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• Historical / auditable database

  - by Mark

  Hi all, This question is related to the schema that can be found in one of my other questions here. Basically in my database I store users, locations, sensors amongst other things. All of these things are editable in the system by users, and deletable. However - when an item is edited or deleted I need to store the old data; I need to be able to see what the data was before the change. There are also non-editable items in the database, such as "readings". They are more of a log really. Readings are logged against sensors, because its the reading for a particular sensor. If I generate a report of readings, I need to be able to see what the attributes for a location or sensor was at the time of the reading. Basically I should be able to reconstruct the data for any point in time. Now, I've done this before and got it working well by adding the following columns to each editable table: valid_from valid_to edited_by If valid_to = 9999-12-31 23:59:59 then that's the current record. If valid_to equals valid_from, then the record is deleted. However, I was never happy with the triggers I needed to use to enforce foreign key consistency. I can possibly avoid triggers by using the extension to the "PostgreSQL" database. This provides a column type called "period" which allows you to store a period of time between two dates, and then allows you to do CHECK constraints to prevent overlapping periods. That might be an answer. I am wondering though if there is another way. I've seen people mention using special historical tables, but I don't really like the thought of maintainling 2 tables for almost every 1 table (though it still might be a possibility). Maybe I could cut down my initial implementation to not bother checking the consistency of records that aren't "current" - i.e. only bother to check constraints on records where the valid_to is 9999-12-31 23:59:59. Afterall, the people who use historical tables do not seem to have constraint checks on those tables (for the same reason, you'd need triggers). Does anyone have any thoughts about this? PS - the title also mentions auditable database. In the previous system I mentioned, there is always the edited_by field. This allowed all changes to be tracked so we could always see who changed a record. Not sure how much difference that might make. Thanks.

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• How does NameScope in WPF works ?

  - by Nicolas Dorier

  I'm having a strange behavior with NameScopes in WPF, I have created a CustomControl called FadingPopup which is a child class of Window with nothing special inside. <Window.Resources> <local:FadingPopup> <Button Name="prec" Content="ahah"></Button> <Button Content="{Binding ElementName=prec, Path=Content}"></Button> </local:FadingPopup> </Window.Resources> In this snippet, the binding doesn't work (always empty). If I move these buttons from the resources to the content of the window like this : <Window ...> <Button Name="prec" Content="ahah"></Button> <Button Content="{Binding ElementName=prec, Path=Content}"></Button> </Window> The binding works as expected. Now, I have tried a mix between these two snippets : <Window...> <Window.Resources> <local:FadingPopup> <Button Name="prec" Content="Haha"></Button> </local:FadingPopup> </Window.Resources> <Button Content="{Binding ElementName=prec, Path=Content}"></Button> </Window> It works as well. Apparently, if the button prec is in the resources it registers itself in the NameScope of the Window. BUT, it seems that the Binding tries to resolve ElementName with the NameScope of the FadingPopup (which is null), thus the binding doesn't work... My first snipped works well if I specify a NameScope in my class FadingPopup : static FadingPopup() { NameScope.NameScopeProperty.OverrideMetadata(typeof(FadingPopup), new PropertyMetadata(new NameScope())); } But I don't like this solution because I don't understand why, in the first snippet, prec is registered in the NameScope of Window, but ElementName is resolved with the NameScope of FadingGroup (which is null by default)... Does someone can explain to me what is going on ? Why my first snippet doesn't work, if I don't specify a default NameScope for FadingGroup ?

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• Sorting a nodeset before passing to xsl:for-each

  - by Zack Mulgrew

  I have a situation where loop through a sorted nodeset and apply a template on each of the nodes: <div id="contractscontainer"> <xsl:for-each select="document"> <xsl:sort select="content[@name='ClientName']/text()" /> <xsl:apply-templates select="." mode="client-contract" /> </xsl:for-each> </div> I want to do something special with the "first" 5 nodes in the node set and render them nested element. The problem is that they need to be in the same order as if they were sorted (as they are in the loop). I had planned on doing this by using two xsl:for-each elements, each with the correct nodes selected from the set. I can't do this, however, because they need to be sorted before I can select the "first" 5. Example: <div id="contractscontainer"> <div class="first-five"> <xsl:for-each select="document[position() < 6]"> <xsl:sort select="content[@name='ClientName']/text()" /> <xsl:apply-templates select="." mode="client-contract" /> </xsl:for-each> </div> <div class="rest-of-them"> <xsl:for-each select="document[position() > 5]"> <xsl:sort select="content[@name='ClientName']/text()" /> <xsl:apply-templates select="." mode="client-contract" /> </xsl:for-each> </div> </div> I don't think this will work because I'm selecting the nodes by position before sorting them, but I can't use xsl:sort outside of the xsl:for-each. Am I approaching this incorrectly?

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• PayPal sandbox Buy Now Problem

  - by Tushar Ahirrao

  Hi , I have paypal sandbox test account. I want to create a 'buy Now' button. I am trying it with GWT. But its even not working with simple HTML form. It displays a 'Buy Now' button on HTML page and after clicking on it redirects to PayPal site. Where it ask to login to buy product but after that it goes on displying message: The email address or password you have entered does not match our records. Please try again. I am using buyer user to purchase product. I am pretty sure about the username and password. Providing here the simple HTML form which I am trying: <form action="https://www.paypal.com/cgi-bin/webscr" method="post" id="payPalForm"> <input type="hidden" name="item_number" value="1"> <input type="hidden" name="cmd" value="_xclick"> <input type="hidden" name="no_note" value="1"> <input type="hidden" name="business" value="[email protected]"> <input type="hidden" name="lc" value="US"> <input type="hidden" name="button_subtype" value="services"> <input type="hidden" name="cn" value="Add special instructions to the seller"> <input type="hidden" name="no_shipping" value="2"> <input type="hidden" name="rm" value="1"> <input type="hidden" name="bn" value="PP-BuyNowBF:btn_paynow_SM.gif:NonHosted"> <input type="hidden" name="variables" value="http://google.com"> <input type="hidden" name="cancel_return" value="http://google.com"> <input type="hidden" name="notify_url" value="http://google.com"> <input type="hidden" name="return" value="http://freelanceswitch.com/payment-complete /"> <input type="hidden" name="currency_code" value="USD"> <input name="item_name" type="hidden" value="Deal Name"> <input name="amount" type="hidden" value="500"> <input type="submit" name="Submit" value="Submit"> </form> Please advice. Thank you.

