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  • How to approach copying objects with smart pointers as class attributes?

    - by tomislav-maric
    From the boost library documentation I read this: Conceptually, smart pointers are seen as owning the object pointed to, and thus responsible for deletion of the object when it is no longer needed. I have a very simple problem: I want to use RAII for pointer attributes of a class that is Copyable and Assignable. The copy and assignment operations should be deep: every object should have its own copy of the actual data. Also, RTTI needs to be available for the attributes (their type may also be determined at runtime). Should I be searching for an implementation of a Copyable smart pointer (the data are small, so I don't need Copy on Write pointers), or do I delegate the copy operation to the copy constructors of my objects as shown in this answer? Which smart pointer do I choose for simple RAII of a class that is copyable and assignable? (I'm thinking that the unique_ptr with delegated copy/assignment operations to the class copy constructor and assignment operator would make a proper choice, but I am not sure) Here's a pseudocode for the problem using raw pointers, it's just a problem description, not a running C++ code: // Operation interface class ModelOperation { public: virtual void operate = (); }; // Implementation of an operation called Special class SpecialModelOperation : public ModelOperation { private: // Private attributes are present here in a real implementation. public: // Implement operation void operate () {}; }; // All operations conform to ModelOperation interface // These are possible operation names: // class MoreSpecialOperation; // class DifferentOperation; // Concrete model with different operations class MyModel { private: ModelOperation* firstOperation_; ModelOperation* secondOperation_; public: MyModel() : firstOperation_(0), secondOperation_(0) { // Forgetting about run-time type definition from input files here. firstOperation_ = new MoreSpecialOperation(); secondOperation_ = new DifferentOperation(); } void operate() { firstOperation_->operate(); secondOperation_->operate(); } ~MyModel() { delete firstOperation_; firstOperation_ = 0; delete secondOperation_; secondOperation_ = 0; } }; int main() { MyModel modelOne; // Some internal scope { // I want modelTwo to have its own set of copied, not referenced // operations, and at the same time I need RAII to work for it, // as soon as it goes out of scope. MyModel modelTwo (modelOne); } return 0; }

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  • Updating an atom with a single value

    - by mikera
    I have a number of atoms in my code where a common requirement is to update them to a new value, regardless of the current value. I therefore find myself writing something like this: (swap! atom-name (fn [_] (identity new-value))) This works but seems pretty ugly and presumably incurs a performance penalty for constructing the anonymous closure. Is there a better way?

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  • OGNL thread safety

    - by Dewfy
    I'm going to reuse OGNL library out of Struts2 scope. I have rather large set of formulas, that is why I would like to precompile all of them: Ognl.parseExpression(expressionString); But I'm not sure if precompiled expression can be used in multi-thread environment. Does anybody knows if it can be used?

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  • Strategy to rename the require_once function?

    - by openfrog
    Rather than just writing a new function called import() i'd like to know if there's a better solution. Otherwise require_once would be included in the scope of import() only, which is bad for any "global" variable there. My import() function would work differently than require_once, but serves the same purpose (enhanced usability).

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  • Determine application version

    - by rayman
    Hi, I wanna know if there is anyway to determine not through the packages, but through applications the version of an application which isnt the current application. let's say right now i am in the scope of app A. and i wanna run an activity from app B. i wanna check before the version code of app B. thanks, ray.

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  • Best Practice: Direct SQL Access vs. Web Service

    - by phsr
    With respect to an application that has both a web and desktop client version: What is the best practice for the desktop client which needs access to a SQL Server? What are the benefits of connecting to the database from the application vs using a web service? Which one provides better security? What type of scope would call for one vs the other (enterprise intranet vs. web app, etc) Are there any other considerations that are necessary when choosing on platform?

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  • No clock with FTDIchip FT2232 MPSSE mode

    - by Simi
    Hello, I'm trying to write/read to an extern device connected to a FTDIchip FT2232 MPSSE mode using SPI. I'm using the SPI function given by FTDI for Labview. I'm doing this: Open_Device - Init_Device - Write/Read - Close_Device The problem is that I don't have a clock signal on the scope when I try to read/write. Do you have a solution? Thanks

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  • How do I create and read non-global variables that aren't destroyed at end of function?

    - by Paul Reilly
    I am attempting to code some plugins to use with MIDI sequencers but have hit a stumbling block. I can't use global-scope variables to store information because multiple instances of the .dll can exist which share memory. How do I create a class (for re-usability purposes in other plugins) containing 2 dimensional array and other variables the content of which is to be shared between functions? If that is possible, how would I read and write the data from the function in the framework where I do the processing?

