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• How to sub with matched groups and variables in Python

  - by Syed

  Hi, new to python. This is probably simple but I haven't found an answer. rndStr = "20101215" rndStr2 = "20101216" str = "Looking at dates between 20110316 and 20110317" outstr = re.sub("(.+)([0-9]{8})(.+)([0-9]{8})",r'\1'+rndStr+r'\2'+rndStr2,str) The output I'm looking for is: Looking at dates between 20101215 and 20101216 But instead I get: P101215101216 The values of the two rndStr's doesn't really matter. Assume its random or taken from user input (I put static vals here to keep it simple). Thanks for any help.

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• Why aren't variables declared in "try" in scope in "catch" or "finally"?

  - by Jon Schneider

  In C# and in Java (and possibly other languages as well), variables declared in a "try" block are not in scope in the corresponding "catch" or "finally" blocks. For example, the following code does not compile: try { String s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } In this code, a compile-time error occurs on the reference to s in the catch block, because s is only in scope in the try block. (In Java, the compile error is "s cannot be resolved"; in C#, it's "The name 's' does not exist in the current context".) The general solution to this issue seems to be to instead declare variables just before the try block, instead of within the try block: String s; try { s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } However, at least to me, (1) this feels like a clunky solution, and (2) it results in the variables having a larger scope than the programmer intended (the entire remainder of the method, instead of only in the context of the try-catch-finally). My question is, what were/are the rationale(s) behind this language design decision (in Java, in C#, and/or in any other applicable languages)?

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• PDO Prepare statement not processing parameters

  - by Danten

  I've exhausted all efforts at what appears to be a trivial problem, but gotten nowhere. There is a simple Prepare statement: $qry = $core->db->prepare("SELECT * FROM users WHERE email = '?'"); $qry->execute(array('[email protected]')); However, no rows are returned. Running the query with the parameters hardcoded into the query results in a successful selection of one row. I've tryed many different methods of doing the prepare, but even it this most simple form it isn't working. The PDO object is stored in a singleton called Core. PDO is using the mysql driver.

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• Cone-Line Segment Intersection 2D

  - by nophnoph

  Hi everyone, I would like to know is there any way to determine if a cone is intersecting with a (finite)line segment. The cone actually a circle located at P(x,y) with theta degree field of view and radius r. The simple visualization can be found here (sorry i can't post the picture here) I'm trying to do it in C# but I don't have any idea how to that, so for now this is what I'm doing : Check if the line segment is intersecting with the circle If the line segment is intersecting with the circle then I check every single point in the line segment using a function I found here. But I don't think this is the best way to do it. Does anyone have an idea? For additional info, I need this function to make some kind of simple vision simulator. Thanks in advance :)

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• efficient thread-safe singleton in C++

  - by user168715

  The usual pattern for a singleton class is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) inst = new Foo(...); return *inst; } However, it's my understanding that this solution is not thread-safe, since 1) Foo's constructor might be called more than once (which may or may not matter) and 2) inst may not be fully constructed before it is returned to a different thread. One solution is to wrap a mutex around the whole method, but then I'm paying for synchronization overhead long after I actually need it. An alternative is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) { pthread_mutex_lock(&mutex); if(inst == NULL) inst = new Foo(...); pthread_mutex_unlock(&mutex); } return *inst; } Is this the right way to do it, or are there any pitfalls I should be aware of? For instance, are there any static initialization order problems that might occur, i.e. is inst always guaranteed to be NULL the first time getInst is called?

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• Undefined Variable? But I defined it...

  - by Rob

  Well before anyone claims that theres a duplicate question... (I've noticed that people who can't answer the question tend to run and look for a duplicate, and then report it.) Here is the duplicate you are looking for: http://stackoverflow.com/questions/2481382/php-claims-my-defined-variable-is-undefined However, this isn't quite a duplicate. It gives me a solution, but I'm not really looking for this particular solution. Here is my problem: Notice: Undefined variable: custom Now here is my code: $headers = apache_request_headers(); // Request the visitor's headers. $customheader = "Header: 7ddb6ffab28bb675215a7d6e31cfc759"; //This is what the header should be. foreach ($headers as $header => $value) { $custom .= "$header: $value"; } Clearly, $custom is defined. According to the other question, it's a global and should be marked as one. But how is it a global? And how can I make it a (non-global)? The script works fine, it still displays what its supposed to and acts correctly, but when I turn on error messages, it simply outputs that notice as well. I suppose its not currently necessary to fix it, but I'd like to anyway, as well as know why its doing this.

