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• Performance of Multiple Joins

  - by geeko

  Greetings Overflowers, I need to query against objects with many/complex spacial conditions. In relational databases that is translated to many joins (possibly 10+). I'm new to this business and wondering whether to go with MS SQL Server 2008 R2 or Oracle 11g or document-based solutions such as RavenDB or simply go with some spacial database (GIS)... Any thoughts ? Regards UPDATE: Thank you all for your answers. Would anybody opt for document/spatial databases ? My database would consist of tens of millions to few billion records. Mostly read-only. Almost no updates unless in case of mistakes in input. Overnight inserts and not that frequent. The join tables are predicted beforehand but the number of self joins (tables joining themselves multiple times) is not. Small pages of results from such queries are going to be viewed on an highly interactive website so response time is critical. Any predictions on how this can perform on MS SQL Server 2008 R2 or Oracle 11g ? I'm also concerned about boosting performance by adding more servers, which one scales better ? How about PostgresQL ?

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• Why doesn't java.lang.Number implement Comparable?

  - by Julien Chastang

  Does anyone know why java.lang.Number does not implement Comparable? This means that you cannot sort Numbers with Collections.sort which seems to me a little strange. Post discussion update: Thanks for all the helpful responses. I ended up doing some more research about this topic. The simplest explanation for why java.lang.Number does not implement Comparable is rooted in mutability concerns. For a bit of review, java.lang.Number is the abstract super-type of AtomicInteger, AtomicLong, BigDecimal, BigInteger, Byte, Double, Float, Integer, Long and Short. On that list, AtomicInteger and AtomicLong to do not implement Comparable. Digging around, I discovered that it is not a good practice to implement Comparable on mutable types because the objects can change during or after comparison rendering the result of the comparison useless. Both AtomicLong and AtomicInteger are mutable. The API designers had the forethought to not have Number implement Comparable because it would have constrained implementation of future subtypes. Indeed, AtomicLong and AtomicInteger were added in Java 1.5 long after java.lang.Number was initially implemented. Apart from mutability, there are probably other considerations here too. A compareTo implementation in Number would have to promote all numeric values to BigDecimal because it is capable of accommodating all the Number sub-types. The implication of that promotion in terms of mathematics and performance is a bit unclear to me, but my intuition finds that solution kludgy.

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• Google local search API - callback never called

  - by Laurent Luce

  Hello, I am trying to retrieve some local restaurants using the LocalSearch Google API. I am initializing the search objects in the OnLoad function and I am calling the searchControl execute function when the user clicks on a search button. The problem is that my function attached to setSearchCompleteCallback never get called. Please let me know what I am doing wrong here. <script src="http://www.google.com/jsapi"></script> <script type="text/javascript"> google.load('maps' , '2'); google.load('search' , '1'); var searcher, searchControl; function OnLoad() { searchControl = new google.search.SearchControl(); searcher = new google.search.LocalSearch(); // create the object // Add the searcher to the SearchControl searchControl.addSearcher(searcher); searchControl.setSearchCompleteCallback(searcher , function() { var results = searcher.results; // Grab the results array // We loop through to get the points for (var i = 0; i < results.length; i++) { var result = results[i]; } }); $('#user_search_address').live('click', function() { g_searchControl.execute('pizza san francisco'); }); } google.setOnLoadCallback(OnLoad); </script>

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• How big can I make an Android application's canvas in terms of pixels?

  - by user279112

  I've determined an estimate of the size of my Android emulator's screen in pixels, although I think its resolution can be changed to other numbers. Quite frankly though that doesn't eliminate the general problem of not knowing how many pixels on each axis I have to work with on my Android applications in general. The main problem I'm trying to solve is this: How do I make sure I don't use a faulty resolution on Android applications if I want to keep things' sizes constant (so that if the application screen shrinks, for instances, objects will still show up just as big - there just won't be as many of them being shown) if I wish to do this with a single universal resolution for each program? Failing that, how do I make sure everything's alright if I try to do everything the same way with maybe a few different pre-set resolutions? Mainly it seems like a relevant question that must be answered before I can come across a complete answer for the general problem is how big can I always make my application in pixels, NOT regarding if and when a user resizes the application's screen to something smaller than the maximum size permitted by the phone and its operating system. I really want to try to keep this simple. If I were doing this for a modern desktop, for instance, I know that if I design the application with a 800x600 canvas, the user can still shrink the application to the point they're not doing themselves any favors, but at least I can basically count on it working right and not being too big for the monitor or something. Is there such a magic resolution for Android, assuming that I'm designing for API levels 3+ (Android 1.5+)? Thanks

