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  • Looking for examples of "real" uses of continuations

    - by Sébastien RoccaSerra
    I'm trying to grasp the concept of continuations and I found several small teaching examples like this one from the Wikipedia article: (define the-continuation #f) (define (test) (let ((i 0)) ; call/cc calls its first function argument, passing ; a continuation variable representing this point in ; the program as the argument to that function. ; ; In this case, the function argument assigns that ; continuation to the variable the-continuation. ; (call/cc (lambda (k) (set! the-continuation k))) ; ; The next time the-continuation is called, we start here. (set! i (+ i 1)) i)) I understand what this little function does, but I can't see any obvious application of it. While I don't expect to use continuations all over my code anytime soon, I wish I knew a few cases where they can be appropriate. So I'm looking for more explicitely usefull code samples of what continuations can offer me as a programmer. Cheers!

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  • Generate exe in .Net

    - by rwallace
    In .Net, you can generate byte code in memory, and presumably save the resulting program to a .exe file. To do the first step, I have the following test code adapted from http://www.code-magazine.com/Article.aspx?quickid=0301051 var name = new AssemblyName(); name.Name = "MyAssembly"; var ad = Thread.GetDomain(); var ab = ad.DefineDynamicAssembly(name, AssemblyBuilderAccess.Run); var mb = ab.DefineDynamicModule("MyModule"); var theClass = mb.DefineType("MathOps", TypeAttributes.Public); var retType = typeof(System.Int32); var parms = new Type[2]; parms[0] = typeof(System.Int32); parms[1] = typeof(System.Int32); var meb = theClass.DefineMethod("ReturnSum", MethodAttributes.Public, retType, parms); var gen = meb.GetILGenerator(); gen.Emit(OpCodes.Ldarg_1); gen.Emit(OpCodes.Ldarg_2); gen.Emit(OpCodes.Add_Ovf); gen.Emit(OpCodes.Stloc_0); gen.Emit(OpCodes.Br_S); gen.Emit(OpCodes.Ldloc_0); gen.Emit(OpCodes.Ret); theClass.CreateType(); How do you do the second step, and save the result to a .exe?

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  • How can I marshall a vector<int> from a C++ dll to a C# application?

    - by mmr
    I have a C++ function that produces a list of rectangles that are interesting. I want to be able to get that list out of the C++ library and back into the C# application that is calling it. So far, I'm encoding the rectangles like so: struct ImagePatch{ int xmin, xmax, ymin, ymax; } and then encoding some vectors: void MyFunc(..., std::vector<int>& rectanglePoints){ std::vector<ImagePatch> patches; //this is filled with rectangles for(i = 0; i < patches.size(); i++){ rectanglePoints.push_back(patches[i].xmin); rectanglePoints.push_back(patches[i].xmax); rectanglePoints.push_back(patches[i].ymin); rectanglePoints.push_back(patches[i].ymax); } } The header for interacting with C# looks like (and works for a bunch of other functions): extern "C" { __declspec(dllexport) void __cdecl MyFunc(..., std::vector<int>& rectanglePoints); } Are there some keywords or other things I can do to get that set of rectangles out? I found this article for marshalling objects in C#, but it seems way too complicated and way too underexplained. Is a vector of integers the right way to do this, or is there some other trick or approach?

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  • PCRE/PHP regex not matching last "item"

    - by superbarney
    Here's a regex that I've cobbled up: /(.*={76}\s)?\s*(.*?)\s\-\-\s(\d{2}\/\d{2}\-\d{2}\s\d{2}:\d{2})\s\s(.*?)\s(http:\/\/service.*?)\s(\-{76})/is and here's the text I will be parsing: http://p.linode.com/7015 and here's the replacement for the matched text: <item>\n\t<title>$2</title>\n\t<pubDate>$pubDate</pubDate>\n\t<description>$4</description>\n\t<link>$5</link>\n</item>\n\n I have almost come up with a regex needed to parse a block of text into RSS 2.0 XML markup. I've tested it with RegExr and RegexBuddy and it works perfectly except for the last "item" where there is no line breaks after the link (Line 269). In short, the problem is the "iProperty" article in the text is not matched. Any regex gurus willing to help me troubleshoot what's wrong? I've tried /(.*={76}\s)?\s*(.*?)\s\-\-\s(\d{2}\/\d{2}\-\d{2}\s\d{2}:\d{2})\s\s(.*?)\s(http:\/\/service.*?)\s*(\-{76})/is Here's the output that I get: http://p.linode.com/7016 but that didn't work as I expected (i.e. a newline would be optional). Thanks!