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• WPF: Bind DataGrid to List<String>

  - by Sam

  Funny, how sometimes the simple things bite me in the behind. I can bind a DataGrid nicely to a Collection of some arbitrary class, using a DataGridTextColumn like this: <DataGridTextColumn Header="Name" Binding="{Binding Name}"/> Now I want to bind a DataGrid to a simple Collection. So since there is no property "Name" or something like that to bind to, how do I write the binding: <DataGridTextColumn Header="Name" Binding="{Binding ???}"/> String has no Property "Value" or something like that. And if I just write {Binding } I'll end up with a one-way-binding, unable to write changes back to the Collection. Thinking about it, I think it is not possible to bind to a collection, so I do need to wrap my string into a class? Or is there a way?

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• iPhone RSS Reader -- parseXML won't Load some XML feeds

  - by JBMJBM

  I am using the SIMPLE RSS reading example found at http://theappleblog.com/2008/08/04/tutorial-build-a-simple-rss-reader-for-iphone/ It uses parseXML to load the RSS feeds. Here is the problem I am having. For the following RSS feed example, I am having trouble getting it to load the feed. Comes up with an error that it cannot connect. However on my Mac RSS Reader it works fine, so I know the link is good. Any ideas on why it cannot load this particular feed but it can load others fine? http://www.okstate.com/rss.dbml?db_oem_id=200&media=news Thanks.

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• Calculating collission for a moving circle, without overlapping the boundaries

  - by Robert Vella

  Let's say I have circle bouncing around inside a rectangular area. At some point this circle will collide with one of the surfaces of the rectangle and reflect back. The usual way I'd do this would be to let the circle overlap that boundary and then reflect the velocity vector. The fact that the circle actually overlaps the boundary isn't usually a problem, nor really noticeable at low velocity. At high velocity it becomes quite clear that the circle is doing something it shouldn't. What I'd like to do is to programmitically take reflection into account and place the circle at it's proper position before displaying it on the screen. This means that I have to calculate the point where it hits the boundary between it's current position and it's future position -- rather than calculating it's new position and then checking if it has hit the boundary. This is a little bit more complicated than the usual circle/rectangle collission problem. I have a vague idea of how I should do it -- basically create a bounding rectangle between the current position and the new position, which brings up a slew of problems of it's own (Since the rectangle is rotated according to the direction of the circle's velocity). However, I'm thinking that this is a common problem, and that a common solution already exists. Is there a common solution to this kind of problem? Perhaps some basic theories which I should look into?

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• Does "Value Restriction" practically mean that there is no higher order functional programming?

  - by Sadache

  Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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• Attributes passed to .build() dont show up in the query

  - by Sebastian

  Hi there guys! Hope your all enjoying your hollydays. Ive run into a pretty funny problem when trying to insert rows into a really really simple database table. The basic idea is pretty simple. The user selects one/multiple users in a multiselect which are supposed to be added to a group. This piece of code will insert a row into the user_group_relationships table, but the users id always @group = Group.find(params[:group_id]) params[:newMember][:users].each do |uid| # For debugging purposes. puts 'Uid:'+uid @rel = @group.user_group_relationships.build( :user_id => uid.to_i ) @rel.save end The user id always gets inserted as null even though it is clearly there. You can see the uid in this example is 5, so it should work. Uid:5 ... SQL (0.3ms) INSERT INTO "user_group_relationships" ("created_at", "group_id", "updated_at", "user_id") VALUES ('2010-12-27 14:03:24.331303', 2, '2010-12-27 14:03:24.331303', NULL) Any ideas why this fails?

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• Examples of both beautiful and ugly java code?

  - by tputkonen

  I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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• Create a link to delete membership in web2py

  - by user1741325

  I'm trying to do something really simple but it's taking me ages to figure out how to do it properly. I want to have a button that simply deletes a member from a group. So in my view I have <div id="del-role">{{=A('Delete Role',_class="btn btn-danger", callback=URL('test'),delete='#del-role')}}</div> However, when I click the button, the only thing I get is a Javascript prompt asking whether I'm sure I want to delete the specified object, yes/no. That's fine but, what I'd really like to do is just auth.del_membership('role') What needs to go in my controller? I do not want any page redirection, I just want to auth.del_membership(role) This seemingly simple thing is taking me forever to understand. Thanks!

