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  • Operators vs Functions in C/C++

    - by user356106
    Someone recently asked me the difference between a C++ standard operator (e.g. new,delete,sizeof) and function (e.g. tan,delete, malloc). By "standard" I mean those provided by default by the compiler suite, and not user defined. Below were the answers I gave, though neither seemed satisfactory. (1) An operator doesn't need any headers to be included to use it : E.g. you can have a call to new without including any headers. However, a function (say free() ) does need headers included, compulsorily. (2) An operator is defined as such (ie as a class operator) somewhere in the standard headers. A function isn't. Can you critique these answers and give me a better idea of the difference?

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  • Operator as and generic classes

    - by abatishchev
    I'm writing .NET On-the-Fly compiler for CLR scripting and want execution method make generic acceptable: object Execute() { return type.InvokeMember(..); } T Execute<T>() { return Execute() as T; /* doesn't work: The type parameter 'T' cannot be used with the 'as' operator because it does not have a class type constraint nor a 'class' constraint */ // also neither typeof(T) not T.GetType(), so on are possible return (T) Execute(); // ok } But I think operator as will be very useful: if result type isn't T method will return null, instead of an exception! Is it possible to do?

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  • Why do I have to give an identifier?

    - by Knowing me knowing you
    In code: try { System.out.print(fromClient.readLine()); } catch(IOException )//LINE 1 { System.err.println("Error while trying to read from Client"); } In code line marked as LINE 1 compiler forces me to give an identifier even though I'm not using it. Why this unnatural constrain? And then if I type an identifier I'm getting warning that identifier isn't used. It just doesn't make sense to me, forcing a programmer to do something unnecesarry and surplus. And after me someone will revise this code and will be wondering if I didn't use this variable on purpouse or I just forgot. So in order to avoid that I have to write additional comment explaining why I do not use variable which is unnecessary in my code. Thanks

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  • How to know record has been updated successfully in php

    - by Lisa Ray
    $sql = "UPDATE...."; if(mysql_query($sql)) { $_SESSION['Trans']="COMMIT"; header("location:result.php"); exit; } else { $_SESSION['Trans']="FAIL"; $_SESSION['errors'] = "Error: Sorry! We are unable to update your Profile, Please contact to PNP HelpDesk."; header("location:result.php"); exit; }//end IF data is getting updated then why compiler is not coming inside IF condition.

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  • Can I add a custom method to Core Data-generated classes?

    - by Andy
    I've got a couple of Core Data-generated class files that I'd like to add custom methods to. I don't need to add any instance variables. How can I do this? I tried adding a category of methods: // ContactMethods.h (my category on Core Data-generated "Contact" class) #import "Contact.h" @interface Contact (ContactMethods) -(NSString*)displayName; @end ... // ContactMethods.m #import "ContactMethods.h" @implementation Contact (ContactMethods) -(NSString*)displayName { return @"Some Name"; // this is test code } @end This doesn't work, though. I get a compiler message that "-NSManagedObject may not respond to 'displayName' " and sure enough, when I run the app, I don't get "Some Name" where I should be seeing it.

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  • How do I replace "this" in Java with something that works.

    - by Luke Alderton
    I'm looking to get the showGUI() method work, the compiler says "this" is not a static variable and cannot be referenced from a static context, what would I use to replace "this"? I've tried test.main (test being the package it's in). The reason I'm using the static method showGUI() is because I need the method to be called from another static method, as well as the startup() method. Below are my two main classes. public class Main extends SingleFrameApplication { @Override protected void startup() { showGUI(); } @Override protected void configureWindow(java.awt.Window root) { } public static Main getApplication() { return Application.getInstance(Main.class); } public static void main(String[] args) { launch(Main.class, args); } public static void showGUI() { show(new GUI(this)); } } public class GUI extends FrameView { public GUI(SingleFrameApplication app) { super(app); initComponents(); } private void initComponents() { //all the GUI stuff is somehow defined here } }

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  • Cast vector<T> to vector<const T>

    - by user345386
    I have a member variable of type vector (where is T is a custom class, but it could be int as well.) I have a function from which I want to return a pointer to this vector, but I don't want the caller to be able to change the vector or it's items. So I want the return type to be const vector* None of the casting methods I tried worked. The compiler keeps complaining that T is not compatible with const T. Here's some code that demonstrates the gist of what I'm trying to do; vector<int> a; const vector<const int>* b = (const vector<const int>* ) (&a); This code doesn't compile for me. Thanks in advance!