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• Bubble sort dropped images based on their names

  - by user2259784

  I have written a simple bubble sort function that sort an array of Image objects based on image names. For some reason my function is not swapping the elements of array when needed ( basically new assignment is not working) Here is my code : listOfFiles = event.dataTransfer.files; sortImages(listOfFiles); function sortImages(listOfFiles) { var re = /[0-9]/; var temp; for( var index=0; index < listOfFiles.length ; index++) { for ( var index2=0; index2 < listOfFiles.length-1 ; index2++) { var one = parseFloat(re.exec(listOfFiles[index2].name )); var two = parseFloat(re.exec(listOfFiles[index2+1].name)); console.log(one + " : " + two); if (one > two) { console.log(listOfFiles[index2+1]); console.log(listOfFiles[index2]); //following three lines don't work temp = listOfFiles[index2+1]; listOfFiles[index2+1] = listOfFiles[index2]; listOfFiles[index2] = temp; console.log(listOfFiles[index2+1]); console.log(listOfFiles[index2]); } } } }

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• Database doesn't update using TransactionScope

  - by Dissonant

  I have a client trying to communicate with a WCF service in a transactional manner. The client passes some data to the service and the service adds the data to its database accordingly. For some reason, the new data the service submits to its database isn't being persisted. When I have a look at the table data in the Server Explorer no new rows are added... Relevant code snippets are below: Client static void Main() { MyServiceClient client = new MyServiceClient(); Console.WriteLine("Please enter your name:"); string name = Console.ReadLine(); Console.WriteLine("Please enter the amount:"); int amount = int.Parse(Console.ReadLine()); using (TransactionScope transaction = new TransactionScope(TransactionScopeOption.Required)) { client.SubmitData(amount, name); transaction.Complete(); } client.Close(); } Service Note: I'm using Entity Framework to persist objects to the database. [OperationBehavior(TransactionScopeRequired = true, TransactionAutoComplete = true)] public void SubmitData(int amount, string name) { DatabaseEntities db = new DatabaseEntities(); Payment payment = new Payment(); payment.Amount = amount; payment.Name = name; db.AddToPayment(payment); //add to Payment table db.SaveChanges(); db.Dispose(); } I'm guessing it has something to do with the TransactionScope being used in the client. I've tried all combinations of db.SaveChanges() and db.AcceptAllChanges() as well, but the new payment data just doesn't get added to the database!

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• NUnit doesn't work well with Assert.AreEqual

  - by stasal

  Hi! I'm new to unit-testing and NUit in particular. I'm just typing some examples from the book which refers to Java and JUnit. But I'm using C# instead. The problem is: I've got a class with overriden methods such as Equals() and GetHashCode(), but when I am trying to compare two objects of this class with Assert.AreEqual() my code is not called, so I get an exception. Assert.True(MyClass.Equals(MyClass2)) does work well. But I don't wanna use this construction instead of Assert.AreEqual(). Where the problem can be? Here is the class: public class Money { public int amount; protected string currency; public Money(int amount, string currency) { this.amount = amount; this.currency = currency; } public new bool Equals(object obj) { if (obj == null) return false; Money money = (Money)obj; return (amount == money.amount) && (Currency().Equals(money.Currency())); } public new int GetHashCode() { return (string.Format("{0}{1}", amount, currency)).GetHashCode(); } public static Money Dollar(int amount) { return new Money(amount, "USD"); } public static Money Franc(int amount) { return new Money(amount, "CHF"); } public Money Times(int multiplier) { return new Money(amount * multiplier, currency); } public string Currency() { return currency; } } And the test method itself: [TestFixture] public class DollarTest { [Test] public void TestMultiplication() { Money five = Money.Dollar(5); Assert.True(Money.Dollar(10).Equals(five.Times(2))); // ok Assert.AreEqual(Money.Dollar(10), five.Times(2)); // fails } } Thanks.