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  • lisp, differences in assignment functions

    - by johnc
    I'm pretty new to lisp, so apologies for what may be a simple question, Whilst I understand the difference between DEFVAR and DEFPARAMETER (defvar only sets undefined variables), and the LET is for local scope only, what is the is the use of SETF as opposed to the other, previously mentioned assignment functions?

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  • HTML Character Identities in Twitter

    - by Patrick Gates
    I'm developing a twitter app, and when I submit a new tweet from php with abrahams twitteroauth and with any special character it submits it to twitter as the HTML identity. I've tried all the html_entity_decode() and the htmlspecialchars_decode() but nothings working. Thank you :)

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  • Question regarding the method local innerclasses accesing the local variables of the method

    - by flash
    Hi I was going through the SCJP book about the innerclasses, and found this statement, it goes something like this. "A method local class can only refer to the local variables which are marked final" and in the explanation the reason specified is about the scope and lifetime of the local class object and the local variables on the heap, But I am unable to understand that.am I missing anything here about 'final'??

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  • Destroy Session in an application

    - by Jibu P C_Adoor
    I have several pages in my application. I have used a session variable called "Session["Variable"]" that is set in page1 and page2. That means The scope should be in page1 and page2. If you go out any of these page will clear the above session variable. Is there any solution to clear the particular session varible in the application level. i.e i don't want to write the code for each and every pages...

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  • Force deletion of slot in boost::signals2

    - by villintehaspam
    Hi! I have found that boost::signals2 uses sort of a lazy deletion of connected slots, which makes it difficult to use connections as something that manages lifetimes of objects. I am looking for a way to force slots to be deleted directly when disconnected. Any ideas on how to work around the problem by designing my code differently are also appreciated! This is my scenario: I have a Command class responsible for doing something that takes time asynchronously, looking something like this (simplified): class ActualWorker { public: boost::signals2<void ()> OnWorkComplete; }; class Command : boost::enable_shared_from_this<Command> { public: ... void Execute() { m_WorkerConnection = m_MyWorker.OnWorkDone.connect(boost::bind(&Command::Handle_OnWorkComplete, shared_from_this()); // launch asynchronous work here and return } boost::signals2<void ()> OnComplete; private: void Handle_OnWorkComplete() { // get a shared_ptr to ourselves to make sure that we live through // this function but don't keep ourselves alive if an exception occurs. shared_ptr<Command> me = shared_from_this(); // Disconnect from the signal, ideally deleting the slot object m_WorkerConnection.disconnect(); OnComplete(); // the shared_ptr now goes out of scope, ideally deleting this } ActualWorker m_MyWorker; boost::signals2::connection m_WorkerConnection; }; The class is invoked about like this: ... boost::shared_ptr<Command> cmd(new Command); cmd->OnComplete.connect( foo ); cmd->Execute(); // now go do something else, forget all about the cmd variable etcetera. the Command class keeps itself alive by getting a shared_ptr to itself which is bound to the ActualWorker signal using boost::bind. When the worker completes, the handler in Command is invoked. Now, since I would like the Command object to be destroyed, I disconnect from the signal as can be seen in the code above. The problem is that the actual slot object is not deleted when disconnected, it is only marked as invalid and then deleted at a later time. This in turn appears to depend on the signal to fire again, which it doesn't do in my case, leading to the slot never expiring. The boost::bind object thus never goes out of scope, holding a shared_ptr to my object that will never get deleted. I can work around this by binding using the this pointer instead of a shared_ptr and then keeping my object alive using a member shared_ptr which I then release in the handler function, but it kind of makes the design feel a bit overcomplicated. Is there a way to force signals2 to delete the slot when disconnecting? Or is there something else I could do to simplify the design? Any comments are appreciated!