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• Spring AOP pointcut that matches annotation on interface

  - by seanizer

  Hello, this is my first post here, so I apologize in advance for any stupidity on my side. I have a service class implemented in Java 6 / Spring 3 that needs an annotation to restrict access by role. I have defined an annotation called RequiredPermission that has as its value attribute one or more values from an enum called OperationType: public @interface RequiredPermission { /** * One or more {@link OperationType}s that map to the permissions required * to execute this method. * * @return */ OperationType[] value();} public enum OperationType { TYPE1, TYPE2; } package com.mycompany.myservice; public interface MyService{ @RequiredPermission(OperationType.TYPE1) void myMethod( MyParameterObject obj ); } package com.mycompany.myserviceimpl; public class MyServiceImpl implements MyService{ public myMethod( MyParameterObject obj ){ // do stuff here } } I also have the following aspect definition: /** * Security advice around methods that are annotated with * {@link RequiredPermission}. * * @param pjp * @param param * @param requiredPermission * @return * @throws Throwable */ @Around(value = "execution(public *" + " com.mycompany.myserviceimpl.*(..))" + " && args(param)" + // parameter object " && @annotation( requiredPermission )" // permission annotation , argNames = "param,requiredPermission") public Object processRequest(final ProceedingJoinPoint pjp, final MyParameterObject param, final RequiredPermission requiredPermission) throws Throwable { if(userService.userHasRoles(param.getUsername(),requiredPermission.values()){ return pjp.proceed(); }else{ throw new SorryButYouAreNotAllowedToDoThatException( param.getUsername(),requiredPermission.value()); } } The parameter object contains a user name and I want to look up the required role for the user before allowing access to the method. When I put the annotation on the method in MyServiceImpl, everything works just fine, the pointcut is matched and the aspect kicks in. However, I believe the annotation is part of the service contract and should be published with the interface in a separate API package. And obviously, I would not like to put the annotation on both service definition and implementation (DRY). I know there are cases in Spring AOP where aspects are triggered by annotations one interface methods (e.g. Transactional). Is there a special syntax here or is it just plain impossible out of the box. PS: I have not posted my spring config, as it seems to be working just fine. And no, those are neither my original class nor method names. Thanks in advance, Sean PPS: Actually, here is the relevant part of my spring config: <aop:aspectj-autoproxy proxy-target-class="false" /> <bean class="com.mycompany.aspect.MyAspect"> <property name="userService" ref="userService" /> </bean>

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• How to optimize my PostgreSQL DB for prefix search?

  - by asmaier

  I have a table called "nodes" with roughly 1.7 million rows in my PostgreSQL db =#\d nodes Table "public.nodes" Column | Type | Modifiers --------+------------------------+----------- id | integer | not null title | character varying(256) | score | double precision | Indexes: "nodes_pkey" PRIMARY KEY, btree (id) I want to use information from that table for autocompletion of a search field, showing the user a list of the ten titles having the highest score fitting to his input. So I used this query (here searching for all titles starting with "s") =# explain analyze select title,score from nodes where title ilike 's%' order by score desc; QUERY PLAN ----------------------------------------------------------------------------------------------------------------------- Sort (cost=64177.92..64581.38 rows=161385 width=25) (actual time=4930.334..5047.321 rows=161264 loops=1) Sort Key: score Sort Method: external merge Disk: 5712kB -> Seq Scan on nodes (cost=0.00..46630.50 rows=161385 width=25) (actual time=0.611..4464.413 rows=161264 loops=1) Filter: ((title)::text ~~* 's%'::text) Total runtime: 5260.791 ms (6 rows) This was much to slow for using it with autocomplete. With some information from Using PostgreSQL in Web 2.0 Applications I was able to improve that with a special index =# create index title_idx on nodes using btree(lower(title) text_pattern_ops); =# explain analyze select title,score from nodes where lower(title) like lower('s%') order by score desc limit 10; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------ Limit (cost=18122.41..18122.43 rows=10 width=25) (actual time=1324.703..1324.708 rows=10 loops=1) -> Sort (cost=18122.41..18144.60 rows=8876 width=25) (actual time=1324.700..1324.702 rows=10 loops=1) Sort Key: score Sort Method: top-N heapsort Memory: 17kB -> Bitmap Heap Scan on nodes (cost=243.53..17930.60 rows=8876 width=25) (actual time=96.124..1227.203 rows=161264 loops=1) Filter: (lower((title)::text) ~~ 's%'::text) -> Bitmap Index Scan on title_idx (cost=0.00..241.31 rows=8876 width=0) (actual time=90.059..90.059 rows=161264 loops=1) Index Cond: ((lower((title)::text) ~>=~ 's'::text) AND (lower((title)::text) ~<~ 't'::text)) Total runtime: 1325.085 ms (9 rows) So this gave me a speedup of factor 4. But can this be further improved? What if I want to use '%s%' instead of 's%'? Do I have any chance of getting a decent performance with PostgreSQL in that case, too? Or should I better try a different solution (Lucene?, Sphinx?) for implementing my autocomplete feature?

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• Problem with type coercion and string concatenation in JavaScript in Greasemonkey script on Firefox

  - by Yi Jiang

  I'm creating a GreaseMonkey script to improve the user interface of the 10k tools Stack Overflow uses. I have encountered an unreproducible and frankly bizarre problem that has confounded me and the others in the JavaScript room on SO Chat. We have yet to find the cause after several lengthy debugging sessions. The problematic script can be found here. Source - Install The problem occurs at line 85, the line after the 'vodoo' comment: return (t + ' (' + +(+f.offensive + +f.spam) + ')'); It might look a little weird, but the + in front of the two variables and the inner bracket is for type coercion, the inner middle + is for addition, and the other ones are for concatenation. Nothing special, but observant reader might note that type coercion on the inner bracket is unnecessary, since both are already type coerced to numbers, and type coercing result is useless when they get concatenated into a string anyway. Not so! Removing the + breaks the script, causing f.offensive and f.spam to be concatenated instead of added together. Adding further console.log only makes things more confusing: console.log(f.offensive + f.spam); // 50 console.log('' + (+f.offensive + +f.spam)); // 5, but returning this yields 50 somehow console.log('' + (+f.offensive + +f.spam) + ''); // 50 Source: http://chat.stackoverflow.com/transcript/message/203261#203261 The problem is that this is unreproducible - running scripts like console.log('a' + (+'3' + +'1') + 'b'); in the Firebug console yields the correct result, as does (function(){ return 'a' + (+'3' + +'1') + 'b'; })(); Even pulling out large chunks of the code and running them in the console does not reproduce this bug: $('.post-menu a[id^=flag-post-]').each(function(){ var f = {offensive: '4', spam: '1'}; if(f){ $(this).text(function(i, t){ // Vodoo - please do not remove the '+' in front of the inner bracket return (t + ' (' + +(+f.offensive + +f.spam) + ')'); }); } }); Tim Stone in the chatroom has reproduction instruction for those who are below 10k. This bug only appears in Firefox - Chrome does not appear to exhibit this problem, leading me to believe that this may be a problem with either Firefox's JavaScript engine, or the Greasemonkey add-on. Am I right? I can be found in the JavaScript room if you want more detail and/or want to discuss this.