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• ADO.NET DataTable/DataRow Thread Safety

  - by Allen E. Scharfenberg

  Introduction A user reported to me this morning that he was having an issue with inconsistent results (namely, column values sometimes coming out null when they should not be) of some parallel execution code that we provide as part of an internal framework. This code has worked fine in the past and has not been tampered with lately, but it got me to thinking about the following snippet: Code Sample lock (ResultTable) { newRow = ResultTable.NewRow(); } newRow["Key"] = currentKey; foreach (KeyValuePair<string, object> output in outputs) { object resultValue = output.Value; newRow[output.Name] = resultValue != null ? resultValue : DBNull.Value; } lock (ResultTable) { ResultTable.Rows.Add(newRow); } (No guarantees that that compiles, hand-edited to mask proprietery information.) Explanation We have this cascading type of locking code other places in our system, and it works fine, but this is the first instance of cascading locking code that I have come across that interacts with ADO .NET. As we all know, members of framework objects are usually not thread safe (which is the case in this situation), but the cascading locking should ensure that we are not reading and writing to ResultTable.Rows concurrently. We are safe, right? Hypothesis Well, the cascading lock code does not ensure that we are not reading from or writing to ResultTable.Rows at the same time that we are assigning values to columns in the new row. What if ADO .NET uses some kind of buffer for assigning column values that is not thread safe--even when different object types are involved (DataTable vs. DataRow)? Has anyone run into anything like this before? I thought I would ask here at StackOverflow before beating my head against this for hours on end :) Conclusion Well, the consensus appears to be that changing the cascading lock to a full lock has resolved the issue. That is not the result that I expected, but the full lock version has not produced the issue after many, many, many tests. The lesson: be wary of cascading locks used on APIs that you do not control. Who knows what may be going on under the covers!

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• Trying to make a plugin system in C++

  - by Pirate for Profit

  I'm making a task-based program that needs to have plugins. Tasks need to have properties which can be easily edited, I think this can be done with Qt's Meta-Object Compiler reflection capabilities (I could be wrong, but I should be able to stick this in a QtPropertyBrowser?) So here's the base: class Task : public QObject { Q_OBJECT public: explicit Task(QObject *parent = 0) : QObject(parent){} virtual void run() = 0; signals: void taskFinished(bool success = true); } Then a plugin might have this task: class PrinterTask : public Task { Q_OBJECT public: explicit PrinterTask(QObject *parent = 0) : Task(parent) {} void run() { Printer::getInstance()->Print(this->getData()); // fictional emit taskFinished(true); } inline const QString &getData() const; inline void setData(QString data); Q_PROPERTY(QString data READ getData WRITE setData) // for reflection } In a nutshell, here's what I want to do: // load plugin // find all the Tasks interface implementations in it // have user able to choose a Task and edit its specific Q_PROPERTY's // run the TASK It's important that one .dll has multiple tasks, because I want them to be associated by their module. For instance, "FileTasks.dll" could have tasks for deleting files, making files, etc. The only problem with Qt's plugin setup is I want to store X amount of Tasks in one .dll module. As far as I can tell, you can only load one interface per plugin (I could be wrong?). If so, the only possible way to do accomplish what I want is to create a FactoryInterface with string based keys which return the objects (as in Qt's Plug-And-Paint example), which is a terrible boilerplate that I would like to avoid. Anyone know a cleaner C++ plugin architecture than Qt's to do what I want? Also, am I safely assuming Qt's reflection capabilities will do what I want (i.e. able to edit an unknown dynamically loaded tasks' properties with the QtPropertyBrowser before dispatching)?

