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  • C++ 'using': Should I use it or should I avoid it?

    - by Mehrdad
    I realize there are subtly different semantics for some of these, because of ADL. In general, though: Which one should I prefer (if any), and why? (Or does it depend on the situation (e.g. inline header vs. implementation?) Also: should I prefer ::std:: over std::? using namespace std; pair<string::const_iterator, string::const_iterator> f(const string &s) { return make_pair(s.begin(), s.end()); } or std::pair<std::string::const_iterator, std::string::const_iterator> f(const std::string &s) { return std::make_pair(s.begin(), s.end()); } or using std::pair; using std::string; pair<string::const_iterator, string::const_iterator> f(const string &s) { return make_pair(s.begin(), s.end()); } or std::pair<std::string::const_iterator, std::string::const_iterator> f(const std::string &s) { using std::make_pair; return make_pair(s.begin(), s.end()); } or std::pair<std::string::const_iterator, std::string::const_iterator> f(const std::string &s) { using namespace std; return make_pair(s.begin(), s.end()); } or something else? (This is assuming I don't have C++11 and auto.)

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  • design suggestion for a message decoder in delphi

    - by stanleyxu2005
    Hi All, I want to implement a RPC module. Different requests are encoded as JSON objects. They will be decoded and then be handled by a request handler. At last a corresponding response will be returned. The demo code looks as follows: type IRequestHandler = interface function Handle(const Request: TAaaRequest): TResponse; function Handle(const Request: TBbbRequest): TResponse; end; TDecoder = class class function Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; end; class function TDecoder.Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; var Method: string; Request: TObject; begin Method := Json['method'].AsString; if (Method = TAaaRequest.ClassName) then begin Request := TAaaRequest.FromJSON(Json); // Casted as TObject if Request <> nil then begin Result := RequestHandler.Handle(TAaaRequest(Request)); Request.Free; end; end else if (Method = TBbbRequest.ClassName) then begin Request := TBbbRequest.FromJSON(Json); // Casted as TObject if Request <> nil then begin Result := RequestHandler.Handle(TBbbRequest(Request)); Request.Free; end; end else Result := CreateErrorResponse('Unknown method: ' + Json.ToString); end; According to the code, the handling of different request types are very similar. If I have 100 different request types, I have to copy and paste the above code block 100 times. This is not clever. I am looking for a better way to do the same logic. My imagination is as follows: TDecoder = class private FRequestTypes: TDictionary<string, TClassInfo>; // Does this work? public constructor Create; destructor Destroy; override; function Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; end; constructor TDecoder.Create; begin FRequestTypes := TDictionary<string, TClassInfo>.Create; FRequestTypes.Add(TAaaRequest.ClassName, TAaaRequest); // Does this work? FRequestTypes.Add(TBbbRequest.ClassName, TBbbRequest); end; destructor TDecoder.Destroy; begin FRequestTypes.Free; inherited; end; function TDecoder.Decode(const Json: TJsonObject; const RequestHandler: IRequestHandler): TResponse; var Method: string; Info: TClassInfo; Request: TObject; begin Method := Json['method'].AsString; if FRequestTypes.ContainsKey(Method) then begin // An universal way Info := FRequestTypes[Method]; Request := Info.FromJSON(Json); // Casted as TObject if Request <> nil then begin Result := RequestHandler.Handle(Info(Request)); // Casted to corresponding class type (e.g. TAaaRequest or TBbbRequest) Request.Free; end; end else Result := CreateErrorResponse('Unknown method: ' + Json.ToString); end; I do not know, if I can write an universal way to handle a great number of different request types. Development environment Delphi 2010. Any hint is appreciated.

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  • Trying to write a std::iterator : Compilation error

    - by Naveen
    I am trying to write an std::iterator for the CArray<Type,ArgType> MFC class. This is what I have done till now: template <class Type, class ArgType> class CArrayIterator : public std::iterator<std::random_access_iterator_tag, ArgType> { public: CArrayIterator(CArray<Type,ArgType>& array_in, int index_in = 0) : m_pArray(&array_in), m_index(index_in) { } void operator++() { ++m_index; } void operator++(int) { ++m_index; } void operator--() { --m_index; } void operator--(int) { --m_index; } void operator+=(int n) { m_index += n; } void operator-=(int n) { m_index -= n; } typename ArgType operator*() const{ return m_pArray->GetAt(m_index); } typename ArgType operator->() const { return m_pArray->GetAt(m_index); } bool operator==(const CArrayIterator& other) const { return m_pArray == other.m_pArray && m_index == other.m_index; } bool operator!=(const CArrayIterator& other) const { return ! (operator==(other)); } private: CArray<Type,ArgType>* m_pArray; int m_index; }; I also provided two helper functions to create the iterators like this: template<class Type, class ArgType> CArrayIterator<Type,ArgType> make_begin(CArray<Type,ArgType>& array_in) { return CArrayIterator<Type,ArgType>(array_in, 0); } template<class Type, class ArgType> CArrayIterator<Type,ArgType> make_end(CArray<Type,ArgType>& array_in) { return CArrayIterator<Type,ArgType>(array_in, array_in.GetSize()); } To test the code, I wrote a simple class A and tried to use it like this: class A { public: A(int n): m_i(n) { } int get() const { return m_i; } private: int m_i; }; struct Test { void operator()(A* p) { std::cout<<p->get()<<"\n"; } }; int main(int argc, char **argv) { CArray<A*, A*> b; b.Add(new A(10)); b.Add(new A(20)); std::for_each(make_begin(b), make_end(b), Test()); return 0; } But when I compile this code, I get the following error: Error 4 error C2784: 'bool std::operator <(const std::_Tree<_Traits &,const std::_Tree<_Traits &)' : could not deduce template argument for 'const std::_Tree<_Traits &' from 'CArrayIterator' C:\Program Files\Microsoft Visual Studio 9.0\VC\include\xutility 1564 Vs8Console Can anybody throw some light on what I am doing wrong and how it can be corrected? I am using VC9 compiler if it matters.

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  • .NET Programmatically invoke screenclick doesn't work?

