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• maintaining a large list in python

  - by Oren

  I need to maintain a large list of python pickleable objects that will quickly execute the following algorithm: The list will have 4 pointers and can: Read\Write each of the 4 pointed nodes Insert new nodes before the pointed nodes Increase a pointer by 1 Pop nodes from the beginning of the list (without overlapping the pointers) Add nodes at the end of the list The list can be very large (300-400 MB), so it shouldnt be contained in the RAM. The nodes are small (100-200 bytes) but can contain various types of data. The most efficient way it can be done, in my opinion, is to implement some paging-mechanism. On the harddrive there will be some database of a linked-list of pages where in every moment up to 5 of them are loaded in the memory. On insertion, if some max-page-size was reached, the page will be splitted to 2 small pages, and on pointer increment, if a pointer is increased beyond its loaded page, the following page will be loaded instead. This is a good solution, but I don't have the time to write it, especially if I want to make it generic and implement all the python-list features. Using a SQL tables is not good either, since I'll need to implement a complex index-key mechanism. I tried ZODB and zc.blist, which implement a BTree based list that can be stored in a ZODB database file, but I don't know how to configure it so the above features will run in reasonable time. I don't need all the multi-threading\transactioning features. No one else will touch the database-file except for my single-thread program. Can anyone explain me how to configure the ZODB\zc.blist so the above features will run fast, or show me a different large-list implementation?

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• How to keep text inside a circle using Cairo?

  - by miguelrios

  I a drawing a graph using Cairo (pycairo specifically) and I need to know how can I draw text inside a circle without overlapping it, by keeping it inside the bounds of the circle. I have this simple code snippet that draws a letter "a" inside the circle: ''' Created on May 8, 2010 @author: mrios ''' import cairo, math WIDTH, HEIGHT = 1000, 1000 #surface = cairo.PDFSurface ("/Users/mrios/Desktop/exampleplaces.pdf", WIDTH, HEIGHT) surface = cairo.ImageSurface (cairo.FORMAT_ARGB32, WIDTH, HEIGHT) ctx = cairo.Context (surface) ctx.scale (WIDTH/1.0, HEIGHT/1.0) # Normalizing the canvas ctx.rectangle(0, 0, 1, 1) # Rectangle(x0, y0, x1, y1) ctx.set_source_rgb(255,255,255) ctx.fill() ctx.arc(0.5, 0.5, .4, 0, 2*math.pi) ctx.set_source_rgb(0,0,0) ctx.set_line_width(0.03) ctx.stroke() ctx.arc(0.5, 0.5, .4, 0, 2*math.pi) ctx.set_source_rgb(0,0,0) ctx.set_line_width(0.01) ctx.set_source_rgb(255,0,255) ctx.fill() ctx.set_source_rgb(0,0,0) ctx.select_font_face("Georgia", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD) ctx.set_font_size(1.0) x_bearing, y_bearing, width, height = ctx.text_extents("a")[:4] print ctx.text_extents("a")[:4] ctx.move_to(0.5 - width / 2 - x_bearing, 0.5 - height / 2 - y_bearing) ctx.show_text("a") surface.write_to_png ("/Users/mrios/Desktop/node.png") # Output to PNG The problem is that my labels have variable amount of characters (with a limit of 20) and I need to set the size of the font dynamically. It must fit inside the circle, no matter the size of the circle nor the size of the label. Also, every label has one line of text, no spaces, no line breaks. Any suggestion?

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• How does Android decide which background resource to draw on the foreground?