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  • making a password-only auth with bcrypt and mongoose

    - by user3081123
    I want to create service that let you login only with password. You type a password and if this password exists - you are logged in and if it's not - username is generated and password is encrypted. I'm having some misunderstandings and hope someone would help me to show where I'm mistaken. I guess, it would look somewhat like this in agularjs First we receive a password in login controller. $scope.signup = function() { var user = { password: $scope.password, }; $http.post('/auth/signup', user); }; Send it via http.post and get in in our node server file. We are provided with a compare password bcrypt function userSchema.methods.comparePassword = function(candidatePassword, cb) { bcrypt.compare(candidatePassword, this.password, function(err, isMatch) { if (err) return cb(err); cb(null, isMatch); }); }; So right now we are creating function to catch our http request app.post('/auth/signup', function(req, res, next) { Inside we use a compair password function to realize if such password exists or not yet. So we have to encrypt a password with bcrypt to make a comparison First we hash it same way as in .pre var encPass; bcrypt.genSalt(10, function(err, salt) { if (err) return next(err); bcrypt.hash(req.body.password, salt, function(err, hash) { if (err) return next(err); encPass=hash; )}; )}; We have encrypted password stored in encPass so now we follow to finding a user in database with this password User.findOne({ password: encPass }, function(err, user) { if (user) { //user exists, it means we should pass an ID of this user to a controller to display it in a view. I don't know how. res.send({user.name}) //like this? How should controller receive this? With $http.post? } else { and now if user doesn't exist - we should create it with user ID generated by my function var nUser = new User({ name: generId(), password: req.body.password }); nUser.save(function(err) { if (err) return next(err); )}; )}; )}; Am I doing anything right? I'm pretty new to js and angular. If so - how do I throw a username back at controller? If someone is interested - this service exists for 100+ symbol passphrases so possibility of entering same passphrase as someone else is miserable. And yeah, If someone logged in under 123 password - the other guy will log in as same user if he entered 123 password, but hey, you are warned to make a big passphrase. So I'm confident about the idea and I only need a help with understanding and realization.

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  • Passing variables, creating instances, self, The mechanics and usage of classes: need explenation

    - by Baf
    I've been sitting over this the whole day and Im a little tired already so please excuse me being brief. Im new to python. I just rewrrote a working program, into a bunch of functions in a class and everzthings messed up. I dont know if its me but Im very surprised i couldn t find a beginners tutorial on how to handle classes on the web so I have a few questions. First of all, in the init section of the class i have declared a bunch of variables with self.variable=something. Is it correct that i should be able to access/modify these variables in every function of the class by using self.variable in that function? In other words by declaring self.variable i have made these variables, global variables in the scope of the class right? If not how do i handle self. ? Secondly how do i correctly pass arguments to the class? some example code would be cool. thirdly how do i call a function of the class outside of the class scope? some example code would be cool. fouthly how do I create an Instance of the class INITIALCLASS in another class OTHERCLASS, passing variables from OTHERCLASS to INITIALCLASS? some example code would be cool. I Want to call a function from OTHERCLASS with arguments from INITIALCLASS. What Ive done so far is. class OTHERCLASS(): def __init__(self,variable1,variable2,variable3): self.variable1=variable1 self.variable2=variable2 self.variable3=variable3 def someotherfunction(self): something=somecode(using self.variable3) self.variable2.append(something) print self.variable2 def somemorefunctions(self): self.variable2.append(variable1) class INITIALCLASS(): def __init__(self): self.variable1=value1 self.variable2=[] self.variable3='' self.DoIt=OTHERCLASS(variable1,variable2,variable3) def somefunction(self): variable3=Somecode #tried this self.DoIt.someotherfunctions() #and this DoIt.someotherfunctions() I clearly havent understood how to pass variables to classes or how to handle self, when to use it and when not, I probably also havent understood how to properly create an isntance of a class. In general i havent udnerstood the mechanics of classes So please help me and explain it to me like i have no Idea( which i dont it seems). Or point me to a thorough video, or readable tutorial. All i find on the web is super simple examples, that didnt help me much. Or just very short definitions of classes and class methods instances etc. I can send you my original code if you guys want, but its quite long. Thanks for the Help Much appreciated!

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  • jpa-Google app engine

    - by megala
    I had created entity in google app engie datastore using JPA.I set the id as follows @Id @GeneratedValue(strategy=GenerationType.SEQUENCE) private Long s; After i deployed my applicaiton it give identity (i.e) unique value.but igive 1001,1002,1003 ....as id.But i wnat 1,2,3,4,5 like that.how to achive this? Thanks in advance

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  • Why does OpenID look so hard to implement?

    - by user198729
    I read through this post: http://stackoverflow.com/questions/741345/how-do-i-implement-direct-identity-based-openid-authentication-with-zend-openid Why does it look so complicated to implement? IMO, it's just to send request to a remote site and retrieve the response. What's the problem those OpenID libraries are dealing with?

