[STL] list iterator not incrementable

[Goldstein]

Hey everybody,

i hope my question wasnt mentionned in FAQ:

Ok, i'm working on a very simple project but when it comes to implementing the methode advance to increment the iterator current, it doesnt work and says list iterator not incrementable, heres the code:

void liste::avancer()
{

courant++;

}

and heres the constructor one:

liste::liste(void)
{
courant = maliste.begin();
}

when i call the 'avancer' method from the main i have an error: list iterator not incrementable

Thanks in advance

[laserlight]

It might be a good idea to post the smallest and simplest program that you expect to compile, but which demonstrates the problem.

[Goldstein]

It might be a good idea to post the smallest and simplest program that you expect to compile, but which demonstrates the problem.

liste.h

#pragma once
#include<list>
#include<iostream>
using namespace std;

class liste
{
list<int> maliste;
list<int>::iterator courant;
public:
liste(void);
void inserer();
void avancer();
void show();
~liste(void);
};

liste.cpp

#include "liste.h"
#include<iterator>


liste::liste(void)
{
courant = maliste.begin(); // to set the pointer on the begining of my list
}


liste::~liste(void)
{
}

void liste::show()
{
for (courant=maliste.begin(); courant!=maliste.end(); courant++) // to show my list
cout << " " << *courant ;


}

void liste::inserer()
{
insert_iterator<list<int>> it(maliste,maliste.begin()); // to insert an element
*it = 2;
}

void liste::avancer()
{

advance(courant,1); // or courant++ : both methods dont work!

}


run.cpp

#include"liste.h"

void main ()
{
liste a;
a.inserer(); // i insert 2 times the value 2
a.inserer();
a.avancer(); // here i want to increment the current iterator but it doesnt work
system("pause");
}

[Paul McKenzie]

liste.h

First you should use code tags when posting code. The code you posted is practically unreadable.

Regards,

Paul McKenzie

[Paul McKenzie]

liste::liste(void)
{
   courant = maliste.begin(); // to set the pointer on the begining of my list
}

There are no items in the list, so this iterator is the same as maliste.end(). Therefore, this iterator cannot br dereferenced, advanced, etc.

void liste::avancer()
{
    advance(courant,1); // or courant++ : both methods dont work!
}

You are now incrementing an invalid iterator, since it was set to end(), and you can't advance past end().

Also:

1) Do not use "using namespace std" in a header file.

2) The main() function returns int, not void.

Regards,

Paul McKenzie