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  • c++ when to put method out side the class

    - by user63898
    i saw that some times in c++ applications using only namespace declarations with header and source file like this : #ifndef _UT_ #define _UT_ #include <string> #include <windows.h> namespace UT { void setRootPath(char* program_path, char* file_path); char * ConvertStringToCharP(std::string str); }; #endif //and then in UT.cpp #include "UT.h" namespace UT { char * ConvertStringToCharP(std::string str) { char * writable = new char[str.size() + 1]; std::copy(str.begin(), str.end(), writable); writable[str.size()] = '\0'; return writable; } void setRootPath(char* program_path, char* file_path) { //... } } is it better then defining classic class with static methods? or just simple class ? dose this method has something better for the compiler linker ? the methods in this namespace are called allot of times .

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  • floats in NSArray

    - by JordanC
    I have an NSArray of floats which I did by encapsulating the floats using [NSNumber numberWithFloat:myFloat] ; Then I passed that array somewhere else and I need to pull those floats out of the array and perform basic arithmatic. When I try [myArray objectAtIndex:i] ; The compiler complains that I'm trying to perform arithmatic on a type id. It also won't let me cast to float or double. Any ideas? This seems like it should be an easy problem. Maybe it will come to me after another cup of coffee, but some help would be appreciated. Thanks.

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  • C/C++: Scanning a TIFF file using LIBTIFF

    - by Matt07
    My problem is to scan a tiff image in C and get all the pixel value (let's say for saving them in a txt file) in C/C++. I scanned the web and i found a library named "TIFFLIB" that should do what i was looking for. I downloaded it using the ubuntu package manager, but the gcc doesn't recognize the library. How do i link the library to the compiler? Have I installed it correctly? Is there any better/easier way to do that?

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  • Why are types found on an imported namepace but not on a fully qualified namespace after retargeting the framework?

    - by Paul Ferguson
    We've just re-targeted a VB.NET project from .Net 2.0 to 3.5. Various framework types are now missing from our project. Wherever the type is referenced using a fully qualified namespace it's missing. If the relevant namespace is imported for the type; it's found. For example, this doesn't find the type Object, with compiler error "System.Object is not defined.": Public Class Foo Inherits System.Object End Class However, this works ok: Imports System Public Class Foo Inherits [Object] End Class I've already tried re-opening the solution with no success.

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  • Is it legal for a C++ reference to be NULL?

    - by BCS
    A while back I ran into a bug the looked something like this: void fn(int &i) { printf(&i == NULL ? "NULL\n" : "!NULL\n"); } int main() { int i; int *ip = NULL; fn(i); // prints !NULL fn(*ip); // prints NULL return 0; } More recently, I ran into this comment about C++ references: [References arguments make] it clear, unlike with pointers, that NULL is not a possible value. But, as show above, NULL is a possible value. So where is the error? In the language spec? (Unlikely.) Is the compiler in error for allowing that? Is that coding guide in error (or a little ambiguous)? Or am I just wandering into the minefield known as undefined behavior?

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  • XCode iPhone OS Deployment Target Tool

    - by Trah Divad
    Problem I'm currently stuck trying to figure out what "iPhone OS Deployment Target" setting to use. I do not want to write conditional code right now, so I'd like the lowest version that runs my application fine. At first I thought it would be 2.0 as I wasn't using any 3.0 features, but then i realized that AVAudioRecorder is a 3.0 API. I don't want to be manually checking EVERY function I use in the documentation. Question Is there a tool that will check the OS availability of each functions you call in your code to figure out what the Deployment Target should be? That tool could be a good old compiler, but the latest version of the iPhone SDK does not come with the PRE-3.0 SDKs.

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  • strenge exception phenomenon in win7

    - by Level 2
    Hello all, I spot some interesting artcles about exception handle in codeproject http://www.codeproject.com/KB/cpp/seexception.aspx after reading, I decided to do some experiment. The first time I try to excute the following code char *p; p[0] = 0; The program died without question. But After serveral time I execute the same problem binary code. It magically did fine. even the following code is doing well. any clue or explain? char *p p[1000] = 'd'; cout<<p[1000]<<endl; my os is windows 7 64bit and compiler is vs2008 rc1.

