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  • Having issues with initializing character array

    - by quandrum
    Ok, this is for homework about hashtables, but this is the simple stuff I thought I was able to do from earlier classes, and I'm tearing my hair out. The professor is not being responsive enough, so I thought I'd try here. We have a hashtable of stock objects.The stock objects are created like so: stock("IBM", "International Business Machines", 2573, date(date::MAY, 23, 1967)) my constructor looks like: stock::stock(char const * const symbol, char const * const name, int sharePrice, date priceDate): symbol(NULL), name(NULL), sharePrice(sharePrice), dateOfPrice(priceDate) { setSymbol(symbol); setName(name); } and setSymbol looks like this: (setName is indentical): void stock::setSymbol(const char* symbol) { if (this->symbol) delete [] this->symbol; this->symbol = new char[strlen(symbol)+1]; strcpy(this->symbol,symbol); } and it refuses to allocate on the line this->symbol = new char[strlen(symbol)+1]; with a std::bad_alloc. name and symbol are declared char * name; char * symbol; I feel like this is exactly how I've done it in previous code.I'm sure it's something silly with pointers. Can anyone help?

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  • Compilation errors calling find_if using a functor

    - by Jim Wong
    We are having a bit of trouble using find_if to search a vector of pairs for an entry in which the first element of the pair matches a particular value. To make this work, we have defined a trivial functor whose operator() takes a pair as input and compares the first entry against a string. Unfortunately, when we actually add a call to find_if using an instance of our functor constructed using a temporary string value, the compiler produces a raft of error messages. Oddly (to me, anyway), if we replace the temporary with a string that we've created on the stack, things seem to work. Here's what the code (including both versions) looks like: typedef std::pair<std::string, std::string> MyPair; typedef std::vector<MyPair> MyVector; struct MyFunctor: std::unary_function <const MyPair&, bool> { explicit MyFunctor(const std::string& val) : m_val(val) {} bool operator() (const MyPair& p) { return p.first == m_val; } const std::string m_val; }; bool f(const char* s) { MyFunctor f(std::string(s)); // ERROR // std::string str(s); // MyFunctor f(str); // OK MyVector vec; MyVector::const_iterator i = std::find_if(vec.begin(), vec.end(), f); return i != vec.end(); } And here's what the most interesting error message looks like: /usr/include/c++/4.2.1/bits/stl_algo.h:260: error: conversion from ‘std::pair, std::allocator , std::basic_string, std::allocator ’ to non-scalar type ‘std::string’ requested Because we have a workaround, we're mostly curious as to why the first form causes problems. I'm sure we're missing something, but we haven't been able to figure out what it is.

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  • dynamic lib can't find static lib

    - by renyufei
    env: gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) app: Bin(main) calls dynamic lib(testb.so), and testb.so contains a static lib(libtesta.a). file list: main.c test.h a.c b.c then compile as: gcc -o testa.o -c a.c ar -r libtesta.a testa.o gcc -shared -fPIC -o testb.so b.c gcc -o main main.c -L. -ltesta -ldl then compile success, but runs an error: ./main: symbol lookup error: ./testb.so: undefined symbol: print code as follows: test.h #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <dlfcn.h> int printa(const char *msg); int printb(const char *msg); a.c #include "test.h" int printa(const char *msg) { printf("\tin printa\n"); printf("\t%s\n", msg); } b.c #include "test.h" int printb(const char *msg) { printf("in printb\n"); printa("called by printb\n"); printf("%s\n", msg); } main.c #include "test.h" int main(int argc, char **argv) { void *handle; int (*dfn)(const char *); printf("before dlopen\n"); handle = dlopen("./testb.so", RTLD_LOCAL | RTLD_LAZY); printf("after dlopen\n"); if (handle == NULL) { printf("dlopen fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dlsym\n"); dfn = dlsym(handle, "printb"); printf("after dlsym\n"); if (dfn == NULL) { printf("dlsym fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dfn\n"); dfn("printb func\n"); printf("after dfn\n"); exit(EXIT_SUCCESS); }

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  • C++0x rvalue references - lvalues-rvalue binding

