(C++) Lazy_init

 

 

Lazy_init is a class

with lazy initialization.

Technical facts

 

 

 

 

 

 

./CppLazy_init/CppLazy_init.pri

 

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INCLUDEPATH += \     ../../Classes/CppLazy_init SOURCES += \     ../../Classes/CppLazy_init/lazy_init.cpp HEADERS  += \     ../../Classes/CppLazy_init/lazy_init.h OTHER_FILES += \     ../../Classes/CppLazy_init/Licence.txt

 

 

 

 

 

./CppLazy_init/lazy_init.h

 

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//--------------------------------------------------------------------------- /* Lazy_init. Class to postpone constructor call upon first use. Copyright 2012-2015 Richel Bilderbeek This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ //--------------------------------------------------------------------------- //From http://www.richelbilderbeek.nl/CppLazy_init.htm //--------------------------------------------------------------------------- #ifndef LAZY_INIT_H #define LAZY_INIT_H #include <string> #include <vector> #include <boost/scoped_ptr.hpp> namespace ribi { /* //How to do this with variadic function templates??? template <class T, typename ... Args> struct LazyInit {   LazyInit(const Args ... args)     : m_args(args)   {   }   const T& Get() const   {     if(!m_data)     {       m_data.reset(new T(m_args));     }     return *m_data;   }   private:   Args ... m_args;   mutable boost::scoped_ptr<T> m_data; }; */ template <class T> struct LazyInit0 {   LazyInit0() : m_data{} {}   const T& Get() const   {     if(!m_data)     {       m_data.reset(new T);     }     return *m_data;   }   private:   mutable boost::scoped_ptr<T> m_data; }; template <class T, typename Arg0> struct LazyInit1 {   LazyInit1(const Arg0 args)     : m_args{args},       m_data{}   {   }   const T& Get() const   {     if(!m_data)     {       m_data.reset(new T(m_args));     }     return *m_data;   }   private:   mutable Arg0 m_args;   mutable boost::scoped_ptr<T> m_data; }; template <class T, typename Arg0, typename Arg1> struct LazyInit2 {   LazyInit2(const Arg0 arg0, const Arg1 arg1)     : m_arg0{arg0},       m_arg1{arg1},       m_data{}   {   }   const T& Get() const   {     if(!m_data)     {       m_data.reset(new T(m_arg0,m_arg1));     }     return *m_data;   }   private:   mutable Arg0 m_arg0;   mutable Arg1 m_arg1;   mutable boost::scoped_ptr<T> m_data; }; struct Lazy_initVersion {   ///Obtain the version of this class   static std::string GetVersion() noexcept;   ///Obtain the version history of this class   static std::vector<std::string> GetVersionHistory() noexcept; }; } //~namespace ribi #endif // LAZY_INIT_H

 

 

 

 

 

./CppLazy_init/lazy_init.cpp

 

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//--------------------------------------------------------------------------- /* Lazy_init. Class to postpone constructor call upon first use. Copyright 2012-2015 Richel Bilderbeek This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ //--------------------------------------------------------------------------- //From http://www.richelbilderbeek.nl/CppLazy_init.htm //--------------------------------------------------------------------------- #include "lazy_init.h" std::string ribi::Lazy_initVersion::GetVersion() noexcept {   return "1.0"; } std::vector<std::string> ribi::Lazy_initVersion::GetVersionHistory() noexcept {   return {     "2012-02-11: version 1.0: initial version"   }; }