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  • deep or shallow copying?

    - by Dervin Thunk
    Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value (deep copy) in C. For instance, passing a char to a function is usually cheaper in space than passing a char* (if there's no need to share the value), since char is 1 byte and pointers are, well, whatever they are in the architecture (4 in my 32 bit machine). ?(When) do you want to pass (big) deep copies to functions? if so, why?

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  • How can I declare a pointer structure?

    - by Y_Y
    This probably is one of the easiest questions ever in C programming language... I have the following code: typedef struct node { int data; struct node * after; struct node * before; }node; struct node head = {10,&head,&head}; Is there a way I can make head to be *head [make it a pointer] and still have the availability to use '{ }' [{10,&head,&head}] to declare an instance of head?

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  • Not sure what happens to my apps objects when using NSURLSession in background - what state is my app in?

    - by Avner Barr
    More of a general question - I don't understand the workings of NSURLSession when using it in "background session mode". I will supply some simple contrived example code. I have a database which holds objects - such that portions of this data can be uploaded to a remote server. It is important to know which data/objects were uploaded in order to accurately display information to the user. It is also important to be able to upload to the server in a background task because the app can be killed at any point. for instance a simple profile picture object: @interface ProfilePicture : NSObject @property int userId; @property UIImage *profilePicture; @property BOOL successfullyUploaded; // we want to know if the image was uploaded to out server - this could also be a property that is queryable but lets assume this is attached to this object @end Now Lets say I want to upload the profile picture to a remote server - I could do something like: @implementation ProfilePictureUploader -(void)uploadProfilePicture:(ProfilePicture *)profilePicture completion:(void(^)(BOOL successInUploading))completion { NSUrlSession *uploadImageSession = ..... // code to setup uploading the image - and calling the completion handler; [uploadImageSession resume]; } @end Now somewhere else in my code I want to upload the profile picture - and if it was successful update the UI and the database that this action happened: ProfilePicture *aNewProfilePicture = ...; aNewProfilePicture.profilePicture = aImage; aNewProfilePicture.userId = 123; aNewProfilePicture.successfullyUploaded = NO; // write the change to disk [MyDatabase write:aNewProfilePicture]; // upload the image to the server ProfilePictureUploader *uploader = [ProfilePictureUploader ....]; [uploader uploadProfilePicture:aNewProfilePicture completion:^(BOOL successInUploading) { if (successInUploading) { // persist the change to my db. aNewProfilePicture.successfullyUploaded = YES; [Mydase update:aNewProfilePicture]; // persist the change } }]; Now obviously if my app is running then this "ProfilePicture" object is successfully uploaded and all is well - the database object has its own internal workings with data structures/caches and what not. All callbacks that may exist are maintained and the app state is straightforward. But I'm not clear what happens if the app "dies" at some point during the upload. It seems that any callbacks/notifications are dead. According to the API documentation- the uploading is handled by a separate process. Therefor the upload will continue and my app will be awakened at some point in the future to handle completion. But the object "aNewProfilePicture" is non existant at that point and all callbacks/objects are gone. I don't understand what context exists at this point. How am I supposed to ensure consistency in my DB and UI (For instance update the "successfullyUploaded" property for that user)? Do I need to re-work everything touching the DB or UI to correspond with the new API and work in a context free environment?

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  • Error when deploying app to the device in iphone

    - by Rafael
    Hi, I'm developing an app with SDK 3.1.2 and it runs in the simulator, but when I try to deploy it in the device it arise de following error: 2010-06-17 17:40:39.592 MyApp[2143:207] *** -[__NSCFDate dateInformation]: unrecognized selector sent to instance 0x21e6a0 2010-06-17 17:40:39.608 MyApp[2143:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSCFDate dateInformation]: Why this doesn't happen for the simulator? Thanks in advanced for your help.