    - by Doug
    This is a follow-on question to http://stackoverflow.com/questions/2748866/c0x-rvalue-references-and-temporaries In the previous question, I asked how this code should work: void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } It seems that the move overload should probably be called because of the implicit temporary, and this happens in GCC but not MSVC (or the EDG front-end used in MSVC's Intellisense). What about this code? void f(std::string &&); //NB: No const string & overload supplied void g1(const char * arg) { f(arg); } void g2(const std::string & arg) { f(arg); } It seems that, based on the answers to my previous question that function g1 is legal (and is accepted by GCC 4.3-4.5, but not by MSVC). However, GCC and MSVC both reject g2 because of clause 13.3.3.1.4/3, which prohibits lvalues from binding to rvalue ref arguments. I understand the rationale behind this - it is explained in N2831 "Fixing a safety problem with rvalue references". I also think that GCC is probably implementing this clause as intended by the authors of that paper, because the original patch to GCC was written by one of the authors (Doug Gregor). However, I don't this is quite intuitive. To me, (a) a const string & is conceptually closer to a string && than a const char *, and (b) the compiler could create a temporary string in g2, as if it were written like this: void g2(const std::string & arg) { f(std::string(arg)); } Indeed, sometimes the copy constructor is considered to be an implicit conversion operator. Syntactically, this is suggested by the form of a copy constructor, and the standard even mentions this specifically in clause 13.3.3.1.2/4, where the copy constructor for derived-base conversions is given a higher conversion rank than other implicit conversions: A conversion of an expression of class type to the same class type is given Exact Match rank, and a conversion of an expression of class type to a base class of that type is given Conversion rank, in spite of the fact that a copy/move constructor (i.e., a user-defined conversion function) is called for those cases. (I assume this is used when passing a derived class to a function like void h(Base), which takes a base class by value.) Motivation My motivation for asking this is something like the question asked in http://stackoverflow.com/questions/2696156/how-to-reduce-redundant-code-when-adding-new-c0x-rvalue-reference-operator-over ("How to reduce redundant code when adding new c++0x rvalue reference operator overloads"). If you have a function that accepts a number of potentially-moveable arguments, and would move them if it can (e.g. a factory function/constructor: Object create_object(string, vector<string>, string) or the like), and want to move or copy each argument as appropriate, you quickly start writing a lot of code. If the argument types are movable, then one could just write one version that accepts the arguments by value, as above. But if the arguments are (legacy) non-movable-but-swappable classes a la C++03, and you can't change them, then writing rvalue reference overloads is more efficient. So if lvalues did bind to rvalues via an implicit copy, then you could write just one overload like create_object(legacy_string &&, legacy_vector<legacy_string> &&, legacy_string &&) and it would more or less work like providing all the combinations of rvalue/lvalue reference overloads - actual arguments that were lvalues would get copied and then bound to the arguments, actual arguments that were rvalues would get directly bound. Questions My questions are then: Is this a valid interpretation of the standard? It seems that it's not the conventional or intended one, at any rate. Does it make intuitive sense? Is there a problem with this idea that I"m not seeing? It seems like you could get copies being quietly created when that's not exactly expected, but that's the status quo in places in C++03 anyway. Also, it would make some overloads viable when they're currently not, but I don't see it being a problem in practice. Is this a significant enough improvement that it would be worth making e.g. an experimental patch for GCC?

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  • MS Detours Library, detouring non win api function

    - by flavour404
    Hi, I want to use the windows detours library to detour a non win api function. The function is part of the Qt library (QtGui4.dll). I am wondering how I would set up the function signature for : void QPainter::drawText ( const QPointF & position, const QString & text ) I had a go with this and it received my usual share of errors, a little explanation of requirements would be interesting as well: void (QPainter * real_drawText)(const QPointF & position, const QString & text) = drawText This is what they look like for TextOut, under the windows API: BOOL (WINAPI * Real_TextOut)(HDC a0, int a1, int a2, LPCWSTR a3, int a4) = TextOutW; BOOL WINAPI Mine_TextOut(HDC hdc,int X,int Y,LPCWSTR text,int textLen) { BOOL rv = Real_TextOut(hdc, X, Y, text, textLen); HWND hWindow = WindowFromDC(hdc); SendTextMessage(hWindow, text); return rv; } Thanks.

