I want to use the find function from the algorithm library on a vector

Question

0

Asked: June 2, 20262026-06-02T21:24:21+00:00 2026-06-02T21:24:21+00:00

I want to use the find function from the algorithm library on a vector

0

I want to use the find function from the algorithm library on a vector object. The vector object is a vector of customers, (Customer is a class I made). I first ran it and it gave me an error in stl_algo.h. I search the web for it and I searched here for it too, I found a question here about it and I ran the same code, but I still got that error.

My code is here:

Header File:

#include <string>
#include <sstream>
#include <map>
#include <vector>

using namespace std;

enum Status {ACTIVE, INACTIVE};

class Customer {
    private:
        // ID Database class for storing customers' ids
        class IdDB {
            private:
                friend class Customer;

                // member field
                static map <string, int> idList;

                // member function
                static int getNumber (const string &threeLetters) {
                    map<string, int>::iterator i = idList.find(threeLetters);

                    if (i == idList.end()) {
                        idList.insert(pair <string, int> (threeLetters, 0));
                        return 0;
                    }else{
                        return ++(i->second);
                    }
                }
        };

        string id;
        string name;
        string address;
        Status status;

        void makeId () {
            string threeLetters = name.substr(0, 3);
            int idNum = IdDB::getNumber(threeLetters);

            stringstream oss;
            oss << threeLetters << idNum;
            id = oss.str();
        }

    public:
        Customer (const string&, const string&, const Status);

        // Accessor Methods
        string &getId ();
        string &getName ();
        string &getAddress ();
        Status getStatus ();

        // Mutator Methods
        void setAddress (const string&);
        void setStatus (const Status);

        // Misc. Methods
        void printStatus ();

        // Equality Operator Overloading
        friend bool operator == (Customer&, Customer&);
};

class CustomerDB {
    private:
        static vector<Customer> customersList;

    public:
        static void addCustomer (const Customer&);
        static void deleteCustomer (Customer&);
};

Source Code:

#include <iostream>
#include <string>
#include <algorithm>
#include "Customer.h"

using namespace std;

map<string, int> Customer::IdDB::idList;

Customer::Customer (const string &cName, const string &cAddress, const Status cStatus) : name(cName), address(cAddress), status(cStatus) {
    makeId();
}

// Accessor Methods
string &Customer::getId () { return id; }
string &Customer::getName () { return name; }
string &Customer::getAddress () { return address; }
Status Customer::getStatus () { return status; }

// Mutator Methods
void Customer::setAddress (const string &newAddress) { address = newAddress; }
void Customer::setStatus (const Status newStatus) { status = newStatus; }

// Misc. Methods
void Customer::printStatus () {
    if (status == ACTIVE)
        cout << "Active";
    else
        cout << "In-Active";
}

vector<Customer> CustomerDB::customersList;

void CustomerDB::addCustomer (const Customer &customer) {
    customersList.push_back(customer);
}

void CustomerDB::deleteCustomer (Customer &customer) {
    vector<Customer>::iterator i;
    i = find(customersList.begin(), customersList.end(), customer); // getting error in here
}

// Equality Operator Overloading
bool operator == (Customer &cust1, Customer &cust2) {
    return cust1.getId() == cust2.getId();
}

after building with Code::Blocks, I got this,

in header file stl_algo.h:

    }

  /// This is an overload used by find() for the RAI case.
  template<typename _RandomAccessIterator, typename _Tp>
    _RandomAccessIterator
    __find(_RandomAccessIterator __first, _RandomAccessIterator __last,
       const _Tp& __val, random_access_iterator_tag)
    {
      typename iterator_traits<_RandomAccessIterator>::difference_type
    __trip_count = (__last - __first) >> 2;

      for (; __trip_count > 0; --__trip_count)
    {
      if (*__first == __val) // error in here exactly getting a red block
        return __first;
      ++__first;

      if (*__first == __val)
        return __first;
      ++__first;

      if (*__first == __val)
        return __first;