  - by Sebi

  I defined two ImageButton which are contained in a LinearLayout in my XML layout file: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/tabs" android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal" android:minHeight="40px" android:background="@drawable/library_tabs_background"> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/button_library" android:layout_width="160px" android:paddingTop="7px" android:layout_height="40px" android:paddingLeft="30px" android:orientation="horizontal"> <ImageButton android:id="@+id/list" android:layout_width="110px" android:layout_height="30px" android:src="@drawable/library_tab1_button_active"> </ImageButton> </LinearLayout> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/button_search" android:layout_width="160px" android:paddingTop="7px" android:layout_height="40px" android:orientation="horizontal"> <ImageButton android:id="@+id/search" android:layout_width="110px" android:layout_height="30px" android:src="@drawable/library_tab2_button_deactive"> </ImageButton> </LinearLayout> </LinearLayout> As one can see in the XML file, also the LinearLayout in which the buttons are contained, a background image is set. This two images (the button background and the linearlayout background) are overlapping. So in some views, the button background is in front of the layout background and in other views (im using a view flipper), the background of the layer is in the foreground. How can i set a clear rule? How does Android decide which BackgroundResource to draw first?

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• Collision detection of huge number of circles

  - by Tomek Tarczynski

  What is the best way to check collision of huge number of circles? It's very easy to detect collision between two circles, but if we check every combination then it is O(n^2) which definitely not an optimal solution. We can assume that circle object has following properties: -Coordinates -Radius -Velocity -Direction Velocity is constant, but direction can change. I've come up with two solutions, but maybe there are some better solutions. Solution 1 Divide whole space into overlapping squares and check for collision only with circles that are in the same square. Squares needs to overlap so there won't be a problem when circle moves from one square to another. Solution 2 At the beginning distances between every pair of circles need to be calculated. If the distance is small then these pair is stored in some list, and we need to check for collision in every update. If the distance is big then we store after which update there can be a collision (it can be calculated because we know the distance and velocitites). It needs to be stored in some kind of priority queue. After previously calculated number of updates distance needs to be checked again and then we do the same procedure - put it on the list or again in the priority queue.

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• SQL 2005 indexed queries slower than unindexed queries

  - by uos??

  Adding a seemingly perfectly index is having an unexpectedly adverse affect on a query performance... -- [Data] has a predictable structure and a simple clustered index of the primary key: ALTER TABLE [dbo].[Data] ADD PRIMARY KEY CLUSTERED ( [ID] ) -- My query, joins on itself looking for a certain kind of "overlapping" records SELECT DISTINCT [Data].ID AS [ID] FROM dbo.[Data] AS [Data] JOIN dbo.[Data] AS [Compared] ON [Data].[A] = [Compared].[A] AND [Data].[B] = [Compared].[B] AND [Data].[C] = [Compared].[C] AND ([Data].[D] = [Compared].[D] OR [Data].[E] = [Compared].[E]) AND [Data].[F] <> [Compared].[F] WHERE 1=1 AND [Data].[A] = @A AND @CS <= [Data].[C] AND [Data].[C] < @CE -- Between a range [Data] has about a quarter-million records so far, 10% to 50% of the data satisfies the where clause depending on @A, @CS, and @CE. As is, the query takes 1 second to return about 300 rows when querying 10%, and 30 seconds to return 3000 rows when querying 50% of the data. Curiously, the estimated/actual execution plan indicates two parallel Clustered Index Scans, but the clustered index is only of the ID, which isn't part of the conditions of the query, only the output. ?? If I add this hand-crafted [IDX_A_B_C_D_E_F] index which I fully expected to improve performance, the query slows down by a factor of 8 (8 seconds for 10% & 4 minutes for 50%). The estimated/actual execution plans show an Index Seek, which seems like the right thing to be doing, but why so slow?? CREATE UNIQUE INDEX [IDX_A_B_C_D_E_F] ON [dbo].[Data] ([A], [B], [C], [D], [E], [F]) INCLUDE ([ID], [X], [Y], [Z]); The Data Engine Tuning wizard suggests a similar index with no noticeable difference in performance from this one. Moving AND [Data].[F] <> [Compared].[F] from the join condition to the where clause makes no difference in performance. I need these and other indexes for other queries. I'm sure I could hint that the query should refer to the Clustered Index, since that's currently winning - but we all know it is not as optimized as it could be, and without a proper index, I can expect the performance will get much worse with additional data. What gives?