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  • Installing Mercurial on Mac OS X 10.6 Snow Leopard

    - by Matthew Rankin
    Installing Mercurial on Mac OS X 10.6 Snow Leopard I installed Mercurial 1.3.1 on Mac OS X 10.6 Snow Leopard from source using the following: cd ~/src curl -O http://mercurial.selenic.com/release/mercurial-1.3.1.tar.gz tar xzvf mercurial-1.3.1.tar.gz cd mercurial-1.3.1 make ALL sudo make install This installs the site-packages files for Mercurial in /usr/local/lib/python2.6/site-packages/. I know that installing Mercurial from the Mac Disk Image will install the files into /Library/Python/2.6/site-packages/, which is the site-packages directory for the Mac OS X default Python install. I have Python 2.6.2+ installed as a Framework with its site-packages directory in: /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages With Mercurial installed this way, I have to issue: PYTHONPATH=/usr/local/lib/python2.6/site-packages:"${PYTHONPATH}" in order to get Mercurial to work. Questions How can I install Mercurial from source with the site-packages in a different directory? Is there an advantage or disadvantage to having the site-packages in the current location? Would it be better in one of the Python site-package directories that already exist? Do I need to be concerned about virtualenv working correctly since I have modified PYTHONPATH (or any other conflicts for that matter)? Reasons for Installing from Source Dan Benjamin of Hivelogic provides the benefits of and instructions for installing Mercurial from source in his article Installing Mercurial on Snow Leopard.

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  • How do you concat multiple rows into one column in SQL Server?

    - by Jason
    I've searched high and low for the answer to this, but I can't figure it out. I'm relatively new to SQL Server and don't quite have the syntax down yet. I have this datastructure (simplified): Table "Users" | Table "Tags": UserID UserName | TagID UserID PhotoID 1 Bob | 1 1 1 2 Bill | 2 2 1 3 Jane | 3 3 1 4 Sam | 4 2 2 ----------------------------------------------------- Table "Photos": | Table "Albums": PhotoID UserID AlbumID | AlbumID UserID 1 1 1 | 1 1 2 1 1 | 2 3 3 1 1 | 3 2 4 3 2 | 5 3 2 | I'm looking for a way to get the all the photo info (easy) plus all the tags for that photo concatenated like CONCAT(username, ', ') AS Tags of course with the last comma removed. I'm having a bear of a time trying to do this. I've tried the method in this article but I get an error when I try to run the query saying that I can't use DECLARE statements... do you guys have any idea how this can be done? I'm using VS08 and whatever DB is installed in it (I normally use MySQL so I don't know what flavor of DB this really is... it's an .mdf file?)

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  • Change userSettings during MSI installation

    - by pagetailor
    Hi, I am trying to modify the userSettings section (Properties.MyApp.Default) in the MyApp.exe.config file during the installation using an MSI installer. I basically implemented it like in this excellent article: http://raquila.com/software/configure-app-config-application-settings-during-msi-install/ The difference is that I am not editing the appSettings but the userSettings section. The problem is that although the code runs fine, the settings are not saved. After the installation the config file contains the old settings I use in my development environment. I also tried to override OnAfterInstall(System.Collections.IDictionary stateSaver) instead of Install(System.Collections.IDictionary stateSaver) but it doesn't make a difference. Here is the code that should change the config values: protected override void OnAfterInstall(IDictionary savedState) { base.OnAfterInstall(savedState); string targetDirectory = Context.Parameters["targetdir"]; string tvdbAccountID = Context.Parameters["TVDBACCID"]; // read other config elements... Properties.Settings.Default.Tvdb_AccountIdentifier = tvdbAccountID; // set other config elements Properties.Settings.Default.Save(); } Any idea how to persist these changes? I already read about Wix but that seems like an overkill to me. Thanks in advance!