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  • Access violation using LocalAlloc()

    - by PaulH
    I have a Visual Studio 2008 Windows Mobile 6 C++ application that is using an API that requires the use of LocalAlloc(). To make my life easier, I created an implementation of a standard allocator that uses LocalAlloc() internally: /// Standard library allocator implementation using LocalAlloc and LocalReAlloc /// to create a dynamically-sized array. /// Memory allocated by this allocator is never deallocated. That is up to the /// user. template< class T, int max_allocations > class LocalAllocator { public: typedef T value_type; typedef size_t size_type; typedef ptrdiff_t difference_type; typedef T* pointer; typedef const T* const_pointer; typedef T& reference; typedef const T& const_reference; pointer address( reference r ) const { return &r; }; const_pointer address( const_reference r ) const { return &r; }; LocalAllocator() throw() : c_( NULL ) { }; /// Attempt to allocate a block of storage with enough space for n elements /// of type T. n>=1 && n<=max_allocations. /// If memory cannot be allocated, a std::bad_alloc() exception is thrown. pointer allocate( size_type n, const void* /*hint*/ = 0 ) { if( NULL == c_ ) { c_ = LocalAlloc( LPTR, sizeof( T ) * n ); } else { HLOCAL c = LocalReAlloc( c_, sizeof( T ) * n, LHND ); if( NULL == c ) LocalFree( c_ ); c_ = c; } if( NULL == c_ ) throw std::bad_alloc(); return reinterpret_cast< T* >( c_ ); }; /// Normally, this would release a block of previously allocated storage. /// Since that's not what we want, this function does nothing. void deallocate( pointer /*p*/, size_type /*n*/ ) { // no deallocation is performed. that is up to the user. }; /// maximum number of elements that can be allocated size_type max_size() const throw() { return max_allocations; }; private: /// current allocation point HLOCAL c_; }; // class LocalAllocator My application is using that allocator implementation in a std::vector< #define MAX_DIRECTORY_LISTING 512 std::vector< WIN32_FIND_DATA, LocalAllocator< WIN32_FIND_DATA, MAX_DIRECTORY_LISTING > > file_list; WIN32_FIND_DATA find_data = { 0 }; HANDLE find_file = ::FindFirstFile( folder.c_str(), &find_data ); if( NULL != find_file ) { do { // access violation here on the 257th item. file_list.push_back( find_data ); } while ( ::FindNextFile( find_file, &find_data ) ); ::FindClose( find_file ); } // data submitted to the API that requires LocalAlloc()'d array of WIN32_FIND_DATA structures SubmitData( &file_list.front() ); On the 257th item added to the vector<, the application crashes with an access violation: Data Abort: Thread=8e1b0400 Proc=8031c1b0 'rapiclnt' AKY=00008001 PC=03f9e3c8(coredll.dll+0x000543c8) RA=03f9ff04(coredll.dll+0x00055f04) BVA=21ae0020 FSR=00000007 First-chance exception at 0x03f9e3c8 in rapiclnt.exe: 0xC0000005: Access violation reading location 0x01ae0020. LocalAllocator::allocate is called with an n=512 and LocalReAlloc() succeeds. The actual Access Violation exception occurs within the std::vector< code after the LocalAllocator::allocate call: 0x03f9e3c8 0x03f9ff04 > MyLib.dll!stlp_std::priv::__copy_trivial(const void* __first = 0x01ae0020, const void* __last = 0x01b03020, void* __result = 0x01b10020) Line: 224, Byte Offsets: 0x3c C++ MyLib.dll!stlp_std::vector<_WIN32_FIND_DATAW,LocalAllocator<_WIN32_FIND_DATAW,512> >::_M_insert_overflow(_WIN32_FIND_DATAW* __pos = 0x01b03020, _WIN32_FIND_DATAW& __x = {...}, stlp_std::__true_type& __formal = {...}, unsigned int __fill_len = 1, bool __atend = true) Line: 112, Byte Offsets: 0x5c C++ MyLib.dll!stlp_std::vector<_WIN32_FIND_DATAW,LocalAllocator<_WIN32_FIND_DATAW,512> >::push_back(_WIN32_FIND_DATAW& __x = {...}) Line: 388, Byte Offsets: 0xa0 C++ MyLib.dll!Foo(unsigned long int cbInput = 16, unsigned char* pInput = 0x01a45620, unsigned long int* pcbOutput = 0x1dabfbbc, unsigned char** ppOutput = 0x1dabfbc0, IRAPIStream* __formal = 0x00000000) Line: 66, Byte Offsets: 0x1e4 C++ If anybody can point out what I may be doing wrong, I would appreciate it. Thanks, PaulH

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  • Problem passing a reference as a named parameter to a variadic function