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• Good resources for building web-app in Tapestry

  - by Rich

  Hi, I'm currently researching into Tapestry for my company and trying to decide if I think we can port our pre-existing proprietary web applications to something better. Currently we are running Tomcat and using JSP for our front end backed by our own framework that eventually uses JDBC to connect to an Oracle database. I've gone through the Tapestry tutorial, which was really neat and got me interested, but now I'm faced with what seems to be a common issue of documentation. There are a lot of things I'd need to be sure that I could accomplish with Tapestry before I'd be ready to commit fully to it. Does anyone have any good resources, be it a book or web article or anything else, that go into more detail beyond what the Tapestry tutorial explains? I am also considering integrating with Hibernate, and have read a little bit about Spring too. I'm still having a hard time understanding how Spring would be more useful than cumbersome in tandem with Tapestry,as they seem to have a lot of overlapping features. An example I read seemed to use Spring to interface with Hibernate, and then Tapestry to Spring, but I was under the impression Tapestry integrates to the same degree with Hibernate. The resource I'm speaking of is http://wiki.apache.org/tapestry/Tapstry5First_project_with_Tapestry5,_Spring_and_Hibernate . I was interested because I hadn't found information anywhere else on how to maintain user levels and sessions through a Tapestry application before, but wasn't exactly impressed by the need to use Spring in the example.

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• 2D Ball Collisions with Corners

  - by Aaron

  I'm trying to write a 2D simulation of a ball that bounces off of fixed vertical and horizontal walls. Simulating collisions with the faces of the walls was pretty simple--just negate the X-velocity for a vertical wall or the Y-velocity for a horizontal wall. The problem is that the ball can also collide with the corners of the walls, where a horizontal wall meets with a vertical wall. I have already figured out how to detect when a collision with a corner is occurring. My question is how the ball should react to this collision--that is, how its X and Y velocities will change as a result. Here's a list of what I already know or know how to find: *The X and Y coordinates of the ball's center during the frame when a collision is detected *The X and Y components of the ball's velocity *The X and Y coordinates of the corner *The angle between the ball's center and the corner *The angle in which the ball is traveling just before the collision *The amount that the ball is overlapping the corner when the collision is detected I'm guessing that it's best to pretend that the corner is an infinitely small circle, so I can treat a collision between the ball and that circle as if the ball were colliding with a wall that runs tangent to the circles at the point of collision. It seems to me that all I need to do is rotate the coordinate system to line up with this imaginary wall, reverse the X component of the ball's velocity under this system, and rotate the coordinates back to the original system. The problem is that I have no idea how to program this. By the way, this is an ideal simulation. I'm not taking anything like friction or the ball's rotation into account. I'm using Objective-C, but I'd really just like a general algorithm or some advice. Many thanks if anyone can help!

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• EF4 and multiple abstract levels

  - by Cedric

  I need to use inheritance with EF4 and the TPH model created from DB. I created a new projet to test simples classes. There is my class model: There is my table in SQL SERVER 2008 : VEHICLE ID : int PK Owner : varchar(50) Consumption : float FirstCirculationDate : date Type : varchar(50) Discriminator : varchar(10) I added a condition in my EDMX on the Discriminator field to differentiate the Scooter, Car, Motorbike and Bike entities. MotorizedVehicle and Vehicle are Abstract. But when I compile, this error appears : Error 3032: Problem in mapping fragments starting at lines 78, 85:EntityTypes EF4InheritanceModel.Scooter, EF4InheritanceModel.Motorbike, EF4InheritanceModel.Car, EF4InheritanceModel.Bike are being mapped to the same rows in table Vehicle. Mapping conditions can be used to distinguish the rows that these types are mapped to. Edit : To Ladislav : I try it and error change to become it for all of my entities : Error 3034: Problem in mapping fragments starting at lines 72, 86:An entity is mapped to different rows within the same table. Ensure these two mapping fragments do not map two groups of entities with overlapping keys to two distinct groups of rows. To Henk (with Ladislay suggestion) : There are all of mappings details : What's wrong ? Thanks

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• Can Internet Explorer bind events to absolute positioned elements ?