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  • WCF identity when moving from dev to prod. environment

    - by Anders Abel
    I have a web service developed with WCF. In the development environment the endpoint has the following identity section under the endpoint configuration. <identity> <dns value="myservice.devdomain.local" /> </identity> myservice.devdomain.local is the dns name used to reach the development version of the service. The binding used is: <basicHttpBinding> <binding name ="myBinding"> <security mode ="TransportCredentialOnly"> <transport clientCredentialType="Windows"/> </security> </binding> </basicHttpBinding> I am about to put this into production. The binding will be the same, but the address will be a new production address myservice.proddomain.local. I have planned to change the dns value in the configuration to myservice.proddomain.local in the production environment. However this MSDN article on WCF Identity makes me worried about the impact on the clients when I change the identity. There are two clients - one .NET and one Java using this service. Both of those have been developed against the dev instance of the service. The idea is to just reconfigure the endpoint used by the clients, without reloading the WSDL. But if the identity is somehow part of the WSDL and the identity changes when deploying to prod that might not work. Will the new identity in the prod version cause issues for the clients that were developed using the dev wsdl? Do the Java and the .NET clients handle this differently?

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  • WPF Sizing of Panels

    - by Mystagogue
    I'm looking for an article or overview of WPF Panel types, that explains the sizing characters of each. For example, here are the panel types: http://msdn.microsoft.com/en-us/library/ms754152.aspx#Panels_derived_elements I've learned (by experiment) that UniformGrid can be given a fixed height, or it can be "auto" where it expands to fit available space. That is great, but what I wanted was for Uniform Grid to shrink to fit its internal content (particularly content that is provided dynamically, at run-time). I don't think it has that ability. So I'd like to know either what other Panel I could use for that purpose, or what Panel I should nest the UniformGrid inside of. But I don't just want an answer to that specific question. I want the sizing dynamics and capabilities of all the Panel types, in summary form, so I can make all these choices as needed. Online I find articles that cover only half the Panel types, and don't give as much information about sizing as I'm describing. Anyone know the link (or book) that has the info I'm seeking? p.s. Since I want the UniformGrid to shrink to the dynamic content I'm providing, I could just keep track of the total height of controls placed within, and then set the height of the UniformGrid. But it would be nice if WPF took care of this for me.

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  • Which languages support *recursive* function literals / anonymous functions?

    - by Hugh Allen
    It seems quite a few mainstream languages support function literals these days. They are also called anonymous functions, but I don't care if they have a name. The important thing is that a function literal is an expression which yields a function which hasn't already been defined elsewhere, so for example in C, &printf doesn't count. EDIT to add: if you have a genuine function literal expression <exp>, you should be able to pass it to a function f(<exp>) or immediately apply it to an argument, ie. <exp>(5). I'm curious which languages let you write function literals which are recursive. Wikipedia's "anonymous recursion" article doesn't give any programming examples. Let's use the recursive factorial function as the example. Here are the ones I know: JavaScript / ECMAScript can do it with callee: function(n){if (n<2) {return 1;} else {return n * arguments.callee(n-1);}} it's easy in languages with letrec, eg Haskell (which calls it let): let fac x = if x<2 then 1 else fac (x-1) * x in fac and there are equivalents in Lisp and Scheme. Note that the binding of fac is local to the expression, so the whole expression is in fact an anonymous function. Are there any others?

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  • What is your preferred tool stack for PHP development in the Windows Environment?

    - by Tim Visher
    I have been developing basic web sites for awhile now with some PHP thrown in for getting dynamic stuff done. However, I recently decided that it was time I got my hands a little dirtier so I wanted to start to play with the underpinnings of Wordpress and other such apps. I work on a Mac at home and have been using Coda for most of my editing needs and I love it. Also, to manage the services stack I use MAMP at home. However, I've begun to realize that for heavy PHP and Web work (AJAX, etc.), more is needed. I'm very interested to hear the kinds of tools more experienced web developers use on a day to day basis to manage the entire work flow. I found this article over on developer tutorials and decided to go with XAMPP (for the moment) for managing the services. However, IDE, Source Control, Debugger, etc. are all up for grabs. Anyway, your thoughts are much appreciated. And, if at all possible, try to describe your entire stack with what each tool fulfills for your development process.

