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• Clojure closures and GC

  - by Ralph

  It is my understanding that the default ClassLoader used in Java (and thus, Clojure) holds on to pointers to any anonymous classes created, and thus, onto lambdas and closures. These are never garbage collected, and so represent a "memory leak". There is some investigation going on for Java 7 or 8 to adding an anonymous ClassLoader that will not retain references to these functions. In the mean time how are people dealing with writing long-running applications in languages like Clojure and Scala, that encourage the use of these constructs? Is there any possibility that Clojure could provide its own anonymous ClassLoader, extending the system one, but not holding onto created classes?

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• "painting" one array onto another using python / numpy

  - by Nate

  I'm writing a library to process gaze tracking in Python, and I'm rather new to the whole numpy / scipy world. Essentially, I'm looking to take an array of (x,y) values in time and "paint" some shape onto a canvas at those coordinates. For example, the shape might be a blurred circle. The operation I have in mind is more or less identical to using the paintbrush tool in Photoshop. I've got an interative algorithm that trims my "paintbrush" to be within the bounds of my image and adds each point to an accumulator image, but it's slow(!), and it seems like there's probably a fundamentally easier way to do this. Any pointers as to where to start looking?

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• Pattern for null settings

  - by user21243

  Hi, I would like to hear your thoughts and ideas about this one. in my application i have controls that are binded to objects properties. but.. the controls always looks like that: a check box, label that explain the settings and then the edited control (for ex: text box) when unchecking the checkbox i disable the text box (using binding) when the checkbox is unchecked i want the property to contain null, and when it is checked i would like the property to contain the text box's text. Of course text box can be NumericUpDown, ComboBox, DatePicker etc.. Do you have any smart way of doing it using binding or do i have to do everything on code; I really would like to a build a control that supports that and re-use it all over Ideas? Thanks,

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• Is it secure to use malloc?

  - by Felix Guerrero

  Somebody told me that allocating with malloc is not secure anymore, I'm not a C/C++ guru but I've made some stuff with malloc and C/C++. Does anyone know about what risks I'm into? Quoting him: [..] But indeed the weak point of C/C++ it is the security, and the Achilles' heel is indeed malloc and the abuse of pointers. C/C++ it is a well known insecure language. [..] There would be few apps in what I would not recommend to continue programming with C++."

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• Reverse Bredth First Search in C#

  - by Ngu Soon Hui

  Anyone has a ready implementation of the Reverse Bredth First Search algorithm in C#? By Reverse Bredth First Search, I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node. Let's see the below figure, this is the output of a Bredth First Search: In my reverse bredth first search, 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found. Any ideas or pointers?

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• Consuming WCF from BizTalk 2006r1

  - by Rob Bowman

  Hi I need to create an Orchestration in BizTalk 2006r1 that will consume a WCF basicHTTP web service. Does anyone have a pointers on how to do this please? The WCF service has been created by another team but I am able to request that they create an additional endpoint with binding configuration set to make calling from BizTalk SOAP adapter possible. I just created a simple test basicHTTP service that runs fine when tested from a command line client. When I got to BizTalk add web reference I am able to browse to the service but then get a message "Failed to add web reference" and it bombs out! Any help gratefully received. Thanks Rob.

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• Notifying when screen is off

  - by Al

  I'm trying to generate a notification which vibrates the phone and plays a sound when the screen is off (cpu turned off). According to the Log messages, the notification is being sent, but the phone doesn't vibrate or play the sound until I turn the screen on again. I tried holding a 2 second temporary wakelock (PowerManager.PARTIAL_WAKE_LOCK), which I thought would be ample time for the notification to be played, but alas, it still doesn't. Any pointers to get the notification to run reliably? I'm testing this on an G1 running Android 1.6. Code I'm using: notif.vibrate = new long[] {100, 1000}; notif.defaults |= Notification.DEFAULT_SOUND; notif.ledARGB = Color.RED; notif.ledOnMS = 1; notif.ledOffMS = 0; notif.flags = Notification.FLAG_SHOW_LIGHTS; notif.flags |= NOTIF_FLAGS; //static var if (!screenOn) { //var which updates when screen turns off/on mWakeLock.acquire(2000); } manager.notify(NOTIF_ID, notif);

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• multiple C++ deletion of a memory pointed by multiple objects

  - by elgcom

  Another c++ pointer deletion question is in the following example: class Foo { public: int *p; ~Foo() { delete p; p = NULL; } }; Foo *f1 = new Foo(); Foo *f2 = new Foo(); f1->p = new int(1); f2->p = f1->p; delete f2; // ok delete f1; // no error? Why I did not get error when calling "delete f1"? didn't I delete the same address (*p) twice? If I directly delete the pointers in the last 2 lines of code, I will get error. delete f2->p; // ok delete f1->p; // error!! *** glibc detected *** double free or corruption (fasttop) ***

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• Rails - Active Record :conditions overrides :select

  - by Nick

  I have a fairly large model and I want to retrieve only a select set of fields for each record in order to keep the JSON string I am building small. Using :select with find works great but my key goal is to use conditional logic with an associated model. Is the only way to do this really with a lamda in a named scope? I'm dreading that perhaps unnecessarily but I'd like to understand if there is a way to make the :select work with a condition. This works: @sites = Site.find :all, :select => 'id,foo,bar' When I try this: @sites = Site.find :all, :select => 'id,foo,bar', :include => [:relatedmodel], :conditions => ["relatedmodel.type in (?)", params[:filters]] The condition works but each record includes all of the Site attributes which makes my JSON string way way too large. Thanks for any pointers!