  - by mark

  Can Internet Explorer bind events to absolute positioned elements ? I can't bind a "click" to an element that is overlapping another. Have tried loads of different ways, here a few tests that don't work in IE: //version 1: $(".classHolder").click(function(){ alert( $(this).html() ); }); //version 2: $(".classHolder").each(function(){ $(this).click(function(){ alert( $(this).html() ); }); }); //version 3: $("#id3").click(function(){ alert( $(this).html() ); }); //version 4: $("#id3").click(function(){ alert( $(this).html() ); }); $("#id3").trigger("click"); // in all trials I tested with and without: // $("img").unbind(); // $("div").unbind(); // just to make sure no "ghost" events were bind into the elements but no success. // replace all [ for < , and all ] for [html] [head] [script src="http://code.jquery.com/jquery-latest.js"][/script] [script type="application/javascript"] $(document).ready(function(){ $("#id3").click(function(){ alert( $(this).html() ); }); $("#id3").trigger("click"); }); [/script] [/head] [body] [div id="id1" style="position:relative;"] [img id="id2" src="http://www.google.co.uk/intl/en_com/images/srpr/logo1w.png" style=";z-index:-1;"/] [div id="id3" class="classHolder" style="position:absolute;border:2px solid red;left:0px;top:0px;width:70px;height:70px;z-index:1002;"]G[/div] [div id="id4" class="classHolder" style="position:absolute;border:2px solid red;left:210px;top:0px;width:25px;height:70px;z-index:1001;"]L[/div] asd asdf asdfg [/div] [/body] [/html]

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• Method that does conditional return of method calling it?

  - by Mattias Konradsson

  Ok this might be a bit of hack but bear with me :) The background is that i'm tired of methods that that some if-statement to that messes up indention for the whole method, like: public SomeClass DoStuff(string inputStr) { SomeClass result =null; if (IsOpenFilter(inputStr)) { .... } return result; } So I was thinking , wouldn't it be neat if I could do something like this instead: public SomeClass DoStuff(string inputStr) { Require(IsOpenFilter(inputStr),null); .... return result; } The idea is that if the statement does not evaluates to true it would return null. If there wasn't a return type for the method it would simply be: Require(IsOpenFilter(inputStr)); I realize that this is kinda overlapping with code contracts but these would be more like "conditional" or "soft" contracts evaluated at runtime rather than compile time. So I guess there's two questions, can this be done somehow? I'm stumped on how to do a conditional return from calling a method. The other question is, is this a good idea? It's a bit weird to monkeypatch the language like this but I'd rather like the way the code reads. I would be even cleaner if it could be put into an attribute above the method: [Require(IsOpenFilter(inputStr))]

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• Comet, responseText and memory usage

  - by ithcy

  Is there a way to clear out the responseText of an XHR object without destroying the XHR object? I need to keep a persistent connection open to a web server to feed live data to a browser. The problem is, there is a relatively large amount of data coming through (several hundred K per second constantly), so memory usage is a big problem, because this connection must remain open for at least several minutes. responseText gets very big very quickly, even though the JSON I send back has been crunched as small as it can get. Due to the way the server-side app works, if I use AJAX-style short polling and just destroy the XHR object when I'm done with it, I miss significant amounts of important data even in the few milliseconds it takes to parse the response, create a new XHR and send it out. I do not have the option to use overlapping requests, as the web server only accepts one connection at a time. (Don't ask.) So Comet is exactly the model I need. What I would like to do is parse each JSON chunk as it comes back from the server, and then clear out responseText so that I can keep using the same connection. However, responseText is read-only. It cannot be directly emptied by any method I have found. Is there a part of the picture I am missing here? Does anyone know any tricks I can use to free up responseText when I'm done reading it? Or is there another place the server responses can go? I am not including code because this is really almost a code-agnostic question. The Javascript routines that spawn the XHRs and handle the returned data are very, very simple.

