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  • Why size_t arguments in template declaration need to be const?

    - by ArunSaha
    I can have std::bitset< 10 > bitsetA; or const size_t LengthB = 20; std::bitset< LengthB > bitsetB; without any problem. But, if the length is not const size_t LengthC = 30; std::bitset< LengthC > bitsetC; // Line 30, say I face the following compilation error 'LengthC' cannot appear in a constant-expression template argument 1 is invalid What is the reason for that? What would be the problem, for compiler and for user code, if line 30 was to be accepted? Is it because LengthC might have some alias?

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  • overriding ctype<wchar_t>

    - by Potatoswatter
    I'm writing a lambda calculus interpreter for fun and practice. I got iostreams to properly tokenize identifiers by adding a ctype facet which defines punctuation as whitespace: struct token_ctype : ctype<char> { mask t[ table_size ]; token_ctype() : ctype<char>( t ) { for ( size_t tx = 0; tx < table_size; ++ tx ) { t[tx] = isalnum( tx )? alnum : space; } } }; (classic_table() would probably be cleaner but that doesn't work on OS X!) And then swap the facet in when I hit an identifier: locale token_loc( in.getloc(), new token_ctype ); … locale const &oldloc = in.imbue( token_loc ); in.unget() >> token; in.imbue( oldloc ); There seems to be surprisingly little lambda calculus code on the Web. Most of what I've found so far is full of unicode ? characters. So I thought to try adding Unicode support. But ctype<wchar_t> works completely differently from ctype<char>. There is no master table; there are four methods do_is x2, do_scan_is, and do_scan_not. So I did this: struct token_ctype : ctype< wchar_t > { typedef ctype<wchar_t> base; bool do_is( mask m, char_type c ) const { return base::do_is(m,c) || (m&space) && ( base::do_is(punct,c) || c == L'?' ); } const char_type* do_is (const char_type* lo, const char_type* hi, mask* vec) const { base::do_is(lo,hi,vec); for ( mask *vp = vec; lo != hi; ++ vp, ++ lo ) { if ( *vp & punct || *lo == L'?' ) *vp |= space; } return hi; } const char_type *do_scan_is (mask m, const char_type* lo, const char_type* hi) const { if ( m & space ) m |= punct; hi = do_scan_is(m,lo,hi); if ( m & space ) hi = find( lo, hi, L'?' ); return hi; } const char_type *do_scan_not (mask m, const char_type* lo, const char_type* hi) const { if ( m & space ) { m |= punct; while ( * ( lo = base::do_scan_not(m,lo,hi) ) == L'?' && lo != hi ) ++ lo; return lo; } return base::do_scan_not(m,lo,hi); } }; (Apologies for the flat formatting; the preview converted the tabs differently.) The code is WAY less elegant. I does better express the notion that only punctuation is additional whitespace, but that would've been fine in the original had I had classic_table. Is there a simpler way to do this? Do I really need all those overloads? (Testing showed do_scan_not is extraneous here, but I'm thinking more broadly.) Am I abusing facets in the first place? Is the above even correct? Would it be better style to implement less logic?

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  • pointer being freed was not allocated. Complex malloc history help

