write - Page 777 - Developer IT

Average performance of binary search algorithm?

- by Passionate Learner

http://en.wikipedia.org/wiki/Binary_search_algorithm#Average_performance BinarySearch(int A[], int value, int low, int high) { int mid; if (high < low) return -1; mid = (low + high) / 2; if (A[mid] > value) return BinarySearch(A, value, low, mid-1); else if (A[mid] < value) return BinarySearch(A, value, mid+1, high); else return mid; } If the integer I'm trying to find is always in the array, can anyone help me write a program that can calculate the average performance of binary search algorithm? I know I can do this by actually running the program and counting the number of calls, but what I'm trying to do here is to do it without calling the function. I'm not asking for a time complexity, I'm trying to calculate the average number of calls. For example, the average number of calls to find a integer in A[2], it would be 1.67 (5/3).

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Sharepoint OLE DB - cannot insert records? "Field not updateable" error

- by Pandincus

I need to write a simple C# .NET application to retrieve, update, and insert some data in a Sharepoint list. I am NOT a Sharepoint developer, and I don't have control over our Sharepoint server. I would prefer not to have to develop this in a proper sharepoint development environment simply because I don't want to have to deploy my application on the Sharepoint server -- I'd rather just access data externally. Anyway, I found out that you can access Sharepoint data using OLE DB, and I tried it successfully using some ADO.NET: var db = DatabaseFactory.CreateDatabase(); DataSet ds = new DataSet(); using (var command = db.GetSqlStringCommand("SELECT * FROM List")) { db.LoadDataSet(command, ds, "List"); } The above works. However, when I try to insert: using (var command = db.GetSqlStringCommand("INSERT INTO List ([HeaderName], [Description], [Number]) VALUES ('Blah', 'Blah', 100)")) { db.ExecuteNonQuery(command); } I get this error: Cannot update 'HeaderName'; field not updateable. I did some Googling and apparently you cannot insert data through OLE DB! Does anyone know if there are some possible workarounds? I could try using Sharepoint Web Services, but I tried that initially and was having a heck of a time authenticating. Is that my only option?

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Rebinding and singleton-behaviour [NInject]

- by Maximilian Csuk

Hi! I have set up a NInject (using version 1.5) binding like this: Bind<ISessionFactory>().ToMethod<ISessionFactory>(ctx => { try { // create session factory, might fail because of database issues like wrong connection string } catch (Exception e) { throw new DatabaseException(e); } }).Using<SingletonBehavior>(); As you can see, this binding uses a singleton behavior but can also throw exception when something is not configured correctly, like a wrong connection string to the database. Now, when the creation of a session factory fails at first (throwing a database exception), NInject doesn't try to create the object again but always returns null. I would need NInject to check for null first and recreate when the instance is null, but of course not when there already is an instance successfully constructed (keeping it singleton). Like this: var a = Kernel.Get<ISessionFactory>(); // might fail, a = null // ... change some database settings var b = Kernel.Get<ISessionFactory>(); // might not fail anymore, b = ISessionFactory object Would I need to write a custom behavior or am I missing something else? Thanks for your answers!

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What's the best practice to setup testing for ASP.Net MVC? What to use/process/etc?

- by melaos

hi there, i'm trying to learn how to properly setup testing for an ASP.Net MVC. and from what i've been reading here and there thus far, the definition of legacy code kind of piques my interests, where it mentions that legacy codes are any codes without unit tests. so i did my project in a hurry not having the time to properly setup unit tests for the app and i'm still learning how to properly do TDD and unit testing at the same time. then i came upon selenium IDE/RC and was using it to test on the browser end. it was during that time too that i came upon the concept of integration testing, so from my understanding it seems that unit testing should be done to define the test and basic assumptions of each function, and if the function is dependent on something else, that something else needs to be mocked so that the tests is always singular and can be run fast. Questions: so am i right to say that the project should have started with unit test with proper mocks using something like rhino mocks. then anything else which requires 3rd party dll, database data access etc to be done via integration testing using selenium? because i have a function which calls a third party dll, i'm not sure whether to write a unit test in nunit to just instantiate the object and pass it some dummy data which breaks the mocking part to test it or just cover that part in my selenium integration testing when i submit my forms and call the dll. and for user acceptance tests, is it safe to say we can just use selenium again? Am i missing something or is there a better way/framework? i'm trying to put in more tests for regression testing, and to ensure that nothing breaks when we put in new features. i also like the idea of TDD because it helps to better define the function, sort of like a meta documentation. thanks!! hope this question isn't too subjective because i need it for my case.

