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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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  • Are closures in javascript recompiled

    - by Discodancer
    Let's say we have this code (forget about prototypes for a moment): function A(){ var foo = 1; this.method = function(){ return foo; } } var a = new A(); is the inner function recompiled each time the function A is run? Or is it better (and why) to do it like this: function method = function(){ return this.foo; } function A(){ this.foo = 1; this.method = method; } var a = new A(); Or are the javascript engines smart enough not to create a new 'method' function every time? Specifically Google's v8 and node.js. Also, any general recommendations on when to use which technique are welcome. In my specific example, it really suits me to use the first example, but I know thath the outer function will be instantiated many times.

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  • Django: order by count of a ForeignKey field?

    - by AP257
    This is almost certainly a duplicate question, in which case apologies, but I've been searching for around half an hour on SO and can't find the answer here. I'm probably using the wrong search terms, sorry. I have a User model and a Submission model. Each Submission has a ForeignKey field called user_submitted for the User who uploaded it. class Submission(models.Model): uploaded_by = models.ForeignKey('User') class User(models.Model): name = models.CharField(max_length=250 ) My question is pretty simple: how can I get a list of the three users with the most Submissions? I trued creating a num_submissions method on the User model: def num_submissions(self): num_submissions = Submission.objects.filter(uploaded_by=self).count() return num_submissions and then doing: top_users = User.objects.filter(problem_user=False).order_by('num_submissions')[:3] but this fails, as do all the other things I've tried. Can I actually do it using a smart database query? Or should I just do something more hacky in the views file?

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  • Custom spring <strike>bean</strike> interceptor

    - by Hari
    Hi, I want to convert some of our internal API into a spring bean spring interceptor that we can use in other projects. This API needs some instantiation and other logic which I want to encapsulate in this bean so that we can just put the bean into our app context with necessary propoerties alone, and this will then apply the logic. I remember having read an article on this somewhere in the past - but cant find it now. Any pointers to something similar will be helpful EDIT: Sorry, I meant a spring interceptor, not a bean - my bad - please see my edit. I want to apply this interceptor to another bean dealing in XML messages.

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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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  • Mutual Information / Entropy Calculation Help

    - by Fillip
    Hi, Hoping someone can give me some pointers with this entropy problem. Say X is chosen randomly from the uniform integer distribution 0-32 (inclusive). I calculate the entropy, H(X) = 32 bits, as each Xi has equal probability of occurring. Now, say the following pseudocode executes. int r = rand(0,1); // a random integer 0 or 1 r = r * 33 + X; How would I work out the mutual information between the two variables r and X? Mutual Information is defined as I(X; Y) = H(X) - H(X|Y) but I don't really understand how to apply the conditional entropy H(X|Y) to this problem. Thanks

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  • ADO.NET Data Service -- non .NET consumers

    - by SwampyFox
    Has anyone come across an example of a non .Net consumer of an ADO.NET Data Service? I am on the second day of looking at what Astoria is and how it can be used. I am also trying to answer why would I use this instead of a web service? After getting my examples running, I kind get the RESTful approach to getting data out the system. And, plugging it into a .net client is incredibly easy. But, then I wondered how a non-.NET consumer would go about it. Any ideas (pointers) definitely appreciated...

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  • Heavy use of templates for mobile platforms

    - by Chris P. Bacon
    I've been flicking through the book Modern C++ Design by Andrei Alexandrescu and it seems interesting stuff. However it makes very extensive use of templates and I would like to find out if this should be avoided if using C++ for mobile platform development (Brew MP, WebOS, iOS etc.) due to size considerations. In Symbian OS C++ the standard use of templates is discouraged, the Symbian OS itself uses them but using an idiom known as thin templates where the underlying implementation is done in a C style using void* pointers with a thin template layered on top of this to achieve type safety. The reason they use this idiom as opposed to regular use of templates is specifically to avoid code bloating. So what are opinions (or facts) on the use of templates when developing applications for mobile platforms.