    - by Martin KS
    I've followed the guides helpfully linked here: http://stackoverflow.com/questions/295778/iphone-debugging-pointer-being-freed-was-not-allocated-errors but the malloc_history is really throwing me for a loop, can anyone shed any light on the following: ALLOC 0x185c600-0x18605ff [size=16384]: thread_a068a4e0 |start | main | UIApplicationMain | -[UIApplication _run] | CFRunLoopRunInMode | CFRunLoopRunSpecific | PurpleEventCallback | _UIApplicationHandleEvent | -[UIApplication sendEvent:] | -[UIApplication handleEvent:withNewEvent:] | -[UIApplication _reportAppLaunchFinished] | CA::Transaction::commit() | CA::Context::commit_transaction(CA::Transaction*) | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CA::Context::commit_layer(_CALayer*, unsigned int, unsigned int, void*) | CA::Render::encode_set_object(CA::Render::Encoder*, unsigned long, unsigned int, CA::Render::Object*, unsigned int) | CA::Render::Layer::encode(CA::Render::Encoder*) const | CA::Render::Image::encode(CA::Render::Encoder*) const | CA::Render::Encoder::encode_data_async(void const*, unsigned long, void (*)(void const*, void*), void*) | CA::Render::Encoder::encode_bytes(void const*, unsigned long) | CA::Render::Encoder::grow(unsigned long) | realloc | malloc_zone_realloc ---- FREE 0x185c600-0x18605ff [size=16384]: thread_a068a4e0 |start | main | UIApplicationMain | -[UIApplication _run] | CFRunLoopRunInMode | CFRunLoopRunSpecific | PurpleEventCallback | _UIApplicationHandleEvent | -[UIApplication sendEvent:] | -[UIApplication handleEvent:withNewEvent:] | -[UIApplication _reportAppLaunchFinished] | CA::Transaction::commit() | CA::Context::commit_transaction(CA::Transaction*) | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CALayerCommitIfNeeded | CA::Context::commit_layer(_CALayer*, unsigned int, unsigned int, void*) | CA::Render::encode_set_object(CA::Render::Encoder*, unsigned long, unsigned int, CA::Render::Object*, unsigned int) | CA::Render::Layer::encode(CA::Render::Encoder*) const | CA::Render::Image::encode(CA::Render::Encoder*) const | CA::Render::Encoder::encode_data_async(void const*, unsigned long, void (*)(void const*, void*), void*) | CA::Render::Encoder::encode_bytes(void const*, unsigned long) | CA::Render::Encoder::grow(unsigned long) | realloc | malloc_zone_realloc ALLOC 0x185e000-0x185e62f [size=1584]: thread_a068a4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[UITableView _userSelectRowAtIndexPath:] | -[UITableView _selectRowAtIndexPath:animated:scrollPosition:notifyDelegate:] | -[PLAlbumView tableView:didSelectRowAtIndexPath:] | -[PLUIAlbumViewController albumView:selectedPhoto:] | PLNotifyImagePickerOfImageAvailability | -[UIImagePickerController _imagePickerDidCompleteWithInfo:] | -[GalleryViewController imagePickerController:didFinishPickingMediaWithInfo:] | UIImageJPEGRepresentation | CGImageDestinationFinalize | _CGImagePluginWriteJPEG | writeOne | _cg_jpeg_start_compress | _cg_jinit_compress_master | _cg_jinit_c_prep_controller | alloc_sarray | alloc_large | malloc | malloc_zone_malloc ---- FREE 0x185e000-0x185e62f [size=1584]: thread_a068a4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[UITableView _userSelectRowAtIndexPath:] | -[UITableView _selectRowAtIndexPath:animated:scrollPosition:notifyDelegate:] | -[PL AlbumView tableView:didSelectRowAtIndexPath:] | -[PLUIAlbumViewController albumView:selectedPhoto:] | PLNotifyImagePickerOfImageAvailability | -[UIImagePickerController _imagePickerDidCompleteWithInfo:] | -[GalleryViewController imagePickerController:didFinishPickingMediaWithInfo:] | UIImageJPEGRepresentation | CGImageDestinationFinalize | _CGImagePluginWriteJPEG | writeOne | _cg_jpeg_abort | free_pool | free ALLOC 0x185c800-0x185ea1f [size=8736]: thread_a068a4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[UITableView _userSelectRowAtIndexPath:] | -[UITableView _selectRowAtIndexPath:animated:scrollPosition:notifyDelegate:] | -[PLAlbumView tableView:didSelectRowAtIndexPath:] | -[PLUIAlbumViewController albumView:selectedPhoto:] | PLNotifyImagePickerOfImageAvailability | -[UIImagePickerController _imagePickerDidCompleteWithInfo:] | -[GalleryViewController imagePickerController:didFinishPickingMediaWithInfo:] | -[UIImage initWithData:] | _UIImageRefFromData | CGImageSourceCreateImageAtIndex | makeImagePlus | _CGImagePluginInitJPEG | initImageJPEG | calloc | malloc_zone_calloc

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  • C# wrapper and Callbacks

    - by fergs
    I'm in the process of writing a C# wrapper for Dallmeier Common API light (Camera & Surviellance systems) and I've never written a wrapper before, but I have used the Canon EDSDK C# wrapper. So I'm using the Canon wrapper as a guide to writing the Dallmeier wrapper. I'm currently having issues with wrapping a callback. In the API manual it has the following: dlm_connect int(unsigned long uLWindowHandle, const char * strIP, const char* strUser1, const char* strPwd1, const char* strUser2, const char* strPwd2, void (*callback)(void *pParameters, void *pResult, void *pInput), void * pInput) Arguments - ulWindowhandle - handle of the window that is passed to the ViewerSDK to display video and messages there - strUser1/2 - names of the users to log in. If only single user login is used strUser2 is - NULL - strPwd1/2 - passwords of both users. If strUser2 is NULL strPwd2 is ignored. Return This function creates a SessionHandle that has to be passed Callback pParameters will be structured: - unsigned long ulFunctionID - unsigned long ulSocketHandle, //handle to socket of the established connection - unsigned long ulWindowHandle, - int SessionHandle, //session handle of the session created - const char * strIP, - const char* strUser1, - const char* strPwd1, - const char* strUser2, - const char * strPWD2 pResult is a pointer to an integer, representing the result of the operation. Zero on success. Negative values are error codes. So from what I've read on the Net and Stack Overflow - C# uses delegates for the purpose of callbacks. So I create a my Callback function : public delegate uint DallmeierCallback(DallPparameters pParameters, IntPtr pResult, IntPtr pInput); I create the connection function [DllImport("davidapidis.dll")] public extern static int dlm_connect(ulong ulWindowHandle, string strIP, string strUser1, string strPwd1, string strUser2, string strPwd2, DallmeierCallback inDallmeierFunc And (I think) the DallPParameters as a struct : [StructLayout(LayoutKind.Sequential)] public struct DallPParameters { public ulong ulfunctionID; public ulong ulsocketHandle; public ulong ulWindowHandle; ... } All of this is in my wrapper class. Am I heading in the right direction or is this completely wrong?

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  • Instruments (Leaks) and NSDateFormatter