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• RegularExpression-esque search matching Objects in List

  - by Pindatjuh

  I'm currently working on an implementation of the following idea, and I was wondering if there is any literature on this subject. Working with Java, but the principle applies on any language with a decent type-system, I like to implement: matching Objects from a List using a RegularExpression-esque search: So let's say I have a List containing List<Object> x = new ArrayList<Object>(); x.add(new Object()); x.add("Hello World"); x.add("Second String"); x.add(5); // Integer (auto-boxing) x.add(6); // Integer Then I create a "Regular Expression" (not working with a stream of characters, but working with a stream of Objects), and instead of character-classes, I use type-system properties: [String][Integer] And this would match one sublist: {Match["Second String", 5]}. The expression: [String:length()<15] Will match two sublist (each of length 1) containing a String which instance is passing the expression instance.length() < 5: {Match["Hello World"],Match["Second String"]}. [Object][Object] Matches any pair in the List: {Match[Object,"Hello World"],Match["Second String", 5]}, in a streamed manner (no overlapping matches). Ofcourse, my implementation will have grouping, lookahead/lookbehinds and is hierarchical (i.e. matching n elements from Lists in Lists), etc. The above merely illustrates the concept. Is there a name for this principle, and is there literature available on it?

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• One-sided rounded buttons in Silverlight

  - by xarzu

  I want to make a collection of buttons in silverlight. They are in a collection that goes from left to right and the buttons are lined up so that they are touching on the left and right sides. Here is the rub: The collection has rounded corners but the buttons in between the end buttons in the collection do not have rounded ends. So basically, for the buttons on the far left and right side of the collection, they have to be somewhat special because they have to have one flat vertical side and one rounded side. Is this possible to do in silverlight without resorting to making a special bitmap for the end buttons? One idea I have is somehow declare a canvas with a bitmap background and then have overlapping ellipse and rectangle <Canvas Height="100" HorizontalAlignment="Left" Margin="189,381,0,0" VerticalAlignment="Top" Width="200" Background="Black"> <Rectangle Fill="#FFF4F4F5" HorizontalAlignment="Left" Stroke="Black" Width="58" Height="61" Canvas.Left="7" Canvas.Top="16" /> <Ellipse Fill="#FFF4F4F5" HorizontalAlignment="Left" Stroke="White" Width="65" StrokeThickness="0" Height="59" Canvas.Left="31" Canvas.Top="17" /> </Canvas>

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• Help on understanding multiple columns on an index?

  - by Xaisoft

  Assume I have a table called "table" and I have 3 columns, a, b, and c. What does it mean to have a non-clustered index on columns a,b? Is a nonclustered index on columns a,b the same as a nonclustered index on columns b,a? (Note the order). Also, Is a nonclustered index on column a the same as a nonclustered index on a,c? I was looking at the website sqlserver performance and they had these dmv scripts where it would tell you if you had overlapping indexes and I believe it was saying that having an index on a is the same as a,b, so it is redundant. Is this true about indexes? One last question is why is the clustered index put on the primary key. Most of the time the primary key is not queried against, so shouldn't the clustered index be on the most queried column. I am probably missing something here like having it on the primary key speeds up joins? Great explanations. Should I turn this into a wiki and change the title index explanation?

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• HLSL - How can I set sampler Min/Mag/Mip filters to disable all filtering/anti-aliasing?

  - by RJFalconer

  I have a tex2D sampler I want to only return precisely those colours that are present on my texture. In the event of a texel overlapping multiple colours, I want it to pick one and have the whole texel be that colour. I think to do this I want to disable mipmapping, or at least trilinear filtering of mips. sampler2D gColourmapSampler : register(s0) = sampler_state { Texture = <gColourmapTexture>; //Defined above MinFilter = None; //Controls sampling. None, Linear, or Point. MagFilter = None; //Controls sampling. None, Linear, or Point. MipFilter = None; //Controls how the mips are generated. None, Linear, or Point. //... }; My problem is I don't really understand Min/Mag/Mip filtering, so am not sure what combination I need to set these in, or if this is even what I am after. MSDN has this to say; D3DSAMP_MAGFILTER: Magnification filter of type D3DTEXTUREFILTERTYPE D3DSAMP_MINFILTER: Minification filter of type D3DTEXTUREFILTERTYPE. D3DSAMP_MIPFILTER: Mipmap filter to use during minification. See D3DTEXTUREFILTERTYPE. D3DTEXF_NONE: When used with D3DSAMP_MIPFILTER, disables mipmapping.