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• Correct way to give users access to additional schemas in Oracle

  - by Jacob

  I have two users Bob and Alice in Oracle, both created by running the following commands as sysdba from sqlplus: create user $blah identified by $password; grant resource, connect, create view to $blah; I want Bob to have complete access to Alice's schema (that is, all tables), but I'm not sure what grant to run, and whether to run it as sysdba or as Alice. Happy to hear about any good pointers to reference material as well -- don't seem to be able to get a good answer to this from either the Internet or "Oracle Database 10g The Complete Reference", which is sitting on my desk.

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• speed up the speed of a sql query to mysql?

  - by fayer

  in my mysql database i've got the geonames database, containing all countries, states and cities. i am using this to create a cascading menu so the user could select where he is from: country - state - county - city. but the main problem is that the query will search through all the 7 millions rows in that table each time i want to get the list of children rows, and that is taking a while 10-15 seconds. i wonder how i could speed this up: caching? table views? reorganizing table structure somehow? and most important, how do i do these things? are there good tutorials you could link to me? i appreciate all help and feedback discussing smart ways of handling this issue!

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• Where is a good place/way to store Windows config files for Python scripts?

  - by thornomad

  I have a script/program I am working on that requires a configuration file (I am using ConfigParser). On linux, I will default to store these variables in ~/.myscript using the os.getenv('HOME') function. With Windows, I know I can use os.getenv('USERPROFILE') to find the User's "home" directory, however, is it a good idea to save a hidden file that way (ie, with the name .myscript)? I don't use Windows, obviously, but wanted to be smart about it for those who do. Is there a standard place/way to store these config variables on Windows?

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• Measuring the performance of classification algorithm

  - by Silver Dragon

  I've got a classification problem in my hand, which I'd like to address with a machine learning algorithm ( Bayes, or Markovian probably, the question is independent on the classifier to be used). Given a number of training instances, I'm looking for a way to measure the performance of an implemented classificator, with taking data overfitting problem into account. That is: given N[1..100] training samples, if I run the training algorithm on every one of the samples, and use this very same samples to measure fitness, it might stuck into a data overfitting problem -the classifier will know the exact answers for the training instances, without having much predictive power, rendering the fitness results useless. An obvious solution would be seperating the hand-tagged samples into training, and test samples; and I'd like to learn about methods selecting the statistically significant samples for training. White papers, book pointers, and PDFs much appreciated!

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• Why is Javascript's Math.floor the slowest way to calculate floor in Javascript?

  - by z5h

  I'm generally not a fan of microbenchmarks. But this one has a very interesting result. http://ernestdelgado.com/archive/benchmark-on-the-floor/ It suggests that Math.floor is the SLOWEST way to calculate floor in Javascript. ~~n, n|n, n&n all being faster. This seems pretty shocking as I would expect that people implementing Javascript in today's modern browsers would be some pretty smart people. Does floor do something important that the other methods fail to do? Is there any reason to use it?

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• implementing type inference

  - by deepblue

  well I see some interesting discussions here about static vs. dynamic typing I generally prefer static typing, due to compile type checking, better documented code,etc. However I do agree that they do clutter up the code if done the way Java does it, for example. so Im about to start building a language of my own and type inference is one of the things that I want to implement, in a functional style language... I do understand that it is a big subject, and Im not trying to create something that has not been done before, just basic inferencing... any pointers on what to read up that will help me with this? preferably something more pragmatic/practical as oppose to more theoretical category theory/type theory texts. If there's a implementation discussion text out here, with data structures/algorithms, that would just be lovely much appreciated

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• Should I go with Varnish instead of nginx?

  - by gotts

  I really like nginx. But recently I've found that varnish gives you an opportunity to implement smart caching revers proxy layer(with URL purging). I have a cluster of mongrels which are pretty resource-intensive so if this caching layer can remove some load from mongrels this can be a great thing. I didn't find a way to implement the caching layer(with for application pages; static content is cacheable of course) same with nginx.. Should I use Varnish instead? What would you recommend?