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  • How do you specify a 64 bit unsigned int const 0x8000000000000000 in VS2008?

    - by Mark Franjione
    I read about the Microsoft specific suffix "i64" for integer constants. I want to do an UNsigned shift to a ULONGLONG. ULONGLONG bigNum64 = 0x800000000000000i64 >> myval; In normal C, I would use the suffix "U", e.g. the similar 32 bit operation would be ULONG bigNum32 = 0x80000000U >> myval; I do NOT want the 2's complement sign extension to propogate through the high bits. I want an UNSIGNED shift on a 64 bit const number. I think my first statement is going to do a SIGNED shift right. I tried 0x800000000000000i64U and 0x800000000000000u64 but got compiler errors.

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  • Pass an event into a constructor

    - by Vaccano
    I have a class that I want to be able the handle the mouse up event for a grid. I tried to create it with a static method call like this: MyDataBinding.BindObjectsToDataGrid(ListOfObjectsToBind, myGrid.MouseUp); The end goal being that in the method I would assign a delegate to the MouseUp PassedInMouseUp += myMethodThatWillHandleTheMouseUp; Looks good here (to me) but the compiler chokes on the first line. It says that I can only use MouseUp with a += or a -=. Clearly I am going about this the wrong way. How can I get a different class to handle the mouse up with out having to: Pass in the whole grid Expose the method that will be handling the mouse up as a public method. Or, is this just a limitation and I will have to do one of the above?

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  • Whats the difference between a C++ and a Cocoa Project in Xcode?

    - by david
    I need to work with TagLib for my project. I've created a framework (and I tried using it as a lib) but the compiler cannot find #include < strings on compiling (No such file or Directory). I've created a test C++ project and it #includes < strings just fine. I've looked at the project settings and I cannot find a difference between them. But the standard cocoa projects obviously so not have the search path set to include C++ libraries (Or am I completely getting it wrong?). I've searched for a solution but no one else seems to have run into this problem.

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  • Hudson's FindBugs plugin reports line number "-1" for bugs. Ideas?

    - by John B.
    Greetings, I have a simple test project set up in Hudson and the project's build process (a batch file) generates a findbugs.xml file. This is processed by Hudson's FindBugs plugin but it shows the line number of the bugs as "-1" instead of their actual line number. A coworker suggested I enable debug info for the compiler. I used the -g "Generate all debugging info" option for javac but nothing seemed to change. My build command is: javac -g -classpath C:\testWebApp1\src -d C:\testWebApp1\build C:\testWebApp1\src\*.java The only other thing in the build.bat file is a call to the FindBug tool (text UI). Here is what the FindBugs Plugin says about the first bug: File: GenerateHellos.java, Line: -1, Type: UUF_UNUSED_FIELD, Priority: Normal, Category: PERFORMANCE Any ideas? Thanks a ton!

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  • F# function calling syntax confusion

    - by Daniel
    I have a piece of code: links |> Seq.map (fun x -> x.GetAttributeValue ("href", "no url")) Which I wanted to rewrite to: links |> Seq.map (fun x -> (x.GetAttributeValue "href" "no url")) But the F# compiler doesn't seem to like that. I was under the impression that these two function calls were interchangeable: f (a, b) (f a b) The error that I get is: The member or object constructor 'GetAttributeValue' taking 2 arguments are not accessible from this code location. All accessible versions of method 'GetAttributeValue' take 2 arguments. Which seems amusing, as it seems to indicate that it needs what I'm giving it. What am I missing here?