    - by Cal
    When I run my iPhone app with Instruments Leaks and parse a bunch of NSDates using NSDateFormatter my memory goes up about 1mb and stays even though these NSDates should be dealloc'd after the parsing (I just discard them if they aren't new). I thought the malloc (in my heaviest stack trace below) could become part of the NSDate but I also thought it could be memory that only used during some intermediate step in parsing. Does anyone know which one it is or how to find out? Also, is there a way to put a breakpoint on NSDate dealloc to see if that memory is really being reclaimed? Here's what my date formatter looks like for parsing these dates: df = [[NSDateFormatter alloc] init]; [df setDateFormat:@"EEE, d MMM yyyy H:m:s z"]; Here's the Heaviest Stack trace when the memory bumps up and stays there: 0 libSystem.B.dylib 208.80 Kb malloc 1 libicucore.A.dylib 868.19 Kb icu::ZoneMeta::getSingleCountry(icu::UnicodeString const&, icu::UnicodeString&) 2 libicucore.A.dylib 868.66 Kb icu::ZoneMeta::getSingleCountry(icu::UnicodeString const&, icu::UnicodeString&) 3 libicucore.A.dylib 868.67 Kb icu::ZoneMeta::getSingleCountry(icu::UnicodeString const&, icu::UnicodeString&) 4 libicucore.A.dylib 868.67 Kb icu::DateFormatSymbols::initZoneStringFormat() 5 libicucore.A.dylib 868.67 Kb icu::DateFormatSymbols::getZoneStringFormat() const 6 libicucore.A.dylib 868.67 Kb icu::SimpleDateFormat::subParse(icu::UnicodeString const&, int&, unsigned short, int, signed char, signed char, signed char*, icu::Calendar&) const 7 libicucore.A.dylib 868.67 Kb icu::SimpleDateFormat::parse(icu::UnicodeString const&, icu::Calendar&, icu::ParsePosition&) const 8 libicucore.A.dylib 868.67 Kb icu::DateFormat::parse(icu::UnicodeString const&, icu::ParsePosition&) const 9 libicucore.A.dylib 868.67 Kb udat_parse 10 CoreFoundation 868.67 Kb CFDateFormatterGetAbsoluteTimeFromString 11 CoreFoundation 868.67 Kb CFDateFormatterCreateDateFromString 12 Foundation 868.67 Kb -[NSDateFormatter getObjectValue:forString:range:error:] 13 Foundation 868.75 Kb -[NSDateFormatter getObjectValue:forString:errorDescription:] 14 Foundation 868.75 Kb -[NSDateFormatter dateFromString:] Thanks!

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  • Please Help Me with my Homework Problem in C++

    - by sil3nt
    Hey there, this is part of a question i got in class, im at the final stretch but this has become a major problem. In it im given a certain value which is called the "gold value" and it is 40.5, this value changes in input. and i have these constants const int RUBIES_PER_DIAMOND = 5; // relative values. * const int EMERALDS_PER_RUBY = 2; const int GOLDS_PER_EMERALDS = 5; const int SILVERS_PER_GOLD = 4; const int COPPERS_PER_SILVER = 5; const int DIAMOND_VALUE = 50; // gold values. * const int RUBY_VALUE = 10; const int EMERALD_VALUE = 5; const float SILVER_VALUE = 0.25; const float COPPER_VALUE = 0.05; which means that basically for every diamond there are 5 rubies, and for every ruby there are 2 emeralds. So on and so forth. and the "gold value" for every diamond for example is 50 (diamond value = 50) this is how much one diamond is worth in golds. my problem is converting 40.5 into these diamonds and ruby values. I know the answer is 4rubies and 2silvers but how do i write the algorithm for this so that it gives the best estimate for every goldvalue that comes along??

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  • Memory leak in Qt signal and slots

    - by Ajay
    Hello, I am running valgrind on my Qt code,and even on successful exit of the application, get the following report from valgrind 8,832 bytes in 92 blocks are still reachable in loss record 12 of 12 at 0x4025390: operator new(unsigned int) (vg_replace_malloc.c:214) ==3339== by 0x4B75F05: QMutex::QMutex(QMutex::RecursionMode) (qmutex.cpp:123) ==3339== by 0x4B77602: QMutexPool::get(void const*) (qmutexpool.cpp:137) ==3339== by 0x4CA0EC2: signalSlotLock(QObject const*) (qobject.cpp:112) ==3339== by 0x4CA3939: QMetaObjectPrivate::connect(QObject const*, int, QObject const*, int, int, int*) (qobject.cpp:2900) ==3339== by 0x4CA5C00: QObject::connect(QObject const*, char const*, QObject const*, char const*, Qt::ConnectionType) (qobject.cpp:2599) I disconnect all signal connections and also delete the objects. The above mentioned leak increases if i increase the amount of signal and slot connections? Can anybody help with this?

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  • Compiler error when overwriting virtual methods

    - by Stefan Hubert
    Using VC71 compiler and get compiler errors, that i don't understand. Here comes the example class A { public: virtual int& myMethod() = 0; virtual const int& myMethod()const = 0; }; class B: public A { public: // generates: error C3241: 'const int &B::myMethod(void)' : this method was not introduced by 'A' virtual const int& A::myMethod() const; virtual int& A::myMethod(); }; when i switch order of both method definitions in B then I see a different compiler error: class B: public A { public: virtual const int& A::myMethod() const; // error C2556: 'const int &B::myMethod(void)' : overloaded function differs only by return type from 'int &B::myMethod(void)' // error C2373: 'B::myMethod' : redefinition; different type modifiers virtual int& A::myMethod(); }; however, if I omit the A:: stuff then i don't get any compiler error: class B: public A { public: virtual int& myMethod(); virtual const int& myMethod() const; }; So, what exactly does A:: in front of my method names and why do i see these diverse compiler errors? Any explanation welcome!

