How to check if the iterator is initialized?

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孤城傲影 2021-02-05 06:30

If I use a default constructor for an iterator, how to check if it was assigned later on?

For pointers, I could do this :

int *p = NULL;
/// some code


      
      
        
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                   情歌与酒
                                             
                
                
                (楼主)
            
              
              
                2021-02-05 07:11
              

            
            
                        
As far as I know you must always initialize your iterators and the easiest way is to make them equal to 'container'.end()
In certain cases it looks like working, we had some problems with code that worked with VC6 and stopped working with VC2010. Look at this example compiled with g++ where it works for the vector but not for the map:

# Test iterator init, compile with: g++ test-iterator.cpp -o test-iterator
#include 
#include 
#include 

int main()
{
    std::vector vec;
    std::vector::iterator it;

    if (it != vec.end())
    {
            std::cout << "vector inside!" << std::endl;
    }
    else
    {
            std::cout << "vector outside!" << std::endl;
    }

    std::map mp;
    std::map::iterator itMap;

    if (itMap != mp.end())
    {
            std::cout << "map inside!" << std::endl;
    }
    else
    {
            std::cout << "map outside!" << std::endl;
    }

    return 0;
}

    
             
                                                        
            
            
              
                
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