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  • Mysterious c debugging problem when trying to utilize printfs

    - by O_O
    Ok, folks. I've never encountered this before and it boggles the mind and is illogical. I have a somewhat complex loop and I want to try and see if everything is working by putting some printf statements. I look the intermediate products using printf and verify that the answer is ok. Then, when I comment out the printf to the intermediate products, the answer is WRONG. Has anyone ever encountered this? This is driving me insane and I don't see how the printfs could change an answer.... X_x If it helps, I am using a c/c++ compiler for a DSP. Thanks for any advice.. Here is a snippet... printf("splitBackground = %d, numWindowPoints = %d\n", splitBackground, numWindowPoints); splitBackground = splitBackground/numWindowPoints; printf("%d ", splitBackground); This is good but when I comment out the first line of code, it turns out to be hugely incorrect. :(

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  • How to explain to a developer that adding extra if - else if conditions is not a good way to "improv

    - by Lilit
    Recently I've bumped into the following C++ code: if (a) { f(); } else if (b) { f(); } else if (c) { f(); } Where a, b and c are all different conditions, and they are not very short. I tried to change the code to: if (a || b || c) { f(); } But the author opposed saying that my change will decrease readability of the code. I had two arguments: 1) You should not increase readability by replacing one branching statement with three (though I really doubt that it's possible to make code more readable by using else if instead of ||). 2) It's not the fastest code, and no compiler will optimize this. But my arguments did not convince him. What would you tell a programmer writing such a code? Do you think complex condition is an excuse for using else if instead of OR?

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  • How to check if TypeIdenitifier(T) is an Object?

    - by John
    I'm creating a generic list class that has a member of type Array(Array of ). The problem is the class descruction,because the class is supposed to be used for types from byte to types inheriting TObject. Specifically: destructor Destroy; var elem:T; begin /*if(T is Tobject) then //Check if T inherits TObject {Compiler error!} for elem in FData do TObject(elem).Free;*/ // do not know how to do it SetLength(FItems,0); //FItems : Array of T inherited Destroy; end; How do I check if T is TObject so I can free every member if the typeidenitifier is a class,for example?

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  • Best environment to port C/C++ code from Linux to Windows.

    - by Simone Margaritelli
    I'd like to make a big project of mine buildable on Windows platforms. The project itself it's written in C/C++ following POSIX standards, with some library dependencies such as libxml2, libcurl and so on. I'm more a Linux developer rather than a Windows developer, so i have no idea of which compiler suite i should use to port the code. Which one offers more compatibility with gcc 4.4.3 i'm using right now? My project needs flex and bison, is there any "ready to use" environment to port such projects to windows platforms? Thanks.

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  • How to reference/link another project in grails workspace without using jar files?

    - by Ivan Alagenchev
    I have a Grails website that references a java core application. I have been successful in adding a .jar dependency to that project; however the java project is in the same workspace as my grails project and I would ultimately like to reference that project directly. I don't want to deal with the added step of creating a new jar file every time that there is a modification to the java project, cleaning and updating my dependencies. I added the java project to my grails' project "Java Build Path" and at first everything seemed to work fine, but when I run grailscompile, the compiler fails to resolve all imports that point to the java project. I am using Spring Source Toolsuite as my IDE.

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  • Class basic operators

    - by swan
    Hi, Is it necessary to have a copy constructor, destructor and operator= in a class that have only static data member, no pointer class myClass{ int dm; public: myClass(){ dm = 1; } ~myClass(){ } // Is this line usefull ? myClass(const myClass& myObj){ // and that operator? this->dm = myObj.dm; } myClass& operator=(const myClass& myObj){ // and that one? if(this != &myObj){ this->dm = myObj.dm; } return *this; } }; I read that the compiler build one for us, so it is better to not have one (when we add a data member we have to update the operators)

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  • iOS sdk question: how do I cast a UIView to a UIImage View (alternativly how do I get a UIImageView from a GestureRecognzer?)