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• Passing a paramter/object to a ruby unit/test before running it using TestRunner

  - by Nahir Khan

  I'm building a tool that automates a process then runs some tests on it's own results then goes to do some other stuff. In trying to clean up my code I have created a separate file that just has the test cases class. Now before I can run these tests, I have to pass the class a couple of parameters/objects before they can be run. Now the problem is that I can't seem to find a way to pass a parameter/object to the test class. Right now I am thinking to generate a Yaml file and read it in the test class but it feels "wrong" to use a temporary file for this. If anyone has a nicer solution that would be great! *********Edit******* Example Code of what I am doing right now: #!/usr/bin/ruby require 'test/unit/ui/console/testrunner' require 'yaml' require 'TS_SampleTestSuite' automatingSomething() importantInfo = getImportantInfo() File.open('filename.yml', 'w') do |f| f.puts importantInfo.to_yaml end Test::Unit::UI::Console::TestRunner.run(TS_SampleTestSuite) Now in the example above TS_SampleTestSuite needs importantInfo, so the first "test case" is a method that just reads in the information from the Yaml file filname.yml. I hope that clears up some confusion.

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• How can I eliminate latency in quicktime streamed video

  - by JJFeiler

  I'm prototyping a client that displays streaming video from a HaiVision Barracuda through a quicktime client. I've been unable to reduce the buffer size below 3.0 seconds... for this application, we need as low a latency as the network allows, and prefer video dropouts to delay. I'm doing the following: - (void)applicationDidFinishLaunching:(NSNotification *)aNotification { NSString *path = [[NSBundle mainBundle] pathForResource:@"haivision" ofType:@"sdp"]; NSError *error = nil; QTMovie *qtmovie = [QTMovie movieWithFile:path error:&error]; if( error != nil ) { NSLog(@"error: %@", [error localizedDescription]); } Movie movie = [qtmovie quickTimeMovie]; long trackCount = GetMovieTrackCount(movie); Track theTrack = GetMovieTrack(movie,1); Media theMedia = GetTrackMedia(theTrack); MediaHandler theMediaHandler = GetMediaHandler(theMedia); QTSMediaPresentationParams myPres; ComponentResult c = QTSMediaGetIndStreamInfo(theMediaHandler, 1,kQTSMediaPresentationInfo, &myPres); Fixed shortdelay = 1<<15; OSErr theErr = QTSPresSetInfo (myPres.presentationID, kQTSAllStreams, kQTSTargetBufferDurationInfo, &shortdelay ); NSLog(@"OSErr %d", theErr); [movieView setMovie:qtmovie]; [movieView play:self]; } I seem to be getting valid objects/structures all the way down to the QTSPres, though the ComponentResult and OSErr are both returning -50. The streaming video plays fine, but the buffer is still 3.0seconds. Any help/insight appreciated. J

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• Referencing not-yet-defined variables - Java

  - by user2537337

  Because I'm tired of solving math problems, I decided to try something more engaging with my very rusty (and even without the rust, very basic) Java skills. I landed on a super-simple people simulator, and thus far have been having a grand time working through the various steps of getting it to function. Currently, it generates an array of people-class objects and runs a for loop to cycle through a set of actions that alter the relationships between them, which I have stored in a 2d integer array. When it ends, I go look at how much they all hate each other. Fun stuff. Trouble has arisen, however, because I would like the program to clearly print what action is happening when it happens. I thought the best way to do this would be to add a string, description, to my "action" class (which stores variables for the actor, reactor, and the amount the relationship changes). This works to a degree, in that I can print a generic message ("A fight has occurred!") with no problem. However, ideally I would like it to be a little more specific ("Person A has thrown a rock at Person B's head!"). This latter goal is proving more difficult: attempting to construct an action with a description string that references actor and reactor gets me a big old error, "Cannot reference field before it is defined." Which makes perfect sense. I believe I'm not quite in programmer mode, because the only other way I can think to do this is an unwieldy switch statement that negates the need for each action to have its own nicely-packaged description. And there must be a neater way. I am not looking for examples of code, only a push in the direction of the right concept to handle this.