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Programmatically Creating fieldset, ol/ul and li tags in ASP.Net, C#

- by Matt

Hi, I need to write an ASP.Net form which will produce the following HTML: <fieldset> <legend>Contact Details</legend> <ol> <li> <label for="name">Name:</label> <input id="name" name="name" class="text" type="text" /> </li> <li> <label for="email">Email address:</label> <input id="email" name="email" class="text" type="text" /> </li> <li> <label for="phone">Telephone:</label> <input id="phone" name="phone" class="text" type="text" /> </li> </ol> </fieldset> However, the fields which are to be added to the form will be determined at runtime, so I need to create the fieldset at runtime and add an ordered list and listitems to it, with labels, textboxes, checkboxes etc as appropriate. I can’t find standard ASP.Net objects which will create these tags. For instance, I’d like to do something like the following in C#: FieldSet myFieldSet = new FieldSet(); myFieldSet.Legend = “Contact Details”; OrderedList myOrderedList = new OrderedList(); ListItem listItem1 = new ListItem(); ListItem listItem2 = new ListItem(); ListItem listItem3 = new ListItem(); // code here which would add labels and textboxes to the ListItems myOrderedList.Controls.Add(listItem1); myOrderedList.Controls.Add(listItem2); myOrderedList.Controls.Add(listItem3); myFieldSet.Controls.Add(myOrderedList); Form1.Controls.Add(myFieldSet); Are there any standard ASP.Net objects which can produce this, or is there some other way of achieving the same result? Matt

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SqlBackup from my client app

- by Robbert Dam

I have an client app that runs on several machines, and connects to a single SQL database. On the client app, the user has the possiblity to use a local SQL (CE) database or connect to a remote SQL database. There is also a box where a backup location can be set. For the backup of the remote SQL database I use the following code: var bdi = new BackupDeviceItem(backupFile, DeviceType.File); var backup = new Backup { Database = "AppDb", Initialize = true }; backup.Devices.Add(bdi); var server = new Server(connection); backup.SqlBackup(server); When developing my application, I wasn't aware that the given backupFile is written on the machine where the SQL server runs! And not on the client machine. What I want is "dump" all the data from my database to a local file. (Why? Because users may enter a network location in the "backup location" box, and backing up SQL immediately to a network location fails. So need to write local first and then copy to the network in that case.) I there an alternative to the method above?

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Using a custom IList obtained through NHibernate

- by Abu Dhabi

Hi.I'm trying to write a web page in .NET, using C# and NHibernate 2.1. The pertinent code looks like this: var whatevervar = session.CreateSQLQuery("select thread_topic, post_time, user_display_name, user_signature, user_avatar, post_topic, post_body from THREAD, [USER], POST, THREADPOST where THREADPOST.thread_id=" + id + " and THREADPOST.thread_id=THREAD.thread_id and [USER].user_id=POST.user_id and POST.post_id=THREADPOST.post_id ORDER BY post_time;").List(); (I have tried to use joins in HQL, but then fell back on this query, due to HQL's unreadability.) The problem is that I'm getting a result that is incompatible with a repeater. When I try this: posts.DataSource = whatevervar.; posts.DataBind(); ...I get this: DataBinding: 'System.Object[]' does not contain a property with the name 'user_avatar'. In an earlier project, I used LINQ to SQL for this same purpose, and it looked like so: var whatevervar = from threads in context.THREADs join threadposts in context.THREADPOSTs on threads.thread_id equals threadposts.thread_id join posts1 in context.POSTs on threadposts.post_id equals posts1.post_id join users in context.USERs on posts1.user_id equals users.user_id orderby posts1.post_time where threads.thread_id == int.Parse(id) select new { threads.thread_topic, posts1.post_time, users.user_display_name, users.user_signature, users.user_avatar, posts1.post_body, posts1.post_topic }; That worked, and now I want to do the same with NHibernate. Unfortunately, I don't know how to make the repeater recognize the fields of the result of the query. Thanks in advance!