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• Adding a generic image field onto a ModelForm in django

  - by Prairiedogg

  I have two models, Room and Image. Image is a generic model that can tack onto any other model. I want to give users a form to upload an image when they post information about a room. I've written code that works, but I'm afraid I've done it the hard way, and specifically in a way that violates DRY. Was hoping someone who's a little more familiar with django forms could point out where I've gone wrong. Update: I've tried to clarify why I chose this design in comments to the current answers. To summarize: I didn't simply put an ImageField on the Room model because I wanted more than one image associated with the Room model. I chose a generic Image model because I wanted to add images to several different models. The alternatives I considered were were multiple foreign keys on a single Image class, which seemed messy, or multiple Image classes, which I thought would clutter my schema. I didn't make this clear in my first post, so sorry about that. Seeing as none of the answers so far has addressed how to make this a little more DRY I did come up with my own solution which was to add the upload path as a class attribute on the image model and reference that every time it's needed. # Models class Image(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') image = models.ImageField(_('Image'), height_field='', width_field='', upload_to='uploads/images', max_length=200) class Room(models.Model): name = models.CharField(max_length=50) image_set = generic.GenericRelation('Image') # The form class AddRoomForm(forms.ModelForm): image_1 = forms.ImageField() class Meta: model = Room # The view def handle_uploaded_file(f): # DRY violation, I've already specified the upload path in the image model upload_suffix = join('uploads/images', f.name) upload_path = join(settings.MEDIA_ROOT, upload_suffix) destination = open(upload_path, 'wb+') for chunk in f.chunks(): destination.write(chunk) destination.close() return upload_suffix def add_room(request, apartment_id, form_class=AddRoomForm, template='apartments/add_room.html'): apartment = Apartment.objects.get(id=apartment_id) if request.method == 'POST': form = form_class(request.POST, request.FILES) if form.is_valid(): room = form.save() image_1 = form.cleaned_data['image_1'] # Instead of writing a special function to handle the image, # shouldn't I just be able to pass it straight into Image.objects.create # ...but it doesn't seem to work for some reason, wrong syntax perhaps? upload_path = handle_uploaded_file(image_1) image = Image.objects.create(content_object=room, image=upload_path) return HttpResponseRedirect(room.get_absolute_url()) else: form = form_class() context = {'form': form, } return direct_to_template(request, template, extra_context=context)

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• Having problem loading data from AppDelegate using UITableView into a flip view, loads first view bu

  - by Ms. Ryann

  AppDelegate: @implementation Ripe_ProduceGuideAppDelegate -(void)applicationDidFinishLaunching:(UIApplication *)application { Greens *apricot = [[Greens alloc] init]; apricot.produceName = @"Apricot"; apricot.produceSight = @"Deep orange or yellow orange in appearance, may have red tinge, no marks or bruises. "; apricot.produceTouch = @"Firm to touch and give to gentle pressure, plump."; apricot.produceSmell = @"Should be Fragrant"; apricot.produceHtoP = @"raw, salads, baked, sauces, glazes, desserts, poached, stuffing."; apricot.produceStore = @"Not ripe: place in brown paper bag, at room temperature and out of direct sunlight, close bag for 2 - 3 days. Last for a week. Warning: Only refrigerate ripe apricots."; apricot.produceBest = @"Spring & Summer"; apricot.producePic = [UIImage imageNamed:@"apricot.jpg"]; Greens *artichoke = [[Greens alloc] init]; artichoke.produceName = @"Artichoke"; artichoke.produceSight = @"Slightly glossy dark green color and sheen, tight petals that are not be too open, no marks, no brown petals or dried out look. Stem should not be dark brown or black."; artichoke.produceTouch = @"No soft spots"; artichoke.produceSmell = @" Should not smell"; artichoke.produceHtoP = @"steam, boil, grill, saute, soups"; artichoke.produceStore = @"Stand up in vase of cold water, keeps for 2 -3 days. Or, place in refrigerator loose without plastic bag. May be frozen, if cooked but not raw."; artichoke.produceBest = @"Spring"; artichoke.producePic = [UIImage imageNamed:@"artichoke.jpg"]; self.produce = [[NSMutableArray alloc] initWithObjects:apricot, artichoke, nil]; [apricot release]; [artichoke release]; FirstView: @implementation ProduceView -(id)initWithIndexPath: (NSIndexPath *)indexPath { if (self == [super init] ){ index = indexPath; } return self; } -(void)viewDidLoad { Ripe_ProduceGuideAppDelegate *delegate = (Ripe_ProduceGuideAppDelegate *) [[UIApplication sharedApplication] delegate]; Greens *thisProduce = [delegate.produce objectAtIndex:index.row]; self.title = thisProduce.produceName; sightView.text = thisProduce.produceSight; touchView.text = thisProduce.produceTouch; smellView.text = thisProduce.produceSmell; picView.image = thisProduce.producePic; } FlipView: @implementation FlipsideViewController @synthesize flipDelegate; -(id)initWithIndexPath: (NSIndexPath *)indexPath { if ( self == [super init]) { index = indexPath; } return self; } -(void)viewDidLoad { Ripe_ProduceGuideAppDelegate *delegate = (Ripe_ProduceGuideAppDelegate *) [[UIApplication sharedApplication] delegate]; Greens*thisProduce = [delegate.produce objectAtIndex:index.row]; self.title = thisProduce.produceName; bestView.text = thisProduce.produceBest; htopView.text = thisProduce.produceHtoP; storeView.text = thisProduce.produceStore; picView.image = thisProduce.producePic; } *the app works, the flip view for Artichoke shows the information for Apricot. Been working on it for two days. I have been working with iPhone apps for two months now and would very much appreciate any assistance with this problem. Thank you very much.