    - by Michael Mrozek
    I'm having problems in Visual Studio 2003 with the following: void foo(const char*& str, ...) { va_list args; va_start(args, str); const char* foo; while((foo = va_arg(args, const char*)) != NULL) { printf("%s\n", foo); } } When I call it: const char* one = "one"; foo(one, "two", "three", NULL); I get: Access violation reading location 0xcccccccc on the printf() line -- va_arg() returned 0xcccccccc. I finally discovered it's the first parameter being a reference that breaks it -- if I make it a normal char* everything is fine. It doesn't seem to matter what the type is; being a reference causes it to fail at runtime. Is this a known problem with VS2003, or is there some way in which that's legal behavior? It doesn't happen in GCC; I haven't tested with newer Visual Studios to see if the behavior goes away

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  • Partial template specialization for more than one typename

    - by Matt Joiner
    In the following code, I want to consider functions (Ops) that have void return to instead be considered to return true. The type Retval, and the return value of Op are always matching. I'm not able to discriminate using the type traits shown here, and attempts to create a partial template specialization based on Retval have failed due the presence of the other template variables, Op and Args. How do I specialize only some variables in a template specialization without getting errors? Is there any other way to alter behaviour based on the return type of Op? template <typename Retval, typename Op, typename... Args> Retval single_op_wrapper( Retval const failval, char const *const opname, Op const op, Cpfs &cpfs, Args... args) { try { CallContext callctx(cpfs, opname); Retval retval; if (std::is_same<bool, Retval>::value) { (callctx.*op)(args...); retval = true; } else { retval = (callctx.*op)(args...); } assert(retval != failval); callctx.commit(cpfs); return retval; } catch (CpfsError const &exc) { cpfs_errno_set(exc.fserrno); LOGF(Info, "Failed with %s", cpfs_errno_str(exc.fserrno)); } return failval; }

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  • how to cout a vector of structs (that's a class member, using extraction operator)

    - by Julz
    hi, i'm trying to simply cout the elements of a vector using an overloaded extraction operator. the vector contians Point, which is just a struct containing two doubles. the vector is a private member of a class called Polygon, so heres my Point.h #ifndef POINT_H #define POINT_H #include <iostream> #include <string> #include <sstream> struct Point { double x; double y; //constructor Point() { x = 0.0; y = 0.0; } friend std::istream& operator >>(std::istream& stream, Point &p) { stream >> std::ws; stream >> p.x; stream >> p.y; return stream; } friend std::ostream& operator << (std::ostream& stream, Point &p) { stream << p.x << p.y; return stream; } }; #endif my Polygon.h #ifndef POLYGON_H #define POLYGON_H #include "Segment.h" #include <vector> class Polygon { //insertion operator needs work friend std::istream & operator >> (std::istream &inStream, Polygon &vertStr); // extraction operator friend std::ostream & operator << (std::ostream &outStream, const Polygon &vertStr); public: //Constructor Polygon(const std::vector<Point> &theVerts); //Default Constructor Polygon(); //Copy Constructor Polygon(const Polygon &polyCopy); //Accessor/Modifier methods inline std::vector<Point> getVector() const {return vertices;} //Return number of Vector elements inline int sizeOfVect() const {return vertices.size();} //add Point elements to vector inline void setVertices(const Point &theVerts){vertices.push_back (theVerts);} private: std::vector<Point> vertices; }; and Polygon.cc using namespace std; #include "Polygon.h" // Constructor Polygon::Polygon(const vector<Point> &theVerts) { vertices = theVerts; } //Default Constructor Polygon::Polygon(){} istream & operator >> (istream &inStream, Polygon::Polygon &vertStr) { inStream >> ws; inStream >> vertStr; return inStream; } // extraction operator ostream & operator << (ostream &outStream, const Polygon::Polygon &vertStr) { outStream << vertStr.vertices << endl; return outStream; } i figure my Point insertion/extraction is right, i can insert and cout using it and i figure i should be able to just...... cout << myPoly[i] << endl; in my driver? (in a loop) or even... cout << myPoly[0] << endl; without a loop? i've tried all sorts of myPoly.at[i]; myPoly.vertices[i]; etc etc also tried all veriations in my extraction function outStream << vertStr.vertices[i] << endl; within loops, etc etc. when i just create a... vector<Point> myVect; in my driver i can just... cout << myVect.at(i) << endl; no problems. tried to find an answer for days, really lost and not through lack of trying!!! thanks in advance for any help. please excuse my lack of comments and formatting also there's bits and pieces missing but i really just need an answer to this problem thanks again

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  • What's pcap_pkthdr there for?

