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  • Want to understand C++ sentry object

    - by Romain Hippeau
    I answered this [question][1] and somebody else had answered as he modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? [1]: http://stackoverflow.com/questions/2688043/call-return-feature-of-classic-cc-with-classes-what-modern-languages-have-it/2688095#2688095 /

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  • Nonstatic conversion functions; Casting different types, e.g. DirectX vector to OpenGL vector

    - by Markus
    I am currently working on a game "engine" that needs to move values between a 3D engine, a physics engine and a scripting language. Since I need to apply vectors from the physics engine to 3D objects very often and want to be able to control both the 3D, as well as the physics objects through the scripting system, I need a mechanism to convert a vector of one type (e.g. vector3d<float>) to a vector of the other type (e.g. btVector3). Unfortunately I can make no assumptions on how the classes/structs are laid out, so a simple reinterpret_cast probably won't do. So the question is: Is there some sort of 'static'/non-member casting method to achieve basically this: vector3d<float> operator vector3d<float>(btVector3 vector) { // convert and return } btVector3 operator btVector3(vector3d<float> vector) { // convert and return } Right now this won't compile since casting operators need to be member methods. (error C2801: 'operator foo' must be a non-static member)

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  • Accommodating null values in a list?

    - by h259bws
    Hi, I'm new to Java and Groovy and am running into trouble with the following Groovy script. I created this whittled down version of a larger script to facilitate debugging. The script is iterating through a list trying to calc a running total of the values of all objects in the list. Some or all of these objects' values may be null. Script import org.apache.commons.lang.math.NumberUtils class Field { def name def value } def fields = [ new Field(name:'Annuities %', value:75), new Field(name:'Other %', value:null), ] //def totalFunding = fields.inject(0) {int total, Field myField - // total + NumberUtils.toInt(myField.value,0) as Integer def totalFunding = fields.inject(0) {int total, Field myField - total + myField?.value as Integer } It gets this error: Exception thrown: java.lang.NullPointerException java.lang.NullPointerException at Script3$_run_closure1.doCall(Script3:15) at Script3.run(Script3:14) What is the correct way to accomodate null values? Thanks, Betsy

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  • Real world examples of Ecmascript functions returning a Reference?

    - by Bergi
    Read the EcmaScript specification, section 8.7 The Reference Specification Type: The Reference type is used to explain the behaviour of such operators as delete, typeof, and the assignment operators. […] A Reference is a resolved name binding. Function calls are permitted to return references. This possibility is admitted purely for the sake of host objects. No built-in ECMAScript function defined by this specification returns a reference and there is no provision for a user-defined function to return a reference. Those last two sentences impressed me. With this, you could do things like coolHostFn() = value (valid syntax, btw). So my question is: Are there any EcmaScript implementations that define host function objects which result in Reference values?

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  • What can you do in the ant Task.init() method?

    - by skiphoppy
    I'm developing a few custom ant tasks that all need to initialize the same objects. I wanted to initialize those object's in a common superclass that extends from Task, in the init() method. But I see from the lifecycle of an ant task that init() gets called before the tasks child elements and attributes are set. So all of the data I need for initializing those objects is unavailable during init(), if I am reading right. So, why is init() called at this point? What do you even know that you could use in init()? What could it be used for? (And is there some other method that I can rely on to be called before execute(), but after my data is available?)

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  • Fault exception trashes a register causing a crash in [NSInvocation invoke]

    - by Mike Weller
    I have an NSOperation which fetches some objects from a core data persistent store and sums up a few totals. Sometimes an object is deleted while the operation in in progress, so a core data fault exception occurs. I try/catch the exception while summing to ignore it because I just want to skip objects that cannot be faulted in. However, when one of these fault exceptions occurs (and I swallow it) there is a crash after the invocation returns in [NSInvocation invoke]. It's a bad memory access when dereferencing the value in r10 which according to GDB on a successful run points to one of these: (gdb) x 0x38388348 0x38388348 <OBJC_IVAR_$_NSInvocation._retdata>: 0x00000008 If a fault exception occured a value of 0x02 is in the register which causes the crash. A quick google search tells me that r10 should be saved by the callee, meaning it is not being restored by whatever code is changing it when this exception occurs. Can anybody explain this? I'm not an expert when it comes to these kinds of low-level details

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  • Framework/tool for processing C++ unit tests with numerical output

    - by David Claridge
    Hi, I am working on a C++ application that uses computer vision techniques to identify various types of objects in a sequence of images. The (1000+) images have been hand-classified, so we have an XML file for each image containing a description of where the objects are actually located in the images. I would like to know if there is a testing framework that can understand/graph results from tests that are numeric, in this case some measure of the error in the program's classification of the images, rather than just pass/fail style unit tests. We would like to use something like CDash/CTest for running these automated tests, and viewing over time how improvements to the vision algorithms are causing the images to be more correctly classified. Does anyone know of a tool/framework that can do this?