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  • Creating a PHP call home "time bomb" to protect my interests

    - by RC
    Hi everyone, I produced a PHP web app for a client some months back that is hosted on their own server. I have still not been paid for this work, and they are giving me the runaround. It turns out that I still have remote admin access to their server, so I can make code changes. What I was thinking of doing was to move the core kernel off-site onto one of my own servers, and program in some kind of callback or include that gets the kernel (critical functions) from my server. Give it two weeks or so for their backups to catch this change, and then pull the plug and exercise leverage. If I do this, they will pay immediately, because the site is a critical one for a very large and influential client of theirs. What is the most effective and easiest way of doing this? What code do I use? Thanks for any pointers.

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  • <audio> elements not working on WordPress

    - by dannystewart
    Hello all, I have a small WordPress site. I do a lot of audio work and I'm trying to post HTML5 audio clips in blog entries on WordPress. For some reason it isn't working. It might have something to do with the style I'm using on my WordPress site but I haven't been able to nail it down. I know my audio tags are valid, as they work elsewhere. Here's an example audio tag: <audio src="http://files.dannystewart.com/dom2008.mp3"></audio> And here's a page demonstrating it not working: http://www.dannystewart.com/html5-audio-test/ I'm quite sure this is something very simple that I've just missed, but any pointers would be appreciated. Thanks!

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  • PL DOC source forge - 2 issues

    - by user1792793
    I'm attempting to use PLDOC source forge (http://pldoc.sourceforge.net/maven-site/) with my code to generate a neat page with comments of my liking. I'm coming across 2 issues, any help would be appreciated. 1 I've been using tags (/**, */) to make comments and this works perfectly for functions, but does not appear in procedures. My Functions and procedures are independent and not in packages, and trying to add comments before the PROCEDURE declaration just gets deleted when saved. 2 if i try to use the recommended method of getting the data directly from teh database (call pldoc.bat -url jdbc:oracle:thin:@localhost:1521:ORCL -user SCOTT -password TIGER -sql SYS_OWNER.DBMS_PIPE,SYS_OWNER.DBMS_OUTPUT), it puts all the available functions and procedures under the user SIS_OWNER (SIS_owner is the only link available on the left hand side). I want to change this so that I can view all the methods in the list instead. Problem with procedures stated in 1 still exists with this method. Please let me know if you have overcome this and any pointers would be great. Thanks

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  • Best way to insert items from a Derived class's constructor into a Base class's private std::vector?

    - by Will
    I have these classes: class Base { ... private: std::vector<X> v; }; class Derived { Derived(X*, int n); } where the constructor of Derived is passed an array of item Xs, which I need to insert into my vector v in the Base class. (X is a smart pointer) Currently I see two ways to do this: 1) Create a function in Base: InsertItem(X*) that will insert an item into the vector. 2) Create a vector in Derived that contains the full list, then get it into Base by moving the entire vector. I dont see any advantages to #2, but was wondering if #1 was a good solution, or if there are better ways to do this. Thanks!

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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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  • How to solve this problem with lists?

    - by osabri
    what i don't understand in my task here what kind of list i can use, and if it should have 2 attributes key and value ? or only value? with pointers to another node ofc the task: "design a function which create a list using input from the keyboard _ the prefered solution. Assume that some magic stops the input; so the length of a list is not known in advance.(alternative solution: a function which creates explicitly a fixed list. However, all other function can not assume any knowledge about the length of lists). Necessary utilities( additional functions to be created): a function which deallocates the memory used for lists and a function which prints the content of the list. let the element of lists contain a letter. Design a function which create a copy of such list. can't also understand the list line !!!!!???

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  • How to extract a couple marked strings from a line (python)

    - by GoJian
    My Friends, I spent quite some time on this one... but cannot yet figure out a better way to do it. I am coding in python, by the way. So, here is a line of text in a file I am working with, for example: "ref|ZP_01631227.1| 3-dehydroquinate synthase [Nodularia spumigena CCY9414]..." How can I extract the two strings "ZP_01631227.1" and "Nodularia spumigena CCY9414" from the line? The pairs of "| |" and brackets are like markers so we know we want to get the strings in between the two... I guess I can probably loop over all the characters in the line and do it the hard way. It just takes so much time... Wondering if there is a python library or other smart ways to do it nicely? Thanks to all!

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  • Create a new output file in ant replace task

    - by Sathish
    Ant replace task does a in-place replacement without creating a new file. The below snippet replaces tokens in any of the *.xml files with the corresponding values from my.properties file. <replace dir="${projects.prj.dir}/config" replacefilterfile="${projects.prj.dir}/my.properties" includes="*.xml" summary="true"/'> I want those *.xml files that had their tokens replaced be created as *.xml.filtered (for e.g.) and still have the original *.xml. Is this possible in Ant with some smart combination of tasks and concepts ?