    - by httpinterpret
    Code snippet from here: void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data) { .... /* retireve the position of the ip header */ ih = (ip_header *) (pkt_data + 14); //length of ethernet header .... What's const struct pcap_pkthdr *header for, when do we need it, how is it populated (since there is no such info in the packet itself as below)?

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  • Silencing GCC warnings when using an "Uncopyable" class

    - by Kazade
    I have several classes that I don't want to be copyable, some of these classes have pointer data members. To make these classes uncopyable I privately inherit the following class template: template <class T> class Uncopyable { protected: Uncopyable() {} virtual ~Uncopyable() {} private: Uncopyable(const Uncopyable &); T & operator=(const T&); }; Which I used like so: class Entity : private Uncopyable<Entity> { } This works fine, however when I compile with -Weffc++ I still get the following warning: class Entity has pointer data members but does not override Entity(const Entity&) or operator=(const Entity&) Why is it still giving me this warning?

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  • What's the C strategy to "imitate" a C++ template ?

    - by Andrei Ciobanu
    After reading some examples on stackoverflow, and following some of the answers for my previous questions (1), I've eventually come with a "strategy" for this. I've come to this: 1) Have a declare section in the .h file. Here I will define the data-structure, and the accesing interface. Eg.: /** * LIST DECLARATION. (DOUBLE LINKED LIST) */ #define NM_TEMPLATE_DECLARE_LIST(type) \ typedef struct nm_list_elem_##type##_s { \ type data; \ struct nm_list_elem_##type##_s *next; \ struct nm_list_elem_##type##_s *prev; \ } nm_list_elem_##type ; \ typedef struct nm_list_##type##_s { \ unsigned int size; \ nm_list_elem_##type *head; \ nm_list_elem_##type *tail; \ int (*cmp)(const type e1, const type e2); \ } nm_list_##type ; \ \ nm_list_##type *nm_list_new_##type##_(int (*cmp)(const type e1, \ const type e2)); \ \ (...other functions ...) 2) Wrap the functions in the interface inside MACROS: /** * LIST INTERFACE */ #define nm_list(type) \ nm_list_##type #define nm_list_elem(type) \ nm_list_elem_##type #define nm_list_new(type,cmp) \ nm_list_new_##type##_(cmp) #define nm_list_delete(type, list, dst) \ nm_list_delete_##type##_(list, dst) #define nm_list_ins_next(type,list, elem, data) \ nm_list_ins_next_##type##_(list, elem, data) (...others...) 3) Implement the functions: /** * LIST FUNCTION DEFINITIONS */ #define NM_TEMPLATE_DEFINE_LIST(type) \ nm_list_##type *nm_list_new_##type##_(int (*cmp)(const type e1, \ const type e2)) \ {\ nm_list_##type *list = NULL; \ list = nm_alloc(sizeof(*list)); \ list->size = 0; \ list->head = NULL; \ list->tail = NULL; \ list->cmp = cmp; \ }\ void nm_list_delete_##type##_(nm_list_##type *list, \ void (*destructor)(nm_list_elem_##type elem)) \ { \ type data; \ while(nm_list_size(list)){ \ data = nm_list_rem_##type(list, tail); \ if(destructor){ \ destructor(data); \ } \ } \ nm_free(list); \ } \ (...others...) In order to use those constructs, I have to create two files (let's call them templates.c and templates.h) . In templates.h I will have to NM_TEMPLATE_DECLARE_LIST(int), NM_TEMPLATE_DECLARE_LIST(double) , while in templates.c I will need to NM_TEMPLATE_DEFINE_LIST(int) , NM_TEMPLATE_DEFINE_LIST(double) , in order to have the code behind a list of ints, doubles and so on, generated. By following this strategy I will have to keep all my "template" declarations in two files, and in the same time, I will need to include templates.h whenever I need the data structures. It's a very "centralized" solution. Do you know other strategy in order to "imitate" (at some point) templates in C++ ? Do you know a way to improve this strategy, in order to keep things in more decentralized manner, so that I won't need the two files: templates.c and templates.h ?