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  • Caught AttributeError while rendering: 'str' object has no attribute '_meta'

    - by D_D
    def broadcast_display_and_form(request): if request.method == 'POST' : form = PostForm(request.POST) if form.is_valid(): post = form.cleaned_data['post'] obj = form.save(commit=False) obj.person = request.user obj.post = post obj.save() readers = User.objects.all() for x in readers: read_obj = BroadcastReader(person = x) read_obj.post = obj read_obj.save() return HttpResponseRedirect('/broadcast') else : form = PostForm() posts = BroadcastReader.objects.filter(person = request.user) return render_to_response('broadcast/index.html', { 'form' : form , 'posts' : posts ,} ) My template: {% extends "base.html" %} {% load comments %} {% block content %} <form action='.' method='POST'> {{ form.as_p }} <p> <input type="submit" value ="send it" /></input> </p> </form> {% get_comment_count for posts.post as comment_count %} {% render_comment_list for posts.post %} {% for x in posts %} <p> {{ x.post.person }} - {{ x.post.post }} </p> {% endfor %} {% endblock %}

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  • Twisted Spread: How to authenticate each RPC with digital signature

    - by kronat
    I have remote objects which talk each others with RPCs, using Twisted Spread. I want that objects authenticate messages, before using them, with digital signatures, but I don't know where to start to implement this. In my head, the Root object must have a public/private key pair, and the Client too. When a message is sent, a digital signature of the hash is added, and when it is received, the signature is checked. Is the Protocol part where I need to add these adds and checks? Thank you

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  • HQL: illegal attempt to dereference collection

    - by skip
    The situation is like this: I have an entity Book that holds a one-to-many relationship with Chapter. Now if I try the query, "from Book book inner join book.chapters chapter where chapter.title like '%hibernate%'", it gives me the desired result. But if I try, "from Book where book.chapters.title like '%hibernate%'", I get the error illegal attempt to dereference collection. The thing is that I only want the collection of Book objects in return and not a collection of pair of Book and Chapter objects in return which I get with the former query. Could someone help me understand?

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  • Direct flow depending on incoming dynamic type

    - by Improfane
    I have a listener class that accepts GUI change events in one method. The incoming event objects have a superclass of a type of GUI Event, the behaviour should depend on the dynamic type of the incoming variable. I wanted to do do lots of methods like: handleGUIEvent(EventChangedX event) handleGUIEvent(EventChangedY event) I am using a single event listener and receiving objects of various types but the behaviour should be different for each. What would you do? I do not want to use a switch statement as this would get unmaintainable.

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  • C# memory / allocation cleanup

    - by Number8
    Some near-code to try to illustrate the question, when are objects marked as available to be garbage-collected -- class ToyBox { public List<Toy> Toys = new List<Toy>(); } class Factory { public ToyBox GetToys() { ToyBox tb = new ToyBox(); tb.Toys.Add(new Toy()); tb.Toys.Add(new Toy()); return tb; } } main() { ToyBox tb = Factory.GetToys(); // After tb is used, does all the memory get cleaned up when tb goes out of scope? } Factory.GetToys() allocates memory. When is that memory cleaned up? I assume that when Factoy.GetToys() returns the ToyBox object, the only reference to the ToyBox object is the one in main(), so when that reference goes out of scope, the Toy objects and the ToyBox object are marked for garbage collection. Is that right? Thanks for any insights...

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  • What would happen to GC if I run process with priority = RealTime?

