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  • Understanding Ruby Enumerable#map (with more complex blocks)

    - by mstksg
    Let's say I have a function def odd_or_even n if n%2 == 0 return :even else return :odd end end And I had a simple enumerable array simple = [1,2,3,4,5] And I ran it through map, with my function, using a do-end block: simple.map do |n| odd_or_even(n) end # => [:odd,:even,:odd,:even,:odd] How could I do this without, say, defining the function in the first place? For example, # does not work simple.map do |n| if n%2 == 0 return :even else return :odd end end # Desired result: # => [:odd,:even,:odd,:even,:odd] is not valid ruby, and the compiler gets mad at me for even thinking about it. But how would I implement an equivalent sort of thing, that works?

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  • What should I do if a IOException is thrown?

    - by Roman
    I have the following 3 lines of the code: ServerSocket listeningSocket = new ServerSocket(earPort); Socket serverSideSocket = listeningSocket.accept(); BufferedReader in = new BufferedReader(new InputStreamReader(serverSideSocket.getInputStream())); The compiler complains about all of these 3 lines and its complain is the same for all 3 lines: unreported exception java.io.IOException; In more details, these exception are thrown by new ServerSocket, accept() and getInputStream(). I know I need to use try ... catch .... But for that I need to know what this exceptions mean in every particular case (how should I interpret them). When they happen? I mean, not in general, but in these 3 particular cases.

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  • Boost::Container::Vector with Enum Template Argument - Not Legal Base Class

    - by CuppM
    Hi, I'm using Visual Studio 2008 with the Boost v1.42.0 library. If I use an enum as the template argument, I get a compile error when adding a value using push_back(). The compiler error is: 'T': is not a legal base class and the location of the error is move.hpp line 79. #include <boost/interprocess/containers/vector.hpp> class Test { public: enum Types { Unknown = 0, First = 1, Second = 2, Third = 3 }; typedef boost::container::vector<Types> TypesVector; }; int main() { Test::TypesVector o; o.push_back(Test::First); return 0; } If I use a std::vector instead it works. And if I resize the Boost version first and then set the values using the [] operator it also works. Is there some way to make this work using push_back()?

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  • Why C++ virtual function defined in header may not be compiled and linked in vtable?

    - by 0xDEAD BEEF
    Situation is following. I have shared library, which contains class definition - QueueClass : IClassInterface { virtual void LOL() { do some magic} } My shared library initialize class member QueueClass *globalMember = new QueueClass(); My share library export C function which returns pointer to globalMember - void * getGlobalMember(void) { return globalMember;} My application uses globalMember like this ((IClassInterface*)getGlobalMember())->LOL(); Now the very uber stuff - if i do not reference LOL from shared library, then LOL is not linked in and calling it from application raises exception. Reason - VTABLE contains nul in place of pointer to LOL() function. When i move LOL() definition from .h file to .cpp, suddenly it appears in VTABLE and everything works just great. What explains this behavior?! (gcc compiler + ARM architecture_)

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  • bridge methods explaination

    - by xdevel2000
    If I do an override of a clone method the compiler create a bridge method to guarantee a correct polymorphism: class Point { Point() { } protected Point clone() throws CloneNotSupportedException { return this; // not good only for example!!! } protected volatile Object clone() throws CloneNotSupportedException { return clone(); } } so when is invoked the clone method the bridge method is invoked and inside it is invoked the correct clone method. But my question is when into the bridge method is called return clone() how do the VM to say that it must invoke Point clone() and not itself again???

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  • About enumerations in Delphi and c++ in 64-bit environments

    - by sum1stolemyname
    I recently had to work around the different default sizes used for enumerations in Delphi and c++ since i have to use a c++ dll from a delphi application. On function call returns an array of structs (or records in delphi), the first element of which is an enum. To make this work, I use packed records (or aligned(1)-structs). However, since delphi selects the size of an enum-variable dynamically by default and uses the smallest datatype possible (it was a byte in my case), but C++ uses an int for enums, my data was not interpreted correctly. Delphi offers a compiler switch to work around this, so the declaration of the enum becomes {$Z4} TTypeofLight = ( V3d_AMBIENT, V3d_DIRECTIONAL, V3d_POSITIONAL, V3d_SPOT ); {$Z1} My Questions are: What will become of my structs when they are compiled on/for a 64-bit environment? Does the default c++ integer grow to 8 Bytes? Are there other memory alignment / data type size modifications (other than pointers)?