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Sweave/R - Automatically generating an appendix that contains all the model summaries/plots/data pro

- by John Horton

I like the idea of making research available at multiple levels of detail i.e., abstract for the casually curious, full text for the more interested, and finally the data and code for those working in the same area/trying to reproduce your results. In between the actual text and the data/code level, I'd like to insert another layer. Namely, I'd like to create a kind of automatically generated appendix that contains the full regression output, diagnostic plots, exploratory graphs data profiles etc. from the analysis, regardless of whether those plots/regressions etc. made it into the final paper. One idea I had was to write a script that would examine the .Rnw file and automatically: Profile all data sets that are loaded (sort of like the Hmisc(?) package) Summarize all regressions - i.e., run summary(model) for all models Present all plots (regardless of whether they made it in the final version) The idea is to make this kind of a low-effort, push-button sort of thing as opposed to a formal appendix written like the rest of a paper. What I'm looking for is some ideas on how to do this in R in a relatively simple way. My hunch is that there is some way of going through the namespace, figuring out what something is and then dumping into a PDF. Thoughts? Does something like this already exist?

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CFHost DNS Resolution - When is it OK to use synchronous API?

- by Jasarien

I went to the iPhone Developer Tech Talk a few months ago and asked one of the gurus there about the lack of NSHost on the iPhone. Some code I was porting to the iPhone made significant use of NSHost throughout its networking code. I was told that NSHost is on the iPhone, but its private. I was also told that NSHost is a synchronous API and that I shouldn't use it anyway. (If anyone could elaborate on why it shouldn't be used, as a bonus, that'd be great.) I can see the caveats of using synchronous API's on the main thread in that they'll block until complete - and that's never a good thing with network code because there are so many factors that could cause the API to block the thread for a significant amount of time. My solution was to write a wrapper around CFHost's asynchronous resolution functions. The result works quite well, and I'm considering releasing it into the public domain. But my question is this: Say my app only resolves a hostname once per run, during the connecting phase, and then cache's it for the rest of the session. During the time it is resolving, a modal screen is shown telling the user "Connecting" with a nice spinner. Does it really matter whether or not the resolution is asynchronous?? The user has to wait to connect anyway, and the resolution is only done on the first connection. Subsequent connections use the cached result of the resolution. When is it OK to be synchronous and when should things be asynchronous?

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Status Code from FTPWebRequest GetResponse method

- by nick

This is slightly tricky. I am uploading files to FTP asynchronously. After uploading each file I am checking the status of the upload operation for that file. This can be done with StatusCode property of the FtpWebResponse object for that request. The code snippet is as give below. System.IO.FileStream fs = System.IO.File.Open(fileName, System.IO.FileMode.Open); while ((iWork = fs.Read(buf, 0, buf.Length)) > 0) requestStream.Write(buf, 0, iWork); requestStream.Close(); FtpWebResponse wrRet = ((FtpWebResponse)state.Request.GetResponse()); There are about 37 StatusCode values as per msdn. I am unaware as to which of these status code values will assure that the file is uploaded successfully. Some of them I used in my code to check for success are : wrRet.StatusCode == FtpStatusCode.CommandOK wrRet.StatusCode == FtpStatusCode.ClosingData wrRet.StatusCode == FtpStatusCode.ClosingControl wrRet.StatusCode == FtpStatusCode.ConnectionClosed wrRet.StatusCode == FtpStatusCode.FileActionOK wrRet.StatusCode == FtpStatusCode.FileStatus But I am unaware of the rest. I need to be sure about these codes because based on the failure or success of the upload operation I have other dependant operations to be carried out. A wrong condition can affect the remaining code. Another thought that crossed my mind was to simply put the above code into a try..catch and not depend on these status codes. With this I would not be depending on the status codes and assuming that any failure will always be directed to the catch block. Kindly let me know if this is the right way. Thanks in advance.

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Unity to dispose of object

- by Johan Levin

Is there a way to make Unit dispose property-injected objects as part of the Teardown? The background is that I am working on an application that uses ASP.NET MVC 2, Unity and WCF. We have written our own MVC controller factory that uses unity to instantiate the controller and WCF proxies are injected using the [Dependency] attribute on public properties of the controller. At the end of the page life cycle the ReleaseController method of the controller factory is called and we call IUnityContainer.Teardown(theMvcController). At that point the controller is disposed as expected but I also need to dispose the injected wcf-proxies. (Actually I need to call Close and/or Abort on them and not Dispose but that is a later problem.) I could of course override the controllers' Dispose methods and clean up the proxies there, but I don't want the controllers to have to know about the lifecycles of the injected interfaces or even that they refer to WCF proxies. If I need to write code myself for this - what would be the best extension point? I'd appreciate any pointer.