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• Help with infrequent segmentation fault in accessing struct

  - by Sarah

  I'm having trouble debugging a segmentation fault. I'd appreciate tips on how to go about narrowing in on the problem. The error appears when an iterator tries to access an element of a struct Infection, defined as: struct Infection { public: explicit Infection( double it, double rt ) : infT( it ), recT( rt ) {} double infT; // infection start time double recT; // scheduled recovery time }; These structs are kept in a special structure, InfectionMap: typedef boost::unordered_multimap< int, Infection > InfectionMap; Every member of class Host has an InfectionMap carriage. Recovery times and associated host identifiers are kept in a priority queue. When a scheduled recovery event arises in the simulation for a particular strain s in a particular host, the program searches through carriage of that host to find the Infection whose recT matches the recovery time (double recoverTime). (For reasons that aren't worth going into, it's not as expedient for me to use recT as the key to InfectionMap; the strain s is more useful, and coinfections with the same strain are possible.) assert( carriage.size() > 0 ); pair<InfectionMap::iterator,InfectionMap::iterator> ret = carriage.equal_range( s ); InfectionMap::iterator it; for ( it = ret.first; it != ret.second; it++ ) { if ( ((*it).second).recT == recoverTime ) { // produces seg fault carriage.erase( it ); } } I get a "Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address..." on the line specified above. The recoverTime is fine, and the assert(...) in the code is not tripped. As I said, this seg fault appears 'randomly' after thousands of successful recovery events. How would you go about figuring out what's going on? I'd love ideas about what could be wrong and how I can further investigate the problem.

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• I've got my 2D/3D conversion working perfectly, how to do perspective

  - by user346992

  Although the context of this question is about making a 2d/3d game, the problem i have boils down to some math. Although its a 2.5D world, lets pretend its just 2d for this question. // xa: x-accent, the x coordinate of the projection // mapP: a coordinate on a map which need to be projected // _Dist_ values are constants for the projection, choosing them correctly will result in i.e. an isometric projection xa = mapP.x * xDistX + mapP.y * xDistY; ya = mapP.x * yDistX + mapP.y * yDistY; xDistX and yDistX determine the angle of the x-axis, and xDistY and yDistY determine the angle of the y-axis on the projection (and also the size of the grid, but lets assume this is 1-pixel for simplicity). x-axis-angle = atan(yDistX/xDistX) y-axis-angle = atan(yDistY/yDistY) a "normal" coordinate system like this --------------- x | | | | | y has values like this: xDistX = 1; yDistX = 0; xDistY = 0; YDistY = 1; So every step in x direction will result on the projection to 1 pixel to the right end 0 pixels down. Every step in the y direction of the projection will result in 0 steps to the right and 1 pixel down. When choosing the correct xDistX, yDistX, xDistY, yDistY, you can project any trimetric or dimetric system (which is why i chose this). So far so good, when this is drawn everything turns out okay. If "my system" and mindset are clear, lets move on to perspective. I wanted to add some perspective to this grid so i added some extra's like this: camera = new MapPoint(60, 60); dx = mapP.x - camera.x; // delta x dy = mapP.y - camera.y; // delta y dist = Math.sqrt(dx * dx + dy * dy); // dist is the distance to the camera, Pythagoras etc.. all objects must be in front of the camera fac = 1 - dist / 100; // this formula determines the amount of perspective xa = fac * (mapP.x * xDistX + mapP.y * xDistY) ; ya = fac * (mapP.x * yDistX + mapP.y * yDistY ); Now the real hard part... what if you got a (xa,ya) point on the projection and want to calculate the original point (x,y). For the first case (without perspective) i did find the inverse function, but how can this be done for the formula with the perspective. May math skills are not quite up to the challenge to solve this. ( I vaguely remember from a long time ago mathematica could create inverse function for some special cases... could it solve this problem? Could someone maybe try?)

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• Should I deal with files longer than MAX_PATH?

  - by John

  Just had an interesting case. My software reported back a failure caused by a path being longer than MAX_PATH. The path was just a plain old document in My Documents, e.g.: C:\Documents and Settings\Bill\Some Stupid FOlder Name\A really ridiculously long file thats really very very very..........very long.pdf Total length 269 characters (MAX_PATH==260). The user wasn't using a external hard drive or anything like that. This was a file on an Windows managed drive. So my question is this. Should I care? I'm not saying can I deal with the long paths, I'm asking should I. Yes I'm aware of the "\?\" unicode hack on some Win32 APIs, but it seems this hack is not without risk (as it's changing the behaviour of the way the APIs parse paths) and also isn't supported by all APIs . So anyway, let me just state my position/assertions: First presumably the only way the user was able to break this limit is if the app she used uses the special Unicode hack. It's a PDF file, so maybe the PDF tool she used uses this hack. I tried to reproduce this (by using the unicode hack) and experimented. What I found was that although the file appears in Explorer, I can do nothing with it. I can't open it, I can't choose "Properties" (Windows 7). Other common apps can't open the file (e.g. IE, Firefox, Notepad). Explorer will also not let me create files/dirs which are too long - it just refuses. Ditto for command line tool cmd.exe. So basically, one could look at it this way: a rouge tool has allowed the user to create a file which is not accessible by a lot of Windows (e.g. Explorer). I could take the view that I shouldn't have to deal with this. (As an aside, this isn't an vote of approval for a short max path length: I think 260 chars is a joke, I'm just saying that if Windows shell and some APIs can't handle 260 then why should I?). So, is this a fair view? Should I say "Not my problem"? Thanks! John

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• Variable mysteriously changing value