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  • Template with constant expression: error C2975 with VC++2008

    - by Arman
    Hello, I am trying to use elements of meta programming, but hit the wall with the first trial. I would like to have a comparator structure which can be used as following: intersect_by<ID>(L1.data, L2.data, "By ID: "); intersect_by<IDf>(L1.data, L2.data, "By IDf: "); Where: struct ID{};// Tag used for original IDs struct IDf{};// Tag used for the file position //following Boost.MultiIndex examples template<typename Tag,typename MultiIndexContainer> void intersect_by( const MultiIndexContainer& L1,const MultiIndexContainer& L2,std::string msg, Tag* =0 /* fixes a MSVC++ 6.0 bug with implicit template function parms / ) { / obtain a reference to the index tagged by Tag */ const typename boost::multi_index::index<MultiIndexContainer,Tag>::type& L1_ID_index= get<Tag>(L1); const typename boost::multi_index::index<MultiIndexContainer,Tag>::type& L2_ID_index= get<Tag>(L2); std::set_intersection( L1_ID_index.begin(), L1_ID_index.end(), L2_ID_index.begin(), L2_ID_index.end(), std::inserter(s, s.begin()), strComparator() // Here I get the C2975 error ); } template<int N> struct strComparator; template<> struct strComparator<0>{ bool operator () (const particleID& id1, const particleID& id2) const { return id1.ID struct strComparator<1{ bool operator () (const particleID& id1, const particleID& id2) const { return id1.IDf }; What I am missing? kind regards Arman.

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  • operator overloading of stream extraction operator in C++ help

    - by Crystal
    I'm having some trouble overloading my stream extraction operator in C++ for a hw assignment. I'm not really sure why I am getting these compile errors since I thought I was doing it right... Here is my code: Complex.h #ifndef COMPLEX_H #define COMPLEX_H class Complex { //friend ostream &operator<<(ostream &output, const Complex &complexObj) const; public: Complex(double = 0.0, double = 0.0); // constructor Complex operator+(const Complex &) const; // addition Complex operator-(const Complex &) const; // subtraction void print() const; // output private: double real; // real part double imaginary; // imaginary part }; #endif Complex.cpp #include <iostream> #include "Complex.h" using namespace std; // Constructor Complex::Complex(double realPart, double imaginaryPart) : real(realPart), imaginary(imaginaryPart) { } // addition operator Complex Complex::operator+(const Complex &operand2) const { return Complex(real + operand2.real, imaginary + operand2.imaginary); } // subtraction operator Complex Complex::operator-(const Complex &operand2) const { return Complex(real - operand2.real, imaginary - operand2.imaginary); } // Overload << operator ostream &Complex::operator<<(ostream &output, const Complex &complexObj) const { cout << '(' << complexObj.real << ", " << complexObj.imaginary << ')'; return output; // returning output allows chaining } // display a Complex object in the form: (a, b) void Complex::print() const { cout << '(' << real << ", " << imaginary << ')'; } main.cpp #include <iostream> #include "Complex.h" using namespace std; int main() { Complex x; Complex y(4.3, 8.2); Complex z(3.3, 1.1); cout << "x: "; x.print(); cout << "\ny: "; y.print(); cout << "\nz: "; z.print(); x = y + z; cout << "\n\nx = y + z: " << endl; x.print(); cout << " = "; y.print(); cout << " + "; z.print(); x = y - z; cout << "\n\nx = y - z: " << endl; x.print(); cout << " = "; y.print(); cout << " - "; z.print(); cout << endl; } Compile erros: complex.cpp(23) : error C2039: '<<' : is not a member of 'Complex' complex.h(5) : see declaration of 'Complex' complex.cpp(24) : error C2270: '<<' : modifiers not allowed on nonmember functions complex.cpp(25) : error C2248: 'Complex::real' : cannot access private member declared in class 'Complex' complex.h(13) : see declaration of 'Complex::real' complex.h(5) : see declaration of 'Complex' complex.cpp(25) : error C2248: 'Complex::imaginary' : cannot access private member declared in class 'Complex' complex.h(14) : see declaration of 'Complex::imaginary' complex.h(5) : see declaration of 'Complex' Thanks!

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  • Containers of reference_wrappers (comparison operators required?)

    - by kloffy
    If you use stl containers together with reference_wrappers of POD types, the following code works just fine: int i = 3; std::vector< boost::reference_wrapper<int> > is; is.push_back(boost::ref(i)); std::cout << (std::find(is.begin(),is.end(),i)!=is.end()) << std::endl; However, if you use non-POD types such as (contrived example): struct Integer { int value; bool operator==(const Integer& rhs) const { return value==rhs.value; } bool operator!=(const Integer& rhs) const { return !(*this == rhs); } }; It doesn't suffice to declare those comparison operators, instead you have to declare: bool operator==(const boost::reference_wrapper<Integer>& lhs, const Integer& rhs) { return boost::unwrap_ref(lhs)==rhs; } And possibly also: bool operator==(const Integer& lhs, const boost::reference_wrapper<Integer>& rhs) { return lhs==boost::unwrap_ref(rhs); } In order to get the equivalent code to work: Integer j = { 0 }; std::vector< boost::reference_wrapper<Integer> > js; js.push_back(boost::ref(j)); std::cout << (std::find(js.begin(),js.end(),j)!=js.end()) << std::endl; Now, I'm wondering if this is really the way it's meant to be done, since it seems impractical. It just seems there should be a simpler solution, e.g. templates: template<class T> bool operator==(const boost::reference_wrapper<T>& lhs, const T& rhs) { return boost::unwrap_ref(lhs)==rhs; } template<class T> bool operator==(const T& lhs, const boost::reference_wrapper<T>& rhs) { return lhs==boost::unwrap_ref(rhs); } There's probably a good reason why reference_wrapper behaves the way it does (possibly to accomodate non-POD types without comparison operators?). Maybe there already is an elegant solution and I just haven't found it.

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  • Call the cast operator of template base class within the derived class

    - by yoni
    I have a template class, called Cell, here the definition: template <class T> class OneCell { ..... } I have a cast operator from Cell to T, here virtual operator const T() const { ..... } Now i have derived class, called DCell, here template <class T> class DCell : public Cell<T> { ..... } I need to override the Cell's cast operator (insert a little if), but after I need to call the Cell's cast operator. In other methods it's should be something like virtual operator const T() const { if (...) { return Cell<T>::operator const T; } else throw ... } but i got a compiler error error: argument of type 'const int (Cell::)()const' does not match 'const int' What can I do? Thank you, and sorry about my poor English.