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  • How to generate a specific CPPDEFINE such as -DOEM="FOO BAR" using Scons

    - by Vineet
    My intention is to end up with a compiler command line including -DOEM="FOO BAR" I have the following in my SConstruct file: opts = Options( 'overrides.py', ARGUMENTS ) opts.Add( 'OEM_NAME', 'Any string can be used here', 'UNDEFINED' ) . . . if (env.Dictionary('OEM_NAME') != 'UNDEFINED'): OEM_DEFINE = 'OEM=' + str(env.Dictionary('OEM_NAME')) env.Append( CPPDEFINES=[ OEM_DEFINE ] ) Then I put the following in the "overrides.py" file: OEM_NAME = "FOO BAR" I seem to end up with "-DOEM=FOO BAR" in the command line that gets generated. Can someone point me in the right direction? Thanks.

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  • Strange exception phenomenon in Windows 7

    - by Level 2
    I spot some interesting articles about exception handle in CodeProject http://www.codeproject.com/KB/cpp/seexception.aspx After reading, I decided to do some experiment. The first time I try to execute the following code char *p; p[0] = 0; The program died without question. But After several times when I executed the same problem binary code, it magically did fine. Even the following code is doing well. Any clue or explanation? char *p p[1000] = 'd'; cout<<p[1000]<<endl; My O/S is Windows 7 64bit and compiler is VS2008 rc1.

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  • How to catch any exception (System.Exception) without a warning in F#?

    - by LLS
    I tried to catch an Exception but the compiler gives warning: This type test or downcast will always hold let testFail () = try printfn "Ready for failing..." failwith "Fails" with | :? System.ArgumentException -> () | :? System.Exception -> () The question is: how to I do it without the warning? (I believe there must be a way to do this, otherwise there should be no warning) Like C# try { Console.WriteLine("Ready for failing..."); throw new Exception("Fails"); } catch (Exception) { }

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  • Precision problems of real numbers in Fortran

    - by saladoil
    I've been trying to use Fortran for my research project, with the GNU Fortran compiler (gfortran), latest version, but I've been encountering some problems in the way it processes real numbers. If you have for example the code: program test implicit none real :: y = 23.234, z z = y * 100000 write(*,*) y, z end program You'll get as output: 23.23999 2323400.0. I find this really strange. Can someone tell me what's exactly happening here? Looking at z I can see that y does retain its precision, so for calculations that shouldn't be a problem I suppose. But why is the output of y not exactly the same as the value that I've specified, and what can I do to make it exactly the same?

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  • Java import from other directory

    - by heldopslippers
    Hi People! I am building a Enterprise Service Bus (ESB) with Java. I won't get into details But I have to build multiple servers who make use of the same classes. I have the following directory structure: /server1 -Main.java /server2 -Main.java /com -Database.java I want to import from the Main.java class for example the Database.class. But of course the following statements won't work: import com.Database; I am working with the javac compiler in the command line (so not eclipse stuff or whatever. just TextMate and the command line). And I found a (pretty stupid) solution by creating a symbolic link in the servers to the com directory. But that is not really an ideal solution. Does anybody have a better one?? THANXS in advanced!! :D

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  • Visual Studio 2010 Compiling C code

    - by Corsen2000
    I have the following code snippet. This is a c file in visual studio 2010. If i try to compile this with the line: int hello = 10; commented out it will compile just fine. If I comment that line in it will not compile. Am I missing something or should I not be using Visual Studio 2010 to compile C code. If this is a Visual Studio problem can anyone recommend a easy to use IDE / Compiler that I can for C. Thank You int* x = (int*) calloc(1, sizeof(int)); *x = 5; //int hello = 10; printf("Hello World! %i", *x); getchar();

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  • Static initialization of a struct with class members

    - by JS Bangs
    I have a struct that's defined with a large number of vanilla char* pointers, but also an object member. When I try to statically initialize such a struct, I get a compiler error. typedef struct { const char* pszA; // ... snip ... const char* pszZ; SomeObject obj; } example_struct; // I only want to assign the first few members, the rest should be default example_struct ex = { "a", "b" }; SomeObject has a public default constructor with no arguments, so I didn't think this would be a problem. But when I try to compile this (using VS), I get the following error: error C2248: 'SomeObject::SomeObject' : cannot access private member declared in class 'SomeObject' Any idea why?

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  • How do you keep Cocoa controllers from getting too big?