  - by Eitan

  I am making a simple tcp/ip chat program for practicing threads and tcp/ip. I was using asynchronous methods but had a problem with concurrency so I went to threads and blocking methods (not asynchronous). I have two private variables defined in the class, not static: string amessage = string.Empty; int MessageLength; and a Thread private Thread BeginRead; Ok so I call a function called Listen ONCE when the client starts: public virtual void Listen(int byteLength) { var state = new StateObject {Buffer = new byte[byteLength]}; BeginRead = new Thread(ReadThread); BeginRead.Start(state); } and finally the function to receive commands and process them, I'm going to shorten it because it is really long: private void ReadThread(object objectState) { var state = (StateObject)objectState; int byteLength = state.Buffer.Length; while (true) { var buffer = new byte[byteLength]; int len = MySocket.Receive(buffer); if (len <= 0) return; string content = Encoding.ASCII.GetString(buffer, 0, len); amessage += cleanMessage.Substring(0, MessageLength); if (OnRead != null) { var e = new CommandEventArgs(amessage); OnRead(this, e); } } } Now, as I understand it only one thread at a time will enter BeginRead, I call Receive, it blocks until I get data, and then I process it. The problem: the variable amessage will change it's value between statements that do not touch or alter the variable at all, for example at the bottom of the function at: if (OnRead != null) "amessage" will be equal to 'asdf' and at if (OnRead != null) "amessage" will be equal to qwert. As I understand it this is indicative of another thread changing the value/running asynchronously. I only spawn one thread to do the receiving and the Receive function is blocking, how could there be two threads in this function and if there is only one thread how does amessage's value change between statements that don't affect it's value. As a side note sorry for spamming the site with these questions but I'm just getting a hang of this threading story and it's making me want to sip cyanide. Thanks in advance. EDIT: Here is my code that calls the Listen Method in the client: public void ConnectClient(string ip,int port) { client.Connect(ip,port); client.Listen(5); } and in the server: private void Accept(IAsyncResult result) { var client = new AbstractClient(MySocket.EndAccept(result)); var e = new CommandEventArgs(client, null); Clients.Add(client); client.Listen(5); if (OnClientAdded != null) { var target = (Control) OnClientAdded.Target; if (target != null && target.InvokeRequired) target.Invoke(OnClientAdded, this, e); else OnClientAdded(this, e); } client.OnRead += OnRead; MySocket.BeginAccept(new AsyncCallback(Accept), null); } All this code is in a class called AbstractClient. The client inherits the Abstract client and when the server accepts a socket it create's it's own local AbstractClient, in this case both modules access the functions above however they are different instances and I couldn't imagine threads from different instances combining especially as no variable is static.

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• Understanding CLR 2.0 Memory Model

  - by Eloff

  Joe Duffy, gives 6 rules that describe the CLR 2.0+ memory model (it's actual implementation, not any ECMA standard) I'm writing down my attempt at figuring this out, mostly as a way of rubber ducking, but if I make a mistake in my logic, at least someone here will be able to catch it before it causes me grief. Rule 1: Data dependence among loads and stores is never violated. Rule 2: All stores have release semantics, i.e. no load or store may move after one. Rule 3: All volatile loads are acquire, i.e. no load or store may move before one. Rule 4: No loads and stores may ever cross a full-barrier (e.g. Thread.MemoryBarrier, lock acquire, Interlocked.Exchange, Interlocked.CompareExchange, etc.). Rule 5: Loads and stores to the heap may never be introduced. Rule 6: Loads and stores may only be deleted when coalescing adjacent loads and stores from/to the same location. I'm attempting to understand these rules. x = y y = 0 // Cannot move before the previous line according to Rule 1. x = y z = 0 // equates to this sequence of loads and stores before possible re-ordering load y store x load 0 store z Looking at this, it appears that the load 0 can be moved up to before load y, but the stores may not be re-ordered at all. Therefore, if a thread sees z == 0, then it also will see x == y. If y was volatile, then load 0 could not move before load y, otherwise it may. Volatile stores don't seem to have any special properties, no stores can be re-ordered with respect to each other (which is a very strong guarantee!) Full barriers are like a line in the sand which loads and stores can not be moved over. No idea what rule 5 means. I guess rule 6 means if you do: x = y x = z Then it is possible for the CLR to delete both the load to y and the first store to x. x = y z = y // equates to this sequence of loads and stores before possible re-ordering load y store x load y store z // could be re-ordered like this load y load y store x store z // rule 6 applied means this is possible? load y store x // but don't pop y from stack (or first duplicate item on top of stack) store z What if y was volatile? I don't see anything in the rules that prohibits the above optimization from being carried out. This does not violate double-checked locking, because the lock() between the two identical conditions prevents the loads from being moved into adjacent positions, and according to rule 6, that's the only time they can be eliminated. So I think I understand all but rule 5, here. Anyone want to enlighten me (or correct me or add something to any of the above?)

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• Silverlight with MVVM Inheritance: ModelView and View matching the Model

  - by moonground.de

  Hello Stackoverflowers! :) Today I have a special question on Silverlight (4 RC) MVVM and inheritance concepts and looking for a best practice solution... I think that i understand the basic idea and concepts behind MVVM. My Model doesn't know anything about the ViewModel as the ViewModel itself doesn't know about the View. The ViewModel knows the Model and the Views know the ViewModels. Imagine the following basic (example) scenario (I'm trying to keep anything short and simple): My Model contains a ProductBase class with a few basic properties, a SimpleProduct : ProductBase adding a few more Properties and ExtendedProduct : ProductBase adding another properties. According to this Model I have several ViewModels, most essential SimpleProductViewModel : ViewModelBase and ExtendedProductViewModel : ViewModelBase. Last but not least, according Views SimpleProductView and ExtendedProductView. In future, I might add many product types (and matching Views + VMs). 1. How do i know which ViewModel to create when receiving a Model collection? After calling my data provider method, it will finally end up having a List<ProductBase>. It containts, for example, one SimpleProduct and two ExtendedProducts. How can I transform the results to an ObservableCollection<ViewModelBase> having the proper ViewModel types (one SimpleProductViewModel and two ExtendedProductViewModels) in it? I might check for Model type and construct the ViewModel accordingly, i.e. foreach(ProductBase currentProductBase in resultList) if (currentProductBase is SimpleProduct) viewModels.Add( new SimpleProductViewModel((SimpleProduct)currentProductBase)); else if (currentProductBase is ExtendedProduct) viewModels.Add( new ExtendedProductViewModels((ExtendedProduct)currentProductBase)); ... } ...but I consider this very bad practice as this code doesn't follow the object oriented design. The other way round, providing abstract Factory methods would reduce the code to: foreach(ProductBase currentProductBase in resultList) viewModels.Add(currentProductBase.CreateViewModel()) and would be perfectly extensible but since the Model doesn't know the ViewModels, that's not possible. I might bring interfaces into game here, but I haven't seen such approach proven yet. 2. How do i know which View to display when selecting a ViewModel? This is pretty the same problem, but on a higher level. Ended up finally having the desired ObservableCollection<ViewModelBase> collection would require the main view to choose a matching View for the ViewModel. In WPF, there is a DataTemplate concept which can supply a View upon a defined DataType. Unfortunately, this doesn't work in Silverlight and the only replacement I've found was the ResourceSelector of the SLExtensions toolkit which is buggy and not satisfying. Beside that, all problems from Question 1 apply as well. Do you have some hints or even a solution for the problems I describe, which you hopefully can understand from my explanation? Thank you in advance! Thomas

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• Share a "deep link" from a Windows 8/WinRT application