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  • Implementing Operator Overloading with Logarithms in C++

    - by Jacob Relkin
    Hello my friends, I'm having some issues with implementing a logarithm class with operator overloading in C++. My first goal is how I would implement the changeBase method, I've been having a tough time wrapping my head around it. My secoond goal is to be able to perform an operation where the left operand is a double and the right operand is a logarithm object. Here's a snippet of my log class: // coefficient: double // base: unsigned int // number: double class _log { double coefficient, number; unsigned int base; public: _log() { base = rand(); coefficient = rand(); number = rand(); } _log operator+ ( const double b ) const; _log operator* ( const double b ) const; _log operator- ( const double b ) const; _log operator/ ( const double b ) const; _log operator<< ( const _log &b ); double getValue() const; bool changeBase( unsigned int base ); }; You guys are awesome, thank you for your time.

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  • Why does virtual assignment behave differently than other virtual functions of the same signature?

    - by David Rodríguez - dribeas
    While playing with implementing a virtual assignment operator I have ended with a funny behavior. It is not a compiler glitch, since g++ 4.1, 4.3 and VS 2005 share the same behavior. Basically, the virtual operator= behaves differently than any other virtual function with respect to the code that is actually being executed. struct Base { virtual Base& f( Base const & ) { std::cout << "Base::f(Base const &)" << std::endl; return *this; } virtual Base& operator=( Base const & ) { std::cout << "Base::operator=(Base const &)" << std::endl; return *this; } }; struct Derived : public Base { virtual Base& f( Base const & ) { std::cout << "Derived::f(Base const &)" << std::endl; return *this; } virtual Base& operator=( Base const & ) { std::cout << "Derived::operator=( Base const & )" << std::endl; return *this; } }; int main() { Derived a, b; a.f( b ); // [0] outputs: Derived::f(Base const &) (expected result) a = b; // [1] outputs: Base::operator=(Base const &) Base & ba = a; Base & bb = b; ba = bb; // [2] outputs: Derived::operator=(Base const &) Derived & da = a; Derived & db = b; da = db; // [3] outputs: Base::operator=(Base const &) ba = da; // [4] outputs: Derived::operator=(Base const &) da = ba; // [5] outputs: Derived::operator=(Base const &) } The effect is that the virtual operator= has a different behavior than any other virtual function with the same signature ([0] compared to [1]), by calling the Base version of the operator when called through real Derived objects ([1]) or Derived references ([3]) while it does perform as a regular virtual function when called through Base references ([2]), or when either the lvalue or rvalue are Base references and the other a Derived reference ([4],[5]). Is there any sensible explanation to this odd behavior?

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  • Seeking STL-aware c++filt

    - by Don Wakefield
    In my development environment, I'm compiling a code base using GNU C++ 3.4.6. Code is under development, and unfortunately crashes now and then. It's nice to be able to run the traceback through a demangler, and I use c++filt 3.4. The problem comes when functions have a number of STL parameters. Consider My_callback::operator()( Status&, std::set<std::string> const&, std::vector<My_parameter*> const&, My_attribute_set const&, std::vector<My_parameter_base*> const&, std::vector<My_parameter> const&, std::set<std::string> const& ) { // ... } When this function is in the traceback, the mangled output on my platform is: (_ZN30My_callbackclER11StatusRKSt3setISsSt4lessISsESaISsEERKSt6vectorIP13My_parameterSaISB_EERK17My_attribute_setRKS9_IP18My_parameter_baseSaISK_EERKS9_ISA_SaISA_EES8_+0x76a) [0x13ffdaa] c++filt kindly demangles it to (My_callback::operator()(Status&, std::set<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&, std::vector<My_parameter*, std::allocator<My_parameter*> > const&, My_attribute_set const&, std::vector<My_parameter_base*, std::allocator<My_parameter_base*> > const&, std::vector<My_parameter, std::allocator<My_parameter> > const&, std::set<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&)+0x76a) [0x13ffdaa] This is the same problem as compiler errors encountered when using templates. However, the STL is a fairly regular and recognizable package of templates. So what I'm hoping is that someone out there has created an enhanced version of c++filt which would dump something closer to the original function signature. Any hints?

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  • Internal class and access to external members.

    - by Knowing me knowing you
    I always thought that internal class has access to all data in its external class but having code: template<class T> class Vector { template<class T> friend std::ostream& operator<<(std::ostream& out, const Vector<T>& obj); private: T** myData_; std::size_t myIndex_; std::size_t mySize_; public: Vector():myData_(nullptr), myIndex_(0), mySize_(0) { } Vector(const Vector<T>& pattern); void insert(const T&); Vector<T> makeUnion(const Vector<T>&)const; Vector<T> makeIntersection(const Vector<T>&)const; class Iterator : public std::iterator<std::bidirectional_iterator_tag,T> { private: T** itData_; public: Iterator()//<<<<<<<<<<<<<------------COMMENT { /*HERE I'M TRYING TO USE ANY MEMBER FROM Vector<T> AND I'M GETTING ERR SAYING: ILLEGAL CALL OF NON-STATIC MEMBER FUNCTION*/} Iterator(T** ty) { itData_ = ty; } Iterator operator++() { return ++itData_; } T operator*() { return *itData_[0]; } bool operator==(const Iterator& obj) { return *itData_ == *obj.itData_; } bool operator!=(const Iterator& obj) { return *itData_ != *obj.itData_; } bool operator<(const Iterator& obj) { return *itData_ < *obj.itData_; } }; typedef Iterator iterator; iterator begin()const { assert(mySize_ > 0); return myData_; } iterator end()const { return myData_ + myIndex_; } }; See line marked as COMMENT. So can I or I can't use members from external class while in internal class? Don't bother about naming, it's not a Vector it's a Set. Thank you.