    - by zoul
    Hello! Do you have some tricks or techniques to break Cocoa controller classes into smaller chunks? I find that whatever I do the controllers end up being one of the more complicated classes in my design. The basic stuff is simple, but once I have several pop-overs or action sheets running, things get uncomfortably complex. It's not that bad, but still I would like to refactor the code into several standalone chunks. I thought about categories, but the code is not that independent (a lot of times it needs to tap into viewWillAppear, for example) and I find that I spend a long time fighting the compiler. I also thought about adding functionality in layers using inheritance, but that feels like a hack.

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  • Design pattern: Polymorphism for list of objects

    - by ziang
    Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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  • What is the Effect of Declaring 'extern "C"' in the Header to a C++ Shared Library?

    - by Adam
    Based on this question I understand the purpose of the construct in linking C libraries with C++ code. Now suppose the following: I have a '.so' shared library compiled with a C++ compiler. The header has a 'typedef stuct' and a number of function declarations. If the header includes the extern "C" declaration... #ifdef __cplusplus extern "C" { #endif // typedef struct ...; // function decls #ifdef __cplusplus } #endif ... what is the effect? Specifically I'm wondering if there are any detrimental side effects of that declaration since the shared library is compiled as C++, not C. Is there any reason to have the extern "C" declaration in this case?

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  • Eclipse RCP: How to troubleshoot plugin dependencies & classpath problems?

    - by paul
    I am working on an RCP project based on eclipse. It has been working fine but recently I thought I'd upgrade it to use a new eclipse version (3.2 - 3.5). After a bit of trouble, it seemed to be working fine. Then I did something. Don't know what. The end result is that I'm getting a classpath error when one of my plugins (A) tries to access a class in one of the dependent plugins (B) (also one of mine). As far as I can see, Plugin A has Plugin B in its' dependency list and the compiler shows no errors. To test, I created a new Plugin C with one class and accessed the class from Plugin A. That works fine. Does anyone have any hints for troubleshooting such issues? A checklist of settings to check? I've been stuggling with this for hours and getting nowhere! Particularly frustrating as it was working until I changed something! Thanks

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  • Clojure warn-on-reflection and type hints

    - by Ralph
    In the following code, I am getting a warning on reflection: (ns com.example (:import [org.apache.commons.cli CommandLine Option Options PosixParser])) (def *help-option* "help") (def *host-option* "db-host") (def *options* (doto (Options.) (.addOption "?" *help-option* false "Show this usage information") (.addOption "h" *host-option* true "Name of the database host"))) (let [^CommandLine command-line (.. (PosixParser.) (parse *options* (into-array String args))) db-host (.getOptionValue command-line "h")] ; WARNING HERE ON .getOptionValue ; Do stuff with db-host ) I have a type hint on command-line. Why the warning? I am using Clojure 1.2 on OS X 10.6.6 (Apple VM). I assume that I do not get a warning on (.addOption ...) because the compiler knows that (Options.) is a org.apache.commons.cli.Options).

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  • Are C++ Templates just Macros in disguise?

    - by Roddy
    I've been programming in C++ for a few years, and I've used STL quite a bit and have created my own template classes a few times to see how it's done. Now I'm trying to integrate templates deeper into my OO design, and a nagging thought keeps coming back to me: They're just a macros, really... You could implement (rather UGLY) auto_ptrs using #defines, if you really wanted to. This way of thinking about templates helps me understand how my code will actually work, but I feel that I must be missing the point somehow. Macros are meant evil incarnate, yet "template metaprogramming" is all the rage. So, what ARE the real distinctions? and how can templates avoid the dangers that #define leads you into, like Inscrutable compiler errors in places where you don't expect them? Code bloat? Difficulty in tracing code? Setting Debugger Breakpoints?

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  • Fast comparison of char arrays?

    - by StackedCrooked
    I'm currently working in a codebase where IPv4 addresses are represented as pointers to u_int8. The equality operator is implemented like this: bool Ipv4Address::operator==(const u_int8 * inAddress) const { return (*(u_int32*) this->myBytes == *(u_int32*) inAddress); } This is probably the fasted solution, but it causes the GCC compiler warning: ipv4address.cpp:65: warning: dereferencing type-punned pointer will break strict-aliasing rules How can I rewrite the comparison correctly without breaking strict-aliasing rules and without losing performance points? I have considered using either memcmp or this macro: #define IS_EQUAL(a, b) \ (a[0] == b[0] && a[1] == b[1] && a[2] == b[2] && a[3] == b[3]) I'm thinking that the macro is the fastest solution. What do you recommend?