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• I have a bunch of template parameters that I want to hide from my users. How can I do this?

  - by Alex

  I have a superclass which is defined in terms of a few internal types it uses. Subclassing is performed as so: template <class InternalType1, class InternalType2> class Super { ... } class Sub : Super <interalTypeClass1, interalTypeClass2> { ... } But when I want to write a function that takes a pointer to the superclass, this happens : template <class InternalType1, class InternalType2> void function(Super<InternalType1, InternalType2>* in) { ... } The user really shouldn't know anything about the inside classes, and should really just concern himself with the use of the function. Some of these template lists become very very large, and expecting the user to pass them every time is wasteful, in my opinion. Any suggestions? EDIT: The function needs to know the internal types in use, so unless there is a way to access template types at compile time, I think there is no solution? Potential solution: Have each class do the following: #define SubTemplateArgs <SubTypeName, SubInternalType1, SubInternalType2> ?

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• Percentage position move

  - by HasanGursoy

  Is there a simple way to move percentage pointer after the value: 120 @ %60 {a} >> 120 @ 60% {a}

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• 2 (or more) ComboBoxes dependent on each other

  - by Mcad001

  Hi, I have an Organisation entity and a Region entity. An object of type Organisation can have one or more Region objects connected to it, thus I have a foreign key in my Region entity to the Organisation Entity. The Organisation and Region objects are pulled from my database using WCF RIA and entity framework. I want to put the Organisation objects in one ComboBox and the Region objects in another ComboBox, and when selecting an organsation having the ComboBox for Region objects automatically only showing regions that are connected to the selected organisation. Should be pretty basic, but the way I've designed it right now it doesnt work at all. So, any hint to how I can achive this? A simple simple codeexample is much appreciated! (I'm using SL4,WCF RIA MVVM)

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• Click at specified client area

  - by VixinG

  Click doesn't work - I don't know why and can't find a solution :( ie. Click(150,215) should move mouse to the client area and click there. [DllImport("user32.dll")] private static extern bool ScreenToClient(IntPtr hWnd, ref Point lpPoint); [DllImport("user32", SetLastError = true)] private static extern int SetCursorPos(int x, int y); static void MouseMove(int x, int y) { Point p = new Point(x * -1, y * -1); ScreenToClient(hWnd, ref p); p = new Point(p.X * -1, p.Y * -1); SetCursorPos(p.X, p.Y); } static void Click(int x, int y) { MouseMove(x, y); SendMessage(hWnd, WM_LBUTTONDOWN, (IntPtr)0x1, new IntPtr(y * 0x10000 + x)); SendMessage(hWnd, WM_LBUTTONUP, (IntPtr)0x1, new IntPtr(y * 0x10000 + x)); } Edit: Of course I can use mouse_event for that, but I would like to see a solution for SendMessage()... [DllImport("user32.dll")] static extern void mouse_event(int dwFlags, int dx, int dy, int dwData, int dwExtraInfo); const int LEFTDOWN = 0x00000002; const int LEFTUP = 0x00000004; static void Click(int x, int y) { MouseMove(x, y); mouse_event((int)(LEFTDOWN), 0, 0, 0, 0); mouse_event((int)(LEFTUP), 0, 0, 0, 0); }

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• lists searches in SYB or uniplate haskell

  - by Chris

  I have been using uniplate and SYB and I am trying to transform a list For instance type Tree = [DataA] data DataA = DataA1 [DataB] | DataA2 String | DataA3 String [DataA] deriving Show data DataB = DataB1 [DataA] | DataB2 String | DataB3 String [DataB] deriving Show For instance, I would like to traverse my tree and append a value to all [DataB] So my first thought was to do this: changeDataB:: Tree -> Tree changeDataB = everywhere(mkT changeDataB') chanegDataB'::[DataB] -> [DataB] changeDataB' <add changes here> or if I was using uniplate changeDataB:: Tree -> Tree changeDataB = transformBi changeDataB' chanegDataB'::[DataB] -> [DataB] changeDataB' <add changes here> The problem is that I only want to search on the full list. Doing either of these searches will cause a search on the full list and all of the sub-lists (including the empty list) The other problem is that a value in [DataB] may generate a [DataB], so I don't know if this is the same kind of solution as not searching chars in a string. I could pattern match on DataA1 and DataB3, but in my real application there are a bunch of [DataB]. Pattern matching on the parents would be extensive. The other thought that I had was to create a data DataBs = [DataB] and use that to transform on. That seems kind of lame, there must be a better solution.