  - by Dave Parker

  I have searched using many different terms and phrases, and waded through many pages of results, but I have (remarkably) not seen anyone else addressing, even asking, about, this issue. So here goes... Ultimate Goal: Allow a user viewing a content-based page (may contain both text and images) within a Windows Store app to share that content with someone else. Description I am working on taking a fair amount of content and making it available for browsing/navigating as a Windows 8/WinRT/Windows Store (we need a consistent name here) application. One of the desired features is to take advantage of the Share Charm, such that someone viewing a page could share that page with someone else. The ideal behavior is for the application to implement the Share Source contract which would share an email message that contained some explanatory text, a link to get the app from the Windows Store, and a "deep link" into the shared page in the application. Solutions Considered We had originally looked at just generating a PDF representation of the page, but there are very few external libraries that would work under WinRT, and having to include externally licensed code would be problematic as well. Writing our own PDF generation code would out of scope. We have also considered generating a Word document or PowerPoint slide using OpenXML, but again, we run up against the limitaions of WinRT. In this case, it is highly unlikely the OpenXML SDK is useable in a WinRT application. Another thought was to pre-generate all of the pages as .pdf files, store them as resources, and when the Share Charm is invoked, share the .pdf file associated with the current page. The problem here is the application will have at least 150 content pages, and depending on how we break the content down, up to over 600. This would likely cause serious bloat. Where We Are At Thus we have come to sharing URIs. From what I can tell, though, the "deep linking" feature is only intended for use on Secondary Tiles tied to your application. Another avenue I considered was registering a protocol like, "my-special-app:" with the OS and having it fire up the application but that would require HKCR registry access, which is outside the WinRT sandbox. If it matters, we are leaning towards an HTML/JS application, rather than XAML/C#, because the converted content will all be in HTML and the WebView control in WinRT is fairly limited. This decision is not yet final, though. Conclusion So, is this possible, and if so, how would it be done or where can I find documentation on it? Thanks, Dave Parker

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• bin_at in dlmalloc

  - by chunhui

  In glibc malloc.c or dlmalloc It said "repositioning tricks"As in blew, and use this trick in bin_at. bins is a array,the space is allocated when av(struct malloc_state) is allocated.doesn't it? the sizeof(bin[i]) is less then sizeof(struct malloc_chunk*)? Who can describe this trick for me? I can't understand the bin_at macro.why they get the bins address use this method?how it works? Very thanks,and sorry for my poor English. /* To simplify use in double-linked lists, each bin header acts as a malloc_chunk. This avoids special-casing for headers. But to conserve space and improve locality, we allocate only the fd/bk pointers of bins, and then use repositioning tricks to treat these as the fields of a malloc_chunk*. */ typedef struct malloc_chunk* mbinptr; /* addressing -- note that bin_at(0) does not exist */ #define bin_at(m, i) \ (mbinptr) (((char *) &((m)->bins[((i) - 1) * 2])) \ - offsetof (struct malloc_chunk, fd)) The malloc_chunk struct like this: struct malloc_chunk { INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */ INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */ struct malloc_chunk* fd; /* double links -- used only if free. */ struct malloc_chunk* bk; /* Only used for large blocks: pointer to next larger size. */ struct malloc_chunk* fd_nextsize; /* double links -- used only if free. */ struct malloc_chunk* bk_nextsize; }; And the bin type like this: typedef struct malloc_chunk* mbinptr; struct malloc_state { /* Serialize access. */ mutex_t mutex; /* Flags (formerly in max_fast). */ int flags; #if THREAD_STATS /* Statistics for locking. Only used if THREAD_STATS is defined. */ long stat_lock_direct, stat_lock_loop, stat_lock_wait; #endif /* Fastbins */ mfastbinptr fastbinsY[NFASTBINS]; /* Base of the topmost chunk -- not otherwise kept in a bin */ mchunkptr top; /* The remainder from the most recent split of a small request */ mchunkptr last_remainder; /* Normal bins packed as described above */ mchunkptr bins[NBINS * 2 - 2]; /* Bitmap of bins */ unsigned int binmap[BINMAPSIZE]; /* Linked list */ struct malloc_state *next; #ifdef PER_THREAD /* Linked list for free arenas. */ struct malloc_state *next_free; #endif /* Memory allocated from the system in this arena. */ INTERNAL_SIZE_T system_mem; INTERNAL_SIZE_T max_system_mem; };

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• Why does the rename() syscall prohibit moving a directory that I can't write to a different director

  - by Daniel Papasian

  I am trying to understand why this design decision was made with the rename() syscall in 4.2BSD. There's nothing I'm trying to solve here, just understand the rationale for the behavior itself. 4.2BSD saw the introduction of the rename() syscall for the purpose of allowing atomic renames/moves of files. From 4.3BSD-Reno/src/sys/ufs/ufs_vnops.c: /* * If ".." must be changed (ie the directory gets a new * parent) then the source directory must not be in the * directory heirarchy above the target, as this would * orphan everything below the source directory. Also * the user must have write permission in the source so * as to be able to change "..". We must repeat the call * to namei, as the parent directory is unlocked by the * call to checkpath(). */ if (oldparent != dp->i_number) newparent = dp->i_number; if (doingdirectory && newparent) { VOP_LOCK(fndp->ni_vp); error = ufs_access(fndp->ni_vp, VWRITE, tndp->ni_cred); VOP_UNLOCK(fndp->ni_vp); So clearly this check was added intentionally. My question is - why? Is this behavior supposed to be intuitive? The effect of this is that one cannot move a directory (located in a directory that one can write) that one cannot write to another directory that one can write to atomically. You can, however, create a new directory, move the links over (assuming one has read access to the directory), and then remove one's write bit on the directory. You just can't do so atomically. % cd /tmp % mkdir stackoverflow-question % cd stackoverflow-question % mkdir directory-1 % mkdir directory-2 % mkdir directory-1/directory-i-cant-write % echo "foo" > directory-1/directory-i-cant-write/contents % chmod 000 directory-1/directory-i-cant-write/contents % chmod 000 directory-1/directory-i-cant-write % mv directory-1/directory-i-cant-write directory-2 mv: rename directory-1/directory-i-cant-write to directory-2/directory-i-cant-write: Permission denied We now have a directory I can't write with contents I can't read that I can't move atomically. I can, however, achieve the same effect non-atomically by changing permissions, making the new directory, using ln to create the new links, and changing permissions. (Left as an exercise to the reader) . and .. are special cased already, so I don't particularly buy that it is intuitive that if I can't write a directory I can't "change .." which is what the source suggests. Is there any reason for this besides it being the perceived correct behavior by the author of the code? Is there anything bad that can happen if we let people atomically move directories (that they can't write) between directories that they can write?

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• Is there a standard way to encode a .NET string into javascript string for use in MS AJAX?