    - by ropstah
    I'm trying to programmatically invoke an onclick event however the click is not received/handled. Am I missing something, or is security preventing the click to be executed? I have a forms application which is invisible. Basically I would like to say: DoDoubleClick(wait, x, y) This should raise two click (mousedown+mouseup) events on screen with the specified wait interval. However the click isn't received in a Flash application in Firefox (which is running at that moment). Here's my code: Form: Public Class Form1 Private WithEvents gmh As GlobalMouseHook Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load gmh = New GlobalMouseHook() Me.Visible = false gmh.DoDoubleClick(50, 800, 600) End Sub Private Sub Form1_FormClosed(ByVal sender As System.Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles MyBase.FormClosed gmh.Dispose() End Sub Private Sub gmh_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles gmh.MouseDown End Sub Private Sub gmh_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles gmh.MouseMove End Sub Private Sub gmh_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles gmh.MouseUp End Sub End Class GlobalMouseHook class: Friend Class GlobalMouseHook Implements IDisposable Private hhk As IntPtr = IntPtr.Zero Private disposedValue As Boolean = False Public Event MouseDown As MouseEventHandler Public Event MouseUp As MouseEventHandler Public Event MouseMove As MouseEventHandler Public Sub New() Hook() End Sub Private Sub Hook() Dim hInstance As IntPtr = LoadLibrary("User32") hhk = SetWindowsHookEx(WH_MOUSE_LL, AddressOf Me.HookProc, hInstance, 0) End Sub Private Sub Unhook() UnhookWindowsHookEx(hhk) End Sub Public Sub DoDoubleClick(ByVal wait As Integer, ByVal x As Integer, ByVal y As Integer) RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Left, 1, x, y, 0)) RaiseEvent MouseUp(Me, Nothing) System.Threading.Thread.Sleep(wait) RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Left, 1, x, y, 0)) RaiseEvent MouseUp(Me, Nothing) End Sub Private Function HookProc(ByVal nCode As Integer, ByVal wParam As UInteger, ByRef lParam As MSLLHOOKSTRUCT) As Integer If nCode >= 0 Then Select Case wParam Case WM_LBUTTONDOWN RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Left, 0, lParam.pt.x, lParam.pt.y, 0)) Case WM_RBUTTONDOWN RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Right, 0, lParam.pt.x, lParam.pt.y, 0)) Case WM_MBUTTONDOWN RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Middle, 0, lParam.pt.x, lParam.pt.y, 0)) Case WM_LBUTTONUP, WM_RBUTTONUP, WM_MBUTTONUP RaiseEvent MouseUp(Nothing, Nothing) Case WM_MOUSEMOVE RaiseEvent MouseMove(Nothing, Nothing) Case WM_MOUSEWHEEL, WM_MOUSEHWHEEL Case Else Console.WriteLine(wParam) End Select End If Return CallNextHookEx(hhk, nCode, wParam, lParam) End Function Private Structure API_POINT Public x As Integer Public y As Integer End Structure Private Structure MSLLHOOKSTRUCT Public pt As API_POINT Public mouseData As UInteger Public flags As UInteger Public time As UInteger Public dwExtraInfo As IntPtr End Structure Private Const WM_MOUSEWHEEL As UInteger = &H20A Private Const WM_MOUSEHWHEEL As UInteger = &H20E Private Const WM_MOUSEMOVE As UInteger = &H200 Private Const WM_LBUTTONDOWN As UInteger = &H201 Private Const WM_LBUTTONUP As UInteger = &H202 Private Const WM_MBUTTONDOWN As UInteger = &H207 Private Const WM_MBUTTONUP As UInteger = &H208 Private Const WM_RBUTTONDOWN As UInteger = &H204 Private Const WM_RBUTTONUP As UInteger = &H205 Private Const WH_MOUSE_LL As Integer = 14 Private Delegate Function LowLevelMouseHookProc(ByVal nCode As Integer, ByVal wParam As UInteger, ByRef lParam As MSLLHOOKSTRUCT) As Integer Private Declare Auto Function LoadLibrary Lib "kernel32" (ByVal lpFileName As String) As IntPtr Private Declare Auto Function SetWindowsHookEx Lib "user32.dll" (ByVal idHook As Integer, ByVal lpfn As LowLevelMouseHookProc, ByVal hInstance As IntPtr, ByVal dwThreadId As UInteger) As IntPtr Private Declare Function CallNextHookEx Lib "user32" (ByVal hhk As IntPtr, ByVal nCode As Integer, ByVal wParam As UInteger, ByRef lParam As MSLLHOOKSTRUCT) As Integer Private Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hhk As IntPtr) As Boolean ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If Unhook() End If Me.disposedValue = True End Sub ' This code added by Visual Basic to correctly implement the disposablepattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByValdisposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub End Class

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  • T-SQL - Date rounding and normalization

    - by arun prakash
    Hi: I have a stored procedure that rounds a column with dates in (yyyy:mm:dd hh:mM:ss) to the nearest 10 minute handle (yyyy:mm:dd hh:mM) 20100303 09:46:3000 ------ 20100303 09:50 but i want to chage it to round it off to the nearest 15 minute handle: 20100303 09:46:3000 ------20100303 09:45 here is my code : IF OBJECT_ID(N'[dbo].[SPNormalizeAddWhen]') IS NOT NULL DROP PROCEDURE [dbo].[SPNormalizeAddWhen] GO CREATE PROCEDURE [dbo].[SPNormalizeAddWhen] As declare @colname nvarchar(20) set @colname='Normalized Add_When' if not exists (select * from syscolumns where id=object_id('Risk') and name=@colname) exec('alter table Risk add [' + @colname + '] datetime') declare @sql nvarchar(500) set @sql='update Risk set [' + @colname + ']=cast(DATEPART(yyyy,[add when]) as nvarchar(4)) + ''-'' + cast(DATEPART(mm,[add when]) as nvarchar(2)) + ''-'' + cast(DATEPART(dd,[add when]) as nvarchar(2)) + '' '' + cast(DATEPART(Hh,[add when]) as nvarchar(2)) + '':'' + cast(round(DATEPART(Mi,[add when]),-1) as nvarchar(2)) ' print @sql exec(@sql) GO

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  • Compiling C++ code with mingw under 12.04

    - by golemit
    I tried to setting up compiling of the C++ projects under my Ubuntu 12.04 by mingw with QT libraries. The idea was to get executable independent from variations of target Windows versions and development environments of my colleagues. It was successfully implemented under OpenSuse 12.2 with mingw32 and some additional libraries including mingw32-libqt4 and some others. Fine. However when trying to do the same under Ubuntu 12.04 with mingw-w64 including latest libraries QT-4.8.3 copied from Windows there were always errors. No luck. The typical errors in these attempts can be seen in attachments. The commands used: qmake -spec /path_to_my_conf/win32-x-g++ my_project.pro make Can someone give a hint of the problem source? I would appreciate a good advice. Serge some exctracts from LOG: ./.obj/moc_xlseditor.o:moc_xlseditor.cpp:(.rdata$_ZTV10GXlsEditor[vtable for GXlsEditor]+0xec): undefined reference to `QDialog::accept()' ./.obj/moc_xlseditor.o:moc_xlseditor.cpp:(.rdata$_ZTV10GXlsEditor[vtable for GXlsEditor]+0xf0): undefined reference to `QDialog::reject()' ./.obj/moc_xlseditor.o:moc_xlseditor.cpp:(.rdata$_ZTV10GXlsEditor[vtable for GXlsEditor]+0x104): undefined reference to `non-virtual thunk to QWidget::devType() const' ./.obj/moc_xlseditor.o:moc_xlseditor.cpp:(.rdata$_ZTV10GXlsEditor[vtable for GXlsEditor]+0x108): undefined reference to `non-virtual thunk to QWidget::paintEngine() const' ./.obj/moc_xlseditor.o:moc_xlseditor.cpp:(.rdata$_ZTV10GXlsEditor[vtable for GXlsEditor]+0x10c): undefined reference to `non-virtual thunk to QWidget::getDC() const' ./.obj/moc_xlseditor.o:moc_xlseditor.cpp:(.rdata$_ZTV10GXlsEditor[vtable for GXlsEditor]+0x110): undefined reference to `non-virtual thunk to QWidget::releaseDC(HDC__*) const' ./.obj/moc_xlseditor.o:moc_xlseditor.cpp:(.rdata$_ZTV10GXlsEditor[vtable for GXlsEditor]+0x114): undefined reference to `non-virtual thunk to QWidget::metric(QPaintDevice::PaintDeviceMetric) const' ./.obj/qrc_images.o:qrc_images.cpp:(.text+0x24): undefined reference to `__imp___Z21qRegisterResourceDataiPKhS0_S0_' ./.obj/qrc_images.o:qrc_images.cpp:(.text+0x64): undefined reference to `__imp___Z23qUnregisterResourceDataiPKhS0_S0_' collect2: ld returned 1 exit status