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  • How to reduce redundant code when adding new c++0x rvalue reference operator overloads

    - by Inverse
    I am adding new operator overloads to take advantage of c++0x rvalue references, and I feel like I'm producing a lot of redundant code. I have a class, tree, that holds a tree of algebraic operations on double values. Here is an example use case: tree x = 1.23; tree y = 8.19; tree z = (x + y)/67.31 - 3.15*y; ... std::cout << z; // prints "(1.23 + 8.19)/67.31 - 3.15*8.19" For each binary operation (like plus), each side can be either an lvalue tree, rvalue tree, or double. This results in 8 overloads for each binary operation: // core rvalue overloads for plus: tree operator +(const tree& a, const tree& b); tree operator +(const tree& a, tree&& b); tree operator +(tree&& a, const tree& b); tree operator +(tree&& a, tree&& b); // cast and forward cases: tree operator +(const tree& a, double b) { return a + tree(b); } tree operator +(double a, const tree& b) { return tree(a) + b; } tree operator +(tree&& a, double b) { return std::move(a) + tree(b); } tree operator +(double a, tree&& b) { return tree(a) + std::move(b); } // 8 more overloads for minus // 8 more overloads for multiply // 8 more overloads for divide // etc which also has to be repeated in a way for each binary operation (minus, multiply, divide, etc). As you can see, there are really only 4 functions I actually need to write; the other 4 can cast and forward to the core cases. Do you have any suggestions for reducing the size of this code? PS: The class is actually more complex than just a tree of doubles. Reducing copies does dramatically improve performance of my project. So, the rvalue overloads are worthwhile for me, even with the extra code. I have a suspicion that there might be a way to template away the "cast and forward" cases above, but I can't seem to think of anything.

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  • C++ Class Access Specifier Verbosity

    - by PolyTex
    A "traditional" C++ class (just some random declarations) might resemble the following: class Foo { public: Foo(); explicit Foo(const std::string&); ~Foo(); enum FooState { Idle, Busy, Unknown }; FooState GetState() const; bool GetBar() const; void SetBaz(int); private: struct FooPartialImpl; void HelperFunction1(); void HelperFunction2(); void HelperFunction3(); FooPartialImpl* m_impl; // smart ptr FooState m_state; bool m_bar; int m_baz; }; I always found this type of access level specification ugly and difficult to follow if the original programmer didn't organize his "access regions" neatly. Taking a look at the same snippet in a Java/C# style, we get: class Foo { public: Foo(); public: explicit Foo(const std::string&); public: ~Foo(); public: enum FooState { Idle, Busy, Unknown }; public: FooState GetState() const; public: bool GetBar() const; public: void SetBaz(int); private: struct FooPartialImpl; private: void HelperFunction1(); private: void HelperFunction2(); private: void HelperFunction3(); private: FooPartialImpl* m_impl; // smart ptr private: FooState m_state; private: bool m_bar; private: int m_baz; }; In my opinion, this is much easier to read in a header because the access specifier is right next to the target, and not a bunch of lines away. I found this especially true when working with header-only template code that wasn't separated into the usual "*.hpp/*.inl" pair. In that scenario, the size of the function implementations overpowered this small but important information. My question is simple and stems from the fact that I've never seen anyone else actively do this in their C++ code. Assuming that I don't have a "Class View" capable IDE, are there any obvious drawbacks to using this level of verbosity? Any other style recommendations are welcome!

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  • C++ string sort like a human being?

    - by Walter Nissen
    I would like to sort alphanumeric strings the way a human being would sort them. I.e., "A2" comes before "A10", and "a" certainly comes before "Z"! Is there any way to do with without writing a mini-parser? Ideally it would also put "A1B1" before "A1B10". I see the question "Natural (human alpha-numeric) sort in Microsoft SQL 2005" with a possible answer, but it uses various library functions, as does "Sorting Strings for Humans with IComparer". Below is a test case that currently fails: #include <set> #include <iterator> #include <iostream> #include <vector> #include <cassert> template <typename T> struct LexicographicSort { inline bool operator() (const T& lhs, const T& rhs) const{ std::ostringstream s1,s2; s1 << toLower(lhs); s2 << toLower(rhs); bool less = s1.str() < s2.str(); std::cout<<s1.str()<<" "<<s2.str()<<" "<<less<<"\n"; return less; } inline std::string toLower(const std::string& str) const { std::string newString(""); for (std::string::const_iterator charIt = str.begin(); charIt!=str.end();++charIt) { newString.push_back(std::tolower(*charIt)); } return newString; } }; int main(void) { const std::string reference[5] = {"ab","B","c1","c2","c10"}; std::vector<std::string> referenceStrings(&(reference[0]), &(reference[5])); //Insert in reverse order so we know they get sorted std::set<std::string,LexicographicSort<std::string> > strings(referenceStrings.rbegin(), referenceStrings.rend()); std::cout<<"Items:\n"; std::copy(strings.begin(), strings.end(), std::ostream_iterator<std::string>(std::cout, "\n")); std::vector<std::string> sortedStrings(strings.begin(), strings.end()); assert(sortedStrings == referenceStrings); }