    - by user439299
    Desired end result: user taps a UIImageView and the image changes to another image (a subsequent tap returns the image to the original state) Problem: I add a (unique) selector to a bunch of UIImageViews (in an array) and point the action at the same function - let's call this function imageTapped: for now. Here is my code so far: -(void)imageTapped:(UITapGestureRecognizer *)tapGesture { UIImageView *view = tapGesture.view; // rest of code... } This code actually works fine but gets a warning when I run it: "Incompatible objective c types initilizing 'struct UIView *', expected 'struct UIImageView *' Any way to get rid of this? Not sure how casting works in objective c... primitive types seem to work fine such as (int)someFloat works fine but (UIImageView)someUiView doesn't work. Like I said, code works alright when I run it but would like to get ride of the compiler warning. Any help would be awesome.... I am very new to objective c (or any non java language for that matter) so be gentle. Thanks in advance.

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  • Normal C++ code in Qt doesnt build and run

    - by Nick
    Hello. I am using Qt under linux, if it matters. I ran successfully under Geany (a simple c++ compiler) the following: //my first program in C++ Hello World! include using namespace std; int main () {cout << "Hello World!"; return 0;} I opened Qt source file and copied the exact same code and i can't build or run. Thank you for your responses to this simple problem.

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  • Android application displays black screen after running

    - by frgnvola
    When I click "Run as an Android Application" on Eclipse, the following is displayed in the console [2014-06-05 20:07:18 - StudentConnect] Android Launch! [2014-06-05 20:07:18 - StudentConnect] adb is running normally. [2014-06-05 20:07:18 - StudentConnect] Performing sandhu.student.connect.SplashActivity activity launch [2014-06-05 20:07:18 - StudentConnect] Using default Build Tools revision 19.0.0 [2014-06-05 20:07:18 - StudentConnect] Refreshing resource folders. [2014-06-05 20:07:18 - StudentConnect] Using default Build Tools revision 19.0.0 [2014-06-05 20:07:18 - StudentConnect] Starting incremental Pre Compiler: Checking resource changes. [2014-06-05 20:07:18 - StudentConnect] Nothing to pre compile! [2014-06-05 20:07:18 - StudentConnect] Starting incremental Package build: Checking resource changes. [2014-06-05 20:07:18 - StudentConnect] Using default Build Tools revision 19.0.0 [2014-06-05 20:07:18 - StudentConnect] Skipping over Post Compiler. [2014-06-05 20:07:20 - StudentConnect] Application already deployed. No need to reinstall. [2014-06-05 20:07:20 - StudentConnect] Starting activity sandhu.student.connect.SplashActivity on device 0f0898b2 [2014-06-05 20:07:21 - StudentConnect] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=sandhu.student.connect/.SplashActivity } [2014-06-05 20:07:21 - StudentConnect] ActivityManager: Warning: Activity not started, its current task has been brought to the front After deployed to my phone, it only displays a black screen. I recently implemented a splash screen, but it was working fine before; however I think it might have something to do with the problem. Here are my java and xml files: MainActivity.java package sandhu.student.connect; import android.app.Activity; import android.os.Bundle; import android.view.KeyEvent; import android.view.View; import android.webkit.WebSettings; import android.webkit.WebView; import android.webkit.WebViewClient; public class MainActivity extends Activity { public WebView student_zangle; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); WebView student_zangle = (WebView) findViewById(R.id.student_zangle); student_zangle.loadUrl("https://zangleweb01.clovisusd.k12.ca.us/studentconnect/"); student_zangle.setWebViewClient(new WebViewClient()); student_zangle.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY); WebSettings settings = student_zangle.getSettings(); settings.setJavaScriptEnabled(true); settings.setBuiltInZoomControls(true); settings.setLoadWithOverviewMode(true); settings.setUseWideViewPort(true); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { WebView student_zangle = (WebView) findViewById(R.id.student_zangle); if ((keyCode == KeyEvent.KEYCODE_BACK) && student_zangle.canGoBack()) { student_zangle.goBack(); return true; } else { finish(); } return super.onKeyDown(keyCode, event); } } activity_main.xml <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/blue" tools:context=".MainActivity" > <WebView android:id="@+id/student_zangle" android:layout_width="match_parent" android:layout_height="match_parent" /> </RelativeLayout> SplashActivity.java package sandhu.student.connect; import android.os.Bundle; import android.preference.PreferenceActivity; public class SplashActivity extends PreferenceActivity { @SuppressWarnings("deprecation") @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); addPreferencesFromResource(R.xml.prefs); } } splash_activity.xml <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/blue" android:orientation="vertical" > <ImageView android:id="@+id/imageView1" android:layout_width="250dp" android:layout_height="100dp" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" android:layout_marginTop="145dp" android:contentDescription="@string/zangle_logo" android:src="@drawable/logo" /> </RelativeLayout> Also, here is a full copy of the logcat error output: 06-05 20:19:46.698: E/Watchdog(817): !@Sync 1952 06-05 20:20:09.971: E/memtrack(16438): Couldn't load memtrack module (No such file or directory) 06-05 20:20:09.971: E/android.os.Debug(16438): failed to load memtrack module: -2 06-05 20:20:11.012: E/memtrack(16451): Couldn't load memtrack module (No such file or directory) 06-05 20:20:11.012: E/android.os.Debug(16451): failed to load memtrack module: -2 06-05 20:20:11.202: E/EnterpriseContainerManager(817): ContainerPolicy Service is not yet ready!!! Please help me figure out what is wrong, or at least point me in the right direction. Thanks in advance.

