Read a List made up of Lists

[doolsta111]

Hi Guys,

I am having issues with reading from a list made up of lists. I dont want to paste my code as it is for an assignment, but here is the basic setup.

i have a class person that has declared

list<char> name;

push to the list;

i have a class School that has declared

list<person> people;

push person to people from the other list;

So now the List name People should contain a single row of names.

when i try to print from the list People i get the following CRAZY error that i have no idea about. I can print from List name without a problem.

This is the code used for printing :

void printList()
{
   list<person>::const_iterator itr;
   
   for (itr = people.begin(); itr != people.end(); itr++ ) {
      cout << *itr;
   }
}

The error message is as follows in g++ compiler

maze5.cpp: In member function 'void School::printList()':
maze5.cpp:78: error: no match for 'operator<<' in 'std::cout << itr. std::_List_const_iterator<_Tp>::operator* [with _Tp = person]()'
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:67: note: candidates are: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>& (*)(std::basic_ostream<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:78: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ios<_CharT, _Traits>& (*)(std::basic_ios<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:90: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:125: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:159: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:102: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:176: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:187: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:191: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:202: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:183: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:218: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:242: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:217: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:265: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:288: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:311: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_streambuf<_CharT, _Traits>*) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:447: note:                 std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:509: note:                 std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, char) [with _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:458: note:                 std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, signed char) [with _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:463: note:                 std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, unsigned char) [with _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:571: note:                 std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const char*) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/bits/ostream.tcc:616: note:                 std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const char*) [with _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:497: note:                 std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const signed char*) [with _Traits = std::char_traits<char>]
/opt/csw/gcc4/lib/gcc/sparc-sun-solaris2.8/4.0.2/../../../../include/c++/4.0.2/ostream:502: note:                 std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const unsigned char*) [with _Traits = std::char_traits<char>]

[sblass92]

It is probably because you don't have a operator<< function declared for your person class. Since it's a class, the compiler won't know how to 'cout' whatever data you want.

I believe this should be something along the lines of what you'd need

ostream& operator<<(ostream& outs, person& x) {
outs << "Name: " << person.name();
return (outs);
}

[doolsta111]

It is probably because you don't have a operator<< function declared for your person class. Since it's a class, the compiler won't know how to 'cout' whatever data you want.

I believe this should be something along the lines of what you'd need

ostream& operator<<(ostream& outs, person& x) {
outs << "Name: " << person.name();
return (outs);
}

Thanks for that. Yes the problem was what you had said there it doesnt know what to print in class. So i iterated within the List School and asked it to run the printfunction in Person. This does what i want.

BUT NOW, the problem im having is that my object of class person is not getting cleared, and the data i cout is coming like this.

person1 , person 1 + person 2, person1, + person2 + person3

Vs
person1, person2, person3.

The reason is i havent cleared the object of Class person before it adds to the list in School Class.

I tried

person Teacher = new person();

(gets error)

but this did not work in the While loop,
and i tried

person Teacher; and this also did not work. (doesnt make any changes)

Anyone have idea on how to clear the object of the class.

[sblass92]

class person{
private: 
list<char> name;
}

If I understand correctly, this is what you've declared in person class and when you assign the name you use name.push() for lists. If its a list, name.clear() is a function provided that will empty your list.

Might I suggest replacing list<char> name; with:

string name;
//This way instead of using name.push(), you can treat name as a //variable and use the assignment operator. 

Teacher.name = "ABCD";
Teacher.name = "EFGH";

The old string will be written over and name will hold "EFGH".

person Teacher = new person();

The reason this did not work is because the new operator will return a pointer to your object in the memory heap.

person* Teacher = new person();

is a valid statement. From what you've posted, the difference between using pointers and copying the new person to your list is a matter of preference. For larger classes, its more efficient to store the pointer in the list rather than copy all the data.