Thanks

EDIT: Here is the build log

Compiling: C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp
In file included from c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/algorithm:63:0,
                 from C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp:5:
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h: In function '_RandomAccessIterator std::__find(_RandomAccessIterator, _RandomAccessIterator, const _Tp&, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Customer*, std::vector<Customer> >, _Tp = Customer]':
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:4403:45:   instantiated from '_IIter std::find(_IIter, _IIter, const _Tp&) [with _IIter = __gnu_cxx::__normal_iterator<Customer*, std::vector<Customer> >, _Tp = Customer]'
C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp:42:66:   instantiated from here
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:162:4: error: no match for 'operator==' in '__first.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = Customer*, _Container = std::vector<Customer>, __gnu_cxx::__normal_iterator<_Iterator, _Container>::reference = Customer&]() == __val'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:162:4: note: candidates are:
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/postypes.h:218:5: note: template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_pair.h:201:5: note: template<class _T1, class _T2> bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_iterator.h:285:5: note: template<class _Iterator> bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_iterator.h:335:5: note: template<class _IteratorL, class _IteratorR> bool std::operator==(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/allocator.h:122:5: note: template<class _T1, class _T2> bool std::operator==(const std::allocator<_T1>&, const std::allocator<_T2>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/allocator.h:127:5: note: template<class _Tp> bool std::operator==(const std::allocator<_Tp1>&, const std::allocator<_Tp1>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2427:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2434:5: note: template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::basic_string<_CharT>&, const std::basic_string<_CharT>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2448:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2460:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/streambuf_iterator.h:194:5: note: template<class _CharT, class _Traits> bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_tree.h:309:5: note: template<class _Val> bool std::operator==(const std::_Rb_tree_iterator<_Tp>&, const std::_Rb_tree_const_iterator<_Val>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_tree.h:846:5: note: template<class _Key, class _Val, class _KeyOfValue, class _Compare, class _Alloc> bool std::operator==(const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&, const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_map.h:877:5: note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator==(const std::map<_Key, _Tp, _Compare, _Alloc>&, const std::map<_Key, _Tp, _Compare, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_multimap.h:795:5: note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator==(const std::multimap<_Key, _Tp, _Compare, _Alloc>&, const std::multimap<_Key, _Tp, _Compare, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_vector.h:1273:5: note: template<class _Tp, class _Alloc> bool std::operator==(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)
C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp:46:6: note: bool operator==(Customer&, Customer&)
C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp:46:6: note:   no known conversion for argument 2 from 'const Customer' to 'Customer&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:4403:45:   instantiated from '_IIter std::find(_IIter, _IIter, const _Tp&) [with _IIter = __gnu_cxx::__normal_iterator<Customer*, std::vector<Customer> >, _Tp = Customer]'
C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp:42:66:   instantiated from here
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:166:4: error: no match for 'operator==' in '__first.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = Customer*, _Container = std::vector<Customer>, __gnu_cxx::__normal_iterator<_Iterator, _Container>::reference = Customer&]() == __val'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:166:4: note: candidates are:
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/postypes.h:218:5: note: template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_pair.h:201:5: note: template<class _T1, class _T2> bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_iterator.h:285:5: note: template<class _Iterator> bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_iterator.h:335:5: note: template<class _IteratorL, class _IteratorR> bool std::operator==(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/allocator.h:122:5: note: template<class _T1, class _T2> bool std::operator==(const std::allocator<_T1>&, const std::allocator<_T2>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/allocator.h:127:5: note: template<class _Tp> bool std::operator==(const std::allocator<_Tp1>&, const std::allocator<_Tp1>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2427:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2434:5: note: template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::basic_string<_CharT>&, const std::basic_string<_CharT>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2448:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2460:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/streambuf_iterator.h:194:5: note: template<class _CharT, class _Traits> bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_tree.h:309:5: note: template<class _Val> bool std::operator==(const std::_Rb_tree_iterator<_Tp>&, const std::_Rb_tree_const_iterator<_Val>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_tree.h:846:5: note: template<class _Key, class _Val, class _KeyOfValue, class _Compare, class _Alloc> bool std::operator==(const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&, const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_map.h:877:5: note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator==(const std::map<_Key, _Tp, _Compare, _Alloc>&, const std::map<_Key, _Tp, _Compare, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_multimap.h:795:5: note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator==(const std::multimap<_Key, _Tp, _Compare, _Alloc>&, const std::multimap<_Key, _Tp, _Compare, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_vector.h:1273:5: note: template<class _Tp, class _Alloc> bool std::operator==(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)
C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp:46:6: note: bool operator==(Customer&, Customer&)
C:\Users\KiKo-SaMa\Desktop\C++\DVD_App\Customer.cpp:46:6: note:   no known conversion for argument 2 from 'const Customer' to 'Customer&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:170:4: error: no match for 'operator==' in '__first.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = Customer*, _Container = std::vector<Customer>, __gnu_cxx::__normal_iterator<_Iterator, _Container>::reference = Customer&]() == __val'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_algo.h:170:4: note: candidates are:
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/postypes.h:218:5: note: template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_pair.h:201:5: note: template<class _T1, class _T2> bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_iterator.h:285:5: note: template<class _Iterator> bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/stl_iterator.h:335:5: note: template<class _IteratorL, class _IteratorR> bool std::operator==(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/allocator.h:122:5: note: template<class _T1, class _T2> bool std::operator==(const std::allocator<_T1>&, const std::allocator<_T2>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/allocator.h:127:5: note: template<class _Tp> bool std::operator==(const std::allocator<_Tp1>&, const std::allocator<_Tp1>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2427:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.h:2434:5: note: template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::basic_string<_CharT>&, const std::basic_string<_CharT>&)
Process terminated with status 1 (0 minutes, 1 seconds)
50 errors, 0 warnings

Report

Leave an answer
Cancel reply

You must login to add an answer.

Need An Account,

1 Answer

Editorial Team · Answer 1 · 2026-06-02T21:24:27+00:00

You should work on your const correctness, the problem is that your equality comparator takes the arguments by non const reference, but the last argument to find is taken by const reference, which means that the compiler cannot use it there.

Incidentally, once you add the const there you will be forced to add const accessors to the data. Also, if your operator only uses the public interface there is no need to declare it as a friend

Sign Up

Sign In

Forgot Password

The Archive Base Latest Questions

I want to use the find function from the algorithm library on a vector

Leave an answerCancel reply

1 Answer

Leave an answer
Cancel reply