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• Django: DatabaseError column does not exist

  - by Rosarch

  I'm having a problem with Django 1.2.4. Here is a model: class Foo(models.Model): # ... ftw = models.CharField(blank=True) bar = models.ForeignKey(Bar) Right after flushing the database, I use the shell: Python 2.6.6 (r266:84292, Sep 15 2010, 15:52:39) [GCC 4.4.5] on linux2 Type "help", "copyright", "credits" or "license" for more information. (InteractiveConsole) >>> from apps.foo.models import Foo >>> Foo.objects.all() Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 67, in __repr__ data = list(self[:REPR_OUTPUT_SIZE + 1]) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 82, in __len__ self._result_cache.extend(list(self._iter)) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 271, in iterator for row in compiler.results_iter(): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/compiler.py", line 677, in results_iter for rows in self.execute_sql(MULTI): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/compiler.py", line 732, in execute_sql cursor.execute(sql, params) File "/usr/local/lib/python2.6/dist-packages/django/db/backends/util.py", line 15, in execute return self.cursor.execute(sql, params) File "/usr/local/lib/python2.6/dist-packages/django/db/backends/postgresql_psycopg2/base.py", line 44, in execute return self.cursor.execute(query, args) DatabaseError: column foo_foo.bar_id does not exist LINE 1: ...t_omg", "foo_foo"."ftw", "foo_foo... What am I doing wrong here?

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• Alternatives to static methods on interfaces for enforcing consistency

  - by jayshao

  In Java, I'd like to be able to define marker interfaces, that forced implementations to provide static methods. For example, for simple text-serialization/deserialization I'd like to be able to define an interface that looked something like this: public interface TextTransformable<T>{ public static T fromText(String text); public String toText(); Since interfaces in Java can't contain static methods though (as noted in a number of other posts/threads: here, here, and here this code doesn't work. What I'm looking for however is some reasonable paradigm to express the same intent, namely symmetric methods, one of which is static, and enforced by the compiler. Right now the best we can come up with is some kind of static factory object or generic factory, neither of which is really satisfactory. Note: in our case our primary use-case is we have many, many "value-object" types - enums, or other objects that have a limited number of values, typically carry no state beyond their value, and which we parse/de-parse thousands of time a second, so actually do care about reusing instances (like Float, Integer, etc.) and its impact on memory consumption/g.c. Any thoughts?

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• IOS : BAD ACCESS when trying to add a new Entity object

  - by Maverick447

  So i'm using coredata to model my relationships . This is the model in brief Type A can have one or more types of type B Type B has a inverse relationship of being associated with one of type A Type B can have one or more types of type C Type C has a inverse relationship of being associated with one of type B From a UI standpoint , I have a Navigation controller with controllers that successively sets up the first A object (VC-1) , then another viewcontroller (VC-2) creates a B object ( I pass in the A object to this controller) and the B object is added to the A object . Similarly the same thing happens with B and C . The third Viewcontroller (VC3) first creates a C object and assigns it to the passed B Object . Also between these viewcontrollers the managedObjectCOntext is also passed . SO my use case is such that while viewcontroller (VC-3) is the top controller a button action will keep creating multiple objects of type C and add them to the same type B object that was passed . Also as part of this function I save the managedObject context after saving each type C . e.g. code in viewcontroller 3 - (void) SaveNewTypeC { TypeC *newtypeC = (Question*)[NSEntityDescription insertNewObjectForEntityForName:@"TypeC" inManagedObjectContext:managedObjectContext]; [newtypeC setProp1:] ; [newtypeC setProp2:] .. .. **[typeBObject addTypeCInTypeBObject:newtypeC];** [section setTotalCObjectCount:[ NSNumber numberWithInt:typeCIndex++]]; NSError *error = nil; if (![managedObjectContext save:&error]) { // Handle error NSLog(@"Unresolved error %@, %@, %@", error, [error userInfo],[error localizedDescription]); exit(-1); // Fail } [newtypeC release]; } - (IBAction)selectedNewButton:(id)sender { [self SaveNewTypeC]; [self startRepeatingTimer]; } The BAD ACCESS seems to appear when the bold line above executes Relating to some HashValue . Any clues on resolving this would be helpful .