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How do I copy or move an NSManagedObject from one context to another?

- by Aeonaut

I have what I assume is a fairly standard setup, with one scratchpad MOC which is never saved (containing a bunch of objects downloaded from the web) and another permanent MOC which persists objects. When the user selects an object from scratchMOC to add to her library, I want to either 1) remove the object from scratchMOC and insert into permanentMOC, or 2) copy the object into permanentMOC. The Core Data FAQ says I can copy an object like this: NSManagedObjectID *objectID = [managedObject objectID]; NSManagedObject *copy = [context2 objectWithID:objectID]; (In this case, context2 would be permanentMOC.) However, when I do this, the copied object is faulted; the data is initially unresolved. When it does get resolved, later, all of the values are nil; none of the data (attributes or relationships) from the original managedObject are actually copied or referenced. Therefore I can't see any difference between using this objectWithID: method and just inserting an entirely new object into permanentMOC using insertNewObjectForEntityForName:. I realize I can create a new object in permanentMOC and manually copy each key-value pair from the old object, but I'm not very happy with that solution. (I have a number of different managed objects for which I have this problem, so I don't want to have to write and update copy: methods for all of them as I continue developing.) Is there a better way?

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Transitive SQL query on same table

- by MiKu

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My Core Animation block isn't working as I'd expect

- by Alex Reynolds

I have a UIView called activityView, which contains two subviews activityIndicator and cancelOperationsButton. These views are embedded in a XIB and wired up to my view controller. I have two methods that deal with activating (showing) and deactivating (hiding) these two subviews: - (void) enableActivityIndicator { [activityIndicator startAnimating]; [cancelOperationsButton setHidden:NO]; } - (void) disableActivityIndicator { [activityIndicator stopAnimating]; [cancelOperationsButton setHidden:YES]; } By themselves, these two methods work fine. To give this a bit of polish, I'd like to add an animation that fades these subviews in and out: - (void) enableActivityIndicator { [activityIndicator startAnimating]; [cancelOperationsButton setHidden:NO]; [UIView beginAnimations:@"fadeIn" context:nil]; [UIView setAnimationDelay:0.0f]; [UIView setAnimationDuration:1.0f]; [UIView setAnimationCurve:UIViewAnimationCurveEaseIn]; activityView.alpha = 1.0f; [UIView commitAnimations]; } - (void) disableActivityIndicator { [UIView beginAnimations:@"fadeOut" context:nil]; [UIView setAnimationDelay:0.0f]; [UIView setAnimationDuration:1.0f]; [UIView setAnimationCurve:UIViewAnimationCurveEaseOut]; activityView.alpha = 0.0f; [UIView commitAnimations]; [activityIndicator stopAnimating]; [cancelOperationsButton setHidden:YES]; } But the animations are not working — the subviews just show up or disappear without the parent view's alpha property having an effect on transparency. How should I write these methods to get the fade-in, fade-out effect I am after?

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Does Firefox on OS X Lion make use of Full Page Zoom for the touchpad? How to customize behavior?

- by Steven Lu

I really like the smooth pinch-zoom of Safari using the touchpad, but the two-finger scroll on Firefox is so much better than the scrolling performance in Safari. So I really like to use Firefox, but then I miss out on two-finger-double-tap to zoom to paragraph width, and the smooth pinch gesture zoom. What I'm wondering is if it is possible to write a Firefox Extension to improve the update rate of the full-page zoom in Firefox that is already functioning via the touchpad pinch gesture. I feel like it is specifically programmed to zoom at certain zoom levels: 100%, 120%, 150% (these are guesses of mine) but I think it would be great if I can get some more control there to make it work more like the zoom functionality in Safari. Also the two-finger-double-tap on a paragraph or element to zoom to it would be really awesome as well. https://developer.mozilla.org/en/Full_page_zoom This seems to indicate (if "full page zoom" is what I think it is) that an extension has the ability to zoom to an arbitrary scale factor, but what remains is to find out if it is possible to obtain or hook the touchpad pinch gesture. Update: I have updated the toolkit.zoomManager.zoomValues option in about:config to include more zoom levels: .3,.5,.67,.8,.9,1,1.01,1.02,1.03,1.04,1.05,1.06,1.07,1.08,1.09,1.1,1.2,1.33,1.5,1.7,2,2.4,3 Notice how I inserted a bunch of entries between 1 and 1.1. But it isn't switching between them any faster (why would it?) so it's less usable than before because of waiting for it to respond fast enough. It's clear that re-rendering the page at a different zoom level requires time and in order for the zoom to be dynamic, some kind of screen capture and scale effect must be performed (which is what Safari does). I guess such a thing is probably doable but I don't think I could pull it off. :-/

