Re: list::end() decrement

On Sunday, July 22, 2012 10:24:58 AM UTC+4:30, JC wrote:
> Just to make sure, is the pre/post decrement operator valid on list:=

>
> list<x> alist = ...; // non-empty
> list<x>::iterator lastiter = -- alist.end();
>
> ... always result in lastiter being a valid forward iterator for the=

>
> The reason I'm asking is because the only reference I was ab=

>
> Thanks!
> J
 
Hi
I reviewed the C++ final draft international standard (N3290), quickly,
but I didn't find anything specific about end() iterator decrement.
BTW, I compiled and ran the following program under GCC 4.7.0
in two cases: list is empty and list isn't empty. It was fine:
#include <list>
#include <iostream>
 
int main()
{
    using namespace std;
    list<int> a_list = {0, 1, 2};
    list<int>::iterator last_iter = --a_list.end();
    cout << *last_iter << '\n';=09
 
    return 0;
}
 
I use the following command:
$ g++ -pedantic -pedantic-errors -std=c++11 list_end_iter.c++
$ ./a.out
2
If the list is empty, 0 is the output.
Also, I compiled and ran the following program under Visual Studio 2008:
#include <list>
#include <iostream>
 
int main()
{
    using namespace std;
    list<int> a_list;
    a_list.push_back(0); a_list.push_back(1); a_list.push_back(2);
    list<int>::iterator last_iter = --a_list.end();
    cout << *last_iter << '\n';
 
    return 0;
}
It was OK, and the output is 2, but if the list is empty,
there is run-time exception with the following message:
list iterator not decrement-able.
 
HTH,
  -- Saeed Amrollahi Boyouki