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  • C++ template function specialization using TCHAR on Visual Studio 2005

    - by Eli
    I'm writing a logging class that uses a templatized operator<< function. I'm specializing the template function on wide-character string so that I can do some wide-to-narrow translation before writing the log message. I can't get TCHAR to work properly - it doesn't use the specialization. Ideas? Here's the pertinent code: // Log.h header class Log { public: template <typename T> Log& operator<<( const T& x ); template <typename T> Log& operator<<( const T* x ); template <typename T> Log& operator<<( const T*& x ); ... } template <typename T> Log& Log::operator<<( const T& input ) { printf("ref"); } template <typename T> Log& Log::operator<<( const T* input ) { printf("ptr"); } template <> Log& Log::operator<<( const std::wstring& input ); template <> Log& Log::operator<<( const wchar_t* input ); And the source file // Log.cpp template <> Log& Log::operator<<( const std::wstring& input ) { printf("wstring ref"); } template <> Log& Log::operator<<( const wchar_t* input ) { printf("wchar_t ptr"); } template <> Log& Log::operator<<( const TCHAR*& input ) { printf("tchar ptr ref"); } Now, I use the following test program to exercise these functions // main.cpp - test program int main() { Log log; log << "test 1"; log << L"test 2"; std::string test3( "test3" ); log << test3; std::wstring test4( L"test4" ); log << test4; TCHAR* test5 = L"test5"; log << test4; } Running the above tests reveals the following: // Test results ptr wchar_t ptr ref wstring ref ref Unfortunately, that's not quite right. I'd really like the last one to be "TCHAR", so that I can convert it. According to Visual Studio's debugger, the when I step in to the function being called in test 5, the type is wchar_t*& - but it's not calling the appropriate specialization. Ideas? I'm not sure if it's pertinent or not, but this is on a Windows CE 5.0 device.

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  • Dynamic libraries are not allowed on iOS but what about this?

    - by tapirath
    I'm currently using LuaJIT and its FFI interface to call C functions from LUA scripts. What FFI does is to look at dynamic libraries' exported symbols and let the developer use it directly form LUA. Kind of like Python ctypes. Obviously using dynamic libraries is not permitted in iOS for security reasons. So in order to come up with a solution I found the following snippet. /* (c) 2012 +++ Filip Stoklas, aka FipS, http://www.4FipS.com +++ THIS CODE IS FREE - LICENSED UNDER THE MIT LICENSE ARTICLE URL: http://forums.4fips.com/viewtopic.php?f=3&t=589 */ extern "C" { #include <lua.h> #include <lualib.h> #include <lauxlib.h> } // extern "C" #include <cassert> // Please note that despite the fact that we build this code as a regular // executable (exe), we still use __declspec(dllexport) to export // symbols. Without doing that FFI wouldn't be able to locate them! extern "C" __declspec(dllexport) void __cdecl hello_from_lua(const char *msg) { printf("A message from LUA: %s\n", msg); } const char *lua_code = "local ffi = require('ffi') \n" "ffi.cdef[[ \n" "const char * hello_from_lua(const char *); \n" // matches the C prototype "]] \n" "ffi.C.hello_from_lua('Hello from LUA!') \n" // do actual C call ; int main() { lua_State *lua = luaL_newstate(); assert(lua); luaL_openlibs(lua); const int status = luaL_dostring(lua, lua_code); if(status) printf("Couldn't execute LUA code: %s\n", lua_tostring(lua, -1)); lua_close(lua); return 0; } // output: // A message from LUA: Hello from LUA! Basically, instead of using a dynamic library, the symbols are exported directly inside the executable file. The question is: is this permitted by Apple? Thanks.

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  • "Hello World" in C++ AMP

    - by Daniel Moth
    Some say that the equivalent of "hello world" code in the data parallel world is matrix multiplication :) Below is the before C++ AMP and after C++ AMP code. For more on what it all means, watch the recording of my C++ AMP introduction (the example below is part of the session). void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { for (int y = 0; y < M; y++) { for (int x = 0; x < N; x++) { float sum = 0; for(int i = 0; i < W; i++) { sum += vA[y * W + i] * vB[i * N + x]; } vC[y * N + x] = sum; } } } Change the function to use C++ AMP and hence offload the computation to the GPU, and now the calling code (which I am not showing) needs no changes and the overall operation gives you really nice speed up for large datasets…  #include <amp.h> using namespace concurrency; void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { array_view<const float,2> a(M, W, vA); array_view<const float,2> b(W, N, vB); array_view<writeonly<float>,2> c(M, N, vC); parallel_for_each( c.grid, [=](index<2> idx) mutable restrict(direct3d) { float sum = 0; for(int i = 0; i < a.x; i++) { sum += a(idx.y, i) * b(i, idx.x); } c[idx] = sum; } ); } Again, you can understand the elements above, by using my C++ AMP presentation slides and recording… Stay tuned for more… Comments about this post welcome at the original blog.

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  • What should a domain object's validation cover?

    - by MarcoR88
    I'm trying to figure out how to do validation of domain objects that need external resources, such as data mappers/dao Firstly here's my code class User { const INVALID_ID = 1; const INVALID_NAME = 2; const INVALID_EMAIL = 4; int getID(); void setID(Int i); string getName(); void setName(String s); string getEmail(); void setEmail(String s); int getErrorsForInsert(); // returns a bitmask for INVALID_* constants int getErrorsForUpdate(); } My worries are about the uniqueness of the email, checking it would require the storage layer. Reading others' code seems that two solutions are equally accepted: both perform the unique validation in data mapper but some set an error state to the DO user.addError(User.INVALID_EMAIL) while others prefer to throw a totally different type of exception that covers only persistence, like: UserStorageException { const INVALID_EMAIL = 1; const INVALID_CITY = 2; } What are the pros and cons of these solutions?