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  • DIY intellisense on XPath - design approach? (WinForms app)

    - by Cheeso
    I read the DIY Intellisense article on code project, which was referenced from the Mimic Intellisense? question here on SO. I wanna do something similar, DIY intellisense, but for XPath not C#. The design approach used there makes sense to me: maintain a tree of terms, and when the "completion character" is pressed, in the case of C#, a dot, pop up the list of possible completions in a textfield. Then allow the user to select a term from the textfield either through typing, arrow keys, or double-click. How would you apply this to XPath autocompletion? should there be an autocomplete key? In XPath there is no obvious separator key like "dot" in C#. should the popup be triggered explicitly in some other way, let's say ctrl-. ? or should the parser try to autocomplete continuously? If I do the autocomplete continuously, how to scale it properly? There are 93 xpath functions, not counting overloads. I certainly don't want to popup a list of 93 choices. How do I decide when I've narrowed it enough to offer a useful lsit of possible completions? How to populate the tree of possible completions? For C#, it's easy: walk the type space via reflection. At a first level, the "syntax tree" for C# seems like a single tree, and the list of completions at any point depends on the graph of nodes you've traversed to that point. Typing System.Console. traverses to a certain node in that tree, and the list of completions is the set of child nodes available at that node in the tree. On the other hand, the xpath syntax seems like it is a "flatter" tree - function names, axis names, literals. Does this make sense? what have I not considered?

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  • UnicodeDecodeError on attempt to save file through django default filebased backend

    - by Ivan Kuznetsov
    When i attempt to add a file with russian symbols in name to the model instance through default instance.file_field.save method, i get an UnicodeDecodeError (ascii decoding error, not in range (128) from the storage backend (stacktrace ended on os.exist). If i write this file through default python file open/write all goes right. All filenames in utf-8. I get this error only on testing Gentoo, on my Ubuntu workstation all works fine. class Article(models.Model): file = models.FileField(null=True, blank=True, max_length = 300, upload_to='articles_files/%Y/%m/%d/') Traceback: File "/usr/lib/python2.6/site-packages/django/core/handlers/base.py" in get_response 100. response = callback(request, *callback_args, **callback_kwargs) File "/usr/lib/python2.6/site-packages/django/contrib/auth/decorators.py" in _wrapped_view 24. return view_func(request, *args, **kwargs) File "/var/www/localhost/help/wiki/views.py" in edit_article 338. new_article.file.save(fp, fi, save=True) File "/usr/lib/python2.6/site-packages/django/db/models/fields/files.py" in save 92. self.name = self.storage.save(name, content) File "/usr/lib/python2.6/site-packages/django/core/files/storage.py" in save 47. name = self.get_available_name(name) File "/usr/lib/python2.6/site-packages/django/core/files/storage.py" in get_available_name 73. while self.exists(name): File "/usr/lib/python2.6/site-packages/django/core/files/storage.py" in exists 196. return os.path.exists(self.path(name)) File "/usr/lib/python2.6/genericpath.py" in exists 18. st = os.stat(path) Exception Type: UnicodeEncodeError at /edit/ Exception Value: ('ascii', u'/var/www/localhost/help/i/articles_files/2010/03/17/\u041f\u0440\u0438\u0432\u0435\u0442', 52, 58, 'ordinal not in range(128)')

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  • ASP.NET 2.0 RijndaelManaged encryption algorithm vs. FIPS

    - by R Rush
    I'm running into an issue with an ASP.NET 2.0 application. Our network folks just upped our security, and now I get the floowing error whenever I try to access the app: "This implementation is not part of the Windows Platform FIPS validated cryptographic algorithms." I've done a little research, and it sounds like ASP.NET uses the RijndaelManaged AES encryption algorithm to encrypt the ViewState of pages... and RijndaelManaged is on the list of algorithms that aren't FIPS compliant. We're certainly not explicitly calling any encryption algorithm... much less anything on the non-compliant list. This ViewState business makes sense to me, I guess. The thing I can't muddle out, though, is what to do about it. I've found a KB article that suggests using a web.config setting to specify a different algorithm... but either that didn't stick, or that algorithm isn't up to snuff, either. So: 1) Is the RijndaelManaged / ViewState thing actually the problem? Or am I barking up the wrong tree? 2) How to I specify what algorithm to use instead of RijndaelManaged? I've got a list of algorithms that are and aren't compliant; I'm just not sure where to plug that information in. Thanks! Richard

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  • Are there some cases where Python threads can safely manipulate shared state?