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• Bring a subview to the top on mouseDown: AND keep receiving events (for dragging)

  - by d11wtq

  Ok, basically I have a view with a series of slightly overlapping subviews. When a subview is clicked, it moves to the top (among other things), by a really simple two-liner: -(void)mouseDown:(NSEvent *)theEvent { if (_selected) { // Don't do anything this subview is already in the foreground return; } NSView *superview = [self superview]; [self removeFromSuperview]; [superview addSubview:self position:NSWindowAbove relativeTo:nil]; } This works fine and seems to be the "normal" way to do this. The problem is that I'm now introducing some drag logic to the view, so I need to respond to -mouseDragged:. Unfortunately, since the view is removed from the view hierarchy and re-added in the process, I can have the view come to the foreground and be dragged in the same mouse action. It only drags if I leave go of the mouse and click on the view again, since the second click doesn't do any view hierarchy juggling. Is there anything I can do that will allow the view to move to the foreground like this, AND continue to receive the subsequent -mouseDragged: and -mouseUp: events that follow? I started along the lines of thinking of overriding -hitTest: in the superview and intercepting the mouseDown event in order to bring the view to the foreground before it actually receives the event. The problem here is, from within -hitTest:, how do I distinguish what type of event I'm actually performing the hit test for? I wouldn't want to move the subview to the foreground for other mouse events, such as mouseMoved etc.

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• Enforce strong type checking in C (type strictness for typedefs)

  - by quinmars

  Is there a way to enforce explicit cast for typedefs of the same type? I've to deal with utf8 and sometimes I get confused with the indices for the character count and the byte count. So it be nice to have some typedefs: typedef unsigned int char_idx_t; typedef unsigned int byte_idx_t; With the addition that you need an explicit cast between them: char_idx_t a = 0; byte_idx_t b; b = a; // compile warning b = (byte_idx_t) a; // ok I know that such a feature doesn't exist in C, but maybe you know a trick or a compiler extension (preferable gcc) that does that. EDIT: I still don't really like the Hungarian notation in general, I couldn't used it for this problem because of project coding conventions, but I used it now in another similar case, where also the types are the same and the meanings are very similar. And I have to admit: it helps. I never would go and declare every integer with a starting "i", but as in Joel's example for overlapping types, it can be life saving.

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• Center a TextBox over the top of a ScrollViewer in WPF.

  - by Eric

  I have a MainView that contains a navigation bar which selects one of many XAML pages to be displayed in the page view pane. The MainView contains a ScrollViewer around the pages. This allows the pages to be whatever size they need to be and the MainView's ScrollViewer scrolls them. This all works great. On one of the pages, I need to (sometimes) center a TextBox in the middle of the page view pane (over the top of the page content). This was easily done by placing both the page content and the TextBox overlapping each other in a Grid (and I hide the TextBox as necessary). This all seems to work great. However, if the page content grows to be larger than the pane, the TextBox is centered not on the pane, but on the full page content. Thus, it moves from center screen down and/or to the right (and eventually off the screen). Bummer. Options: Remove the ScrollViewer from the MainView. This would require placing one on every page! Argh. Do option #1, and create a ScrolledPage base class. This is a lot of work, and I'm worried about tools issues (Blend issues). It also requires changing every page (to subclass this page). Somehow override the ScrollViewer on just this page. Then, place another ScrollViewer on the page content to Scroll it. Option 3 seems preferable, because it contains the issue to just modifying this page (instead of changing the rest of the pages). However, I can't figure out how to do it. Ideas? Thanks in advance! Eric

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• InvalidOperationException when executing SqlCommand with transaction