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  • sql server swap data between rows problem

    - by AmRoSH
    I was asking b4 about swaping query to swap data between rows in same table and i got that qurey ALTER PROCEDURE [dbo].[VehicleReservationsSwap] -- Add the parameters for the stored procedure here (@FirstVehicleID int, @secondVehicleID int, @WhereClause nvarchar(2000)) AS BEGIN Create Table #Temp ( VehicleID int ,VehicleType nvarchar(100) ,JoinId int ) DECLARE @SQL varchar(8000) SET @SQL ='Insert into #Temp (VehicleID,VehicleType,JoinId) SELECT VehicleID,VehicleType,CASE WHEN VehicleID = ' + Cast(@FirstVehicleID as varchar(10)) + ' then ' + Cast(@secondVehicleID as varchar(10)) + ' ELSE ' + Cast(@FirstVehicleID as varchar(10)) + ' END AS JoinId FROM Reservations WHERE VehicleID in ( ' + Cast(@FirstVehicleID as varchar(10)) + ' , ' + Cast(@secondVehicleID as varchar(10)) + ' )' + @WhereClause EXEC(@SQL) --swap values UPDATE y SET y.VehicleID = #Temp.VehicleID ,y.VehicleType = #Temp.VehicleType FROM Reservations y INNER JOIN #Temp ON y.VehicleID = #Temp.JoinId WHERE y.VehicleID in (@FirstVehicleID,@secondVehicleID) Drop Table #Temp END this query take 2 parameters and swaping all rows returned for each parameter. the problem is the query swaps just if each parameter (forign key) has values I need to make swaping in case if one of them has no vlue. I hope if some one can help me in that . Thanks,

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  • Extract all related class type aliasing and enum into one file or not

    - by Chen OT
    I have many models in my project, and some other classes just need the class declaration and pointer type aliasing. It does not need to know the class definition, so I don't want to include the model header file. I extract all the model's declaration into one file to let every classes reference one file. model_forward.h class Cat; typedef std::shared_ptr<Cat> CatPointerType; typedef std::shared_ptr<const Cat> CatConstPointerType; class Dog; typedef std::shared_ptr<Dog> DogPointerType; typedef std::shared_ptr<const Dog> DogConstPointerType; class Fish; typedef std::shared_ptr<Fish> FishPointerType; typedef std::shared_ptr<const Fish> FishConstPointerType; enum CatType{RED_CAT, YELLOW_CAT, GREEN_CAT, PURPLE_CAT} enum DogType{HATE_CAT_DOG, HUSKY, GOLDEN_RETRIEVER} enum FishType{SHARK, OCTOPUS, SALMON} Is it acceptable practice? Should I make every unit, which needs a class declaration, depends on one file? Does it cause high coupling? Or I should put these pointer type aliasing and enum definition inside the class back? cat.h class Cat { typedef std::shared_ptr<Cat> PointerType; typedef std::shared_ptr<const Cat> ConstPointerType; enum Type{RED_CAT, YELLOW_CAT, GREEN_CAT, PURPLE_CAT} ... }; dog.h class Dog { typedef std::shared_ptr<Dog> PointerType; typedef std::shared_ptr<const Dog> ConstPointerType; enum Type{HATE_CAT_DOG, HUSKY, GOLDEN_RETRIEVER} ... } fish.h class Fish { ... }; Any suggestion will be helpful.

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  • a question in NS c programming

    - by bahar
    Hi I added a new patch to my NS and I've seen thise two errors. Does anyone Know what I can do? error: specialization of 'bool std::less<_Tp::operator()(const _Tp&, const _Tp&) const [with _Tp = _AlgorithmTime]' in different namespace from definition of 'bool std::less<_Tp::operator()(const _Tp&, const _Tp&) const [with _Tp = _AlgorithmTime]' and the errors are from this code typedef struct _AlgorithmTime { // Round. int round; // Fase. int fase; // Valore massimo di fase. int last_fase; public: _AlgorithmTime() { round = 0; fase = 0; last_fase = 0; } // Costruttore. _AlgorithmTime(int r, int f, int l) { round = r; fase = f; last_fase = l; } // Costruttore. _AlgorithmTime(const _AlgorithmTime & t) { round = t.round; fase = t.fase; last_fase = t.last_fase; } // Operatore di uguaglianza. bool operator== (struct _AlgorithmTime & t) { return ((t.fase == fase) && (t.round == round)); } // Operatore minore. bool operator < (struct _AlgorithmTime & t) { if (round < t.round) return true; if (round > t.round) return false; if (fase < t.fase) return true; return false; } // Operatore maggiore. bool operator > (struct _AlgorithmTime & t) { if (round > t.round) return true; if (round < t.round) return false; if (fase > t.fase) return true; return false; } void operator++ () { if (fase == last_fase) { round++; fase = 0; return; } fase++; } void operator-- () { if (fase == 0) { round--; fase = last_fase; return; } fase--; } }AlgorithmTime; template< bool std::less::operator()(const AlgorithmTime & t1, const AlgorithmTime & t2)const { if (t1.round < t2.round) return true; if (t1.round t2.round) return false; if (t1.fase < t2.fase) return true; return false; } Thanks

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  • Create a date from Credit Card expire in MMYY format

    - by Sophtware
    I need to convert a credit card expire field from MMYY to a date field I can use in a MS SQL query so I can compute when credit cards are expiring in the future. Basically, I need to go from MMYY to MM/DD/YYYY, where the day part could just be '01' (the first of the month). I'm looking for credit cards that are expiring next month from a database. The problem I'm running into is when next month is the first month of the next year. Here's the code I have for determining expired card: (CAST(SUBSTRING(CCExpire,3,2) as int) + 2000 < YEAR(GETDATE())) or ( (CAST(SUBSTRING(CCExpire,3,2) as int) + 2000 = YEAR(GETDATE())) AND (CAST(SUBSTRING(CCExpire,1,2) as int) < MONTH(GETDATE())) ) And here's the code for cards expiring this month: (CAST(SUBSTRING(CCExpire,3,2) as int) + 2000 = YEAR(GETDATE())) AND (CAST(SUBSTRING(CCExpire,1,2) as int) = MONTH(GETDATE())) Now I need code for cards expiring next month...

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  • Error in SQL. Can not find it.