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• Rails Model has_many with multiple foreign_keys

  - by Kenzie

  Relatively new to rails and trying to model a very simple family "tree" with a single Person model that has a name, gender, father_id and mother_id (2 parents). Below is basically what I want to do, but obviously I can't repeat the :children in a has_many (the first gets overwritten). class Person < ActiveRecord::Base belongs_to :father, :class_name => 'Person' belongs_to :mother, :class_name => 'Person' has_many :children, :class_name => 'Person', :foreign_key => 'mother_id' has_many :children, :class_name => 'Person', :foreign_key => 'father_id' end Is there a simple way to use has_many with 2 foreign keys, or maybe change the foreign key based on the object's gender? Or is there another/better way altogether? Thanks!

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• SQL return ORDER BY result as an array

  - by EarthMind

  Is it possible to return groups as an associative array? I'd like to know if a pure SQL solution is possible. Note that I release that I could be making things more complex unnecessarily but this is mainly to give me an idea of the power of SQL. My problem: I have a list of words in the database that should be sorted alphabetically and grouped into separate groups according to the first letter of the word. For example: ape broom coconut banana apple should be returned as array( 'a' => 'ape', 'apple', 'b' => 'banana', 'broom', 'c' => 'coconut' ) so I can easily created sorted lists by first letter (i.e. clicking "A" only shows words starting with a, "B" with b, etc. This should make it easier for me to load everything in one query and make the sorted list JavaScript based, i.e. without having to reload the page (or use AJAX). Side notes: I'm using PostgreSQL but a solution for MySQL would be fine too so I can try to port it to PostgreSQL. Scripting language is PHP.

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• Looking for .NET library capable of reading HDF4 file format

  - by Gart

  Does anybody know a simple library to read data from HDF files in .NET framework?

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• In the generic programming/TMP world what exactly is a model / a policy and a "concept" ?

  - by Hassan Syed

  I'd like to know the precise yet succinct definitions of these three concepts in one place. The quality of the answer should depend on the following two points. Show a simple code snippet to show how and what the concept/technique is used for. Be simple enough to understand so that a programmer without any exposure to this area can grasp it. Note: There are probably many correct answers since each concept has many different facets. If there are a lot of good answers I will eventually turn the question into CW and aggregate the answers. -- Post Accept Edit -- Boost has a nice article on generic programming concepts

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• Not a statement?

  - by abelenky

  I have a simple little code fragment that is frustrating me: HashSet<long> groupUIDs = new HashSet<long>(); groupUIDs.Add(uid)? unique++ : dupes++; At compile time, it generates the error: Only assignment, call, increment, decrement, and new object expressions can be used as a statement HashSet.Add is documented to return a bool, so the ternary (?) operator should work, and this looks like a completely legitimate way to track the number of unique and duplicate items I add to a hash-set. When I reformat it as a if-then-else, it works fine. Can anyone explain the error, and if there is a way to do this as a simple ternary operator?

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• adding org.springframework.test package to spring-2.5.6-SEC01.jar in netbeans

  - by John

  This is probably very simple, however I can't get this to work. I want to use AbstractDependencyInjectionSpringContextTest class which is in org.springframework.test package. This package is not included in Netbeans' spring library, so I want to add it. So what I have tried so far is: copy and paste "test" directory (downloaded from spring) into the Netbeans' spring-2.5.6-SEC01.jar file (copy it to org.springframework directory in that jar so I can use org.springframework.test to import it). If I go to project/libraries in Netbeans it is there, but when I try to import org.springframework.test.*; the autocomplition doesn't give me the option to choose test directory from org.soringframework package. create a new library which points to "test" directory and add it to the project- as there is no any jar file in "test" I'm not sure what path should I use to import it. I'm pretty sure this is something very simple but I'm still a novice and can't figure this out.

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• MySQL SELECT WHERE returning empty with long numbers, although they are there

  - by brybam

  Alright, so basically the most simple query ever... I've done this a million times... SELECT * FROM purchased_items WHERE uid = '$uid' if $uid == 123 It works fine and returns all data in rows where uid is 123 if $uid == 351565051447743 It returns empty... I'm positive 351565051447743 is a possible uid in some rows, i literally copied and pasted it into the table. $uid is a string, and is being passed as a string. This is something i've done a million times, and i've never had this simple query not work. Any ideas why this is not working?

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