    - by erikg
    Some discussion in another question has encouraged me to to better understand cases where locking is required in multithreaded Python programs. Per this article on threading in Python, I have several solid, testable examples of pitfalls that can occur when multiple threads access shared state. The example race condition provided on this page involves races between threads reading and manipulating a shared variable stored in a dictionary. I think the case for a race here is very obvious, and fortunately is eminently testable. However, I have been unable to evoke a race condition with atomic operations such as list appends or variable increments. This test exhaustively attempts to demonstrate such a race: from threading import Thread, Lock import operator def contains_all_ints(l, n): l.sort() for i in xrange(0, n): if l[i] != i: return False return True def test(ntests): results = [] threads = [] def lockless_append(i): results.append(i) for i in xrange(0, ntests): threads.append(Thread(target=lockless_append, args=(i,))) threads[i].start() for i in xrange(0, ntests): threads[i].join() if len(results) != ntests or not contains_all_ints(results, ntests): return False else: return True for i in range(0,100): if test(100000): print "OK", i else: print "appending to a list without locks *is* unsafe" exit() I have run the test above without failure (100x 100k multithreaded appends). Can anyone get it to fail? Is there another class of object which can be made to misbehave via atomic, incremental, modification by threads? Do these implicitly 'atomic' semantics apply to other operations in Python? Is this directly related to the GIL?

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  • kick off a map reduce job from my java/mysql webapp

    - by Brian
    Hi guys, I need a bit of archecture advice. I have a java based webapp, with a JPA based ORM backed onto a mysql relational database. Now, as part of the application I have a batch job that compares thousands of database records with each other. This job has become too time consuming and needs to be parallelized. I'm looking at using mapreduce and hadoop in order to do this. However, I'm not too sure about how to integrate this into my current architecture. I think the easiest initial solution is to find a way to push data from mysql into hadoop jobs. I have done some initial research on this and found the following relevant information and possibilities: 1) https://issues.apache.org/jira/browse/HADOOP-2536 this gives an interesting overview of some inbuilt JDBC support 2) This article http://architects.dzone.com/articles/tools-moving-sql-database describes some third party tools to move data from mysql to hadoop. To be honest I'm just starting out with learning about hbase and hadoop but I really don't know how to integrate this into my webapp. Any advice is greatly appreciated. cheers, Brian

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  • NHibernate Session per Call in WCF - How to Rollback

    - by Corey Coogan
    I've implemented some components to use WCF with both an IoC Container (StructureMap) and the Session per Call pattern. The NHibernate stuff is most taken from here: http://realfiction.net/Content/Entry/133. It seems to be OK, but I want to open a transaction with each call and commit at the end, rather than just Flush() which how its being done in the article. Here's where I am running into some problems and could use some advice. I haven't figured out a good way to rollback. I realize I can check the CommunicationState and if there's an exception, rollback, like so: public void Detach(InstanceContext owner) { if (Session != null) { try { if(owner.State == CommunicationState.Faulted) RollbackTransaction(); else CommitTransaction(); } finally { Session.Dispose(); } } } void CommitTransaction() { if(Session.Transaction != null && Session.Transaction.IsActive) Session.Transaction.Commit(); } void RollbackTransaction() { if (Session.Transaction != null && Session.Transaction.IsActive) Session.Transaction.Rollback(); } However, I almost never return a faulted state from a service call. I would typically handle the exception and return an appropriate indicator on my response object and rollback the transaction myself. The only way I can think of handling this would be to inject not only repositories into my WCF services, but also an ISession so I can rollback and handle the way I want. That doesn't sit well with me and seems kind of leaky. Anyone else handling the same problem?