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Is there a standard lexer/parser tool for Python?

- by Salim Fadhley

A volunteer job requires us to convert a large number of LaTeX documents into ePub format. It's a series of open-source fiction book which has so far only been produced only on paper via a print on demand service. We'd like to be able to offer the book to users of book-reader devices (such as Kindle) which require the ePub format for best results. Fortunately, ePub is a very simple format, however there's no trivial way for LaTeX to produce the XHTML outut required. We experimented with alternative LaTeX compilers (e.g. plastex) but in the end we figured that it would probably be a lot easier to simply write our own compiler which understands a tiny subset of the LaTeX language and compiles directly to XHTML / ePub. Previously I used a tool on Windows called GOLD. This allowed me to go directly from BNF grammars to a stub parser. It also alllowed me to implement the parser in any language I liked. (I'd choose Python). This product has to work on Linux, so I'm wondering if there's an equivalent toolchain that works as well under Ubutnu / Eclipse / Python. The idea is that we will take the grammar of TeX and just implement a teeny subset of that, but we do not want to spend a huge amount of time worrying about grammar and parsing. A parser generator would obviously save us a great deal of time. Sal UPDATE 1: Bonus marks for a solution with excellent documentation or tutorials.

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jQuery Equal Height Divs

- by griegs

If i have the following harkup; <div> <div> <div id='sameHeight'>One<br>two<br>three</div> <div id='sameHeight'>four</div> <div id='sameHeight'>five</div> <div> <div> <div id='sameHeight'>four</div> <div id='sameHeight'>six</div> <div id='sameHeight'>seven<br>eight</div> <div> </div> How can I ensure that all divs marked as "sameHeight" are the same height as their counterparts in the other div? I had a look at equalHeights plugin but that assumes all divs side by side are in the same parent. I need one that can either traverse parents or allow me to specify parents. Is there such a thing or do I need to write it?

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Adding an application to OpenWithList with Inno Setup

- by Ben McCann

I'm trying to write an installer for an app I created. I found a suggestion elsewhere that I was trying to follow and it mostly worked. My app is now in the "Open With" list. However, the app won't run at all. Could it be that it's because the app is not being started in its directory, so it can't find the dlls? Root: HKCR; Subkey: ".xls\OpenWithList\docs.exe"; Flags: uninsdeletekey noerror Root: HKCR; Subkey: ".ods\OpenWithList\docs.exe"; Flags: uninsdeletekey noerror Root: HKCR; Subkey: "applications\docs.exe\shell\open\command"; ValueType: string; ValueData: """{app}\docs.exe"" ""%1?"""; Flags: uninsdeletekey noerror Root: HKCU; Subkey: "Software\Classes\.xls\OpenWithList\docs.exe"; Flags: uninsdeletekey Root: HKCU; Subkey: "Software\Classes\.ods\OpenWithList\docs.exe"; Flags: uninsdeletekey Root: HKCU; Subkey: "Software\Classes\applications\docs.exe\shell\open\command"; ValueType: string; ValueData: """{app}\docs.exe"" ""%1"""; Flags: uninsdeletekey

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pass objective c object and primitive type into a void *

- by user674669

I want to pass 2 variables: UIImage * img int i into another method that only takes a (void *) I tried making a C struct containing both img and i struct MyStruct { UIImage *img; int i; } but xcode gives me an error saying "ARC forbids Objective-C objects in structs or unions" The next thing I tried is to write an objective-c class MyStruct2 containing img and i, alloc-initing an instance of it and typecasting it as (__bridge void*) before passing it to the method. Seems little involved for my use case. Seems like there should be a better way. What's the simplest way to achieve this? Thank you. Edit based on comments: I have to use void * as it is required by the UIView API. I created a selector as mentioned by UIVIew API + (void)setAnimationDidStopSelector:(SEL)selector Please see documentation for setAnimationDidStopSelector at http://developer.apple.com/library/ios/#documentation/uikit/reference/UIView_Class/UIView/UIView.html . It says ... The selector should be of the form: - (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context I want to pass both img and i into the (void *)context argument.