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• Can't append to array using string field name [$] when performing update on array fields

  - by Haraldo

  rowsI am attempting to perform a mongodb update on each field in an array of records. An example schema is below: { "_id" : ObjectId("508710f16dc636ec07000022"), "summary" : "", "uid" : "ABCDEF", "username" : "bigcheese", "name" : "Name of this document", "status_id" : 0, "rows" : [ { "score" : 12, "status_id" : 0, "uid" : 1 }, { "score" : 51, "status_id" : 0, "uid" : 2 } ] } So far I have been able to perform single updates like this: db.mycollection.update({"uid":"ABCDEF","rows.uid":1}, {$set:{"rows.$.status_id":1}},false,false) However, I am struggling as to how to perform an update that will update all array records to a status_id of 1 (for instance). Below is how I imagine it should work: db.mycollection.update({"uid":"ABCDEF"}, {$set:{"rows.$.status_id":1}},false,true) However I get the error: can't append to array using string field name [$] I have tried for quite a while with no luck. Any pointers?

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• how to open many files simultaneously for reading in c

  - by monkeyking

  I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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• Windows Phone 7 and C++/CLI

  - by Fabio Ceconello

  Microsoft recently released tools and documentation for its new Phone 7 platform, which to the dismay of those who have a big C++ codebase (like me) doesn't support native development anymore. Although I've found speculation about this decision being reversed, I doubt it. So I was thinking how viable would be to make this codebase available to Phone 7 by adapting it to compile under C++/CLI. Of course the user interface parts couldn't be ported, but I'm not sure about the rest. Anyone had a similar experience? I'm not talking about code that does heavy low-level stuff - but there's a quite frequent use of templates and smart pointers.

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• Using windows CopyFile function to copy all files with certain name format

  - by Ben313

  Hello! I am updating some C code that copys files with a certain name. basically, I have a directory with a bunch of files named like so: AAAAA.1.XYZ AAAAA.2.ZYX AAAAA.3.YZX BBBBB.1.XYZ BBBBB.2.ZYX Now, In the old code, they just used a call to ShellExecute and used xcopy.exe. to get all the files starting with AAAAA, they just gave xcopy the name of the file as AAAAA.* and it knew to copy all of the files starting with AAAAA. now, im trying to get it to copy with out having to use the command line, and I am running into trouble. I was hoping CopyFile would be smart enough to handle AAAAA.* as the file to be copied, but it doesnt at all do what xcopy did. So, any Ideas on how to do this without the external call to xcopy.exe?

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• C 64-bit Pointer Alignment

  - by DuneBug

  Are pointers on a 64-bit system still 4 byte aligned (similar to a double on a 32 bit system)? Or are they note 8 byte aligned? For example, on a 64-bit system how big is the following data structure: struct a { void* ptr; char myChar; } Would the pointer by 8 byte aligned, causing 7 bytes of padding for the character (total = 8 + 8 = 16)? Or would the pointer be 4 byte aligned (4 bytes + 4 bytes) causing 3 bytes of padding (total = 4 + 4 + 4 = 12)? Thanks, Ryan

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• Render asp.net repeater as-and-when chunks of html is ready (streaming)

  - by sash

  The problem is to render huge reports. Basically we have lots of data that get rendered in html reports (mostly using repeater or gridview). As it so happens, the data started out small and now we have tons of it. There are lots of such reports already built so total rewrite is not an option. Heck, the business is not even letting us page the data. Now server memory is shooting up each time we try to render some reports. So the question is - is there some way we can bind data to repeater and have it stream html to browser as and when chunks are ready? That way we hope to not bring all that data into app server at once. I'm thinking we'll use a datareader or something to get parts of data and render it to browser. Any pointers, links, ideas?

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• When to pass by value?

  - by Dervin Thunk

  Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value in C. Let me rephrase. When do you purposefully use C's pass-by-value for large objects? Or, when do you care that the object argument is fully copied in a local variable? EDIT: Now that I think about it, if you can avoid pointers, then do. Nowadays, "deep" copying is possible for mostly everything in small apps, and shallow copying is more prone to pointer bugs. Maybe.

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• Implementing implicitly shared classes outside of Qt

  - by Timothy Baldridge

  I'm familiar with the way Qt uses D-pointers for managing data. How do I do this in my code? I tried this method: 1) move all data into a struct 2) add a QAtomicInt to the struct 3) implement a = operator and change my constructor/deconstructor to check-up on the reference count. The issue is, when I go to do a shallow copy of the object, I get an error about QObject declaring = as private. How then do I accomplish this? Here's an example of my copy operator: HttpRequest & HttpRequest::operator=(const HttpRequest &other) { other.d->ref.ref(); if (!d->ref.deref()) delete d; d = other.d; return *this; } Am I going about this the wrong way?

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• php $_REQUEST data is only half-decoded

  - by hackmaster.a

  I am retrieving a url via querystring. I need to pass it again to the next page. When I retrieve it the first time, using $_REQUEST['url'], only the slashes are decoded, e.g: http://example.com/search~S10?/Xllamas&searchscope=10&SORT=D/Xllamas&searchscope=10&SORT=D&SUBKEY=llamas/51%2C64%2C64%2CB/browse The php docs page for urldecode advises against decoding request data, and says that it will already be decoded. I need it either completely decoded, so I can encode it again without double-encoding some parts, or not decoded at all. I'm not sure why my experience of this data is incongruous with the php docs. Appreciate any help or pointers to same!!

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