Hi,

I am no std specialist, I just don't understand why visual studio
compiler returns me an error when I write :


int main(int argc,char* argv[])
{
   list<string> strlist;

   strlist.push_back("I");
   strlist.push_back("cant");
   strlist.push_back("compile");

   strlist.erase(strlist.begin() + 1); // doesn't work

   list<string>::const_iterator i = strlist.begin();

   strlist.erase(++i); // works !!

   return 0;
}


any hint ??


many thanks.

mat
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Mathieu Prevost <prevost@stanford.edu> wrote:
>I am no std specialist, I just don't understand why visual studio
>compiler returns me an error when I write :
>
>int main(int argc,char* argv[])
>{
>   list<string> strlist;
>   strlist.push_back("I");
>   strlist.push_back("cant");
>   strlist.push_back("compile");
>   strlist.erase(strlist.begin() + 1); // doesn't work

Because strlist is a list<> which is a linked list and does
not support random access iterators: you cannot arbitrarily
jump through the list to any point, but must instead increment
your way there one by one. This would have worked if your
container was, say, a vector, where random access is cool...


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Mathieu Prevost <prevost@stanford.edu> wrote:

> Hi,
>
> I am no std specialist, I just don't understand why visual studio
> compiler returns me an error when I write :
>
>
> int main(int argc,char* argv[])
> {
>    list<string> strlist;
>
>    strlist.push_back("I");
>    strlist.push_back("cant");
>    strlist.push_back("compile");
>
>    strlist.erase(strlist.begin() + 1); // doesn't work

Since strlist.begin() is an iterator, not a pointer, it doesn't support
operator+(int);  Take a look at the standard, Stroustrup (3rd Edition),
or Generic Programming and the STL (Austern).  Austern is the clearest.

>
>    list<string>::const_iterator i = strlist.begin();
>
>    strlist.erase(++i); // works !!

Iterators are supposed to support this.

>
>    return 0;
> }
>
>
> any hint ??
>

--
Harry Erwin, <http://mason.gmu.edu/~herwin>, Sr SW Analyst,
PhD cand (informatics/computational sci) modeling how bats
echolocate (def Sept), and Adj Prof of CS (data struct/adv C++).


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Harry Erwin wrote:
>
> Mathieu Prevost <prevost@stanford.edu> wrote:
...
> >    strlist.erase(strlist.begin() + 1); // doesn't work
>
> Since strlist.begin() is an iterator, not a pointer, it doesn't support

More accurately, it's because it is a reversible iterator, but not a
random-access iterator.


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On 31 Aug 1999 17:17:29 GMT, James Kuyper <kuyper@wizard.net> wrote:

:
: Harry Erwin wrote:
: >
: > Mathieu Prevost <prevost@stanford.edu> wrote:
: ...
: > >    strlist.erase(strlist.begin() + 1); // doesn't work
: >
: > Since strlist.begin() is an iterator, not a pointer, it doesn't support
:
: More accurately, it's because it is a reversible iterator, but not a
: random-access iterator.

More accurately, it's because it is a bidirectional iterator obtained
from a reversible container.

John


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