c++ - Error when calling std::find on a user-defined object -


so keep error message called:

no match 'operator==' in '(&__first) >std::_list_iterator<_tp>::operator* _tp = course == __val'

in following code:

int main(){   course not_found("not_found", "not_found", 0);   course x("comp2611", "computer organiaztion", 2);   hashtable<course> q(not_found, 17, 36);    q.insert(x); }    template <class hashedobj> class hashtable{ public:   hashtable(const hashedobj& notfound, int bucket, int base);   void insert(const hashedobj& x);  private:   const hashedobj item_not_found;   vector<list<hashedobj> > thelist; };  template <class hashedobj> void hashtable<hashedobj>::insert(const hashedobj& x){   list<hashedobj>& whichlist = thelist[hash(x)];   typename list<hashedobj>::iterator itr;   itr = std::find(thelist[0].begin(), thelist[0].end(), x);   if(itr == thelist[hash(x)].end())     whichlist.insert(thelist[hash(x)].begin(), x); }

i tested , understand error line

itr = std::find(thelist[0].begin(), thelist[0].end(), x);

but don't know fix it. think calling standard find function here, apparently not work.

the class course defined correctly think, because tested in other classes before.

the code is:

class course{ public: course(string code, string name, int credit):     _code(code), _name(name), _credit(credit){}  string _code;  private: string _name; int _credit;  friend int hash(course x); };   int hash(course x){     int sum = 0;     for(int = 0; < x._name.size(); i++)         sum+=_name[i];      return sum % 35; }

find uses operator== compare parameter looking value of iterator. course class has no such operator==. need implement it.

class course { public:   // bla bla   friend   bool operator==(const course& x, const course& y)   { return your-comparison-code-here; } };

as james kanze points out: can use std::find_if , provide comparison functor/lambda.


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