    - by kmsboy
    Error in SQL. Can not find it. DECLARE @year VARCHAR (4), @month VARCHAR (2), @day VARCHAR (2), @weekday VARCHAR (2), @hour VARCHAR (2), @archivePath VARCHAR (128), @archiveName VARCHAR (128), @archiveFullName VARCHAR (128) SET @year = CAST(DATEPART(yyyy, GETDATE()) AS VARCHAR) SET @month = CAST(DATEPART(mm, GETDATE()) AS VARCHAR) SET @day = CAST(DATEPART(dd, GETDATE()) AS VARCHAR) SET @weekday = CAST(DATEPART (dw, GETDATE()) AS VARCHAR) SET @hour = CAST(DATEPART (hh, GETDATE()) AS VARCHAR) SET @archivePath = 'd:\1c_new\backupdb\' SET @archiveName = 'TransactionLog_' + @year + '_' + @month + '_' + @day + '_' + @hour + '.bak' SET @archiveFullName = @archivePath + @archiveName BACKUP LOG [xxx] TO DISK = @archiveFullName WITH INIT , NOUNLOAD , NAME = N'?????????? ??? ??????????', SKIP , STATS = 10, DESCRIPTION = N'?????????? ??? ??????????', NOFORMAT

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  • PHP use of undefined constant error