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  • Passing around a SqlConnection

    - by Chris
    I have created a TransactionScope and within the scope various items are created and updated in the database. During this process I make a lot of calls to the database. Originally I opened a SqlConnection in the beginning of the TransactionScope and passed it around to any function that made a DB call then I closed the connection after all the calls are made and before the transaction commits. Is it better to do this or to open and close a connection for each call?

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  • Move an object in the direction of a bezier curve?

    - by Sent1nel
    I have an object with which I would like to make follow a bezier curve and am a little lost right now as to how to make it do that based on time rather than the points that make up the curve. .::Current System::. Each object in my scene graph is made from position, rotation and scale vectors. These vectors are used to form their corresponding matrices: scale, rotation and translation. Which are then multiplied in that order to form the local transform matrix. A world transform (Usually the identity matrix) is then multiplied against the local matrix transform. class CObject { public: // Local transform functions Matrix4f GetLocalTransform() const; void SetPosition(const Vector3f& pos); void SetRotation(const Vector3f& rot); void SetScale(const Vector3f& scale); // Local transform Matrix4f m_local; Vector3f m_localPostion; Vector3f m_localRotation; // rotation in degrees (xrot, yrot, zrot) Vector3f m_localScale; } Matrix4f CObject::GetLocalTransform() { Matrix4f out(Matrix4f::IDENTITY); Matrix4f scale(), rotation(), translation(); scale.SetScale(m_localScale); rotation.SetRotationDegrees(m_localRotation); translation.SetTranslation(m_localTranslation); out = scale * rotation * translation; } The big question I have are 1) How do I orientate my object to face the tangent of the Bezier curve? 2) How do I move that object along the curve without just setting objects position to that of a point on the bezier cuve? Heres an overview of the function thus far void CNodeControllerPieceWise::AnimateNode(CObject* pSpatial, double deltaTime) { // Get object latest pos. Vector3f posDelta = pSpatial->GetWorldTransform().GetTranslation(); // Get postion on curve Vector3f pos = curve.GetPosition(m_t); // Get tangent of curve Vector3f tangent = curve.GetFirstDerivative(m_t); } Edit: sorry its not very clear. I've been working on this for ages and its making my brain turn to mush. I want the object to be attached to the curve and face the direction of the curve. As for movement, I want to object to follow the curve based on the time this way it creates smooth movement throughout the curve.

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  • How do I go about link web content in a database with a nested set model?

    - by wb
    My nested set table is as follows. create table depts ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) , abbrv nvarchar(20) ); Test departments. insert into depts (lft, rgt, name, abbrv) values (1, 14, 'root', 'r'); insert into depts (lft, rgt, name, abbrv) values (2, 3, 'department 1', 'd1'); insert into depts (lft, rgt, name, abbrv) values (4, 5, 'department 2', 'd2'); insert into depts (lft, rgt, name, abbrv) values (6, 13, 'department 3', 'd3'); insert into depts (lft, rgt, name, abbrv) values (7, 8, 'sub department 3.1', 'd3.1'); insert into depts (lft, rgt, name, abbrv) values (9, 12, 'sub department 3.2', 'd3.2'); insert into depts (lft, rgt, name, abbrv) values (10, 11, 'sub sub department 3.2.1', 'd3.2.1'); My web content table is as follows. create table content ( id int identity(0, 1) , dept_id int , page_name nvarchar(60) , content ntext ); Test content. insert into content (dept_id, page_name, content) values (3, 'index', '<h2>welcome to department 3!</h2>'); insert into content (dept_id, page_name, content) values (4, 'index', '<h2>welcome to department 3.1!</h2>'); insert into content (dept_id, page_name, content) values (6, 'index', '<h2>welcome to department 3.2.1!</h2>'); insert into content (dept_id, page_name, content) values (2, 'what-doing', '<h2>what is department 2 doing?/h2>'); I'm trying to query the correct page content (from the content table) based on the url given. I can easily accomplish this task with a root department. However, querying a department with multiple depths is proving to be a little harder. For example: http://localhost/departments.asp?d3/ (Should return <h2>welcome to department 3!</h2>) http://localhost/departments.asp?d2/what-doing (Should return <h2>what is department 2 doing?</h2>) I'm not sure if this can be create in one query or if there will need to be a recursive function of some sort. Also, if there is nothing after the last / then assume we want the index page. How can this be accomplished? Thank you.

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