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  • boost::enable_if class template method

    - by aaa
    I got class with template methods that looks at this: struct undefined {}; template<typename T> struct is_undefined : mpl::false_ {}; template<> struct is_undefined<undefined> : mpl::true_ {}; template<class C> struct foo { template<class F, class V> typename boost::disable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } template<class F, class V> typename boost::enable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } }; apparently, both templates are instantiated, resulting in compile time error. is instantiation of template methods different from instantiation of free functions? I have fixed this differently, but I would like to know what is up. Thank you

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  • Poco C++ library on OSX 10.8.2: Undefined symbols for architecture x86_64

    - by Arman
    I'm trying to use Poco C++ library to do the simple http requests in C++ on Mac OS X 10.8.2. I installed Poco, copy-pasted the http_request.cc code from this tutorial, ran it with 'g++ -o http_get http_get.cc -lPocoNet', but got: Undefined symbols for architecture x86_64: "Poco::StreamCopier::copyStream(std::basic_istream<char, std::char_traits<char> >&, std::basic_ostream<char, std::char_traits<char> >&, unsigned long)", referenced from: _main in ccKuZb1g.o "Poco::URI::URI(char const*)", referenced from: _main in ccKuZb1g.o "Poco::URI::~URI()", referenced from: _main in ccKuZb1g.o "Poco::URI::getPathAndQuery() const", referenced from: _main in ccKuZb1g.o "Poco::URI::getPort() const", referenced from: _main in ccKuZb1g.o "Poco::Exception::displayText() const", referenced from: _main in ccKuZb1g.o "typeinfo for Poco::Exception", referenced from: GCC_except_table1 in ccKuZb1g.o ld: symbol(s) not found for architecture x86_64 collect2: ld returned 1 exit status Have been struggling with this for couple of hours. Any idea how to fix this? Thanks in advance!

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  • What is PHP for C# ReadBytes(stream langth)?

    - by Ole Jak
    What is PHP for C# (asuming we open some local (on server) file instead of OpenFileDialog private const int HEADER_LENGTH = 13; stream = File.OpenRead(openFileDialog.FileName); header = ReadBytes(stream, HEADER_LENGTH); And will we be able to do something like this in PHP as a next step private const byte SIGNATURE1 = 0x46; private const byte SIGNATURE2 = 0x4C; private const byte SIGNATURE3 = 0x56; if ((SIGNATURE1 != header[0]) || (SIGNATURE2 != header[1]) || (SIGNATURE3 != header[2])) throw new InvalidDataException("Not a valid FLV file!.");

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  • How can I reuse a base class function in a derived class

    - by Armen Ablak
    Let's say we have these four classes: BinaryTree, SplayTree (which is a sub-class of BinaryTree), BinaryNode and SplayNode (which is a sub-class of BinaryNode). In class BinaryTree I have 2 Find functions, like this bool Find(const T &) const; virtual Node<T> * Find(const T &, Node<T> *) const; and in SplayTree I would like to reuse the second one, because it works in the same way (for example) as in SplayTree, the only thing different is the return type, which is SplayNode. I thought it might be enough if I use this line in SplayTree.cpp using BinaryTree::Find; but it isn't. So, how can I do this?

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  • Type for use in template object to compare double values

    - by DaClown
    I got this n-dimensional point object: template <class T, unsigned int dimension> class Obj { protected: T coords[dimension]; static const unsigned int size = dimension; public: Obj() { }; Obj(T def) { for (unsigned int i = 0; i < size; ++i) coords[i]=def; }; Obj(const Obj& o) { for (unsigned int i = 0; i < size; ++i) coords[i] = o.coords[i]; } const Obj& operator= (const Obj& rhs) { if (this != &rhs) for (unsigned int i = 0; i < size; ++i) coords[i] = rhs.coords[i]; return *this; } virtual ~Obj() { }; T get (unsigned int id) { if (id >= size) throw std::out_of_range("out of range"); return coords[id]; } void set (unsigned int id, T t) { if (id >= size) throw std::out_of_range("out of range"); coords[id] = t; } }; and a 3D point class which uses Obj as base class: template <class U> class Point3DBase : public Obj<U,3> { typedef U type; public: U &x, &y, &z; public: Point3DBase() : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { }; Point3DBase(U def) : Obj<U,3>(def), x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { }; Point3DBase(U x_, U y_, U z_) : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { x = x_; y = y_; z= z_; }; Point3DBase(const Point3DBase& other) : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { x = other.x; y = other.y; z = other.z; } // several operators ... }; The operators, basically the ones for comparison, use the simple compare-the-member-object approach like: virtual friend bool operator== (const Point3DBase<U> &lhs, const Point3DBase<U> rhs) { return (lhs.x == rhs.x && lhs.y == rhs.y && lhs.z == rhs.z); } Then it occured to me that for the comparion of double values the simply equality approach is not very useful since double values should be compared with an error margin. What would be the best approach to introduce an error margin into the point? I thought about an epsDouble type as template parameter but I can't figure out how to achieve this.