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  • TextAppearance_Holo_Large - No resource found

    - by npmaster
    When compiling my app I get the following error: android-apt-compiler: ... \res\values-v14\styles.xml:12: error: Error retrieving parent for item: No resource found that matches the given name '@android:style/TextAppearance_Holo_Large. The code it is complaining about is: <style name="Title" parent="@android:style/TextAppearance_Holo_Large"> <item name="android:layout_height">wrap_content</item> <item name="android:layout_width">wrap_content</item> </style> I checked my manifest file and I have set the SDK to: <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="17" /> Which i believe allows for using the Holo Themes. I am using Android Studio though I doubt that is the cause of the error. Any ideas what I am doing wrong?

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  • how to use replace_regex_copy() from boost::algorithm library?

    - by Vincenzo
    This is my code: #include <string> #include <boost/algorithm/string/regex.hpp> string f(const string& s) { using namespace boost::algorithm; return replace_regex_copy(s, "\\w", "?"); } This is what compiler says: no matching function for call to ‘replace_regex_copy(const std::basic_string<char, std::char_traits<char>, std::allocator<char> >&, std::string, std::string) The link to the library: http://www.boost.org/doc/libs/1_43_0/doc/html/boost/algorithm/replace_regex_copy.html Could anyone please help? Thanks! ps. Boost library is in place, since other functions from it work fine.

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  • Calling C++ function from C.

    - by claws
    I know this. Calling C function from C++: If my application was in C++ and I had to call functions from a library written in C. Then I would have used //main.cpp extern "C" void C_library_function(int x, int y);//prototype C_library_function(2,4);// directly using it. This wouldn't mangle the name C_library_function and linker would find the same name in its input *.lib files and problem is solved. Calling C++ function from C??? But here I'm extending a large application which is written in C and I need to use a library which is written in C++. Name mangling of C++ is causing trouble here. Well I cannot use C++ compiler over my C project because thats breaking lot of other stuff. What is the way out? By the way I'm using MSVC

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  • can a program written in C be faster than one written in OCaml and translated to C?

    - by Ole Jak
    So I have some cool Image Processing algorithm. I have written it in OCaml. It performs well. I now I can compile it as C code with such command ocamlc -output-obj -o foo.c foo.ml (I have a situation where I am not alowed to use OCaml compiler to bild my programm for my arcetecture, I can use only specialy modified gcc. so I will compile that programm with sometyhing like gcc -L/usr/lib/ocaml foo.c -lcamlrun -lm -lncurses and Itll run on my archetecture.) I want to know in general case can a program written in C be faster than one written in OCaml and translated to C?

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