    - by user272899
    Using a great script to grab details from imdb, I would like to thank Fabian Beiner. Just one error i have encountered with it is: Use of undefined constant sys_get_temp_dir assumed 'sys_get_temp_dir' in '/path/to/directory' on line 49 This is the complete script <?php /** * IMDB PHP Parser * * This class can be used to retrieve data from IMDB.com with PHP. This script will fail once in * a while, when IMDB changes *anything* on their HTML. Guys, it's time to provide an API! * * @link http://fabian-beiner.de * @copyright 2010 Fabian Beiner * @author Fabian Beiner (mail [AT] fabian-beiner [DOT] de) * @license MIT License * * @version 4.1 (February 1st, 2010) * */ class IMDB { private $_sHeader = null; private $_sSource = null; private $_sUrl = null; private $_sId = null; public $_bFound = false; private $_oCookie = '/tmp/imdb-grabber-fb.tmp'; const IMDB_CAST = '#<a href="/name/(\w+)/" onclick="\(new Image\(\)\)\.src=\'/rg/castlist/position-(\d|\d\d)/images/b\.gif\?link=/name/(\w+)/\';">(.*)</a>#Ui'; const IMDB_COUNTRY = '#<a href="/Sections/Countries/(\w+)/">#Ui'; const IMDB_DIRECTOR = '#<a href="/name/(\w+)/" onclick="\(new Image\(\)\)\.src=\'/rg/directorlist/position-(\d|\d\d)/images/b.gif\?link=name/(\w+)/\';">(.*)</a><br/>#Ui'; const IMDB_GENRE = '#<a href="/Sections/Genres/(\w+|\w+\-\w+)/">(\w+|\w+\-\w+)</a>#Ui'; const IMDB_MPAA = '#<h5><a href="/mpaa">MPAA</a>:</h5>\s*<div class="info-content">\s*(.*)\s*</div>#Ui'; const IMDB_PLOT = '#<h5>Plot:</h5>\s*<div class="info-content">\s*(.*)\s*<a#Ui'; const IMDB_POSTER = '#<a name="poster" href="(.*)" title="(.*)"><img border="0" alt="(.*)" title="(.*)" src="(.*)" /></a>#Ui'; const IMDB_RATING = '#<b>(\d\.\d/10)</b>#Ui'; const IMDB_RELEASE_DATE = '#<h5>Release Date:</h5>\s*\s*<div class="info-content">\s*(.*) \((.*)\)#Ui'; const IMDB_RUNTIME = '#<h5>Runtime:</h5>\s*<div class="info-content">\s*(.*)\s*</div>#Ui'; const IMDB_SEARCH = '#<b>Media from&nbsp;<a href="/title/tt(\d+)/"#i'; const IMDB_TAGLINE = '#<h5>Tagline:</h5>\s*<div class="info-content">\s*(.*)\s*</div>#Ui'; const IMDB_TITLE = '#<title>(.*) \((.*)\)</title>#Ui'; const IMDB_URL = '#http://(.*\.|.*)imdb.com/(t|T)itle(\?|/)(..\d+)#i'; const IMDB_VOTES = '#&nbsp;&nbsp;<a href="ratings" class="tn15more">(.*) votes</a>#Ui'; const IMDB_WRITER = '#<a href="/name/(\w+)/" onclick="\(new Image\(\)\)\.src=\'/rg/writerlist/position-(\d|\d\d)/images/b\.gif\?link=name/(\w+)/\';">(.*)</a>#Ui'; const IMDB_REDIRECT = '#Location: (.*)#'; /** * Public constructor. * * @param string $sSearch */ public function __construct($sSearch) { if (function_exists(sys_get_temp_dir)) { $this->_oCookie = tempnam(sys_get_temp_dir(), 'imdb'); } $sUrl = $this->findUrl($sSearch); if ($sUrl) { $bFetch = $this->fetchUrl($this->_sUrl); $this->_bFound = true; } } /** * Little REGEX helper. * * @param string $sRegex * @param string $sContent * @param int $iIndex; */ private function getMatch($sRegex, $sContent, $iIndex = 1) { preg_match($sRegex, $sContent, $aMatches); if ($iIndex > count($aMatches)) return; if ($iIndex == null) { return $aMatches; } return $aMatches[(int)$iIndex]; } /** * Little REGEX helper, I should find one that works for both... ;/ * * @param string $sRegex * @param int $iIndex; */ private function getMatches($sRegex, $iIndex = null) { preg_match_all($sRegex, $this->_sSource, $aMatches); if ((int)$iIndex) return $aMatches[$iIndex]; return $aMatches; } /** * Save an image. * * @param string $sUrl */ private function saveImage($sUrl) { $sUrl = trim($sUrl); $bolDir = false; if (!is_dir(getcwd() . '/posters')) { if (mkdir(getcwd() . '/posters', 0777)) { $bolDir = true; } } $sFilename = getcwd() . '/posters/' . preg_replace("#[^0-9]#", "", basename($sUrl)) . '.jpg'; if (file_exists($sFilename)) { return 'posters/' . basename($sFilename); } if (is_dir(getcwd() . '/posters') OR $bolDir) { if (function_exists('curl_init')) { $oCurl = curl_init($sUrl); curl_setopt_array($oCurl, array ( CURLOPT_VERBOSE => 0, CURLOPT_HEADER => 0, CURLOPT_RETURNTRANSFER => 1, CURLOPT_TIMEOUT => 5, CURLOPT_CONNECTTIMEOUT => 5, CURLOPT_REFERER => $sUrl, CURLOPT_BINARYTRANSFER => 1)); $sOutput = curl_exec($oCurl); curl_close($oCurl); $oFile = fopen($sFilename, 'x'); fwrite($oFile, $sOutput); fclose($oFile); return 'posters/' . basename($sFilename); } else { $oImg = imagecreatefromjpeg($sUrl); imagejpeg($oImg, $sFilename); return 'posters/' . basename($sFilename); } return false; } return false; } /** * Find a valid Url out of the passed argument. * * @param string $sSearch */ private function findUrl($sSearch) { $sSearch = trim($sSearch); if ($aUrl = $this->getMatch(self::IMDB_URL, $sSearch, 4)) { $this->_sId = 'tt' . preg_replace('[^0-9]', '', $aUrl); $this->_sUrl = 'http://www.imdb.com/title/' . $this->_sId .'/'; return true; } else { $sTemp = 'http://www.imdb.com/find?s=all&q=' . str_replace(' ', '+', $sSearch) . '&x=0&y=0'; $bFetch = $this->fetchUrl($sTemp); if( $this->isRedirect() ) { return true; } else if ($bFetch) { if ($strMatch = $this->getMatch(self::IMDB_SEARCH, $this->_sSource)) { $this->_sUrl = 'http://www.imdb.com/title/tt' . $strMatch . '/'; unset($this->_sSource); return true; } } } return false; } /** * Find if result is redirected directly to exact movie. */ private function isRedirect() { if ($strMatch = $this->getMatch(self::IMDB_REDIRECT, $this->_sHeader)) { $this->_sUrl = $strMatch; unset($this->_sSource); unset($this->_sHeader); return true; } return false; } /** * Fetch data from given Url. * Uses cURL if installed, otherwise falls back to file_get_contents. * * @param string $sUrl * @param int $iTimeout; */ private function fetchUrl($sUrl, $iTimeout = 15) { $sUrl = trim($sUrl); if (function_exists('curl_init')) { $oCurl = curl_init($sUrl); curl_setopt_array($oCurl, array ( CURLOPT_VERBOSE => 0, CURLOPT_HEADER => 1, CURLOPT_FRESH_CONNECT => true, CURLOPT_RETURNTRANSFER => 1, CURLOPT_TIMEOUT => (int)$iTimeout, CURLOPT_CONNECTTIMEOUT => (int)$iTimeout, CURLOPT_REFERER => $sUrl, CURLOPT_FOLLOWLOCATION => 0, CURLOPT_COOKIEFILE => $this->_oCookie, CURLOPT_COOKIEJAR => $this->_oCookie, CURLOPT_USERAGENT => 'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6' )); $sOutput = curl_exec($oCurl); if ($sOutput === false) { return false; } $aInfo = curl_getinfo($oCurl); if ($aInfo['http_code'] != 200 && $aInfo['http_code'] != 302) { return false; } $sTmpHeader = strpos($sOutput, "\r\n\r\n"); $this->_sHeader = substr($sOutput, 0, $sTmpHeader); $this->_sSource = str_replace("\n", '', substr($sOutput, $sTmpHeader+1)); curl_close($oCurl); return true; } else { $sOutput = @file_get_contents($sUrl, 0); if (strpos($http_response_header[0], '200') === false){ return false; } $this->_sSource = str_replace("\n", '', (string)$sOutput); return true; } return false; } /** * Returns the cast. */ public function getCast($iOutput = null, $bMore = true) { if ($this->_sSource) { $sReturned = $this->getMatches(self::IMDB_CAST, 4); if (is_array($sReturned)) { if ($iOutput) { foreach ($sReturned as $i => $sName) { if ($i >= $iOutput) break; $sReturn[] = $sName; } return implode(' / ', $sReturn) . (($bMore) ? '&hellip;' : ''); } return implode(' / ', $sReturned); } return $sReturned; } return 'n/A'; } /** * Returns the cast as links. */ public function getCastAsUrl($iOutput = null, $bMore = true) { if ($this->_sSource) { $sReturned1 = $this->getMatches(self::IMDB_CAST, 4); $sReturned2 = $this->getMatches(self::IMDB_CAST, 3); if (is_array($sReturned1)) { if ($iOutput) { foreach ($sReturned1 as $i => $sName) { if ($i >= $iOutput) break; $aReturn[] = '<a href="http://www.imdb.com/name/' . $sReturned2[$i] . '/">' . $sName . '</a>';; } return implode(' / ', $aReturn) . (($bMore) ? '&hellip;' : ''); } return implode(' / ', $sReturned); } return '<a href="http://www.imdb.com/name/' . $sReturned2 . '/">' . $sReturned1 . '</a>';; } return 'n/A'; } /** * Returns the countr(y|ies). */ public function getCountry() { if ($this->_sSource) { $sReturned = $this->getMatches(self::IMDB_COUNTRY, 1); if (is_array($sReturned)) { return implode(' / ', $sReturned); } return $sReturned; } return 'n/A'; } /** * Returns the countr(y|ies) as link(s). */ public function getCountryAsUrl() { if ($this->_sSource) { $sReturned = $this->getMatches(self::IMDB_COUNTRY, 1); if (is_array($sReturned)) { foreach ($sReturned as $sCountry) { $aReturn[] = '<a href="http://www.imdb.com/Sections/Countries/' . $sCountry . '/">' . $sCountry . '</a>'; } return implode(' / ', $aReturn); } return '<a href="http://www.imdb.com/Sections/Countries/' . $sReturned . '/">' . $sReturned . '</a>'; } return 'n/A'; } /** * Returns the director(s). */ public function getDirector() { if ($this->_sSource) { $sReturned = $this->getMatches(self::IMDB_DIRECTOR, 4); if (is_array($sReturned)) { return implode(' / ', $sReturned); } return $sReturned; } return 'n/A'; } /** * Returns the director(s) as link(s). */ public function getDirectorAsUrl() { if ($this->_sSource) { $sReturned1 = $this->getMatches(self::IMDB_DIRECTOR, 4); $sReturned2 = $this->getMatches(self::IMDB_DIRECTOR, 1); if (is_array($sReturned1)) { foreach ($sReturned1 as $i => $sDirector) { $aReturn[] = '<a href="http://www.imdb.com/name/' . $sReturned2[$i] . '/">' . $sDirector . '</a>'; } return implode(' / ', $aReturn); } return '<a href="http://www.imdb.com/name/' . $sReturned2 . '/">' . $sReturned1 . '</a>'; } return 'n/A'; } /** * Returns the genre(s). */ public function getGenre() { if ($this->_sSource) { $sReturned = $this->getMatches(self::IMDB_GENRE, 1); if (is_array($sReturned)) { return implode(' / ', $sReturned); } return $sReturned; } return 'n/A'; } /** * Returns the genre(s) as link(s). */ public function getGenreAsUrl() { if ($this->_sSource) { $sReturned = $this->getMatches(self::IMDB_GENRE, 1); if (is_array($sReturned)) { foreach ($sReturned as $i => $sGenre) { $aReturn[] = '<a href="http://www.imdb.com/Sections/Genres/' . $sGenre . '/">' . $sGenre . '</a>'; } return implode(' / ', $aReturn); } return '<a href="http://www.imdb.com/Sections/Genres/' . $sReturned . '/">' . $sReturned . '</a>'; } return 'n/A'; } /** * Returns the mpaa. */ public function getMpaa() { if ($this->_sSource) { return implode('' , $this->getMatches(self::IMDB_MPAA, 1)); } return 'n/A'; } /** * Returns the plot. */ public function getPlot() { if ($this->_sSource) { return implode('' , $this->getMatches(self::IMDB_PLOT, 1)); } return 'n/A'; } /** * Download the poster, cache it and return the local path to the image. */ public function getPoster() { if ($this->_sSource) { if ($sPoster = $this->saveImage(implode("", $this->getMatches(self::IMDB_POSTER, 5)), 'poster.jpg')) { return $sPoster; } return implode('', $this->getMatches(self::IMDB_POSTER, 5)); } return 'n/A'; } /** * Returns the rating. */ public function getRating() { if ($this->_sSource) { return implode('', $this->getMatches(self::IMDB_RATING, 1)); } return 'n/A'; } /** * Returns the release date. */ public function getReleaseDate() { if ($this->_sSource) { return implode('', $this->getMatches(self::IMDB_RELEASE_DATE, 1)); } return 'n/A'; } /** * Returns the runtime of the current movie. */ public function getRuntime() { if ($this->_sSource) { return implode('', $this->getMatches(self::IMDB_RUNTIME, 1)); } return 'n/A'; } /** * Returns the tagline. */ public function getTagline() { if ($this->_sSource) { return implode('', $this->getMatches(self::IMDB_TAGLINE, 1)); } return 'n/A'; } /** * Get the release date of the current movie. */ public function getTitle() { if ($this->_sSource) { return implode('', $this->getMatches(self::IMDB_TITLE, 1)); } return 'n/A'; } /** * Returns the url. */ public function getUrl() { return $this->_sUrl; } /** * Get the votes of the current movie. */ public function getVotes() { if ($this->_sSource) { return implode('', $this->getMatches(self::IMDB_VOTES, 1)); } return 'n/A'; } /** * Get the year of the current movie. */ public function getYear() { if ($this->_sSource) { return implode('', $this->getMatches(self::IMDB_TITLE, 2)); } return 'n/A'; } /** * Returns the writer(s). */ public function getWriter() { if ($this->_sSource) { $sReturned = $this->getMatches(self::IMDB_WRITER, 4); if (is_array($sReturned)) { return implode(' / ', $sReturned); } return $sReturned; } return 'n/A'; } /** * Returns the writer(s) as link(s). */ public function getWriterAsUrl() { if ($this->_sSource) { $sReturned1 = $this->getMatches(self::IMDB_WRITER, 4); $sReturned2 = $this->getMatches(self::IMDB_WRITER, 1); if (is_array($sReturned1)) { foreach ($sReturned1 as $i => $sWriter) { $aReturn[] = '<a href="http://www.imdb.com/name/' . $sReturned2[$i] . '/">' . $sWriter . '</a>'; } return implode(' / ', $aReturn); } return '<a href="http://www.imdb.com/name/' . $sReturned2 . '/">' . $sReturned1 . '</a>'; } return 'n/A'; } } ?>