    - by Bobb
    I have a C# app which runs with priority RealTime. It was all fine until I made few hectic changes in past 2 days. Now it runs out of memory in few hours. I am trying to find whether it is a memory leak I created of this is because I consume lot more objects than before and GC simply cant collect them because it runs with same priority. My question is - what could happen to GC when it tries to collect objects in application with RealTime priority (there is also at least one thread running with Highest thread priority)? (P.S. by realtime priority I mean Process.GetCurrentProcess().PriorityClass = ProcessPriorityClass.RealTime) Sorry forgot to tell. GC is in Server mode

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  • designing database tables using JDBC

    - by Noona
    I am creating a users table using JDBC and mysql, each user has a permissions list that comprises Integer values, I am wondering if I should use an array for storing these values and then have only 1 record for this user in the table, or simply create a new table that comprises 2 columns: user ID and permissions, and then have multiple records for each user that specify the user name in one columns and one permission value in the second column, the second option seems to be redundant since a permission value is a simple object that isn't associated with any other objects (like a student and courses list for example, because the course is associated with many other objects, like grade, teacher, etc, so in this case it is natural to have multiple records), but the first one seems to be a bit unnatural to me, so if someone has experience with these things and direct me? thanks

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  • NSSortdescriptor, finding the path to the key I wish to use for sorting.

    - by RickiG
    Hi I am using an NSSortdescriptor to sort a collection of NSArrays, I then came across a case where the particular NSArray to be sorted contains an NSDictionary who contains an NSDictionary. I would like to sort from the string paired with a key in the last dictionary. This is how I would reference the string: NSDictionary *productDict = [MyArray objectAtIndex:index]; NSString *dealerName = [[productDict objectForKey:@"dealer"] objectForKey:@"name"]; How would I use the dealerName in my NSSortdescriptor to sort the array? NSSortDescriptor * sortDesc = [[NSSortDescriptor alloc] initWithKey:/* ? */ ascending:YES]; sortedDealerArray = [value sortedArrayUsingDescriptors:sortDesc]; [sortDesc release]; Hope someone could help me a bit with how I go about sorting according to keys inside objects inside other objects:) Thank you.

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  • Sort a list of pointers.

    - by YuppieNetworking
    Hello all, Once again I find myself failing at some really simple task in C++. Sometimes I wish I could de-learn all I know from OO in java, since my problems usually start by thinking like Java. Anyways, I have a std::list<BaseObject*> that I want to sort. Let's say that BaseObject is: class BaseObject { protected: int id; public: BaseObject(int i) : id(i) {}; virtual ~BaseObject() {}; }; I can sort the list of pointer to BaseObject with a comparator struct: struct Comparator { bool operator()(const BaseObject* o1, const BaseObject* o2) const { return o1->id < o2->id; } }; And it would look like this: std::list<BaseObject*> mylist; mylist.push_back(new BaseObject(1)); mylist.push_back(new BaseObject(2)); // ... mylist.sort(Comparator()); // intentionally omitted deletes and exception handling Until here, everything is a-ok. However, I introduced some derived classes: class Child : public BaseObject { protected: int var; public: Child(int id1, int n) : BaseObject(id1), var(n) {}; virtual ~Child() {}; }; class GrandChild : public Child { public: GrandChild(int id1, int n) : Child(id1,n) {}; virtual ~GrandChild() {}; }; So now I would like to sort following the following rules: For any Child object c and BaseObject b, b<c To compare BaseObject objects, use its ids, as before. To compare Child objects, compare its vars. If they are equal, fallback to rule 2. GrandChild objects should fallback to the Child behavior (rule 3). I initially thought that I could probably do some casts in Comparator. However, this casts away constness. Then I thought that probably I could compare typeids, but then everything looked messy and it is not even correct. How could I implement this sort, still using list<BaseObject*>::sort ? Thank you

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  • How should I build a simple database package for my python application?

    - by Carson Myers
    I'm building a database library for my application using sqlite3 as the base. I want to structure it like so: db/ __init__.py users.py blah.py etc.py So I would do this in Python: import db db.users.create('username', 'password') I'm suffering analysis paralysis (oh no!) about how to handle the database connection. I don't really want to use classes in these modules, it doesn't really seem appropriate to be able to create a bunch of "users" objects that can all manipulate the same database in the same ways -- so inheriting a connection is a no-go. Should I have one global connection to the database that all the modules use, and then put this in each module: #users.py from db_stuff import connection Or should I create a new connection for each module and keep that alive? Or should I create a new connection for every transaction? How are these database connections supposed to be used? The same goes for cursor objects: Do I create a new cursor for each transaction? Create just one for each database connection?

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  • Counting number of GC cleanups on an object

    - by tsps
    How do I keep a count of the number of times that objects of a specific class (type?) are getting disposed in the lifetime of my application. Imagine I have a class A, now, I want to count how many times the objects of A get collected by the GC. I hope I am phrasing this right because I was asked this in an interview today and the answer I gave did not satisfy the interviewer. And this is what I imagine he was trying to ask. What I said was that one could keep a static field called count in the class A and increment it in the Finalize() call of that object. The answer he was expecting was something called a static block. I've never heard of this in .NET/C#. Can someone explain what's this static block?

