c++ - Unable to insert smart pointer into map -


i trying insert smart pointer, p_pointer pointing towards foo class map, program not compile. therefore tried use normal pointer foo* , program compile. far, have been able use p_pointer normal pointer without issue surprised not work. if can explain me why not work...

*additionally, have posted here , people have complained code being messy before. time made use of code blocks function "format use astyle". please let me know if still not enough.

    #include <iostream>     #include<map>     #include<string>     using namespace std;      template <class t>     class p_pointer     {     public:         t* cp;         size_t* refptr;          size_t* counter()         {             return refptr;         }     //default constructor         p_pointer():cp(0),refptr(new size_t(1)) {}         p_pointer(t*t):cp(t),refptr(new size_t(1)) {}     //copy constructor         p_pointer (const p_pointer&s):cp(s.cp),refptr(s.refptr)         {             refptr=s.refptr;             cp=s.cp;             *refptr=*refptr+1;         }     //destructor         ~p_pointer()         {              if(--*refptr==0)             {                 delete cp;                 delete refptr;             }         }      //assignment operator         p_pointer&operator=(const p_pointer&s)         {             ++*s.refptr;     //freeing left hand size if last 1             if(--*refptr==0)             {                 delete cp;                 delete refptr;             }             cp=s.cp;             refptr=s.refptr;         }          operator bool()         {             return cp;         }          t*&operator->()         {             if(cp)                 return cp;              else throw std::runtime_error("uninitialized player");         }          t operator*()         {             if(cp)                 return *cp;             else throw std::runtime_error("uninitialized player");         }     };      class foo     {};   //method 1(work)     int main()     {         map<foo*,int> x;         foo* y=new foo();         x[y]=1;     }  //method 2 (does not work)  int main() {     map<p_pointer<foo>,int> x;     p_pointer<foo> y=new foo();     x[y]=1; }

the error message is: first time posting error message. copied content build messages , paste here. please let me know if not optimal way

||=== build: debug in trial 821 (compiler: gnu gcc compiler) ===| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h||in instantiation of 'bool std::less<_tp>::operator()(const _tp&, const _tp&) const [with _tp = p_pointer]':| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_map.h|498|required 'std::map<_key, _tp, _compare, _alloc>::mapped_type& std::map<_key, _tp, _compare, _alloc>::operator[](const key_type&) [with _key = p_pointer; _tp = int; _compare = std::less >; _alloc = std::allocator, int> >; std::map<_key, _tp, _compare, _alloc>::mapped_type = int; std::map<_key, _tp, _compare, _alloc>::key_type = p_pointer]'| c:\trial 821\main.cpp|80|required here| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|error: no match 'operator<' (operand types 'const p_pointer' , 'const p_pointer')| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: candidates are:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: operator<(int, int) | c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: no known conversion argument 2 'const p_pointer' 'int'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_pair.h|220|note: template constexpr bool std::operator<(const std::pair<_t1, _t2>&, const std::pair<_t1, _t2>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_pair.h|220|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::pair<_t1, _t2>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|298|note: template bool std::operator<(const std::reverse_iterator<_iterator>&, const std::reverse_iterator<_iterator>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|298|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::reverse_iterator<_iterator>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|348|note: template bool std::operator<(const std::reverse_iterator<_iterator>&, const std::reverse_iterator<_iteratorr>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|348|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::reverse_iterator<_iterator>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|1072|note: template bool std::operator<(const std::move_iterator<_iterator>&, const std::move_iterator<_iteratorr>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|1072|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::move_iterator<_iterator>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|1078|note: template bool std::operator<(const std::move_iterator<_iterator>&, const std::move_iterator<_iterator>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_iterator.h|1078|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::move_iterator<_iterator>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\basic_string.h|2588|note: template bool std::operator<(const std::basic_string<_chart, _traits, _alloc>&, const std::basic_string<_chart, _traits, _alloc>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\basic_string.h|2588|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::basic_string<_chart, _traits, _alloc>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\basic_string.h|2600|note: template bool std::operator<(const std::basic_string<_chart, _traits, _alloc>&, const _chart*)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\basic_string.h|2600|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::basic_string<_chart, _traits, _alloc>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\basic_string.h|2612|note: template bool std::operator<(const _chart*, const std::basic_string<_chart, _traits, _alloc>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\basic_string.h|2612|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: mismatched types 'const _chart*' , 'p_pointer'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_tree.h|980|note: template bool std::operator<(const std::_rb_tree<_key, _val, _keyofvalue, _compare, _alloc>&, const std::_rb_tree<_key, _val, _keyofvalue, _compare, _alloc>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_tree.h|980|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::_rb_tree<_key, _val, _keyofvalue, _compare, _alloc>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\array|242|note: template bool std::operator<(const std::array<_tp, _nm>&, const std::array<_tp, _nm>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\array|242|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::array<_tp, _nm>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\tuple|857|note: template constexpr bool std::operator<(const std::tuple<_args1 ...>&, const std::tuple<_args2 ...>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\tuple|857|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::tuple<_args1 ...>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_map.h|1017|note: template bool std::operator<(const std::map<_key, _tp, _compare, _alloc>&, const std::map<_key, _tp, _compare, _alloc>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_map.h|1017|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::map<_key, _tp, _compare, _alloc>'| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_multimap.h|920|note: template bool std::operator<(const std::multimap<_key, _tp, _compare, _alloc>&, const std::multimap<_key, _tp, _compare, _alloc>&)| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_multimap.h|920|note: template argument deduction/substitution failed:| c:\codeblocks\mingw\lib\gcc\mingw32\4.9.2\include\c++\bits\stl_function.h|371|note: 'const p_pointer' not derived 'const std::multimap<_key, _tp, _compare, _alloc>'| ||=== build failed: 1 error(s), 3 warning(s) (0 minute(s), 0 second(s)) ===|

your problem can found in error message: no match 'operator<' (operand types 'const p_pointer' , 'const p_pointer')|. in order use map custom type (p_pointer in case), type needs declare comparison operator < used sort keys in map. you'll need implement < operator, , should fix error. (other errors may show replace though.)

again, recommend using existing std::shared_ptr rather re-implementing yourself, unless have reason not so.


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