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  • Combining Multiple SVG Transformations

    - by Andi
    I'm new to Snap.svg and SVG and experimenting with transformations (an illustraiting plunk can be found here). Basically I'm trying to move, scale and rotate a shape according to its configuration. This is what I've found out so far: rotating around a point is possible with rotate(angle, x, y) there is no direct transform method to scale around a point but it can be done as described in "SVG Essentials" However combining these transforms doesn't give me the expected result - my expected calculated center of the shape differs from the rendered one. Can anyone give me some pointers on how to correctly put these transforms together? Regards, Andi

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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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  • Document Not Saved Error in Excel.

    - by Sowmya
    This is my code snippet for comparing 2 excel files. I call this function from my QTP scripts. I get this error quite often which causes my test script to fail. Any pointers will be appreciated. Set objExcel = CreateObject("Excel.Application") objExcel.Application.Visible = False objExcel.DisplayAlerts = False Set objWorkbook1= objExcel.Workbooks.Open(excelFile1) Set objWorkbook2= objExcel.Workbooks.Open(excelFile2) Set objWorksheet1= objWorkbook1.Worksheets(1) Set objWorksheet2= objWorkbook2.Worksheets(1) <Code that compares the 2 files & marks the cell in red where there is a mismatch) objWorkbook2.Save ERROR MESSAGE: Document not saved. Function file: C:\Program Files\Mercury Interactive\QuickTest Professional\Tests\ReusableFunctions.qfl Line (33): "objWorkbook2.Save".

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  • JUnit4 + Eclipse "An internal error occured during Launching"

    - by Mike
    Hello I'm trying to run JUnit4 test cases on Eclipse 3.4.2 but it's not even starting for me. I am sure that I properly have junit-4.7.jar in my build path and the test application. Here is a simple example that illustrates my problem package test; import org.junit.Before; import org.junit.Test; public class UTest { @Test public void test() { } @Before public void setUp() throws Exception { } } This compiles fine Then I do "Run JUnit Test case" from Eclipse and I get an error dialog with this message "Launching UTest' has encountered a problem An internal error occurred during: "Launching UTest". java.lang.NullPointerException I'm not sure how to figure out what exactly generating this NullPointerException. Some pointers would be appreciated

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  • Why increase pointer by two while finding loop in linked list, why not 3,4,5?

    - by GG
    I had a look at question already which talk about algorithm to find loop in a linked list. I have read Floyd's cycle-finding algorithm solution, mentioned at lot of places that we have to take two pointers. One pointer( slower/tortoise ) is increased by one and other pointer( faster/hare ) is increased by 2. When they are equal we find the loop and if faster pointer reaches null there is no loop in the linked list. Now my question is why we increase faster pointer by 2. Why not something else? Increasing by 2 is necessary or we can increase it by X to get the result. Is it necessary that we will find a loop if we increment faster pointer by 2 or there can be the case where we need to increment by 3 or 5 or x.

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  • Can we create a class from a xml file ?

    - by panzerschreck
    Hello, Is it possible to create a class dynamically by reading an xml file ( in java preferably) ? if yes, please provide pointers on how to do it. In the process of development, we have come up with a class that has 5 attributes, all these attributes correspond to an entry in the xml file, now if the user adds/modifies the xml entry the object corresponding to it must change automatically, one approach would be generate the source code, before compile time.Is there any other way ? Is there any common pattern to model such changes in the system ? Thanks,

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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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  • 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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  • Renaming files: Visual Studio vs Version control

    - by Benjol
    The problem with renaming files is that if you want to take advantage of Visual Studio refactoring, you really need to do it from inside Visual Studio. But most (not all*) version control system also want to be the ones doing the renaming. One solution is to use integrated source control, but this is not always available, and in some cases is pretty clunky. I'd personally be more comfortable using source control separately, outside of Visual Studio, but I'm not sure how to manage this question of file renames. So, for those of you that use Visual Studio, which source control do you use? Do you use a VS integration (which one?) and otherwise, how do you resolve this renaming problem? (* git is smart enough to work it out for itself)

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