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  • Strategy for Storing Multiple Nullable Booleans in SQL

    - by Eric J.
    I have an object (happens to be C#) with about 20 properties that are nullable booleans. There will be perhaps a few million such objects persisted to a SQL database (currently SQL Server 2008 R2, but MySQL may need to be supported in the future). The instances themselves are relatively large because they contain about a paragraph of text as well as some other unrelated properties. For a given object instance, most of the properties will be null most of the time. When users search for instances of such objects, they will select perhaps 1-3 of the nullable boolean properties and search for instances where at least one of those 1-3 properties is non-null (OR search). My first thought is to persist the object to a single table with nullable BIT columns representing the nullable boolean properties. However, this strategy will require one index per BIT column to avoid performing a table scan when searching. Further, each index would not be particularly selective since there are only three possible values per index. Is there a better way to approach this problem?

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  • Why do Java and C# not have implicit conversions to boolean?

    - by Shaun
    Since I started Java it's been very aggravating for me that it doesn't support implicit conversions from numeric types to booleans, so you can't do things like: if (flags & 0x80) { ... } instead you have to go through this lunacy: if ((flags & 0x80) != 0) { ... } It's the same with null and objects. Every other C-like language I know including JavaScript allows it, so I thought Java was just moronic, but I've just discovered that C# is the same (at least for numbers, don't know about null/objects): http://msdn.microsoft.com/en-us/library/c8f5xwh7(VS.71).aspx Microsoft changed it on purpose from C++, so why? Clearly I'm missing something. Why change (what I thought was) the most natural thing in the world to make it longer to type? What on Earth is wrong with it?

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  • JButton and next/previous object of treemap

    - by supacat
    I have this problem: 1) There are objects placed in the TreeMap through the JTextField. (Phonebook-like program). 2)There are buttons that implement view of available records in TreeMap. When you click on these buttons next / previous available objects of TreeMap displaying in JTextField. (scroll through the available records). I tried this code, but I didn't work :/ btn[4].addActionListener(new ActionListener(){ Iterator iter = tree.keySet().iterator(); public void actionPerformed(ActionEvent e) { if (iter.hasNext()){ String str = iter.next().toString(); fldFio.setText(str); fldNumber.setText(tree.get(str)); } } });

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  • Get/Set nested property values

    - by Daniel Deer
    I'll try to be more descriptive here. A Few Q's: using: var foo = new Foo() { Bar = new Bar() { Value = "Value" } }; var value = DataBinder.Eval(foo, "Bar.Value"); Or: This one It is possible to retrieve an internal nested property using property path syntax. Is there a way to set/trigger a nested property (a regular property not DependencyProperty) easily with some kind of simple mechanisms as described here? I want to acheive something like: string newValue = "Hello World!"; DataBinder.EvalSet(foo, "Bar.Value", NewValue); Is there any mechanism that support both property path (for nested objects) and XPATHs (if the objects are XPATH navigable of course) ? again, that supports get and set options. Thanks, DD

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  • How can I write this Table Valued Function as a Stored Procedure?

    - by Alex
    I have the following TVF for fulltext search: FUNCTION [dbo].[Fishes_FullTextSearch] (@searchtext nvarchar(4000), @limitcount int) RETURNS TABLE AS RETURN SELECT * FROM Fishes INNER JOIN CONTAINSTABLE(Fishes, *, @searchtext, @limitcount) AS KEY_TBL ON Fishes.Id = KEY_TBL.[KEY] When I'm using this TVF, it doesn't return a collection of objects of type Fish (which I want!) - instead LINQ creates a new result type which includes all "Fish" fields and the fields Key and Rank. In another question, it was suggested that I rewrite this TVF into a stored procedure for it to return Fish objects only. Can someone help me do this please? Also, it needs to be ordered by Rank. Thank you!

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  • ubuntu server can`t install any package on internet

    - by user963587
    I have a Ubuntu-server. I am trying to install Vsftpd but it shows the : Reading package lists... Done Building dependency tree Reading state information... Done E: Couldn't find package vsftpd After that I checked internet connection by ping 4.2.2.4 and there was no problem in internet connection. I tried to apt-get update but it was not possible it shows: Err http://us.archive.ubuntu.com lucid Release.gpg Temporary failure resolving 'us.archive.ubuntu.com'

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