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  • How does compilation work with AOP?

    - by alee
    I need quick answer to a simple thing in AOP. If i have a code deployed at client side and i have written new aspects, which i want in the client side software. do i have to "recompile" complete software with "original" code and new "AOP" code? (with aop compiler)? i.e. do i need the source code of original program with source code of new AOP and compile 'em boht? P.S: I am asking in general, not being specific to any language.

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  • EHsc vc EHa (synchronous vs asynchronous exception handling)

    - by watson1180
    Could you give a bullet list of practical differences/implication? I read relevant MSDN article, but my understanding asynchronous exceptions is still a bit hazy. I am writing a test suite using Boost.Test and my compiler emits a warning that EHa should be enabled: warning C4535: calling _set_se_translator() requires /EHa The project itself uses only plain exceptions (from STL) and doesn't need /EHa switch. Do I have to recompile it with /EHa switch to make the test suite work properly? My feeling is that I need /EHa for the test suit only. Thank you and happy new year.

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  • Opening Large (24 GB) File In C

    - by zacaj
    I'm trying to read in a 24 GB XML file in C, but it won't work. I'm printing out the current position using ftell() as I read it in, but once it gets to a big enough number, it goes back to a small number and starts over, never even getting 20% through the file. I assume this is a problem with the range of the variable that's used to store the position (long), which can go up to about 4,000,000,000 according to http://msdn.microsoft.com/en-us/library/s3f49ktz%28VS.80%29.aspx, while my file is 25,000,000,000 bytes in size. A long long should work, but how would I change what my compiler(Cygwin/mingw32) uses or get it to have fopen64?

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  • problems with overloaded function members C++

    - by Dr Deo
    I have declared a class as class DCFrameListener : public FrameListener, public OIS::MouseListener, public OIS::KeyListener { bool keyPressed(const OIS::KeyEvent & kEvt); bool keyReleased(const OIS::KeyEvent &kEvt); //*******some code missing************************ }; But if i try defining the members like this bool DCFrameListener::keyPressed(const OIS::KeyEvent kEvt) { return true; } The compiler refuses with this error error C2511: 'bool DCFrameListener::keyPressed(const OIS::KeyEvent)' : overloaded member function not found in 'DCFrameListener' see declaration of 'DCFrameListener' Why is this happening, yet i declared the member keyPressed(const OIS::KeyEvent) in my function declaration. any help will be appreciated. Thanks

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  • 2-byte (UCS-2) wide strings under GCC

    - by Seva Alekseyev
    Hi all, when porting my Visual C++ project to GCC, I found out that the wchar_t datatype is 4-byte UTF-32 by default. I could override that with a compiler option, but then the whole wcs* (wcslen, wcscmp, etc.) part of RTL is rendered unusable, since it assumes 4-byte wide strings. For now, I've reimplemented 5-6 of these functions from scratch and #defined my implementations in. But is there a more elegant option - say, a build of GCC RTL with 2-byte wchar-t quietly sitting somewhere, waiting to be linked? The specific flavors of GCC I'm after are Xcode on Mac OS X, Cygwin, and the one that comes with Debian Linux Etch.

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  • how to create a new variant in bjam

    - by steve jaffe
    I've tried reading the documentation but it is rather impenetrable so I'm hoping someone may have a simple answer. I want to define a new 'variant', based on 'debug', which just adds some macro definitions to the compiler command line, eg "-DSOMEMACRO". I think I may be able to do this as a "sub-variant" of debug, or else just define a new variant copying 'debug', but I'm not even sure where to do this. It looks like feature.jam in $BOOST_BUILD_DIR/build may be the place. Perhaps what I really want is simply a new 'feature' but it's still not clear to me exactly what I need to do and where, and I don't know if a 'feature' allows me to direct the build products to a different directory to the 'debug' build. Any suggestions will be appreciated. (In case you're wondering, I have to use bjam since it has been adopted as our corporate standard.)

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  • Problem with array of elements of a structure type

    - by kobac
    I'm writing an app in Visual Studio C++ and I have problem with assigning values to the elements of the array, which is array of elements of structure type. Compiler is reporting syntax error for the assigning part of the code. Is it possible in anyway to assign elements of array which are of structure type? typedef struct { CString x; double y; } Point; Point p[3]; p[0] = {"first", 10.0}; p[1] = {"second", 20.0}; p[2] = {"third", 30.0};

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  • Why calling ISet<dynamic>.Contains() compiles, but throws an exception at runtime?

