iterator and ostream

[ghost1111]

this is just an example not actual code if you were using iterator and list. You were using ostream and you wanted to cout statement how would you do that.

void example(std::ostream& os)
{
  std::list<example>::iterator dummy;
  for (dummy=example.begin(); dummy !=example.end(); ++dummy)
	{
	    std::advance(dummy,1);
	    os << *dummy << "\t";//here what im talking about
	}
}

[keskiverto]

http://www.cplusplus.com/reference/iterator/
states:

has the ability to iterate through the elements of that range using a set of operators (with at least the increment (++) and dereference (*) operators).

and continues with comparing pointer and iterator ...

Perhaps you should write a compilable code and test what that *dummy does in practise?


While you are there, please consider the ramifications of having both ++dummy on line 4 and std::advance(dummy,1) on line 6.

[ghost1111]

i have tested just want to understand what wrong because i do test it i get an error at line 7 even thought this is just example. the ostream& os is the problem

[JLBorges]

#include <iostream>
#include <list>
#include <iterator>

struct example { int value ; /* ...... */ };
std::ostream& operator<< ( std::ostream& stm, example ex )
{ return stm << '{' << ex.value << '}' ; }

std::list<example> my_list { {12}, {83}, {54}, {76}, {21}, {90}, {64}, {38}, {47}, {61} } ;

void example( std::ostream& os )
{
    // note: the name of the function'example' hides the name of the type 'example'
    // std::list<example>::iterator dummy; // *** error: 'example' is not the name of a type
    std::list< struct example >::iterator dummy ; // fixed: use an extended type specifier

    // iterate through the list using iterators (print every element in the list)
    for( dummy = my_list.begin(); dummy != my_list.end(); ++dummy ) os << *dummy << ' ' ;
    os << '\n' ;

    // iterate through the list using iterators (print every element in the list)
    for( dummy = my_list.begin(); dummy != my_list.end(); std::advance(dummy,1) ) os << *dummy << ' ' ;
    os << '\n' ;

    // iterate through the list using iterators (let the compiler figure out the type of the terator)
    for( auto iter = my_list.begin(); iter != my_list.end(); ++iter ) os << *iter << ' ' ;
    os << '\n' ;

    // iterate through the list using iterators (let the compiler figure out the type of the terator)
    for( auto iter = my_list.begin(); iter != my_list.end(); iter = std::next(iter) ) os << *iter << ' ' ;
    os << '\n' ;

    // iterate through the list using iterators (let the compiler figure out how to write the loop)
    for( const auto& ex : my_list ) os << ex << ' ' ;
    os << '\n' ;

    // iterate through the list using iterators (print every element in an even position in the list)
    for( auto iter = my_list.begin(); iter != my_list.end(); ++iter )
    {
        os << *iter++ << "      " ;
        if( iter == my_list.end() ) break ;
    }
    os << '\n' ;

    // iterate through the list using iterators (print every element in an even position in the list)
    for( auto iter = my_list.begin(); iter != my_list.end(); iter = std::next(iter) )
    {
        os << *iter << "      " ;
        std::advance(iter,1) ;
        if( iter == my_list.end() ) break ;
    }
    os << '\n' ;

    // iterate through the list using iterators (print every element in an odd position in the list)
    for( auto iter = my_list.begin(); iter != my_list.end(); ++iter )
    {
        ++iter ;
        if( iter == my_list.end() ) break ;
        os << "     " << *iter << ' ' ;
    }
    os << '\n' ;

    // iterate through the list using iterators (print every element in an odd position in the list)
    for( auto iter = my_list.begin(); iter != my_list.end(); std::advance(iter,1) )
    {
        iter = std::next(iter) ;
        if( iter == my_list.end() ) break ;
        os << "     " << *iter << ' ' ;
    }
    os << '\n' ;
}

int main()
{
    example(std::cout) ;
}

http://coliru.stacked-crooked.com/a/65f09a08f459a0fe