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  • C++ multiple definition error

    - by user231536
    Starting with sth's answer to this question: http://stackoverflow.com/questions/3023760/c-template-specialization I was wondering how to resolve multiple definition errors if the following code is put in a header file included multiple times by different .cc files and linked together: template <typename T> class C { static const int K; static ostream& print(ostream& os, const T& t) { return os << t;} }; // general case template <typename T> const int C<T>::K = 1; // specialization template <> const int C<int>::K = 2;

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  • "Forced constness" in std::map<std::vector<int>,double> > ?

    - by Peter Jansson
    Consider this program: #include <map> #include <vector> typedef std::vector<int> IntVector; typedef std::map<IntVector,double> Map; void foo(Map& m,const IntVector& v) { Map::iterator i = m.find(v); i->first.push_back(10); }; int main() { Map m; IntVector v(10,10); foo(m,v); return 0; } Using g++ 4.4.0, I get his compilation error: test.cpp: In function 'void foo(Map&, const IntVector&)': test.cpp:8: error: passing 'const std::vector<int, std::allocator<int> >' as 'this' argument of 'void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = int, _Alloc = std::allocator<int>]' discards qualifiers I would expect this error if I was using Map::const_iterator inside foo but not using a non-const iterator. What am I missing, why do I get this error?

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  • python object to native c++ pointer

    - by Lodle
    Im toying around with the idea to use python as an embedded scripting language for a project im working on and have got most things working. However i cant seem to be able to convert a python extended object back into a native c++ pointer. So this is my class: class CGEGameModeBase { public: virtual void FunctionCall()=0; virtual const char* StringReturn()=0; }; class CGEPYGameMode : public CGEGameModeBase, public boost::python::wrapper<CGEPYGameMode> { public: virtual void FunctionCall() { if (override f = this->get_override("FunctionCall")) f(); } virtual const char* StringReturn() { if (override f = this->get_override("StringReturn")) return f(); return "FAILED TO CALL"; } }; Boost wrapping: BOOST_PYTHON_MODULE(GEGameMode) { class_<CGEGameModeBase, boost::noncopyable>("CGEGameModeBase", no_init); class_<CGEPYGameMode, bases<CGEGameModeBase> >("CGEPYGameMode", no_init) .def("FunctionCall", &CGEPYGameMode::FunctionCall) .def("StringReturn", &CGEPYGameMode::StringReturn); } and the python code: import GEGameMode def Ident(): return "Alpha" def NewGamePlay(): return "NewAlpha" def NewAlpha(): import GEGameMode import GEUtil class Alpha(GEGameMode.CGEPYGameMode): def __init__(self): print "Made new Alpha!" def FunctionCall(self): GEUtil.Msg("This is function test Alpha!") def StringReturn(self): return "This is return test Alpha!" return Alpha() Now i can call the first to functions fine by doing this: const char* ident = extract< const char* >( GetLocalDict()["Ident"]() ); const char* newgameplay = extract< const char* >( GetLocalDict()["NewGamePlay"]() ); printf("Loading Script: %s\n", ident); CGEPYGameMode* m_pGameMode = extract< CGEPYGameMode* >( GetLocalDict()[newgameplay]() ); However when i try and convert the Alpha class back to its base class (last line above) i get an boost error: TypeError: No registered converter was able to extract a C++ pointer to type class CGEPYGameMode from this Python object of type Alpha I have done alot of searching on the net but cant work out how to convert the Alpha object into its base class pointer. I could leave it as an object but rather have it as a pointer so some non python aware code can use it. Any ideas?

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