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  • I asked this yesterday, after the input given I'm still having trouble implementing..

    - by Josh
    I'm not sure how to fix this or what I did wrong, but whenever I enter in a value it just closes out the run prompt. So, seems I do have a problem somewhere in my coding. Whenever I run the program and input a variable, it always returns the same answer.."The content at location 76 is 0." On that note, someone told me that "I don't know, but I suspect that Program A incorrectly has a fixed address being branched to on instructions 10 and 11." - mctylr but I'm not sure how to fix that.. I'm trying to figure out how to incorporate this idea from R Samuel Klatchko.. I'm still not sure what I'm missing but I can't get it to work.. const int OP_LOAD = 3; const int OP_STORE = 4; const int OP_ADD = 5; ... const int OP_LOCATION_MULTIPLIER = 100; mem[0] = OP_LOAD * OP_LOCATION_MULTIPLIER + ...; mem[1] = OP_ADD * OP_LOCATION_MULTIPLIER + ...; operand = memory[ j ] % OP_LOCATION_MULTIPLIER; operation = memory[ j ] / OP_LOCATION_MULTIPLIER; I'm new to programming, I'm not the best, so I'm going for simplicity. Also this is an SML program. Anyway, this IS a homework assignment and I'm wanting a good grade on this. So I was looking for input and making sure this program will do what I'm hoping they are looking for. Anyway, here are the instructions: Write SML (Simpletron Machine language) programs to accomplish each of the following task: A) Use a sentinel-controlled loop to read positive number s and compute and print their sum. Terminate input when a neg number is entered. B) Use a counter-controlled loop to read seven numbers, some positive and some negative, and compute + print the avg. C) Read a series of numbers, and determine and print the largest number. The first number read indicates how many numbers should be processed. Without further a due, here is my program. All together. int main() { const int READ = 10; const int WRITE = 11; const int LOAD = 20; const int STORE = 21; const int ADD = 30; const int SUBTRACT = 31; const int DIVIDE = 32; const int MULTIPLY = 33; const int BRANCH = 40; const int BRANCHNEG = 41; const int BRANCHZERO = 41; const int HALT = 43; int mem[100] = {0}; //Making it 100, since simpletron contains a 100 word mem. int operation; //taking the rest of these variables straight out of the book seeing as how they were italisized. int operand; int accum = 0; // the special register is starting at 0 int j; // This is for part a, it will take in positive variables in a sent-controlled loop and compute + print their sum. Variables from example in text. memory [0] = 1010; memory [01] = 2009; memory [02] = 3008; memory [03] = 2109; memory [04] = 1109; memory [05] = 4300; memory [06] = 1009; j = 0; //Makes the variable j start at 0. while ( true ) { operand = memory[ j ]%100; // Finds the op codes from the limit on the memory (100) operation = memory[ j ]/100; //using a switch loop to set up the loops for the cases switch ( operation ){ case 10: //reads a variable into a word from loc. Enter in -1 to exit cout <<"\n Input a positive variable: "; cin >> memory[ operand ]; break; case 11: // takes a word from location cout << "\n\nThe content at location " << operand << "is " << memory[operand]; break; case 20:// loads accum = memory[ operand ]; break; case 21: //stores memory[ operand ] = accum; break; case 30: //adds accum += mem[operand]; break; case 31: // subtracts accum-= memory[ operand ]; break; case 32: //divides accum /=(memory[ operand ]); break; case 33: // multiplies accum*= memory [ operand ]; break; case 40: // Branches to location j = -1; break; case 41: //branches if acc. is < 0 if (accum < 0) j = 5; break; case 42: //branches if acc = 0 if (accum == 0) j = 5; break; case 43: // Program ends exit(0); break; } j++; } return 0; }

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  • OpenCL - incremental summation during compute

    - by user1721997
    I'm absolutelly novice in OpenCL programming. For my app. (molecular simulaton) I wrote a kernel for calculate intermolecular potential of lennard-jones liquid. In this kernel I need to compute cumulative value of the potential of all particles with one: __kernel void Molsim(__global const float* inmatrix, __global float* fi, const int c, const float r1, const float r2, const float r3, const float rc, const float epsilon, const float sigma, const float h1, const float h23) { float fi0; float fi1; float d; unsigned int i = get_global_id(0); //number of particles (typically 2000) if(c!=i) { // potential before particle movement d=sqrt(pow((0.5*h1-fabs(0.5*h1-fabs(inmatrix[c*3]-inmatrix[i*3]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(inmatrix[c*3+1]-inmatrix[i*3+1]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(inmatrix[c*3+2]-inmatrix[i*3+2]))),2.0)); if(d<rc) { fi0=4.0*epsilon*(pow(sigma/d,12.0)-pow(sigma/d,6.0)); } else { fi0=0; } // potential after particle movement d=sqrt(pow((0.5*h1-fabs(0.5*h1-fabs(r1-inmatrix[i*3]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(r2-inmatrix[i*3+1]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(r3-inmatrix[i*3+2]))),2.0)); if(d<rc) { fi1=4.0*epsilon*(pow(sigma/d,12.0)-pow(sigma/d,6.0)); } else { fi1=0; } // cumulative difference of potentials fi[0]+=fi1-fi0; } } My problem is in the line: fi[0]+=fi1-fi0;. In the one-element vector fi[0] are wrong results. I read something about sum reduction, but I do not know how to do it during the calculation. Exist any simple solution of my problem?