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  • Make OS open directory in Python

    - by Vidar
    I am writing a program in Python, and want to get it to make the OS open the current working directory, making for instance Windows open explorer.exe and navigating to the wanted directory. Any ideas on how to do this? The directory is already given by os.getcwd. Cross platform methods preferred :)

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  • Assigning IDs to instances of a class (Pythonic)

    - by mellort
    I want to have each instance of some class have a unique integer identifier based on the order that I create them, starting with (say) 0. In Java, I could do this with a static class variable. I know I can emulate the same sort of behavior with Python, but what would be the most 'Pythonic' way to do this? Thanks

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  • Are comonads a good fit for modeling the Wumpus world?

    - by Tim Stewart
    I'm trying to find some practical applications of a comonad and I thought I'd try to see if I could represent the classical Wumpus world as a comonad. I'd like to use this code to allow the Wumpus to move left and right through the world and clean up dirty tiles and avoid pits. It seems that the only comonad function that's useful is extract (to get the current tile) and that moving around and cleaning tiles would not use be able to make use of extend or duplicate. I'm not sure comonads are a good fit but I've seen a talk (Dominic Orchard: A Notation for Comonads) where comonads were used to model a cursor in a two-dimensional matrix. If a comonad is a good way of representing the Wumpus world, could you please show where my code is wrong? If it's wrong, could you please suggest a simple application of comonads? module Wumpus where -- Incomplete model of a world inhabited by a Wumpus who likes a nice -- tidy world but does not like falling in pits. import Control.Comonad -- The Wumpus world is made up of tiles that can be in one of three -- states. data Tile = Clean | Dirty | Pit deriving (Show, Eq) -- The Wumpus world is a one dimensional array partitioned into three -- values: the tiles to the left of the Wumpus, the tile occupied by -- the Wumpus, and the tiles to the right of the Wumpus. data World a = World [a] a [a] deriving (Show, Eq) -- Applies a function to every tile in the world instance Functor World where fmap f (World as b cs) = World (fmap f as) (f b) (fmap f cs) -- The Wumpus world is a Comonad instance Comonad World where -- get the part of the world the Wumpus currently occupies extract (World _ b _) = b -- not sure what this means in the Wumpus world. This type checks -- but does not make sense to me. extend f w@(World as b cs) = World (map world as) (f w) (map world cs) where world v = f (World [] v []) -- returns a world in which the Wumpus has either 1) moved one tile to -- the left or 2) stayed in the same place if the Wumpus could not move -- to the left. moveLeft :: World a -> World a moveLeft w@(World [] _ _) = w moveLeft (World as b cs) = World (init as) (last as) (b:cs) -- returns a world in which the Wumpus has either 1) moved one tile to -- the right or 2) stayed in the same place if the Wumpus could not move -- to the right. moveRight :: World a -> World a moveRight w@(World _ _ []) = w moveRight (World as b cs) = World (as ++ [b]) (head cs) (tail cs) initWorld = World [Dirty, Clean, Dirty] Dirty [Clean, Dirty, Pit] -- cleans the current tile cleanTile :: Tile -> Tile cleanTile Dirty = Clean cleanTile t = t Thanks!

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  • Workflow State not changing in asp.net

    - by shail
    hi i m trying to change the state for workflow from one state to another on button click its working fine with windows but not with web application and its instance id does not persist i have used SqlWorkflowPersistenceService also. what can b the solution for this. thanks

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  • Can any language potentially be used to create any program?

    - by Matt
    I've heard that given a programmer with enough time and skill in any particular language and enough lines of code, then any program could be created with any given language. I know its certainly not going to be cost-efficient, for instance, to rewrite Adobe Photoshop in BASIC, but could a good enough and patient enough programmer potentially create any program in any language?

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  • Explicitly accessing banked registers on ARM

    - by Demiurg
    According to the ARM manual, it should be possible to access the banked registers for a specific CPU mode as, for instance, "r13_svc". When I try to do this gcc yells at me with the following error: immediate expression requires a # prefix -- `mov r2,sp_svc' What's wrong?