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  • error: switch quantity not an integer

    - by nikeunltd
    I have researched my issue all over StackOverflow and multi-google links, and I am still confused. I figured the best thing for me is ask... Im creating a simple command line calculator. Here is my code so far: const std::string Calculator::SIN("sin"); const std::string Calculator::COS("cos"); const std::string Calculator::TAN("tan"); const std::string Calculator::LOG( "log" ); const std::string Calculator::LOG10( "log10" ); void Calculator::set_command( std::string cmd ) { for(unsigned i = 0; i < cmd.length(); i++) { cmd[i] = tolower(cmd[i]); } command = cmd; } bool Calculator::is_legal_command() const { switch(command) { case TAN: case SIN: case COS: case LOG: case LOG10: return true; break; default: return false; break; } } the error i get is: Calculator.cpp: In member function 'bool Calculator::is_trig_command() const': Calculator.cpp: error: switch quantity not an integer Calculator.cpp: error: 'Calculator::TAN' cannot appear in a constant-expression Calculator.cpp: error: 'Calculator::SIN' cannot appear in a constant-expression Calculator.cpp: error: 'Calculator::COS' cannot appear in a constant-expression The mighty internet, it says strings are allowed to be used in switch statements. Thanks everyone, I appreciate your help.

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  • How to encrypt an NSString in Objective C with DES in ECB-Mode?

    - by blauesocke
    Hi, I am trying to encrypt an NSString in Objective C on the iPhone. At least I wan't to get a string like "TmsbDaNG64lI8wC6NLhXOGvfu2IjLGuEwc0CzoSHnrs=" when I encode "us=foo;pw=bar;pwAlg=false;" by using this key: "testtest". My problem for now is, that CCCrypt always returns "4300 - Parameter error" and I have no more idea why. This is my code (the result of 5 hours google and try'n'error): NSString *token = @"us=foo;pw=bar;pwAlg=false;"; NSString *key = @"testtest"; const void *vplainText; size_t plainTextBufferSize; plainTextBufferSize = [token length]; vplainText = (const void *) [token UTF8String]; CCCryptorStatus ccStatus; uint8_t *bufferPtr = NULL; size_t bufferPtrSize = 0; size_t *movedBytes; bufferPtrSize = (plainTextBufferSize + kCCBlockSize3DES) & ~(kCCBlockSize3DES - 1); bufferPtr = malloc( bufferPtrSize * sizeof(uint8_t)); memset((void *)bufferPtr, 0x0, bufferPtrSize); // memset((void *) iv, 0x0, (size_t) sizeof(iv)); NSString *initVec = @"init Vec"; const void *vkey = (const void *) [key UTF8String]; const void *vinitVec = (const void *) [initVec UTF8String]; ccStatus = CCCrypt(kCCEncrypt, kCCAlgorithmDES, kCCOptionECBMode, vkey, //"123456789012345678901234", //key kCCKeySizeDES, NULL,// vinitVec, //"init Vec", //iv, vplainText, //"Your Name", //plainText, plainTextBufferSize, (void *)bufferPtr, bufferPtrSize, movedBytes); NSString *result; NSData *myData = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes]; result = [myData base64Encoding];

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  • Am I deleting this properly?

    - by atch
    I have some struct: struct A { const char* name_; A* left_; A* right_; A(const char* name):name_(name), left_(nullptr), right_(nullptr){} A(const A&); //A(const A*);//ToDo A& operator=(const A&); ~A() { /*ToDo*/ }; }; /*Just to compile*/ A& A::operator=(const A& pattern) { //check for self-assignment if (this != &pattern) { void* p = new char[sizeof(A)]; } return *this; } A::A(const A& pat) { void* p = new char[sizeof(A)]; A* tmp = new (p) A("tmp"); tmp->~A(); delete tmp;//I WONDER IF HERE I SHOULD USE DIFFERENT delete[]? } int _tmain(int argc, _TCHAR* argv[]) { A a("a"); A b = a; cin.get(); return 0; } Guys I know this is far from ideal and far from finished. But please don't tell me the answer how to do it properly. I'm trying to figure it out myself. The only think I would like to know if I'm deleting my memory in proper way. Thanks.