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  • Identifier is undefined

    - by hawk
    I wrote the following code in C++ using VS2012 Express. void ac_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Irrelevant code omitted. } vector<int> ac_benchmark_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, double &time) { // Prepare the container for the results vector<int> matches(num_records * num_patterns); Trie T; Node* trie = T.addWord(records, num_records, record_length); // error line ac_search(num_patterns, pattern_length, patterns, num_records, record_length, records, matches.data(), trie); // Irrelevant code omitted. return matches; } I get the error identifier "ac_search" is undefined at the function invoking line. I am a bit confused here. because the function ac_search is declared as a global (not inside any container). Why can't I call it at this place? Am I missing something? Update I tried ignore irrelevant code and then included it gradually and found that everything is fine until I include the outer loop of ac_search I get the aforementioned error. here is updated code of the function ac_search: void ac_cpu_string_search(uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Loop over all records //for (uint record_number = 0; record_number < num_records; ++record_number) //{ // // Loop over all patterns for (uint pattern_number = 0; pattern_number < num_patterns; ++pattern_number) { // Execute string search const char *ptr_record = &records[record_number * record_length]; const char *ptr_match = std::strstr(ptr_record, &patterns[pattern_number * pattern_length]); // If pattern was found, then calculate offset, otherwise result is -1 if (ptr_match) { matches[record_number * num_patterns + pattern_number] = static_cast<int>(std::distance(ptr_record, ptr_match)); } else { matches[record_number * num_patterns + pattern_number] = -1; } // } //} } Update 2 I think the error has something to do with the function addWord which belongs to the class Trie. When I commented out this function, I did not get the error anymore. Node* Trie::addWord(const char *records, uint num_records, uint record_length) { // Loop over all records for (uint record_number = 0; record_number < num_records; ++record_number) { const char *ptr_record = &records[record_number * record_length]; string s = ptr_record; Node* current = root; if ( s.length() == 0 ) { current->setWordMarker(); // an empty word return; } for ( int i = 0; i < s.length(); i++ ) { Node* child = current->findChild(s[i]); if ( child != NULL ) { current = child; } else { Node* tmp = new Node(); tmp->setContent(s[i]); current->appendChild(tmp); current = tmp; } if ( i == s.length() - 1 ) current->setWordMarker(); } return current; } void ac_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Irrelevant code omitted. } vector<int> ac_benchmark_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, double &time) { // Prepare the container for the results vector<int> matches(num_records * num_patterns); Trie T; Node* trie = T.addWord(records, num_records, record_length); // error line ac_search(num_patterns, pattern_length, patterns, num_records, record_length, records, matches.data(), trie); // Irrelevant code omitted. return matches; }

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  • Overloading stream insertion without violating information hiding?

    - by Chris
    I'm using yaml-cpp for a project. I want to overload the << and >> operators for some classes, but I'm having an issue grappling with how to "properly" do this. Take the Note class, for example. It's fairly boring: class Note { public: // constructors Note( void ); ~Note( void ); // public accessor methods void number( const unsigned long& number ) { _number = number; } unsigned long number( void ) const { return _number; } void author( const unsigned long& author ) { _author = author; } unsigned long author( void ) const { return _author; } void subject( const std::string& subject ) { _subject = subject; } std::string subject( void ) const { return _subject; } void body( const std::string& body ) { _body = body; } std::string body( void ) const { return _body; } private: unsigned long _number; unsigned long _author; std::string _subject; std::string _body; }; The << operator is easy sauce. In the .h: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ); And in the .cpp: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ) { out << v.number() << v.author() << v.subject() << v.body(); return out; } No sweat. Then I go to declare the >> operator. In the .h: void operator >> ( const YAML::Node& node, Note& note ); But in the .cpp I get: void operator >> ( const YAML::Node& node, Note& note ) { node[0] >> ? node[1] >> ? node[2] >> ? node[3] >> ? return; } If I write things like node[0] >> v._number; then I would need to change the CV-qualifier to make all of the Note fields public (which defeats everything I was taught (by professors, books, and experience))) about data hiding. I feel like doing node[0] >> temp0; v.number( temp0 ); all over the place is not only tedious, error-prone, and ugly, but rather wasteful (what with the extra copies). Then I got wise: I attempted to move these two operators into the Note class itself, and declare them as friends, but the compiler (GCC 4.4) didn't like that: src/note.h:44: error: ‘YAML::Emitter& Note::operator<<(YAML::Emitter&, const Note&)’ must take exactly one argument src/note.h:45: error: ‘void Note::operator(const YAML::Node&, Note&)’ must take exactly one argument Question: How do I "properly" overload the >> operator for a class Without violating the information hiding principle? Without excessive copying?

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  • C++, function pointer to the template function pointer

    - by Ian
    I am having a pointer to the common static method class MyClass { private: static double ( *pfunction ) ( const Object *, const Object *); ... }; pointing to the static method class SomeClass { public: static double getA ( const Object *o1, const Object *o2); ... }; Initialization: double ( *MyClass::pfunction ) ( const Object *o1, const Object *o2 ) = &SomeClass::getA; I would like to convert this pointer to the static template function pointer: template <class T> static T ( *pfunction ) ( const Object <T> *, const Object <T> *); //Compile error where: class SomeClass { public: template <class T> static double getA ( const Object <T> *o1, const Object <T> *o2); ... }; But there is some error... Thanks for your help...