    - by Andrey Breslav
    Please, help me to explain the following behavior: dynamic d = 1; ISet<dynamic> s = new HashSet<dynamic>(); s.Contains(d); The code compiles with no errors/warnings, but at the last line I get the following exception: Unhandled Exception: Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 'System.Collections.Generic.ISet<object>' does not contain a definition for 'Contains' at CallSite.Target(Closure , CallSite , ISet`1 , Object ) at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1) at FormulaToSimulation.Program.Main(String[] args) in As far as I can tell, this is related to dynamic overload resolution, but the strange things are (1) If the type of s is HashSet<dynamic>, no exception occurs. (2) If I use a non-generic interface with a method accepting a dynamic argument, no exception occurs. Thus, it looks like this problem is related particularly with generic interfaces, but I could not find out what exactly causes the problem. Is it a bug in the compiler/typesystem, or legitimate behavior?

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  • Are there any C++ tools that detect misuse of static_cast, dynamic_cast, and reinterpret_cast?

    - by chrisp451
    The answers to the following question describe the recommended usage of static_cast, dynamic_cast, and reinterpret_cast in C++: http://stackoverflow.com/questions/332030/when-should-static-cast-dynamic-cast-and-reinterpret-cast-be-used Do you know of any tools that can be used to detect misuse of these kinds of cast? Would a static analysis tool like PC-Lint or Coverity Static Analysis do this? The particular case that prompted this question was the inappropriate use of static_cast to downcast a pointer, which the compiler does not warn about. I'd like to detect this case using a tool, and not assume that developers will never make this mistake.

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  • VB.Net List.Find. Pass values to predicate

    - by Beta033
    Having a bit of trouble using the List.Find with a custom predicate i have a function that does this private function test () Dim test As Integer = keys.Find(AddressOf FindByOldKeyAndName).NewKey here's the function for the predicate Private Shared Function FindByOldKeyAndName(ByVal k As KeyObj) As Boolean If k.OldKey = currentKey.OldKey And k.KeyName = currentKey.KeyName Then Return True Else Return False End If End Function by doing it this way means i have to have a shared "currentKey" object in the class, and i know there has to be a way to pass in the values i'm interested in of CurrentKey (namely, keyname, and oldkey) ideally i'd like to call it by something like keys.Find(AddressOf FindByOldKeyAndName(Name,OldVal)) however when i do this i get compiler errors. How do i call this method and pass in the values?

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  • c99 goto past initialization

    - by R Samuel Klatchko
    While debugging a crash, I came across this issue in some code: int func() { char *p1 = malloc(...); if (p1 == NULL) goto err_exit; char *p2 = malloc(...); if (p2 == NULL) goto err_exit; ... err_exit: free(p2); free(p1); return -1; } The problem occurs when the first malloc fails. Because we jump across the initialization of p2, it contains random data and the call to free(p2) can crash. I would expect/hope that this would be treated the same way as in C++ where the compiler does not allow a goto to jump across an initialization. My question: is jumping across an initialization allowed by the standard or is this a bug in gcc's implementation of c99?

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  • Looking for marg_setValue fix in iPhoneOS

    - by John Smith
    I am trying to compile a library originally written for Cocoa. Things are good until it looks for the function marg_setValue(). It says there is a syntax error before char in marg_setValue(argumentList,argumentOffset,char,(char)lua_toboolean(state,luaArgument)); (it's talking about the third argument, not (char) ) I am trying to port LuaObjectiveCBridge to the iPhone. It has two choices, either using Runtime or Foundation. I have discovered there are some problems with foundation so I am trying runtime. But the compiler is not co-operating.

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  • Returning NSNull from actionForLayer:forKey

    - by MrHen
    If I implement the CALayer delegate method actionForLayer:forKey I can return [NSNull null] to force the CALayer to not animate any changes. Unfortunately, [NSNull null] doesn't implement the CAAction delegate and XCode kicks out the following warning: warning: class 'NSNull' does not implement the 'CAAction' protocol Here is the method code: - (id<CAAction>)actionForLayer:(CALayer *)theLayer forKey:(NSString *)theKey { //This disables the animations when moving things around //Also, don't animate the selection box. It was doing weird things if(undoGroupStarted || theLayer == self.selectionBox) { return [NSNull null]; } else { return nil; } } Am I doing something wrong? Is returning [NSNull null] bad behavior? If so, what is another way to do what I am trying to do here? If not, how do I make the compiler happy?