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  • c# reflection: How can I invoke a method with an out parameter ?

    - by ldp615
    I want expose WebClient.DownloadDataInternal method like below: [ComVisible(true)] public class MyWebClient : WebClient { private MethodInfo _DownloadDataInternal; public MyWebClient() { _DownloadDataInternal = typeof(WebClient).GetMethod("DownloadDataInternal", BindingFlags.NonPublic | BindingFlags.Instance); } public byte[] DownloadDataInternal(Uri address, out WebRequest request) { _DownloadDataInternal.Invoke(this, new object[] { address, out request }); } } WebClient.DownloadDataInternal has a out parameter, I don't know how to invoke it. Help!

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  • pattern to transfer search model to dao

    - by zeroed
    We have a dao as a project (jar file). Clients use its interfaces and factories to operate with database. Using standard CRUD operations, dao allows you to search an entity by some search criteria. What is the best way to represent this criteria? Is transfer object appropriate pattern in this situation? How should client create SearchModel instance? Please, share. Regards.

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  • What is sender?

    - by marty
    I can't find this answer anywhere. What does it mean when there's a sender parameter in a method header? Does it represent the instance that called it, or the method that called it?

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  • Floating point numbers in XML

    - by Jamie
    what is the best way to handle floating point numbers in XML? If I have, for instance: double a = 123.456; and I would like to keep it as <A> 123.456 </A> simply using ... myDoc.createTextNode(a.ToString()); is fine? Or should it be done with some Globalization stuff to make it region-independent?

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  • Is it possible to do DNS-based ACLs on a Cisco ASA?

    - by pickles
    Short of using static IP addresses, is it possible to have a Cisco ASA use a DNS name rather than an IP address? For instance, if I want to limit a host in the DMZ to access only one particular web service, but that web service might be globally load balanced or using DynDNS or cloud, how can the ACL be expressed so that a fixed IP address isn't used and the admin doesn't have to keep opening and closing down IP addresses?

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  • rotate image with php - any degree

    - by Luis
    How to rotate an image with PHP, any degree, without having the filled space? For instance, if I rotate an image 10 degrees, the image rotates fine but the container around (square) gets filled with black. Is it possible to get rid of this, when for example merging 2 images?

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  • Does UIScrollView have a special content view for making the scrolling possible?

    - by mystify
    I wonder if UIScrollView has got an "hidden" subview acting as an container for the content. If I scroll a scroll view, is that content view moved up/down in the scroll view? Or is the scrolling offset applied to the bounds of that UIScrollView instance? Or: Does UIScrollView use an additional view as container, or is all content added directly to the view? The documentation doesn't tell much about wether it has a content container or not.

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  • How to create a database binding using Windows Builder Pro?

    - by Tiago
    For the first time, I'm creating a Java Swing application. I'm using Windows Builder Pro in Eclipse, and a MySQL database (already setup up). Let's say I have a combo box, and I want (for instance) all 'name' fields from a 'certain' table appear. How can I setup that binding? I know how to programatically handle the connection and query code, what I would like to know is how to make that binding in Eclipse.

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  • Javascript: Static member variable containing object instances

    - by tom
    I have the following: function Preferences() { } Preferences.players = { 'player1': new Player() } players is a static member variable of Preferences and I'm trying to make it an object containing an instance of a Player. However, it doesn't appear to let me do this. It seems like it will allow me to define players if I make it a non-static member variable however. Like so: function Preferences() { var players = { 'player1' : new Player() } } Is it possible to create a static member variable containing instances of an object in JS?

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  • Add a datatable to a data set

    - by Jibu P C_Adoor
    Hii... I have a data table 'dt1' that is belongs to 'ds1'. I have created another instance of dataset 'ds2' and try to add the datatable 'dt1' to 'ds2'. Now i got one exception 'DataTable already belongs to another data set'. Is there any reliable way to add the dt1 to ds2?

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