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Datastore performance, my code or the datastore latency

- by fredrik

I had for the last month a bit of a problem with a quite basic datastore query. It involves 2 db.Models with one referring to the other with a db.ReferenceProperty. The problem is that according to the admin logs the request takes about 2-4 seconds to complete. I strip it down to a bare form and a list to display the results. The put works fine, but the get accumulates (in my opinion) way to much cpu time. #The get look like this: outputData['items'] = {} labelsData = Label.all() for label in labelsData: labelItem = label.item.name if labelItem not in outputData['items']: outputData['items'][labelItem] = { 'item' : labelItem, 'labels' : [] } outputData['items'][labelItem]['labels'].append(label.text) path = os.path.join(os.path.dirname(__file__), 'index.html') self.response.out.write(template.render(path, outputData)) #And the models: class Item(db.Model): name = db.StringProperty() class Label(db.Model): text = db.StringProperty() lang = db.StringProperty() item = db.ReferenceProperty(Item) I've tried to make it a number of different way ie. instead of ReferenceProperty storing all Label keys in the Item Model as a db.ListProperty. My test data is just 10 rows in Item and 40 in Label. So my questions: Is it a fools errand to try to optimize this since the high cpu usage is due to the problems with the datastore or have I just screwed up somewhere in the code? ..fredrik

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Best practices for Java logging from multiple threads?

- by Jason S

I want to have a diagnostic log that is produced by several tasks managing data. These tasks may be in multiple threads. Each task needs to write an element (possibly with subelements) to the log; get in and get out quickly. If this were a single-task situation I'd use XMLStreamWriter as it seems like the best match for simplicity/functionality without having to hold a ballooning XML document in memory. But it's not a single-task situation, and I'm not sure how to best make sure this is "threadsafe", where "threadsafe" in this application means that each log element should be written to the log correctly and serially (one after the other and not interleaved in any way). Any suggestions? I have a vague intuition that the way to go is to use a queue of log elements (with each one able to be produced quickly: my application is busy doing real work that's performance-sensitive), and have a separate thread which handles the log elements and sends them to a file so the logging doesn't interrupt the producers. The logging doesn't necessarily have to be XML, but I do want it to be structured and machine-readable. edit: I put "threadsafe" in quotes. Log4j seems to be the obvious choice (new to me but old to the community), why reinvent the wheel...

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Does WPF break an Entity Framework ObjectContext?

- by David Veeneman

I am getting started with Entity Framework 4, and I am getting ready to write a WPF demo app to learn EF4 better. My LINQ queries return IQueryable<T>, and I know I can drop those into an ObservableCollection<T> with the following code: IQueryable<Foo> fooList = from f in Foo orderby f.Title select f; var observableFooList = new ObservableCollection<Foo>(fooList); At that point, I can set the appropriate property on my view model to the observable collection, and I will get WPF data binding between the view and the view model property. Here is my question: Do I break the ObjectContext when I move my foo list to the observable collection? Or put another way, assuming I am otherwise handling my ObjectContext properly, will EF4 properly update the model (and the database)? The reason why I ask is this: NHibernate tracks objects at the collection level. If I move an NHibernate IList<T> to an observable collection, it breaks NHibernate's change tracking mechanism. That means I have to do some very complicated object wrapping to get NHibernate to work with WPF. I am looking at EF4 as a way to dispense with all that. So, to get EF4 working with WPF, is it as simple as dropping my IQueryable<T> results into an ObservableCollection<T>. Does that preserve change-tracking on my EDM entity objects? Thanks for your help.