  - by Rich Andrews

  I'm trying to pass the output of a SQL Server exception to the client using the RegisterStartUpScript method of the MS ScriptManager. This works fine for some errors but when the exception contains single quotes the alert fails. I dont want to only escape single quotes though - Is there a standard function i can call to escape any special chars for use in Javascript? string scriptstring = "alert('" + ex.Message + "');"; ScriptManager.RegisterStartupScript(this, this.GetType(), "Alert", scriptstring , true); Thanks tpeczek, the code almost worked for me :) but with a slight amendment (the escaping of single quotes) it works a treat. I've included my amended version here... public class JSEncode { /// <summary> /// Encodes a string to be represented as a string literal. The format /// is essentially a JSON string. /// /// The string returned includes outer quotes /// Example Output: "Hello \"Rick\"!\r\nRock on" /// </summary> /// <param name="s"></param> /// <returns></returns> public static string EncodeJsString(string s) { StringBuilder sb = new StringBuilder(); sb.Append("\""); foreach (char c in s) { switch (c) { case '\'': sb.Append("\\\'"); break; case '\"': sb.Append("\\\""); break; case '\\': sb.Append("\\\\"); break; case '\b': sb.Append("\\b"); break; case '\f': sb.Append("\\f"); break; case '\n': sb.Append("\\n"); break; case '\r': sb.Append("\\r"); break; case '\t': sb.Append("\\t"); break; default: int i = (int)c; if (i < 32 || i > 127) { sb.AppendFormat("\\u{0:X04}", i); } else { sb.Append(c); } break; } } sb.Append("\""); return sb.ToString(); } } As mentioned below - original source: here

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• windows phone deserialization json

  - by user2042227

  I have a weird issue. so I am making a few calls in my app to a webservice, which replies with data. However I am using a token based login system, so the first time the user enters the app I get a token from the webservice to login for that specific user and that token returns only that users details. The problem I am having is when the user changes I need to make the calls again, to get the new user's details, but using visual studio's breakpoint debugging, it shows the new user's token making the call however the problem is when the json is getting deserialized, it is as if it still reads the old data and deserializes that, when I exit my app with the new user it works fine, so its as if it is reading cached values, but I have no idea how to clear it? I am sure the new calls are being made and the problem lies with the deserializing, but I have tried clearing the values before deserializing them again, however nothing works. am I missing something with the json deserializer, how van I clear its cached values? here I make the call and set it not to cache so it makes a new call everytime: client.Headers[HttpRequestHeader.CacheControl] = "no-cache"; var token_details = await client.DownloadStringTaskAsync(uri); and here I deserialize the result, it is at this section the old data gets shown, so the raw json being shown inside "token_details" is correct, only once I deserialize the token_details, it shows the wrong data. deserialized = JsonConvert.DeserializeObject(token_details); and the class I am deserializing into is a simple class nothing special happening here, I have even tried making the constructor so that it clears the values each time it gets called. public class test { public string status { get; set; } public string name{ get; set; } public string birthday{ get; set; } public string errorDes{ get; set; } public test() { status = ""; name= ""; birthday= ""; errorDes= ""; } } uri's before making the calls: {https://whatever.co.za/token/?code=BEBCg==&id=WP7&junk=121edcd5-ad4d-4185-bef0-22a4d27f2d0c} - old call "UBCg==" - old reply {https://whatever.co.za/token/?code=ABCg==&id=WP7&junk=56cc2285-a5b8-401e-be21-fec8259de6dd} - new call "UBCg==" - new response which is the same response as old call as you can see i did attach a new GUID everytime i make the call, but then the new uri is read before making the downloadstringtaskasync method call, but it returns with the old data

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• How can I capture the keystroke that triggers "CellEndEdit" on a DataGridView in C#?

  - by Andy Stampor

  I have a DataGridView that is set to EditOnF2. I do some special processing of data in the CellEndEdit eventhandler that sets the value of the cell. I still want the functionality of the EditOnKeystrokeOrF2 of reverting to the original value when the Esc key is pressed. Unfortunately, at the CellEndEdit eventhandler, I don't see a way to tell what caused the CellEndEdit event to be fired. I only want to change the value of the cell if the Esc key is not pressed. How can I tell if it was or not? Edit: It is worth noting that the KeyDown event does not get fired when the cell is being edited, nor for the final ending keystroke. Edit2: I have tried the KeyPreview suggestion, but the form still does not capture the Escape key being pressed. Edit3: I've been experimenting with trying to get this working. I originally posted some of the following as a separate post, but feel it might be more relevant to include it here. I have a cell in a DataGridView that is now set to EditProgrammatically. To capture the keystroke that starts an edit, I am setting the cell.Value equal to the keystroke. However, this ruins the "Escape" functionality of the cell - when you press escape, instead of reverting to the original value, it reverts to the keystroke that I programmatically inserted into the cell. I believe that if I could set the "EditedFormattedValue" on a cell, this would be where I want to put my keystroke value, however this appears to be read only. How can I accomplish what I am attempting? An example to clarify: If the cell has a value of "54.3" in it, and I press the "9" key, it begins editing the cell and places a "9" there. If I hit Escape, instead of reverting to "54.3" it reverts to "9". What I want is for it to return to its original value of "54.3". So, I am trying to tackle this issue from both the beginning and the end. I think the real problem is that I am overwriting the original value and have no way to determine if I should revert it or not. Edit4: It looks like CellValidating might be worth using, but I am seeing strange behavior when I experiment with it. In a new project, I create the DataGridView and register for the various events and see that CellValidating is fired before the CellEndEdit. However, in my project where I am trying to get this to work, CellEndEdit is firing BEFORE CellValidating. Any ideas on what the difference might be?