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• Problem importing Oracle .dmp file

  - by BitFiddler

  So I have looked at all the suggested ways of importing .dmp files and non of them seem to answer this question: where does the data go once you import it? Context: I created a user like so: SQL> create user IMPORTER identified by "12345"; SQL> grant connect, unlimited tablespace, resource to IMPORTER; I then ran the 'imp' command as follows: C:\>imp system/password FROMUSER=OVIEDOE TOUSER=IMPORTER file=c:\database1.dmp Now there were 9 .dmp files, after each one it asked me for the next one and then I received the message "Import terminated successfully with warnings." The warning was: Warning: the objects were exported by OVIEDOE, not by you import done in WE8MSWIN1252 character set and AL16UTF16 NCHAR character set export client uses WE8ISO8859P1 character set (possible charset conversion) IMP-00046: using FILESIZE value from export file of 2147483648 Now it says it was terminated successfully so my assumption (I am new to oracle so this may be wrong) is that the data was loaded. However, when I use SQL developer to connect to the database and look under the 'tables' node under the IMPORTER user, there is nothing there. What is going on? Did the data load? If so, where can I find it?

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• How to play simultaneous multiply audio sources in Silverlight

  - by Shurup

  I want to play simultaneous multiply audio sources in Silverlight. So I've created a prototype in Silverlight 4 that should play a two mp3 files containing the same ticks sound with an intervall 1 second. So these files must be sounded as one sound if they will be played together with any whole second offsets (0 and 1, 0 and 2, 1 and 1 seconds, etc.) I my prototype I use two MediaElement (me and me2) objects. DateTime startTime; private void Play_Clicked(object sender, RoutedEventArgs e) { me.SetSource(new FileStream(file1), FileMode.Open))); me2.SetSource(new FileStream(file2), FileMode.Open))); var timer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(1) }; timer.Tick += RefreshData; timer.Start(); } First file should be played at 00:00 sec. and the second in 00:02 second. void RefreshData(object sender, EventArgs e) { if(me.CurrentState != MediaElementState.Playing) { startTime = DateTime.Now; me.Play(); return; } var elapsed = DateTime.Now - startTime; if(me2.CurrentState != MediaElementState.Playing && elapsed >= TimeSpan.FromSeconds(2)) { me2.Play(); ((DispatcherTimer)sender).Stop(); } } The tracks played every time different and not simultaneous as they should (as one sound).

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• Initial capacity of collection types, i.e. Dictionary, List

  - by Neil N

  Certain collection types in .Net have an optional "Initial Capacity" constructor param. i.e. Dictionary<string, string> something = new Dictionary<string,string>(20); List<string> anything = new List<string>(50); I can't seem to find what the default initial capacity is for these objects on MSDN. If I know I will only be storing 12 or so items in a dictionary, doesn't it make sense to set the initial capacity to something like 20? My reasoning is, assuming the capacity grows like it does for a StringBuiler, which doubles each time the capacity is hit, and each re-allocation is costly, why not pre-set the size to something you know will hold your data, with some extra room just in case? If the initial capacity is 100, and I know I will only need a dozen or so, it seems as though the rest of that allocated RAM is allocated for nothing. Please spare me the "premature optimization" speil for the O(n^n)th time. I know it won't make my apps any faster or save any meaningful amount of memory, this is mostly out of curiosity.

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• d3: Coloring Multiple Lines from Nested Data

  - by diet_coke

  I'm currently assembling some line graphs with circles at the datapoints from arrays of JSON objects formatted like so: var data = [{ "name": "metric1", "datapoints": [ [10.0, 1333519140], [48.0, 1333519200] ] }, { "name": "metric2", "datapoints": [ [48.0, 1333519200], [12.0, 1333519260] ] }] I want to have a color for each metric, so I'm trying to color them based on the index of the object within the array data. The code I have currently for just placing the circles looks like: // We bind an svg group to each metric. var metric_groups = this.vis.selectAll("g.metric_group") .data(data).enter() .append("g") .attr("class", "metric_group"); // Then bind a circle for each datapoint. var circles = metric_groups.selectAll("circle") .data(function(d) { return d.datapoints; }); circles.enter().append("circle") .attr("r", 3.5); Now if I change that last bit to something like: circles.enter().append("circle") .attr("r", 3.5); .style("fill", function(d,i) { return i%2 ? "red" : "blue"; } I get alternating red and blue circles, as could be expected. Taking some advice from Nested Selections : 'Nesting and Index', I tried: circles.enter().append("circle") .attr("r", 3.5); .style("fill", function(d,i,j) { return j%2 ? "red" : "blue"; } Which doesn't work (j is undefined), presumably because we are in the named property datapoints, rather than an array element. How might I go about doing the coloring that I want without changing my data structure? Thanks!