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  • boost variant static_visitor problem picking correct function

    - by Steve
    I'm sure I'm having a problem with template resolution here, but I'm not sure why I'm having the problem. I have a static visitor I'm passing to boost variant where i've had to do template specialization for certain cases. The case for everything except for MyClass should throw in the static_visitor below. Unfortunately, when the visitor is applied to pull a MyClass out, it selects the most generic case rather than the exact match. I would type each case explicitly, but that will be rather long. So, why is the compiler resolving the most generic case over the exact match, and is there anyway to fix it template<> class CastVisitor<MyClass>:public boost::static_visitor<MyClass> { public: template<typename U> MyClass operator()(const U & i) const { throw std::exception("Unable to cast"); } MyClass operator()(const MyClass& i) { return i; } };

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  • Prevent Erroneous Property Assignment

    - by Gordon
    Porting android applications to iphone applications always gives me the following pattern that I accidentally create: - (void) myFunc:(id)prop { self.property = property; } Which instead should be: - (void) myFunc:(id)prop { self.property = prop; } This always causes my program to quietly break because property gets reset to its existing value rather than being set to the new value, 'prop'. I cannot name the parameter 'prop' to 'property' since the compile complains that the parameter masks the instance variables visibility. Is there a good way to avoid this situation? There are no compiler warnings. Is there a way to make xcode prevent this? I cannot see very many situations where you would set a property to the value of its underlying instance variable (maybe to trigger a KVO binding?), but I don't see myself doing that in majority of cases. I understand the above code is synthetic and should be done with @synthesize, but I am just using it as a simplified example to illustrate my point.

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  • Why Java cannot find my constructor?

    - by Roman
    Well, maybe it is a stupid question, but I cannot resolve this problem. In my ServiceBrowser class I have this line: ServiceResolver serviceResolver = new ServiceResolver(ifIndex, serviceName, regType, domain); And compiler complains about it. It says: cannot find symbol symbol : constructor ServiceResolver(int,java.lang.String,java.lang.String,java.lang.String) This is strange, because I do have a constructor in the ServiceResolver: public void ServiceResolver(int ifIndex, String serviceName, String regType, String domain) { this.ifIndex = ifIndex; this.serviceName = serviceName; this.regType = regType; this.domain = domain; } ADDED: I removed void from the constructor and it works! Why?

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  • Setting enum values to 4-byte strings - why?

    - by psychotik
    I saw code similar to this in the Mac OS SDK: enum { kAudioFileStreamProperty_ReadyToProducePackets = 'redy', kAudioFileStreamProperty_FileFormat = 'ffmt', kAudioFileStreamProperty_DataFormat = 'dfmt', kAudioFileStreamProperty_FormatList = 'flst', kAudioFileStreamProperty_MagicCookieData = 'mgic', kAudioFileStreamProperty_AudioDataByteCount = 'bcnt', kAudioFileStreamProperty_AudioDataPacketCount = 'pcnt', kAudioFileStreamProperty_MaximumPacketSize = 'psze', kAudioFileStreamProperty_DataOffset = 'doff', kAudioFileStreamProperty_ChannelLayout = 'cmap', kAudioFileStreamProperty_PacketToFrame = 'pkfr', kAudioFileStreamProperty_FrameToPacket = 'frpk', kAudioFileStreamProperty_PacketToByte = 'pkby', kAudioFileStreamProperty_ByteToPacket = 'bypk', kAudioFileStreamProperty_PacketTableInfo = 'pnfo', kAudioFileStreamProperty_PacketSizeUpperBound = 'pkub', kAudioFileStreamProperty_AverageBytesPerPacket = 'abpp', kAudioFileStreamProperty_BitRate = 'brat' }; It's the first time I've seen this - I assume the compiler assigns the 32-bit integer equivalent of the strings to the enum values. I cannot think of a single good reason why this might be preferred over using simple integers. It looks hideous in a debugger (how do you tell which of these values corresponds to 1919247481?) and makes debugging just hard in general. So, is there any reason where assigning such strings to enum values actually makes sense.

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