no match for operator in std operator

Question

I am a C   newbie I tried out my first program here To my eyes this program is correct    include  lt iostream gt   using namespace std   class mystruct       private          int m a          float m b       public          mystruct int x  float y                            m a   x                  m b   y                  int main              mystruct m   mystruct 5 3 14            cout  lt  lt   my structure    lt  lt  m  lt  lt  endl           return 0      However I am getting sooo many errors Can t figure out why   cout cpp  In function    int main       cout cpp 26 29  error  no match for    operator lt  lt     in    std  operator lt  lt   with  Traits   std  char traits lt char gt       amp  std  cout     const char   my structure      lt  lt  m    cout cpp 26 29  note  candidates are   usr include c   4 6 ostream 110 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  std  basic ostream lt  CharT   Traits gt     ostream type amp      std  basic ostream lt  CharT   Traits gt     ostream type amp     with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 110 7  note    no known conversion for argument 1 from    mystruct    to    std  basic ostream lt char gt     ostream type amp      std  basic ostream lt char gt     ostream type amp    aka std  basic ostream lt char gt  amp      std  basic ostream lt char gt  amp        usr include c   4 6 ostream 119 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  std  basic ostream lt  CharT   Traits gt     ios type amp      std  basic ostream lt  CharT   Traits gt     ios type amp     with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt   std  basic ostream lt  CharT   Traits gt     ios type   std  basic ios lt char gt    usr include c   4 6 ostream 119 7  note    no known conversion for argument 1 from    mystruct    to    std  basic ostream lt char gt     ios type amp      std  basic ostream lt char gt     ios type amp    aka std  basic ios lt char gt  amp      std  basic ios lt char gt  amp        usr include c   4 6 ostream 129 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  std  ios base amp      std  ios base amp     with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 129 7  note    no known conversion for argument 1 from    mystruct    to    std  ios base amp      std  ios base amp       usr include c   4 6 ostream 167 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  long int   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 167 7  note    no known conversion for argument 1 from    mystruct    to    long int     usr include c   4 6 ostream 171 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  long unsigned int   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 171 7  note    no known conversion for argument 1 from    mystruct    to    long unsigned int     usr include c   4 6 ostream 175 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  bool   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 175 7  note    no known conversion for argument 1 from    mystruct    to    bool     usr include c   4 6 bits ostream tcc 93 5  note  std  basic ostream lt  CharT   Traits gt  amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  short int   with  CharT   char   Traits   std  char traits lt char gt    usr include c   4 6 bits ostream tcc 93 5  note    no known conversion for argument 1 from    mystruct    to    short int     usr include c   4 6 ostream 182 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  short unsigned int   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 182 7  note    no known conversion for argument 1 from    mystruct    to    short unsigned int     usr include c   4 6 bits ostream tcc 107 5  note  std  basic ostream lt  CharT   Traits gt  amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  int   with  CharT   char   Traits   std  char traits lt char gt    usr include c   4 6 bits ostream tcc 107 5  note    no known conversion for argument 1 from    mystruct    to    int     usr include c   4 6 ostream 193 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  unsigned int   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 193 7  note    no known conversion for argument 1 from    mystruct    to    unsigned int     usr include c   4 6 ostream 202 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  long long int   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 202 7  note    no known conversion for argument 1 from    mystruct    to    long long int     usr include c   4 6 ostream 206 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  long long unsigned int   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 206 7  note    no known conversion for argument 1 from    mystruct    to    long long unsigned int     usr include c   4 6 ostream 211 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  double   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 211 7  note    no known conversion for argument 1 from    mystruct    to    double     usr include c   4 6 ostream 215 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  float   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 215 7  note    no known conversion for argument 1 from    mystruct    to    float     usr include c   4 6 ostream 223 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  long double   with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 223 7  note    no known conversion for argument 1 from    mystruct    to    long double     usr include c   4 6 ostream 227 7  note  std  basic ostream lt  CharT   Traits gt     ostream type amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  const void    with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     ostream type   std  basic ostream lt char gt    usr include c   4 6 ostream 227 7  note    no known conversion for argument 1 from    mystruct    to    const void      usr include c   4 6 bits ostream tcc 121 5  note  std  basic ostream lt  CharT   Traits gt  amp  std  basic ostream lt  CharT   Traits gt   operator lt  lt  std  basic ostream lt  CharT   Traits gt     streambuf type    with  CharT   char   Traits   std  char traits lt char gt   std  basic ostream lt  CharT   Traits gt     streambuf type   std  basic streambuf lt char gt    usr include c   4 6 bits ostream tcc 121 5  note    no known conversion for argument 1 from    mystruct    to    std  basic ostream lt char gt     streambuf type   aka std  basic streambuf lt char gt        usr include c   4 6 bits basic string h 2693 5  note  template lt class  CharT  class  Traits  class  Alloc gt  std  basic ostream lt  CharT   Traits gt  amp  std  operator lt  lt  std  basic ostream lt  CharT   Traits gt  amp   const std  basic string lt  CharT   Traits   Alloc gt  amp    usr include c   4 6 ostream 451 5  note  template lt class  CharT  class  Traits gt  std  basic ostream lt  CharT   Traits gt  amp  std  operator lt  lt  std  basic ostream lt  CharT   Traits gt  amp    CharT   usr include c   4 6 ostream 456 5  note  template lt class  CharT  class  Traits gt  std  basic ostream lt  CharT   Traits gt  amp  std  operator lt  lt  std  basic ostream lt  CharT   Traits gt  amp   char   usr include c   4 6 ostream 462 5  note  template lt class  Traits gt  std  basic ostream lt char   Traits gt  amp  std  operator lt  lt  std  basic ostream lt char   Traits gt  amp   char   usr include c   4 6 ostream 468 5  note  template lt class  Traits gt  std  basic ostream lt char   Traits gt  amp  std  operator lt  lt  std  basic ostream lt char   Traits gt  amp   signed char   usr include c   4 6 ostream 473 5  note  template lt class  Traits gt  std  basic ostream lt char   Traits gt  amp  std  operator lt  lt  std  basic ostream lt char   Traits gt  amp   unsigned char   usr include c   4 6 ostream 493 5  note  template lt class  CharT  class  Traits gt  std  basic ostream lt  CharT   Traits gt  amp  std  operator lt  lt  std  basic ostream lt  CharT   Traits gt  amp   const  CharT    usr include c   4 6 bits ostream tcc 323 5  note  template lt class  CharT  class  Traits gt  std  basic ostream lt  CharT   Traits gt  amp  std  operator lt  lt  std  basic ostream lt  CharT   Traits gt  amp   const char    usr include c   4 6 ostream 510 5  note  template lt class  Traits gt  std  basic ostream lt char   Traits gt  amp  std  operator lt  lt  std  basic ostream lt char   Traits gt  amp   const char    usr include c   4 6 ostream 523 5  note  template lt class  Traits gt  std  basic ostream lt char   Traits gt  amp  std  operator lt  lt  std  basic ostream lt char   Traits gt  amp   const signed char    usr include c   4 6 ostream 528 5  note  template lt class  Traits gt  std  basic ostream lt char   Traits gt  amp  std  operator lt  lt  std  basic ostream lt char   Traits gt  amp   const unsigned char