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How to improve Java performance on Informix for Windows

- by Michal Niklas

I have problem with performance of Java UDR functions on Informix on Windows. On this server I already have some functions in C and SPL. I chose one function to write it in those 3 languages and I measured performance of this function on test table. Function calculates some kind of checksum so it does not use any db libraries etc. only string and math operations. I observed performance on 30k records with SQL like: select function(txt) from _tmp_perf_test and I changed function to 'function_c, function_spl or function_java. My performance tests showed that C function is the fastest, SPL function is about 5 times slower, where Java is 100 (one hundred!) times slower than C. I checked it few times and 1:100 ratio didn't improve. I changed Java function to simply return length of the string but even this do not help so it looks, that there is general problem with Java function invocation, because there was no difference in time between Java function that calculate checksum and Java function that returns length of the string. I increased JVM_MAX_HEAP_SIZE to 128 and it not helped too. I use IBM Informix Dynamic Server Version 11.50.TC6DE. The same test on Linux server: IBM Informix Dynamic Server Version 11.50.FC6 show more "normal" results, i.e. Java is slower from C and SPL but only 2 to 5 times. What can I do to improve Java performance on Informix server on Windows? More info about Java on servers: c:\Informix\extend\krakatoa\jre\bin>java -version java version "1.5.0" Java(TM) 2 Runtime Environment, Standard Edition (build pwi32dev-20081129a (SR9-0 )) IBM J9 VM (build 2.3, J2RE 1.5.0 IBM J9 2.3 Windows Server 2003 x86-32 j9vmwi3223-20081129 (JIT enabled) J9VM - 20081126_26240_lHdSMr JIT - 20081112_1511ifx1_r8 GC - 200811_07) JCL - 20081129 [root@informix11 bin]# ./java -version java version "1.5.0" Java(TM) 2 Runtime Environment, Standard Edition (build pxa64devifx-20071025 (SR6b)) IBM J9 VM (build 2.3, J2RE 1.5.0 IBM J9 2.3 Linux amd64-64 j9vmxa6423-20071005 (JIT enabled) J9VM - 20071004_14218_LHdSMr JIT - 20070820_1846ifx1_r8 GC - 200708_10) JCL - 20071025

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Why avoid increment ("++") and decrement ("--") operators in JavaScript?

- by artlung

I'm a big fan of Douglas Crockford's writing on JavaScript, particularly his book JavaScript: The Good Parts. It's made me a better JavaScript programmer and a better programmer in general. One of his tips for his jslint tool is this : ++ and -- The ++ (increment) and -- (decrement) operators have been known to contribute to bad code by encouraging excessive trickiness. They are second only to faulty architecture in enabling to viruses and other security menaces. There is a plusplus option that prohibits the use of these operators. This has always struck my gut as "yes, that makes sense," but has annoyed me when I've needed a looping condition and can't figure out a better way to control the loop than a while( a < 10 )do { a++ } or for (var i=0;i<10;i++) { } and use jslint. It's challenged me to write it differently. I also know in the distant past using things, in say PHP like $foo[$bar++] has gotten me in trouble with off-by-one errors. Are there C-like languages or other languages with similarities that that lack the "++" and "--" syntax or handle it differently? Are there other rationales for avoiding "++" and "--" that I might be missing? UPDATE -- April 9, 2010: In the video Crockford on JavaScript -- Part 5: The End of All Things, Douglas Crockford addresses the ++ issue more directly and with more detail. It appears at 1:09:00 in the timeline. Worth a watch.

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Extension Method for copying properties form object to another, with first attempt

- by James

Hi All, Im trying to write an extension method that I can use to copy values from one object property to another object of a different type, as long as the property names and types match exactly. This is what I have: public static T CopyFrom<T>(this T toObject, object fromObject) { var fromObjectType = fromObject.GetType(); var fromProperties = fromObjectType.GetProperties(); foreach (PropertyInfo toProperty in toObject.GetType().GetProperties()) { PropertyInfo fromProperty = fromObjectType.GetProperty(toProperty.Name); if (fromProperty != null) // match found { // check types var fromType = fromProperty.PropertyType.UnderlyingSystemType; var toType = toProperty.PropertyType.UnderlyingSystemType; if (toType.IsAssignableFrom(fromType)) { toProperty.SetValue(toObject, fromProperty.GetValue(fromObject, null), null); } } } return toObject; } This is working great for non boxed types, but Nullable<T> returns false when I call toType.IsAssignableFrom(fromType) because its type is Nullable<T> and is not the underlying type T. I read here that GetType() should unbox the Nullable<T> so it returns T but if I call that on PropertyInfo.PropertyType I get ReflectedMemberInfo and not the type T im looking for. I think im missing something obvious here, so I thought I would throw it open to SO to get some advice. Anyone have any ideas? Thanks, Jamee

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