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  • RSS feed created with PHP only shows the title in the feed reader

    - by James Simpson
    I am using the following PHP code to generate the XML for an RSS feed, but it doesn't seem to be working correctly. No short description is displayed in the feed reader, all I see is the title of the article. Also, all of the articles say they were published at the same time. This is the first time I have tried to setup an RSS feed, so I'm sure I've made several stupid mistakes. $result = mysql_query("SELECT * FROM blog ORDER BY id DESC LIMIT 10"); $date = date(DATE_RFC822); header('Content-type: text/xml'); echo ("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"); echo ("<rss version=\"2.0\">\n"); echo ("<channel>\n"); echo ("<lastBuildDate>$date</lastBuildDate>\n"); echo ("<pubDate>$date</pubDate>\n"); echo ("<title>my website name</title>\n"); echo ("<description><![CDATA[the description]]></description>\n"); echo ("<link>http://my-domain.com</link>\n"); echo ("<language>en</language>\n"); $ch=100; while ($a = mysql_fetch_array($result)) { $headline = htmlentities(stripslashes($a['subject'])); $posturl = $a[perm_link]; $content = $a['post']; $date = date(DATE_RFC822, $a['posted']); echo ("<item>\n"); echo ("<title>$headline</title>\n"); echo ("<link>$posturl</link>\n"); echo ("<description><![CDATA[$content]]></description>\n"); echo ("<guid isPermaLink=\"true\">$posturl</guid>\n"); echo ("<pubDate>$date2</pubDate>\n"); echo ("</item>\n"); } echo ("</channel>\n"); echo ("</rss>\n");

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  • iPhone: understanding field crash reports: unrecognized selector?

    - by quixoto
    Hi all, A user of my app out in the field seems to having bad crash-at-app-start issues. I got him to send me the .crash files from his PC. After "symbolicating" them according to this article, I get what looks from the stack like a unrecognized selector fail. But the top line of code corresponding to my process is an unambiguous message send that gets executed hundreds of times without issue in my app normally. Needless to say, I never repro this issue myself. Can the crash report lie? Could this stack indicate anything besides unrecognized selector? Thanks for any insight. Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x00000000, 0x00000000 Crashed Thread: 0 Thread 0 Crashed: 0 libSystem.B.dylib 0x000790a0 __kill + 8 1 libSystem.B.dylib 0x00079090 kill + 4 2 libSystem.B.dylib 0x00079082 raise + 10 3 libSystem.B.dylib 0x0008d20a abort + 50 4 libstdc++.6.dylib 0x00044a1c __gnu_cxx::__verbose_terminate_handler() + 376 5 libobjc.A.dylib 0x000057c4 _objc_terminate + 104 6 libstdc++.6.dylib 0x00042dee __cxxabiv1::__terminate(void (*)()) + 46 7 libstdc++.6.dylib 0x00042e42 std::terminate() + 10 8 libstdc++.6.dylib 0x00042f12 __cxa_throw + 78 9 libobjc.A.dylib 0x000046a4 objc_exception_throw + 64 10 CoreFoundation 0x00094174 -[NSObject doesNotRecognizeSelector:] + 108 11 CoreFoundation 0x00093afa ___forwarding___ + 482 12 CoreFoundation 0x000306c8 _CF_forwarding_prep_0 + 40 13 MyAppProcess 0x000147c6 -[ImageLoader imageSmallForColor:style:] (ImageLoader.m:180) .... /* many more frames... */

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  • MS SQL datetime precision problem