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  • How to convert between different currencies?

    - by sil3nt
    Hey there, this is part of a question i got in class, im at the final stretch but this has become a major problem. In it im given a certain value which is called the "gold value" and it is 40.5, this value changes in input. and i have these constants const int RUBIES_PER_DIAMOND = 5; // relative values. * const int EMERALDS_PER_RUBY = 2; const int GOLDS_PER_EMERALDS = 5; const int SILVERS_PER_GOLD = 4; const int COPPERS_PER_SILVER = 5; const int DIAMOND_VALUE = 50; // gold values. * const int RUBY_VALUE = 10; const int EMERALD_VALUE = 5; const float SILVER_VALUE = 0.25; const float COPPER_VALUE = 0.05; which means that basically for every diamond there are 5 rubies, and for every ruby there are 2 emeralds. So on and so forth. and the "gold value" for every diamond for example is 50 (diamond value = 50) this is how much one diamond is worth in golds. my problem is converting 40.5 into these diamonds and ruby values. I know the answer is 4rubies and 2silvers but how do i write the algorithm for this so that it gives the best estimate for every goldvalue that comes along?? please help!, im at my wits end

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  • C++, name collision across different namespace

    - by aaa
    hello. I am baffled by the following name collision: namespace mp2 { boost::numeric::ublas::matrix_range<M> slice(M& m, const R1& r1, const R2& r2) { namespace ublas = boost::numeric::ublas; ublas::range r1_(r1.begin(), r1.end()), r2_(r2.begin(), r2.end()); return ublas::matrix_range<M>(m, r1_, r2_); } double energy(const Wavefunction &wf) { const Wavefunction::matrix& C = wf.coefficients(); int No = wf.occupied().size(); foreach (const Basis::MappedShell& P, basis.shells()) { slice(C, range(No), range(P)); the error from g++4.4 is 7 In file included from mp2.cpp:1: 8 /usr/include/boost/numeric/ublas/fwd.hpp: In function âdouble mp2::energy(const Wavefunction&)â: 9 /usr/include/boost/numeric/ublas/fwd.hpp:32: error: âboost::numeric::ublas::sliceâ is not a function, 10 ../../src/mp2/energy.hpp:98: error: conflict with âtemplate<class M, class R1, class R2> boost::numeric::ublas::matrix_range<M> mp2::slice(M&, const R1&, const R2&)â 11 ../../src/mp2/energy.hpp:123: error: in call to âsliceâ 12 /usr/include/boost/numeric/ublas/fwd.hpp:32: error: âboost::numeric::ublas::sliceâ is not a function, 13 ../../src/mp2/energy.hpp:98: error: conflict with âtemplate<class M, class R1, class R2> boost::numeric::ublas::matrix_range<M> mp2::slice(M&, const R1&, const R2&)â 14 ../../src/mp2/energy.hpp:129: error: in call to âsliceâ 15 make: *** [mp2.lo] Error 1 ublas segment is namespace boost { namespace numeric { namespace ublas { typedef basic_slice<> slice; why is slice in ublas collides with slice in mp2? I and fairly certain there is no using namespace ublas in the code and in includes. thank you

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  • C++ Pointer member function with templates assignment with a member function of another class

    - by Agusti
    Hi, I have this class: class IShaderParam{ public: std::string name_value; }; template<class TParam> class TShaderParam:public IShaderParam{ public: void (TShaderParam::*send_to_shader)( const TParam&,const std::string&); TShaderParam():send_to_shader(NULL){} TParam value; void up_to_shader(); }; typedef TShaderParam<float> FloatShaderParam; typedef TShaderParam<D3DXVECTOR3> Vec3ShaderParam; In another class, I have a vector of IShaderParams* and functions that i want to send to "send_to_shader". I'm trying assign the reference of these functions like this: Vec3ShaderParam *_param = new Vec3ShaderParam; _param-send_to_shader = &TShader::setVector3; This is the function: void TShader::setVector3(const D3DXVECTOR3 &vec, const std::string &name){ //... } And this is the class with IshaderParams*: class TShader{ std::vector params; public: Shader effect; std::string technique_name; TShader(std::string& afilename):effect(NULL){}; ~TShader(); void setVector3(const D3DXVECTOR3 &vec, const std::string &name); When I compile the project with Visual Studio C++ Express 2008 I recieve this error: Error 2 error C2440: '=' :can't make the conversion 'void (__thiscall TShader::* )(const D3DXVECTOR3 &,const std::string &)' a 'void (__thiscall TShaderParam::* )(const TParam &,const std::string &)' c:\users\isagoras\documents\mcv\afoc\shader.cpp 127 Can I do the assignment? No? I don't know how :-S Yes, I know that I can achieve the same objective with other techniques, but I want to know how can I do this..

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  • Argument type deduction, references and rvalues

    - by uj2
    Consider the situation where a function template needs to forward an argument while keeping it's lvalue-ness in case it's a non-const lvalue, but is itself agnostic to what the argument actually is, as in: template <typename T> void target(T&) { cout << "non-const lvalue"; } template <typename T> void target(const T&) { cout << "const lvalue or rvalue"; } template <typename T> void forward(T& x) { target(x); } When x is an rvalue, instead of T being deduced to a constant type, it gives an error: int x = 0; const int y = 0; forward(x); // T = int forward(y); // T = const int forward(0); // Hopefully, T = const int, but actually an error forward<const int>(0); // Works, T = const int It seems that for forward to handle rvalues (without calling for explicit template arguments) there needs to be an forward(const T&) overload, even though it's body would be an exact duplicate. Is there any way to avoid this duplication?

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