  - by Serhat Özgel

  I have this code, running parallel in two separate threads. It works fine for a few times, but at some random point it throws InvalidOperationException: The transaction is either not associated with the current connection or has been completed. At the point of exception, I am looking inside the transaction with visual studio and verify its connection is set normally. Also command.Transaction._internalTransaction. _transactionState is set to Active and IsZombied property is set to false. This is a test application and I am using Thread.Sleep for creating longer transactions and causing overlaps. Why may the exception being thrown and what can I do about it? IDbCommand command = new SqlCommand("Select * From INFO"); IDbConnection connection = new SqlConnection(connectionString); command.Connection = connection; IDbTransaction transaction = null; try { connection.Open(); transaction = connection.BeginTransaction(); command.Transaction = transaction; command.ExecuteNonQuery(); // Sometimes throws exception Thread.Sleep(forawhile); // For overlapping transactions running in parallel transaction.Commit(); } catch (ApplicationException exception) { if (transaction != null) { transaction.Rollback(); } } finally { connection.Close(); }

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• CSS Multiple multi-column divs

  - by accelerate

  I have a bunch of items (text, image, mixed content, etc) that I want to display. The user can define what row and what column that item appears in. For example, in row 1, there could be two items/columns, both images. In row two, there could be three items / columns, one with an image, two others as pure text. Oh, and the user may specify the width of any particular column/image/item. I have a solution that uses multiple tables that works. In essence, each row is a new table. This works for the most part. I'm wondering if I can use just divs? Now my CSS foo is lacking, and I tried to copy examples from the web, and I haven't been able to get it working. Right now I have something like this: `[for each row] [for each column] [content] ` But everything is overlapping each other. I've also tried using "position: relative", but things look even more borked. So can divs actually be used for multiple rows and different number of columns?

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• Delphi Performance: Case Versus If

  - by Andreas Rejbrand

  I guess there might be some overlapping with previous SO questions, but I could not find a Delphi-specific question on this topic. Suppose that you want to check if an unsigned 32-bit integer variable "MyAction" is equal to any of the constants ACTION1, ACTION2, ... ACTIONn, where n is - say 1000. I guess that, besides being more elegant, case MyAction of ACTION1: {code}; ACTION2: {code}; ... ACTIONn: {code}; end; if much faster than if MyAction = ACTION1 then // code else if MyAction = ACTION2 then // code ... else if MyAction = ACTIONn then // code; I guess that the if variant takes time O(n) to complete (i.e. to find the right action) if the right action ACTIONi has a high value of i, whereas the case variant takes a lot less time (O(1)?). Am I correct that switch is much faster? Am I correct that the time required to find the right action in the switch case actually is independent of n? I.e. is it true that it does not really take any longer to check a million cases than to check 10 cases? How, exactly, does this work?

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• Is this a safe/valid hash method implementation?

  - by Sean

  I have a set of classes to represent some objects loaded from a database. There are a couple variations of these objects, so I have a common base class and two subclasses to represent the differences. One of the key fields they have in common is an id field. Unfortunately, the id of an object is not unique across all variations, but within a single variation. What I mean is, a single object of type A could have an id between, say, 0 and 1,000,000. An object of type B could have an id between, 25,000 and 1,025,000. This means there's some overlap of id numbers. The objects are just variations of the same kind of thing, though, so I want to think of them as such in my code. (They were assigned ids from different sets for legacy reasons.) So I have classes like this: @class BaseClass @class TypeAClass : BaseClass @class TypeBClass : BaseClass BaseClass has a method (NSNumber *)objectId. However instances of TypeA and TypeB could have overlapping ids as discussed above, so when it comes to equality and putting these into sets, I cannot just use the id alone to check it. The unique key of these instances is, essentially, (class + objectId). So I figured that I could do this by making the following hash function on the BaseClass: -(NSUInteger)hash { return (NSUInteger)[self class] ^ [self.objectId hash]; } I also implemented isEqual like so: - (BOOL)isEqual:(id)object { return (self == object) || ([object class] == [self class] && [self.objectId isEqual:[object objectId]]); } This seems to be working, but I guess I'm just asking here to make sure I'm not overlooking something - especially with the generation of the hash by using the class pointer in that way. Is this safe or is there a better way to do this?

