcpp gives me errors in compilation. #include <iostream> using namespace std; int mul1(int a,int b) { return a * b; } int div1(int a,int b) { return a / b; } int sum1(int a,int b) { return a + b; } int sub1(int a,int b) { return a - b; } int main() { int a=1; int b=5; cout << mul1(a,b) << endl; cout << div1(a,b) << endl; cout << sum1(a,b) << endl; cout << sub1(a,b) << endl; int *funPtr1(int, int); int *funPtr2(int, int); funPtr1 = sum1; funPtr2 = mul1; cout << funPtr1(a,b) << endl; cout << funPtr2(a,b) << endl; system("PAUSE"); return 0; } 38 assignment of function int* funPtr1(int, int)' 38 cannot convertint ()(int, int)' to `int*()(int, int)' in assignment Task 2 is to create array of pointers to those functions named tabFunPtr. How to do that ?

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• How to produce precisely-timed tone and silence?

  - by Bob Denny

  I have a C# project that plays Morse code for RSS feeds. I write it using Managed DirectX, only to discover that Managed DirectX is old and deprecated. The task I have is to play pure sine wave bursts interspersed with silence periods (the code) which are precisely timed as to their duration. I need to be able to call a function which plays a pure tone for so many milliseconds, then Thread.Sleep() then play another, etc. At its fastest, the tones and spaces can be as short as 40ms. It's working quite well in Managed DirectX. To get the precisely timed tone I create 1 sec. of sine wave into a secondary buffer, then to play a tone of a certain duration I seek forward to within x milliseconds of the end of the buffer then play. I've tried System.Media.SoundPlayer. It's a loser because you have to Play(), Sleep(), then Stop() for arbitrary tone lengths. The result is a tone that is too long, variable by CPU load. It takes an indeterminate amount of time to actually stop the tone. I then embarked on a lengthy attempt to use NAudio 1.3. I ended up with a memory resident stream providing the tone data, and again seeking forward leaving the desired length of tone remaining in the stream, then playing. This worked OK on the DirectSoundOut class for a while (see below) but the WaveOut class quickly dies with an internal assert saying that buffers are still on the queue despite PlayerStopped = true. This is odd since I play to the end then put a wait of the same duration between the end of the tone and the start of the next. You'd think that 80ms after starting Play of a 40 ms tone that it wouldn't have buffers on the queue. DirectSoundOut works well for a while, but its problem is that for every tone burst Play() it spins off a separate thread. Eventually (5 min or so) it just stops working. You can see thread after thread after thread exiting in the Output window while running the project in VS2008 IDE. I don't create new objects during playing, I just Seek() the tone stream then call Play() over and over, so I don't think it's a problem with orphaned buffers/whatever piling up till it's choked. I'm out of patience on this one, so I'm asking in the hopes that someone here has faced a similar requirement and can steer me in a direction with a likely solution.

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