User · Answer

Object is a collection of methods and variables.You can't print the variables in object by just cout operation . if you want to show the things inside the object you have to declare either a getter or a display text method in class.

ex

#include <iostream>

using namespace std;

class mystruct

{
private:
    int m_a;
    float m_b;

public:
    mystruct(int x, float y)
    {
            m_a = x;
            m_b = y;
    }
    public:
    void getm_aAndm_b()
    {
        cout<<m_a<<endl;
        cout<<m_b<<endl;
    }



};

int main()
{

    mystruct m = mystruct(5,3.14);

    cout << "my structure " << endl;
    m.getm_aAndm_b();
    return 0;

}

Not that this is just a one way of doing it

User · Answer

Obviously  the standard library provided operator does not know what to do with your user defined type mystruct  It only works for predefined data types  To be able to use it for your own data type  You need to overload operator  lt  lt  to take your user defined data type

User · Answer

You need to overload operator  lt  lt  for mystruct class  Something like  -  friend ostream amp  operator  lt  lt   ostream amp  os  const mystruct amp  m        os  lt  lt  m m a  lt  lt      lt  lt  m m b  lt  lt  endl      return os       See here

User · Answer

There s only one error      cout cpp 26 29  error  no match for    operator lt  lt     in    std  operator lt  lt   with  Traits   std  char traits      amp  std  cout     const char   my structure      lt  lt  m      This means that the compiler couldn t find a matching overload for operator lt  lt   The rest of the output is the compiler listing operator lt  lt  overloads that didn t match  The third line actually says this      cout cpp 26 29  note  candidates are

[c++] no match for ‘operator<<’ in ‘std::operator

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