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• BinaryFormatter in C# a good way to read files?

  - by mr-pac

  I want to read a binary file which was created outside of my program. One obvious way in C# to read a binary file is to define class representing the file and then use a BinaryReader and read from the file via the Read* methods and assign the return values to the class properties. What I don't like with the approach is that I manually have to write code that reads the file, although the defined structure represents how the file is stored. I also have to keep the order correct when I read. After looking a bit around I came across the BinaryFormatter which can automatically serialize and deserialze object in binary format. One great advantage would be that I can read and also write the file without creating additional code. However I wonder if this approach is good for files created from other programs on not just serialized .NET objects. Take for example a graphics format file like BMP. Would it be a good idea to read the file with a BinaryFormatter or is it better to manually and write via BinaryReader and BinaryWriter? Or are there any other approaches which suit better? I'am not looking for concrete examples but just for an advice what is the best way to implement that.

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• Extend DOMElement object

  - by Comma

  How could I exdend objects provided with Document Object Model? Seems that there is no way according to this [issue][2]. class Application_Model_XmlSchema extends DOMElement { const ELEMENT_NAME = 'schema'; /** * @var DOMElement */ private $_schema; /** * @param DOMDocument $document * @return void */ public function __construct(DOMDocument $document) { $this->setSchema($document->getElementsByTagName(self::ELEMENT_NAME)->item(0)); } /** * @param DOMElement $schema * @return void */ public function setSchema(DOMElement $schema){ $this->_schema = $schema; } /** * @return DOMElement */ public function getSchema(){ return $this->_schema; } /** * @param string $name * @param array $arguments * @return mixed */ public function __call($name, $arguments) { if (method_exists($this->_schema, $name)) { return call_user_func_array( array($this->_schema, $name), $arguments ); } } } $version = $this->getRequest()->getParam('version', null); $encoding = $this->getRequest()->getParam('encoding', null); $source = 'http://www.w3.org/2001/XMLSchema.xsd'; $document = new DOMDocument($version, $encoding); $document->load($source); $xmlSchema = new Application_Model_XmlSchema($document); $xmlSchema->getAttribute('version'); I got an error: Warning: DOMElement::getAttribute(): Couldn't fetch Application_Model_XmlSchema in C:\Nevermind.php on line newvermind

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• What's the best way of accessing a DRb object (e.g. Ruby Queue) from Scala (and Java)?

  - by Tom Morris

  I have built a variety of little scripts using Ruby's very simple Queue class, and share the Queue between Ruby and JRuby processes using DRb. It would be nice to be able to access these from Scala (and maybe Java) using JRuby. I've put together something Scala and the JSR-223 interface to access jruby-complete.jar. import javax.script._ class DRbQueue(host: String, port: Int) { private var engine = DRbQueue.factory.getEngineByName("jruby") private var invoker = engine.asInstanceOf[Invocable] engine.eval("require \"drb\" ") private var queue = engine.eval("DRbObject.new(nil, \"druby://" + host + ":" + port.toString + "\")") def isEmpty(): Boolean = invoker.invokeMethod(this.queue, "empty?").asInstanceOf[Boolean] def size(): Long = invoker.invokeMethod(this.queue, "length").asInstanceOf[Long] def threadsWaiting: Long = invoker.invokeMethod(this.queue, "num_waiting").asInstanceOf[Long] def offer(obj: Any) = invoker.invokeMethod(this.queue, "push", obj.asInstanceOf[java.lang.Object]) def poll(): Any = invoker.invokeMethod(this.queue, "pop") def clear(): Unit = { invoker.invokeMethod(this.queue, "clear") } } object DRbQueue { var factory = new ScriptEngineManager() } (It conforms roughly to java.util.Queue interface, but I haven't declared the interface because it doesn't implement the element and peek methods because the Ruby class doesn't offer them.) The problem with this is the type conversion. JRuby is fine with Scala's Strings - because they are Java strings. But if I give it a Scala Int or Long, or one of the other Scala types (List, Set, RichString, Array, Symbol) or some other custom type. This seems unnecessarily hacky: surely there has got to be a better way of doing RMI/DRb interop without having to use JSR-223 API. I could either make it so that the offer method serializes the object to, say, a JSON string and takes a structural type of only objects that have a toJson method. I could then write a Ruby wrapper class (or just monkeypatch Queue) to would parse the JSON. Is there any point in carrying on with trying to access DRb from Java/Scala? Might it just be easier to install a real message queue? (If so, any suggestions for a lightweight JVM-based MQ?)