    - by Nailuj
    I have a situation where two persons might work on the same order (stored in an MS SQL database) from two different computers. To prevent data loss in the case where one would save his copy of the order first, and then a little later the second would save his copy and overwrite the first, I've added a check against the lastSaved field (datetime) before saving. The code looks roughly like this: private bool orderIsChangedByOtherUser(Order localOrderCopy) { // Look up fresh version of the order from the DB Order databaseOrder = orderService.GetByOrderId(localOrderCopy.Id); if (databaseOrder != null && databaseOrder.LastSaved > localOrderCopy.LastSaved) { return true; } else { return false; } } This works for most of the time, but I have found one small bug. If orderIsChangedByOtherUser returns false, the local copy will have its lastSaved updated to the current time and then be persisted to the database. The value of lastSaved in the local copy and the DB should now be the same. However, if orderIsChangedByOtherUser is run again, it sometimes returns true even though no other user has made changes to the DB. When debugging in Visual Studio, databaseOrder.LastSaved and localOrderCopy.LastSaved appear to have the same value, but when looking closer they some times differ by a few milliseconds. I found this article with a short notice on the millisecond precision for datetime in SQL: Another problem is that SQL Server stores DATETIME with a precision of 3.33 milliseconds (0. 00333 seconds). The solution I could think of for this problem, is to compare the two datetimes and consider them equal if they differ by less than say 10 milliseconds. My question to you is then: are there any better/safer ways to compare two datetime values in MS SQL to see if they are exactly the same?

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  • LINQ to SQL and DataPager

    - by Jonathan S.
    I'm using LINQ to SQL to search a fairly large database and am unsure of the best approach to perform paging with a DataPager. I am aware of the Skip() and Take() methods and have those working properly. However, I'm unable to use the count of the results for the datapager, as they will always be the page size as determined in the Take() method. For example: var result = (from c in db.Customers where c.FirstName == "JimBob" select c).Skip(0).Take(10); This query will always return 10 or fewer results, even if there are 1000 JimBobs. As a result, the DataPager will always think there's a single page, and users aren't able to navigate across the entire result set. I've seen one online article where the author just wrote another query to get the total count and called that. Something like: int resultCount = (from c in db.Customers where c.FirstName == "JimBob" select c).Count(); and used that value for the DataPager. But I'd really rather not have to copy and paste every query into a separate call where I want to page the results for obvious reasons. Is there an easier way to do this that can be reused across multiple queries? Thanks.

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  • Best way to enforce inter-table constraints inside database

    - by FerranB
    I looking for the best way to check for inter-table constraints an step forward of foreing keys. For instance, to check if a date child record value is between a range date on two parent rows columns. For instance: Parent table ID DATE_MIN DATE_MAX ----- ---------- ---------- 1 01/01/2009 01/03/2009 ... Child table PARENT_ID DATE ---------- ---------- 1 01/02/2009 1 01/12/2009 <--- HAVE TO FAIL! ... I see two approaches: Create materialized views on-commit as shown in this article (or other equivalent on other RDBMS). Use stored-procedures and triggers. Any other approach? Which is the best option? UPDATE: The motivation of this question is not about "putting the constraints on database or on application". I think this is a tired question and anyone does the way she loves. And, I'm sorry for detractors, I'm developing with constraints on database. From here, the question is "which is the best option to manage inter-table constraints on database?". I'm added "inside database" on the question title. UPDATE 2: Some one added the "oracle" tag. Of course materialized views are oracle-tools but I'm interested on any option regardless it's on oracle or others RDBMSs.

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  • LaTeX printing only first two pages of a document