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• Cordova - Scrolling with a fixed header and footer (ios)

  - by Samu Singh

  Using Cordova (phonegap) & bootstrap to make a mobile application, testing on IOS for now. Getting an issue with a header and footer bar that are fixed with scrollable content in the middle. When tapping to scroll, the header/footer bar moves down or up with the content but then snaps back to place as soon as the scrolling completes. If I use -webkit-overflow-scrolling: touch; it works as expected, but it makes it really awkward to scroll through the content, and if you scroll passed the end, it only scrolls the header or footer (with elastic overflow) until you stop for a second. here's my html for the header/footer bars: <div id="headerBar"> <div class="container-fluid" style="background-color: #1569C7"> <div class="row"> <div class="col-xs-3 text-left"> <button id="logoutButton" type="button" class="btn btn-default"> Log Out </button> <button type="button" class="btn btn-default" id="restoreQuestionFeedButton"> <span class="glyphicon glyphicon-chevron-left"></span> </button> </div> <div class="col-xs-6 text-center" style="height: 55px"> <strong id="usernameText"></strong> </div> <div class="col-xs-3 text-right"> <button id="oldCreatQuestionButton" type="button" class="btn btn-default"> <span class="glyphicon glyphicon-plus"></span> </button> </div> </div> </div> </div> <div id="footerBar"> <div class="container-fluid" style="padding: 0"> <div class="row text-center"> <button id="createQuestionButton" type="button" class="btn btn-default footerButton"> <span class="glyphicon glyphicon-plus"></span> <strong>Ask a new free question!</strong> </button> </div> </div> </div> And here is the related CSS: #headerBar { position: fixed; z-index: 100; top: 0; left: 0; width: 100%; background-color: #1569C7; } #footerBar { position: fixed; z-index: 100; bottom: 0; left: 0; width: 100%; background-color: #1569C7 !important; }

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• Make a compiled binary run at native speed flawlessly without recompiling from source on a another system?

  - by unknownthreat

  I know that many people, at a first glance of the question, may immediately yell out "Java", but no, I know Java's qualities. Allow me to elaborate my question first. Normally, when we want our program to run at a native speed on a system, whether it be Windows, Mac OS X, or Linux, we need to compile from source codes. If you want to run a program of another system in your system, you need to use a virtual machine or an emulator. While these tools allow you to use the program you need on the non-native OS, they sometimes have problems of performance and glitches. We also have a newer compiler called "JIT Compiler", where the compiler will parse the bytecode program to native machine language before execution. The performance may increase to a very good extent with JIT Compiler, but the performance is still not the same as running it on a native system. Another program on Linux, WINE, is also a good tool for running Windows program on Linux system. I have tried running Team Fortress 2 on it, and tried experiment with some settings. I got ~40 fps on Windows at its mid-high setting on 1280 x 1024. On Linux, I need to turn everything low at 1280 x 1024 to get ~40 fps. There are 2 notable things though: Polygon model settings do not seem to affect framerate whether I set it low or high. When there are post-processing effects or some special effects that require manipulation of drawn pixels of the current frame, the framerate will drop to 10-20 fps. From this point, I can see that normal polygon rendering is just fine, but when it comes to newer rendering methods that requires graphic card to the job, it slows down to a crawl. Anyway, this question is rather theoretical. Is there anything we can do at all? I see that WINE can run STEAM and Team Fortress 2. Although there are flaws, they can run at lower setting. Or perhaps, I should also ask, "is it possible to translate one whole program on a system to another system without recompiling from source and get native speed?" I see that we also have AOT Compiler, is it possible to use it for something like this? Or there are so many constraints (such as DirectX call or differences in software architecture) that make it impossible to have a flawless and not native to the system program that runs at native speed?

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• How to load a springframework ApplicationContext from Jython

  - by staticman

  I have a class that loads a springframework application context like so: package com.offlinesupport; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class OfflineScriptSupport { private static ApplicationContext appCtx; public static final void initialize() { appCtx = new ClassPathXmlApplicationContext( new String[] { "mycontext.spring.xml" } ); } public static final ApplicationContext getApplicationContext() { return appCtx; } public static final void main( String[] args ) { System.out.println( "Starting..." ); initialize(); System.out.println( "loaded" ); } } The class OfflineScriptSupport, and the file mycontext.spring.xml are each deployed into separate jars (along with other classes and resources in their respective modules). Lets say the jar files are OfflineScriptSupport.jar and *MyContext.jar". mycontext.spring.xml is put at the root of the jar. In a Jython script (*myscript.jy"), I try to call the initialize method to create the application context: from com.offlinesupport import OfflineScriptSupport OfflineScriptSupport.initialize(); I execute the Jython script with the following command (from Linux): jython -Dpython.path=spring.jar:OfflineScriptSupport.jar:MyContext.jar myscript.jy The Springframework application context cannot find the mycontext.spring.xml file. It displays the following error: java.io.FileNotFoundException: class path resource [mycontext.spring.xml] cannot be opened because it does not exist at org.springframework.core.io.ClassPathResource.getInputStream(ClassPathResource.java:137) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:167) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:148) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:126) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:142) at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:113) at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:81) at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:89) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:269) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:87) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:72) at com.offlinesupport.OfflineScriptSupport.initialize(OfflineScriptSupport.java:27) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) If I run the jar directly from Java (using the main entry point in OfflineScriptSupport) it works and there is no error thrown. Is there something special about the way Jython handles classpaths making the Springframework's ClassPathXmlApplicationContext not work (i.e. not be able to find resource files in the classpath)?

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• Algorithm for finding symmetries of a tree

  - by Paxinum

  I have n sectors, enumerated 0 to n-1 counterclockwise. The boundaries between these sectors are infinite branches (n of them). The sectors live in the complex plane, and for n even, sector 0 and n/2 are bisected by the real axis, and the sectors are evenly spaced. These branches meet at certain points, called junctions. Each junction is adjacent to a subset of the sectors (at least 3 of them). Specifying the junctions, (in pre-fix order, lets say, starting from junction adjacent to sector 0 and 1), and the distance between the junctions, uniquely describes the tree. Now, given such a representation, how can I see if it is symmetric wrt the real axis? For example, n=6, the tree (0,1,5)(1,2,4,5)(2,3,4) have three junctions on the real line, so it is symmetric wrt the real axis. If the distances between (015) and (1245) is equal to distance from (1245) to (234), this is also symmetric wrt the imaginary axis. The tree (0,1,5)(1,2,5)(2,4,5)(2,3,4) have 4 junctions, and this is never symmetric wrt either imaginary or real axis, but it has 180 degrees rotation symmetry if the distance between the first two and the last two junctions in the representation are equal. Edit: This is actually for my research. I have posted the question at mathoverflow as well, but my days in competition programming tells me that this is more like an IOI task. Code in mathematica would be excellent, but java, python, or any other language readable by a human suffices. Here are some examples (pretend the double edges are single and we have a tree) http://www2.math.su.se/~per/files.php?file=contr_ex_1.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_2.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_5.pdf Example 1 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,3). Example 2 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,1). Example 5 is described as (0,1,4,5)(1,2,3,4) with distances (2). So, given the description/representation, I want to find some algorithm to decide if it is symmetric wrt real, imaginary, and rotation 180 degrees. The last example have 180 degree symmetry. (These symmetries corresponds to special kinds of potential in the Schroedinger equation, which has nice properties in quantum mechanics.)

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