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  • Custom types as key for a map - C++

    - by Appu
    I am trying to assign a custom type as a key for std::map. Here is the type which I am using as key. struct Foo { Foo(std::string s) : foo_value(s){} bool operator<(const Foo& foo1) { return foo_value < foo1.foo_value; } bool operator>(const Foo& foo1) { return foo_value > foo1.foo_value; } std::string foo_value; }; When used with std::map, I am getting the following error. error C2678: binary '<' : no operator found which takes a left-hand operand of type 'const Foo' (or there is no acceptable conversion) c:\program files\microsoft visual studio 8\vc\include\functional 143 If I change the struct like the below, everything worked. struct Foo { Foo(std::string s) : foo_value(s) {} friend bool operator<(const Foo& foo,const Foo& foo1) { return foo.foo_value < foo1.foo_value; } friend bool operator>(const Foo& foo,const Foo& foo1) { return foo.foo_value > foo1.foo_value; } std::string foo_value; }; Nothing changed except making the operator overloads as friend. I am wondering why my first code is not working? Any thoughts?

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  • function objects versus function pointers

    - by kumar_m_kiran
    Hi All, I have two questions related to function objects and function pointers, Question : 1 When I read the different uses sort algorithm of STL, I see that the third parameter can be a function objects, below is an example class State { public: //... int population() const; float aveTempF() const; //... }; struct PopLess : public std::binary_function<State,State,bool> { bool operator ()( const State &a, const State &b ) const { return popLess( a, b ); } }; sort( union, union+50, PopLess() ); Question : Now, How does the statement, sort(union, union+50,PopLess()) work? PopLess() must be resolved into something like PopLess tempObject.operator() which would be same as executing the operator () function on a temporary object. I see this as, passing the return value of overloaded operation i.e bool (as in my example) to sort algorithm. So then, How does sort function resolve the third parameter in this case? Question : 2 Question Do we derive any particular advantage of using function objects versus function pointer? If we use below function pointer will it derive any disavantage? inline bool popLess( const State &a, const State &b ) { return a.population() < b.population(); } std::sort( union, union+50, popLess ); // sort by population PS : Both the above references(including example) are from book "C++ Common Knowledge: Essential Intermediate Programming" by "Stephen C. Dewhurst". I was unable to decode the topic content, thus have posted for help. Thanks in advance for your help.

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  • Immutable classes in C++

    - by ereOn
    Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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  • C++0x rvalue references and temporaries

    - by Doug
    (I asked a variation of this question on comp.std.c++ but didn't get an answer.) Why does the call to f(arg) in this code call the const ref overload of f? void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } My intuition says that the f(string &&) overload should be chosen, because arg needs to be converted to a temporary no matter what, and the temporary matches the rvalue reference better than the lvalue reference. This is not what happens in GCC and MSVC. In at least G++ and MSVC, any lvalue does not bind to an rvalue reference argument, even if there is an intermediate temporary created. Indeed, if the const ref overload isn't present, the compilers diagnose an error. However, writing f(arg + 0) or f(std::string(arg)) does choose the rvalue reference overload as you would expect. From my reading of the C++0x standard, it seems like the implicit conversion of a const char * to a string should be considered when considering if f(string &&) is viable, just as when passing a const lvalue ref arguments. Section 13.3 (overload resolution) doesn't differentiate between rvalue refs and const references in too many places. Also, it seems that the rule that prevents lvalues from binding to rvalue references (13.3.3.1.4/3) shouldn't apply if there's an intermediate temporary - after all, it's perfectly safe to move from the temporary. Is this: Me misreading/misunderstand the standard, where the implemented behavior is the intended behavior, and there's some good reason why my example should behave the way it does? A mistake that the compiler vendors have somehow all made? Or a mistake based on common implementation strategies? Or a mistake in e.g. GCC (where this lvalue/rvalue reference binding rule was first implemented), that was copied by other vendors? A defect in the standard, or an unintended consequence, or something that should be clarified?

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  • How do I refactor code into a subroutine but allow for early exit?

    - by deworde
    There's a really obvious refactoring opportunity in this (working) code. bool Translations::compatibleNICodes(const Rule& rule, const std::vector<std::string>& nicodes) { bool included = false; // Loop through the ni codes. for(std::vector<std::string> iter = nicodes.begin(); iter != nicodes.end(); ++iter) { // Match against the ni codes of the rule if(rule.get_ni1() == *iter) { // If there's a match, check if the rule is include or exclude const std::string flag = rule.get_op1(); // If include, code is included unless a later rule excludes it if(flag == "INCLUDE"){ included = true; } // If exclude, code is specifically excluded else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni2() == *iter) { const std::string flag = rule.get_op2(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni3() == *iter) { const std::string flag = rule.get_op3(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni4() == *iter) { const std::string flag = rule.get_op4(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni5() == *iter) { const std::string flag = rule.get_op5(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } } return included; } The problem is that I can't get around the problem that I want to exit early if it's an exclude statement. Note that I can't change the structure of the Rule class. Any advice?

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  • Optimization in Common Decalaration

    - by Pratik
    Its a 3-tier ASP.NET Website Project In Data Layer there is class "Common Decalaration" in which lot of common things are mentioned. Something this way : public class CommonDeclartion { #region Common Messages public const string RECORD_INSERT_MSG = "Record Inserted Successfully "; public const string RECORD_UPDATE_MSG = "Record Updated Successfully"; public const string RECORD_DELETE_MSG = "Record Deleted Successfully"; public const string ERROR_MSG = "Error Ocuured while Perfoming This Action."; public const string UserID_Incorrect = "Please Enter The Correct User ID."; public const string RECORD_ALREADY_EXIT = "Record Already Exit"; public const string NO_RECORD = "No Record found."; #endregion } Can this be more optimized in terms of : 1.Perfomance 2.Security(if any) 3.Code Readablity or Reusablity I thought of using enum but can't figure that out : enum CommonMessages { RECORD_INSERT_MSG "Record Inserted Successfully.", RECORD_UPDATE_MSG "Record Updated Successfully.", RECORD_DELETE_MSG "Record Deleted Successfully.", ERROR_MSG "Error Ocuured while Perfoming This Action.", UserID_Incorrect "Please Enter The Correct User ID.", RECORD_ALREADY_EXIT "Record Already Exit.", NO_RECORD "No Record found.", } or else should keep them in some collections like dictionary/NameValueCollection or so or i have to keep them in XML in form of key/value pair and reterive from it ? What can be better way keeping in mind 1.Perfomance 2.Security(if any) 3.Code Readablity or Reusablity

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