    - by Peter Flom
    I am working in LaTeX, and when I create a pdf file (using LaTeX button or pdfLaTeX button or using yap) the pdf has only the first two pages. No errors. It just stops. If I make the first page longer by adding text, it still stops at end of 2nd page. Any ideas? OK, responding to first comment, here is the code \documentclass{article} \title{Outline of Book} \author{Peter L. Flom} \begin{document} \maketitle \section*{Preface} \subsection*{Audience} \subsection*{What makes this book different?} \subsection*{Necessary background} \subsection*{How to read this book} \section{Introduction} \subsection{The purpose of logistic regression} \subsection{The need for logistic regression} \subsection{Types of logistic regression} \section{General issues in logistic regression} \subsection{Transforming independent and dependent variables} \subsection{Interactions} \subsection{Model selection} \subsection{Parameter estimates, confidence intervals, p values} \subsection{Summary and further reading} \section{Dichotomous logistic regression} \subsection{Introduction, theory, examples} \subsection{Exploratory plots and analysis} \subsection{Basic model fitting} \subsection{Advanced and special issues in model fitting} \subsection{Diagnostic and descriptive plots and analysis} \subsection{Traps and gotchas} \subsection{Power analysis} \subsection{Summary and further reading} \subsection{Exercises} \section{Ordinal logistic regression} \subsection{Introduction, theory, examples} \subsubsection{Introduction - what are ordinal variables?} \subsubsection{Theory of the model} \subsubsection{Examples for this chapter} \subsection{Exploratory plots and analysis} \subsection{Basic model fitting} \subsection{Advanced and special issues in model fitting} \subsection{Diagnostic and descriptive plots and analysis} \subsection{Traps and gotchas} \subsection{Power analysis} \subsection{Summary and further reading} \subsection{Exercises} \section{Multinomial logistic regression} \subsection{Introduction, theory, examples} \subsection{Exploratory plots and analysis} \subsection{Basic model fitting} \subsection{Advanced and special issues in model fitting} \subsection{Diagnostic and descriptive plots and analysis} \subsection{Traps and gotchas} \subsection{Power analysis} \subsection{Summary and further reading} \subsection{Exercises} \section{Choosing a model} \subsection{NOIR and its problems} \subsection{Linear vs. ordinal} \subsection{Ordinal vs. multinomial} \subsection{Summary and further reading} \subsection{Exercises} \section{Extensions and related models} \subsection{Other logistic models} \subsection{Multilevel models - PROC NLMIXED and GLIMMIX} \subsection{Loglinear models - PROC CATMOD} \section{Summary} \end{document} thanks Peter

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  • Javascript: prototypal inheritance and the prototype property

    - by JanD
    Hi, I have a simple code fragment in JS working with prototype inheritance. function object(o) { function F() {} F.prototype = o; return new F(); } //the following code block has a alternate version var mammal = { color: "brown", getColor: function() { return this.color; } } var myCat = object(mammal); myCat.meow = function(){return "meow";} that worked fine but adding this: mammal.prototype.kindOf = "predator"; does not. ("mammal.prototype is undefined") Since I guessed that object maybe have no prototype I rewrote it, replacing the var mammal={... block with: function mammal() { this.color = "brown"; this.getColor = function() { return this.color; } } which gave me a bunch of other errors: "Function.prototype.toString called on incompatible object" and if I try to call _myCat.getColor() "myCat.getColor is not a function" Now I am totally confused. After reading Crockford, and Flanagan I did not get the solution for the errors. So it would be great if somebody knows... - why is the prototype undefined in the first example (which is foremost concern; I thought the prototype of explicitly set in the object() function) - why get I these strange errors trying to use the mammal function as prototype object in the object() function? Edit by the Creator of the Question: These two links helped a lot too: Prototypes_in_JavaScript on the spheredev wiki explains the way the prototype property works relativily simple. What it lacks is some try-out code examples. Some good examples are provided by Morris John's Article. I personally find the explanations are not that easy as in the first link, but still very good. The most difficult part even after I actually got it is really not to confuse the .prototype propery with the internal [[Prototype]] of an object.

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  • Delphi: Fast(er) widestring concatenation

    - by Ian Boyd
    i have a function who's job is to convert an ADO Recordset into html: class function RecordsetToHtml(const rs: _Recordset): WideString; And the guts of the function involves a lot of wide string concatenation: while not rs.EOF do begin Result := Result+CRLF+ '<TR>'; for i := 0 to rs.Fields.Count-1 do Result := Result+'<TD>'+VarAsString(rs.Fields[i].Value)+'</TD>'; Result := Result+'</TR>'; rs.MoveNext; end; With a few thousand results, the function takes, what any user would feel, is too long to run. The Delphi Sampling Profiler shows that 99.3% of the time is spent in widestring concatenation (@WStrCatN and @WstrCat). Can anyone think of a way to improve widestring concatenation? i don't think Delphi 5 has any kind of string builder. And Format doesn't support Unicode. And to make sure nobody tries to weasel out: pretend you are implementing the interface: IRecordsetToHtml = interface(IUnknown) function RecordsetToHtml(const rs: _Recordset): WideString; end; Update One I thought of using an IXMLDOMDocument, to build up the HTML as xml. But then i realized that the final HTML would be xhtml and not html - a subtle, but important, difference. Update Two Microsoft knowledge base article: How To Improve String Concatenation Performance

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