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  • C++ overloading virtual = operator

    - by taz
    Hello, here is the code for my question: class ICommon { public: virtual ICommon& operator=(const ICommon & p)const=0; }; class CSpecial : public ICommon { public: CSpecial& operator=(const CSpecial & cs) { //custom operations return *this; } }; CSpecial obj; Basically: I want the interface ICommon to force it's descendants to implement = operator but don't want to have any typecasts in the implementation. The compiler says "can't instantiate an abstract class. Any help/advice will be appreciated.

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  • Why can't I access a const vector with iterator?

    - by tsubasa
    My example is as below. I found out the problem is with "const" in function void test's parameter. I don't know why the compiler does not allow. Could anybody tell me? Thanks. vector<int> p; void test(const vector<int> &blah) { vector<int>::iterator it; for (it=blah.begin(); it!=blah.end(); it++) { cout<<*it<<" "; } } int main() { p.push_back(1); p.push_back(2); p.push_back(3); test(p); return 0; }

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  • Do you put a super() call a the beginning of your constructors?

    - by sleske
    This is a question about coding style and recommended practices: As explained in the answers to the question unnecessary to put super() in constructor?, if you write a constructor for a class that is supposed to use the default (no-arg) constructor from the superclass, you may call super() at the beginning of your constructor: public MyClass(int parm){ super(); // leaving this out makes no difference // do stuff... } but you can also omit the call; the compiler will in both cases act as if the super() call were there. So then, do you put the call into your constructors or not? On the one hand, one might argue that including the super() makes things more explicit. OTOH, I always dislike writing redundant code, so personally I tend to leave it out; I do however regularly see it in code from others. What are your experiences? Did you have problems with one or the other approach? Do you have coding guidelines which prescribe one approach?

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  • What is the proper way to declare a specialization of a template for another template type?

    - by Head Geek
    The usual definition for a specialization of a template function is something like this: class Foo { [...] }; namespace std { template<> void swap(Foo& left, Foo& right) { [...] } } // namespace std But how do you properly define the specialization when the type it's specialized on is itself a template? Here's what I've got: template <size_t Bits> class fixed { [...] }; namespace std { template<size_t Bits> void swap(fixed<Bits>& left, fixed<Bits>& right) { [...] } } // namespace std Is this the right way to declare swap? It's supposed to be a specialization of the template function std::swap, but I can't tell whether the compiler is seeing it as such, or whether it thinks that it's an overload of it or something.

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  • File IO, Handling CRLF

    - by aCuria
    Hi, i am writing a program that takes a file and splits it up into multiple small files of a user specified size, then join the multiple small files back again. 1) the code must work for c, c++ 2) i am compiling with multiple compilers. I am reading and writing to the files by using the stl functions fread() and fwrite() The problem I am having pertains to CRLF. If the file I am reading from contains CRLF, then I want to retain it when i split and join the files back together. If the file contains LF, then i want to retain LF. Unfortunately, fread() seems to store CRLF as \n (I think), and whatever is written by fwrite() is compiler-dependent. How do i approach this problem? Thanks.

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  • StructureMap - Injecting a dependency into a base class?

    - by David
    In my domain I have a handful of "processor" classes which hold the bulk of the business logic. Using StructureMap with default conventions, I inject repositories into those classes for their various IO (databases, file system, etc.). For example: public interface IHelloWorldProcessor { string HelloWorld(); } public class HelloWorldProcessor : IHelloWorldProcessor { private IDBRepository _dbRepository; public HelloWorldProcessor(IDBRepository dbRepository) { _dbRepository = dbrepository; } public string HelloWorld(){ return _dbRepository.GetHelloWorld(); } } Now, there are some repositories that I'd like to be available to all processors, so I made a base class like this: public class BaseProcessor { protected ICommonRepository _commonRepository; public BaseProcessor(ICommonRepository commonRepository) { _commonRepository = commonRepository; } } But when my other processors inherit from it, I get a compiler error on each one saying that there's no constructor for BaseProcessor which takes zero arguments. Is there a way to do what I'm trying to do here? That is, to have common dependencies injected into a base class that my other classes can use without having to write the injections into each one?

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