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• java: libraries for immutable functional-style data structures

  - by Jason S

  This is very similar to another question (Functional Data Structures in Java) but the answers there are not particularly useful. I need to use immutable versions of the standard Java collections (e.g. HashMap / TreeMap / ArrayList / LinkedList / HashSet / TreeSet). By "immutable" I mean immutable in the functional sense (e.g. purely functional data structures), where updating operations on the data structure do not change the original data, but instead return a new instance of the same kind of data structure. Also typically new and old instances of the data structure will share immutable data to be efficient in time and space. From what I can tell my options include: Functional Java Scala Clojure but I'm not sure whether any of these are particularly appealing to me. I have a few requirements/desirements: the collections in question should be usable directly in Java (with the appropriate libraries in the classpath). FJ would work for me; I'm not sure if I can use Scala's or Clojure's data structures in Java w/o having to use the compilers/interpreters from those languages and w/o having to write Scala or Clojure code. Core operations on lists/maps/sets should be possible w/o having to create function objects with confusing syntaxes (FJ looks slightly iffy) They should be efficient in time and space. I'm looking for a library which ideally has done some performance testing. FJ's TreeMap is based on a red-black tree, not sure how that rates. Documentation / tutorials should be good enough so someone can get started quickly using the data structures. FJ fails on that front. Any suggestions?

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• How to design app to be modular / support plugins

  - by Lee

  I'm currently in the process of refactoring my webplayer so that we'll be more easily able to run it on our other internet radio stations. Much of the setup between these players will be very similar, however, some will need to have different UI plugins / other plugins. Currently in the webplayer I do something like this in it's init(): _this.ui = new UI(); _this.ui.playlist = new Playlist(); _this.ui.channelDropdown = new ChannelDropdown(); _this.ui.timecode = ne Timecode(); etc etc This works fine but that blocks me into requiring those objects at run time. What I'd like to do is be able to add those based on the stations needs. Basically my question is, do I need to add some kind of "addPlugin()" functionality here? And if I do that, do I need to constantly check from my WebPlayer object if that plugin exists before it attempts to use it? Like... if (_hasPlugin('playlist')) this.plugins.playlist.add(track); I apologize if some of this might not be clear... really trying to get my head wrapped around all of this. I feel I'm closer but I'm still stuck. Any advice on how I should proceed with this would be greatly appreciated. Thanks in advance, Lee

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• For business people to manage, keep binary images in MySQL or just the urls?

  - by Michael Mao

  Hello everyone: I am working on a task to enable image uploading and auto-scaling(from full sized to thumbnail) by jQuery & PHP. I can naturally come up with two approaches : First, store both images as binary objects directly into MySQL; Second, store only urls to the images and keep the images somewhere on server. The images are for everyone to view, so there are no security restrictions, as far as I know. Personally I don't have any preference, however, at the end of the day, it is the business people that are going to manage the images as part of the system(CRUD). So I am wondering which seems to be a bit better for them? Of course I am building a easy-to-use, visualize web interface for the staff to control the process, but I am not sure if that is enough. Lessons told me that if I don't think for the future and seek the most flexible approach, the I will probably screw myself sooner or later. PS. The following link is what I've found so far, which is pretty cool, no flash involved :) Andrew Valum's ajax image upload jQuery plugin

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