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• 3.1.3 and 3.2 different behaviour

  - by teo

  I'm using a custom cell in tableView with a UITextField - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease]; UITextField *txtField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 280, 24)]; txtField.placeholder = @"<Enter Text>"; txtField.textAlignment = UITextAlignmentLeft; txtField.clearButtonMode = UITextFieldViewModeAlways; txtField.autocapitalizationType = UITextAutocapitalizationTypeNone; txtField.autocorrectionType = UITextAutocorrectionTypeNo; [cell.contentView addSubview:txtField]; [txtField release]; } } This works fine and the UITextField covers the cell. When i run this with 3.2 sdk or on the iPad the UITextField isn't aligned properly to the left, overlapping the cell and i have to use a UITextField width of 270 instead of 280 UITextField *txtField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 270, 24)]; It seems something is wrong the pixel ratio. How can this be fixed? Is there a way to determine the version of os the device has ( 3.1.2, 3.1.3, 3.2 or maybe even the 4.0) or can it be done another way? Thank you Teo

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• What is the base open source java package to filter/match URLs?

  - by Boaz

  Hi, I have an high performance application which deals with URLs. For every URL it needs to retrieve the appropriate settings from a predefined pool. Every settings object is associated with a URL pattern which indicates which URLs should use these settings. The matching rules are as follows: "google.com" match pattern should match all URLs pointing to the google domain (thus, maps.google.com and www.google.com/match are matched). "*.google.com" should match all URLs pointing to a subdomain of google.com (thus, maps.google.com matches, but google.com and www.google.com don't). "maps.google.com" should match all URLs pointing to this specific subdomain. Apart from the above rules, every match rule can contain a path, which means that the path part of the URL should start with the match rule path. So: "*.google.com/maps" matches "maps.google.com/maps" but not "maps.google.com/advanced". As you can see the rules above are overlapping. In the case two rules exist which match the same URL the most specific should apply. The list above is ranked from least specific to most specific. This seems to be such a standard problem that I was hoping to use a ready made library rather than program my self. Google reveals a couple of options but without a clear way to choose between them. What would you recommend as a good library for this task? Thanks, Boaz

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• Calculate location and number of intersections between multiple date/time ranges?

  - by Patricker

  I need to calculate the location of intersections between multiple date ranges, and the number of overlapping intersections. Then I need to show which date/time ranges overlap each of those intersecting sections. It is slightly more complicated than that so I'll do my best to explain by providing an example. I am working in VB.Net, but C# examples are acceptable as well as I work in both. We have several high risk tasks that involve the same system. Below I have three example jobs named HR1/2/3/4 with start and end date/times. HR1 {1/6/2010 10:00 - 1/6/2010 15:00} HR2 {1/6/2010 11:00 - 1/6/2010 18:00} HR3 {1/6/2010 12:00 - 1/6/2010 14:00} HR4 {1/6/2010 18:00 - 1/6/2010 20:00} What I want the end result to be is shown below. I am having trouble describing it any way but by example. HRE1 {1/6/2010 10:00 - 1/6/2010 11:00} - Intersects 1 {End Time Split 1, for readability only, not needed in solution} HRE1 {1/6/2010 11:00 - 1/6/2010 12:00} - Intersects 2 HRE2 {1/6/2010 11:00 - 1/6/2010 12:00} - Intersects 2 {End Time Split 2, for readability only, not needed in solution} HRE1 {1/6/2010 12:00 - 1/6/2010 14:00} - Intersects 3 HRE2 {1/6/2010 12:00 - 1/6/2010 14:00} - Intersects 3 HRE3 {1/6/2010 12:00 - 1/6/2010 14:00} - Intersects 3 {End Time Split 3, for readability only, not needed in solution} HRE1 {1/6/2010 14:00 - 1/6/2010 15:00} - Intersects 2 HRE2 {1/6/2010 14:00 - 1/6/2010 15:00} - Intersects 2 {End Time Split 4, for readability only, not needed in solution} HRE2 {1/6/2010 15:00 - 1/6/2010 18:00} - Intersects 1 {End Time Split 5, for readability only, not needed in solution} HR4 {1/6/2010 18:00 - 1/6/2010 20:00} - Intersects 1 Any help would be greatly appreciated.

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